JP2001083557A - Laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser device which is usable for a light source of an exposure device, allows the downsizing of the device and facilitate maintenance and to suppress the widening of wavelength width occurring in the non-linear effect of an optical element to be used. SOLUTION: After an incident laser beam LB 3 of about 1.5 μm in wavelength is amplified by an optical fiber amplifier 22 of a first stage, the laser beam is amplified by an optical fiber amplifier 25 of a second stage and the laser beam after the amplification is converted to UV light by frequency conversion. A narrow band-filter 24A and an isolator IS 3 are arranged between the optical fiber amplifiers 22 and 25, by which ASE(amplified spontaneous emission) noise, etc., are decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser device for generating ultraviolet light, and more particularly to a semiconductor device and an image pickup device (CCD).
Etc.), a liquid crystal display element, a plasma display element, and a light source for measurement or a light source of an exposure apparatus used in a photolithography process for manufacturing a micro device such as a thin film magnetic head.

[0002]

2. Description of the Related Art For example, an exposure apparatus used in a photolithography process for manufacturing a semiconductor integrated circuit uses a circuit pattern precisely drawn on a reticle (photomask) as a mask and a photoresist as a substrate. The coated wafer is optically reduced and projected and exposed. Minimum pattern size (resolution) on the wafer during this exposure
Is one of the simplest and most effective methods for reducing the wavelength of the exposure light (exposure wavelength). Here, a description will be given of some conditions to be provided for configuring an exposure light source, together with the realization of a shorter wavelength of exposure light.

First, a light output of, for example, several watts is required. This is necessary to shorten the time required for exposing and transferring the integrated circuit pattern and to increase the throughput. Second, when the exposure light is ultraviolet light having a wavelength of 300 nm or less, optical materials that can be used as a refraction member (lens) of the projection optical system are limited, and it becomes difficult to correct chromatic aberration. Therefore, monochromaticity of the exposure light is required, and the spectral line width of the exposure light is required to be about 1 pm or less.

Third, since the temporal coherence (coherence) increases with the narrowing of the spectral line width, an unnecessary interference pattern called speckle occurs when light having a narrow line width is irradiated as it is. . Therefore, in order to suppress the occurrence of speckle, it is necessary to reduce the spatial coherence of the exposure light source. One of the conventional short-wavelength light sources that satisfies these conditions is a light source that uses an excimer laser whose oscillation wavelength itself is a short wavelength, and the other is the generation of harmonics of an infrared or visible laser. It is a light source utilizing the above.

Among them, the former short wavelength light source is K
An rF excimer laser (wavelength: 248 nm) is used, and an exposure apparatus using an ArF excimer laser (wavelength: 193 nm) having a shorter wavelength is currently being developed. Furthermore, it has been proposed the use of F ₂ laser is a fellow excimer laser (wavelength 157 nm). However, these excimer lasers are large in size and the oscillation frequency is about several kHz at present, so that it is necessary to increase the energy per pulse in order to increase the irradiation energy per unit time. There have been various problems such as the fact that the transmittance of the optical component tends to fluctuate due to so-called compaction, etc., and that the maintenance is complicated and the cost is high.

As the latter method, there is a method of converting long-wavelength light (infrared light or visible light) into shorter-wavelength ultraviolet light by utilizing the second-order nonlinear optical effect of a nonlinear optical crystal. . For example, in the literature `` ¨Longitudinally diode pumped cont
inuous wave 3.5W green laser¨, LY Liu, M. Oka,
W. Wiechmann and S. Kubota; Optics Letters, vol.1
9, p189 (1994) "discloses a laser light source that converts the wavelength of light from a solid-state laser excited by semiconductor laser light. In this conventional example, 1 is emitted from the Nd: YAG laser.
A method is described in which a 064 nm laser beam is wavelength-converted by using a nonlinear optical crystal to generate a 266 nm beam of a fourth harmonic. Note that a solid-state laser is a general term for a laser whose laser medium is solid.

[0007] For example, in Japanese Patent Application Laid-Open No. 8-334803, a laser light generator provided with a semiconductor laser and a wavelength converter for converting light from the laser light generator into ultraviolet light by a nonlinear optical crystal are used. There has been proposed an array laser in which a plurality of laser elements are bundled in a matrix (for example, 10 × 10).

[0008]

In the conventional array laser having such a configuration, the optical output of the entire apparatus can be increased while the optical output of each laser element is suppressed low. The burden on the user can be reduced. However, on the other hand, since the individual laser elements are independent, it is necessary to match the oscillation spectrum of the entire laser element to about 1 pm or less in the entire width in consideration of application to an exposure apparatus.

For this reason, for example, in order for each laser element to autonomously oscillate in a single longitudinal mode having the same wavelength, the resonator length of each laser element is adjusted, or a wavelength selection element is provided in the resonator. Or had to be inserted. But,
These methods have problems such as that the adjustment is delicate, and that the more laser elements that compose, the more complicated the configuration is required to oscillate the whole at the same wavelength.

On the other hand, an injection seed method is well known as a method for actively converting a plurality of lasers to a single wavelength (for example, “Walter Koechner; Solid-stadium”).
te Laser Engineering, 3rd Edition, Springer Series
in Optical Science, Vol.1, Springer-Verlag, ISBN
0-387-53756-2, p246-249 "). This is because the light from a single laser light source with a narrow oscillation spectrum line width is split into a plurality of laser elements, and this laser light is used as a guided wave to tune the oscillation wavelength of each laser element, and This is a method of narrowing the width. However, this method has a problem that the structure is complicated because an optical system for branching the seed light to each laser element and a tuning control unit for the oscillation wavelength are required.

Further, such an array laser can significantly reduce the size of the entire device as compared with a conventional excimer laser, but it is still difficult to reduce the output beam diameter of the entire array to several cm or less. Was. In addition, the array laser configured as described above is expensive because a wavelength conversion unit is required for each array, and it is expensive when a part of the laser elements forming the array is misaligned or when the optical element is configured. In the event that damage occurs to the laser element, it is necessary to disassemble the entire array once, take out the laser element, adjust it, and reassemble the array in order to adjust this laser element. there were.

It is also conceivable to construct such a light source using an optical fiber. However, if strong light is simply propagated using an optical fiber, Self Phase Modulation (hereinafter, referred to as “Self Phase Modulation”) caused by the nonlinear effect of the optical fiber is considered.
"SPM"), Stimulated Raman Scattering
(Hereinafter referred to as "SRS"), Stimulated Brillouin S
There is a disadvantage that the wavelength width of the propagating light is widened due to the influence of cattering (hereinafter referred to as “SBS”). Due to such spread of the wavelength width, the spectral line width of the exposure light is reduced by 1 p.
The margin (margin) for reducing the value to about m or less is reduced.

In view of the above, it is a first object of the present invention to provide a laser apparatus which can be used as a light source of an exposure apparatus, can be downsized, and can be easily maintained. It is a second object of the present invention to provide a laser device capable of suppressing the spread of the wavelength width due to the nonlinear effect of the optical element used.

It is a third object of the present invention to provide a laser device capable of increasing the oscillation frequency, reducing the spatial coherence, and narrowing the overall oscillation spectrum line width with a simple configuration. I do.

[0015]

SUMMARY OF THE INVENTION A first laser device according to the present invention is a laser device for generating single-wavelength ultraviolet light, and has a single-wavelength laser within a wavelength range from infrared to visible. A laser light generator (11) for generating light, a plurality of optical fiber amplifiers (22, 25) for sequentially amplifying the laser light generated from the laser light generator, and a plurality of optical fiber amplifiers arranged between the plurality of optical fiber amplifiers; (18) having a narrow band filter (24A) and an isolator (IS3), and a wavelength converter for converting the laser light amplified by the optical amplifier into ultraviolet light using a nonlinear optical crystal. (20).

In this case, in order to temporally remove ASE (Amplified Spontanious Emission) between the plurality of stages of optical fiber amplifiers, an element which acts as a gate for turning on only when pulsed light passes, for example, an acousto-optical element ( AOM) or an electro-optical element (EOM) may be inserted. Further, a second laser device according to the present invention is a laser device that generates a single wavelength ultraviolet light, and generates a single wavelength laser light within a wavelength range from an infrared region to a visible region. Section (11), a plurality of amplifying optical fibers (22, 25) for amplifying the laser light generated from the laser light generating section, and an excitation light generating light source (23A) for generating a plurality of amplifying excitation lights. , A narrow band filter (24A) or isolator (IS3) disposed between the plurality of amplifying optical fibers, and a bypass member (21B, 21C, 21B, 21C, 21B) for passing the excitation light in parallel with the narrow band filter or isolator. 30), and a wavelength conversion unit (20) for converting the wavelength of the laser light amplified by the optical amplification unit into ultraviolet light using a nonlinear optical crystal. The third laser device according to the present invention is a laser device that generates a single-wavelength ultraviolet light, and has a single-wavelength laser light within a wavelength range from an infrared region to a visible region. And a plurality of stages of optical fiber amplifiers (2) for sequentially amplifying the laser light generated from the laser light generating unit.
2, 25), a plurality of pumping light generating light sources (23A, 23D) for generating pumping light for each of the plurality of stages of amplification optical fibers, and a narrow space disposed between the plurality of stages of amplification optical fibers. A band-pass filter (24A), an optical amplifier (18C) in which a reflection film for reflecting excitation light is formed at an end of an optical fiber coupled to both sides of the narrow band filter, and amplified by the optical amplifier. A wavelength converter (20) for converting the wavelength of the laser light into ultraviolet light using a nonlinear optical crystal.

Further, a fourth laser device according to the present invention comprises:
A laser device for generating a single-wavelength ultraviolet light, comprising: a laser light generator (11) for generating a single-wavelength laser light within a wavelength range from an infrared region to a visible region; An optical modulator (12) for converting the generated laser light into a pulse light having a predetermined frequency and a predetermined width; and an optical fiber amplifier (22, 22) for amplifying the laser light having passed through the light modulator.
25), and a wavelength converter (20) for converting the wavelength of the laser light amplified by the optical amplifier into ultraviolet light using a nonlinear optical crystal. The width of the pulse light converted by the unit is set to be wider than the pulse width for obtaining a predetermined wavelength width with the finally generated ultraviolet light.

A fifth laser device of the present invention is a laser device for generating a single-wavelength ultraviolet light, and generates a single-wavelength laser light within a wavelength range from an infrared region to a visible region. A laser light generator (11), an optical fiber amplifier (25) for amplifying the laser light generated from the laser light generator, and a transmission optical fiber (26) for propagating the laser light amplified by the optical fiber amplifier. An optical amplifier (18D) having a narrow-band filter (24A) disposed between the optical fiber amplifier and the transmission optical fiber; A wavelength converter (20) for converting the wavelength into light.

According to each of the laser devices of the present invention, the laser light generating unit is a small-sized light source having a narrow oscillation spectrum, such as a DFB (Distributed Feedback) semiconductor laser having a controlled oscillation wavelength or a fiber laser. Can be used. A single-wavelength laser beam from the laser light generating section is amplified by a multi-stage optical fiber amplifier, and then converted to ultraviolet light by a nonlinear optical crystal, thereby providing a high-output, single-wavelength, narrow-spectrum ultraviolet light. You can get light. Therefore, it is possible to provide a laser device that is small and easy to maintain.

In this case, as the optical fiber amplifier,
For example, erbium (Er) -doped optical fiber amplifier (EDFA), ytterbium (Yb) -doped optical fiber amplifier (Y
DFA), praseodymium (Pr) -doped optical fiber amplifier (PDFA), or thulium (Tm) -doped optical fiber amplifier (TDFA) can be used. The wavelength width may be widened due to the non-linear effect.

In the nonlinear effect, the SPM (Self Phase M
odulation) and SRS (Stimulated Raman Scatteri)
ng) increases as the fiber length increases. For example, in a simple model, the wavelength width spread due to SPM is proportional to the fiber length. Therefore, by shortening the fiber length, the spread of the wavelength width due to SPM can be reduced. When the light intensity at which SRS starts to occur is defined as the SRS threshold, the SRS threshold is inversely proportional to the fiber length. Therefore, by reducing the fiber length, the SR
By increasing the S threshold and making SRS less likely to occur,
The effect of suppressing the spread of the wavelength width of the output of the optical fiber amplifier can be obtained. In both cases of SPM and SRS, shortening the fiber length can reduce the wavelength width spread.

Next, SRS and SBS (Stimulated Bri
Llouin Scattering is a phenomenon in which light propagating through a fiber is scattered by phonons and is scattered by phonon sidebands. The wavelength of the light scattered by the phonon sideband differs from the original wavelength by the wavelength of the phonon, and the wavelength width is wider than the original wavelength width.
Further, in SRS and SBS, the light scattered in the phonon sideband is coherently amplified, and the intensity increases. In particular, when noise having a wavelength corresponding to the phonon sideband exists, it becomes a seed (seed light) and is amplified, so that the intensity of the scattered light increases, and the SR
The influence of the wavelength width spread by S and SBS becomes remarkable. Therefore, it is necessary to reduce seed noise in order to reduce the influence of SRS and SBS.

Therefore, in the above-mentioned present invention, first, a narrow band filter and an isolator are inserted into a connection portion of a plurality of stages of optical fiber amplifiers, so that an amplified
Reduces ontanious emission (hereinafter referred to as “ASE”) noise. Thereby, SRS and SBS can be reduced. Another method is to insert an isolator between a plurality of stages of optical fiber amplifiers.
Can be reduced, so that the effects of SRS and SBS can be reduced. Furthermore, the ASE can be reduced by inserting a narrow band filter between the optical fiber amplifiers in a plurality of stages, and the narrow band filter can block the light scattered by Raman scattering, so that the scattered light can be amplified coherently. And the effect of SRS is reduced.

In these cases, the propagation of the excitation light is blocked by the isolator or the narrow band filter. Therefore, a bypass member is provided so that the excitation light can be transmitted to the optical fiber amplifier before and after the isolator or the narrow band filter. In this bypass member, wavelength division multiplexing (WDM) for coupling is used.
By using the element, the excitation light can be used efficiently.

Next, also in the optical fiber amplifier having the bidirectional pumping structure, the spread of the wavelength width due to the non-linear effect is reduced by arranging the narrow band filter at the connection portion.
Furthermore, if a film that reflects the excitation light is formed on the end face of the optical fiber coupled to both ends of the narrow band filter, the excitation light injected from both the front and rear sides is reflected and propagates in opposite directions. Then, return to the original optical fiber amplifier. As a result, W for bypassing the above-described excitation light is obtained.
This eliminates the need for a multiplexer for DM, simplifies the configuration, and eliminates the insertion loss of WDM.

Next, as still another method, the waveform of the pulse light converted by the light modulator is converted into a pulse width for obtaining a predetermined wavelength width with finally generated ultraviolet light, that is, a required frequency width. There is also a method of using a waveform having a width several times longer than the pulse width determined by the transfer limit (for example, about 2 ns to 5 ns) and having a pulse transition time almost maximum. In this case, the pulse width of the output light is shortened by utilizing the bleaching of the gain in the final stage optical fiber amplifier.

That is, since the frequency spread due to the SPM is proportional to the time change of the light intensity, the longer the pulse transition time in which the time change of the light intensity is gradual, the smaller the frequency spread. Therefore, the influence of SPM can be reduced by using a pulse having a long pulse width and a long transition time. on the other hand,
There is a trade-off that the influence of SBS increases as the pulse width increases. In a simple model, the threshold, the light intensity at which SBS begins to occur, is inversely proportional to the pulse width. However, in the last stage optical fiber amplifier in which SBS is most problematic, the bleaching of the gain occurs, so that the pulse width of the output light is short, and the adverse effect of the wide pulse width is reduced.

Further, as another method, SRS from a high-power optical fiber amplifier at the final stage to an optical fiber for transmission is used.
There is a method of inserting a narrow band filter at the connection part in order to suppress the propagation of the noise. AS by the narrow band filter
E can be reduced and propagation of the SRS is suppressed, and the spread of the wavelength width of the propagated light is reduced. When an erbium-doped optical fiber amplifier (EDFA) is used as the optical fiber amplifier, for example, (980 ± 10) nm and (1480 nm ± 30) nm are used as the excitation light.
Of light can be used. However, the excitation wavelength is 980.
When the nm band is used, the gain per unit length is larger than when the 1480 nm band is used. Therefore,
The fiber length required to obtain a desired gain can be reduced, and ASE, which is a main cause of noise, can be reduced. Therefore, the noise of the optical fiber amplifier can be reduced in the 980 nm band excitation as compared with the 1480 nm band excitation.

It should be noted that ytterbium (Yb) -doped
The excitation light of the optical fiber and the optical fiber doped with erbium and ytterbium is (970 ±
10) nm light can be used. In each of these laser devices, the light splitting means (14, 16-1 to 16-
m), and the optical amplifiers (18-1 to 18-n)
It is preferable that the wavelength converter is independently provided for each of the plurality of laser beams, and the wavelength converter collectively converts the wavelengths of the laser beams output from the plurality of optical amplifiers. By sequentially giving a predetermined optical path length difference to the laser light branched by the light branching means, the spatial coherence of the finally bundled laser light can be reduced. Further, since each laser beam is generated from a common laser beam generator, the spectral line width of the finally obtained ultraviolet light is narrow.

Further, the laser light can be easily modulated at a high frequency of, for example, about 100 kHz by an optical modulator or the like. Each pulse light is an aggregate of, for example, about 100 pulse lights at predetermined time intervals. Therefore,
Compared to using excimer laser light (frequency is about several kHz), the pulse energy can be reduced to about 1/1000 to 1/10000 to obtain the same illuminance.
When used as an exposure light source, there is almost no change in transmittance of the optical member due to compaction or the like, and exposure can be performed stably and with high accuracy.

Next, regarding the configuration of the wavelength converter of the present invention, the second harmonic generation (SHG) of a plurality of nonlinear optical crystals will be described.
And the sum frequency generation (SFG), the frequency of which is an integral multiple of the fundamental wave (the wavelength is 1 / integer)
Can be easily output. Then, for example, the wavelength is 1.5 μm in the laser light generating section.
m, in particular, a laser beam limited to 1.544 to 1.552 μm, and the wavelength converter generates an eighth harmonic of the fundamental wave, so that a wavelength of 193 is substantially the same as that of the ArF excimer laser. UV light of １９194 nm is obtained. In addition, the laser light generating section emits laser light having a wavelength of about 1.5 μm, particularly 1.57 to 1.58 μm, and the wavelength conversion section generates a tenth harmonic of the fundamental wave. , ultraviolet light 157~158nm of F ₂ laser and substantially the same wavelength can be obtained. Similarly, for example, a laser beam generator emits a laser beam having a wavelength around 1.1 μm, particularly 1.099 to 1.106 μm, and a wavelength converter generates a seventh harmonic of the fundamental wave. Depending on the configuration, ultraviolet light having substantially the same wavelength as the F ₂ laser can be obtained.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In this example, the laser device of the present invention is applied to an ultraviolet light source for an exposure light source in an ultraviolet region of a projection exposure apparatus such as a stepper or a step-and-scan method, or an ultraviolet light generator that can be used as a light source for alignment and various inspections. is there.

FIG. 1A shows an ultraviolet light generating apparatus according to the present embodiment. A laser beam LB1 having a wavelength of 1.544 μm and comprising a wave (CW) is generated. The laser light LB1 is incident on an optical modulation element 12 as an optical modulator via an isolator IS1 for blocking light in the opposite direction, where it is converted into a pulsed laser light LB2, Incident on.

The laser beam LB2 incident on the optical branching amplifier 4
First, an optical fiber amplifier 1 as an optical amplification unit in the previous stage
After being amplified by passing through the splitter 3, the light enters the planar waveguide type splitter 14 as the first optical splitter via the isolator IS2, and is split into m laser beams having substantially the same intensity. m is an integer of 2 or more, and in this example, m = 4. The optical fiber amplifier 13 is an erbium-doped optical fiber amplifier (Erbium) in order to amplify light in the same wavelength range (around 1.544 μm in this example) as the laser beam LB1 generated from the single-wavelength oscillation laser 11.
-Doped Fiber Amplifier (EDFA) is used. The optical fiber amplifier 13 is supplied with pumping light having a wavelength of 980 nm from a pumping semiconductor laser (not shown) via a coupling wavelength division multiplexing device (not shown). Erbium-doped optical fiber amplifier (E
(980 ± 10) nm or (1480 nm)
(± 30 nm) excitation light can be used. However, in order to prevent the wavelength from spreading due to the non-linear effect, it is desirable to use a laser beam having a wavelength of (980 ± 10) nm as the excitation light and to shorten the fiber length. This is also desirable in that the noise of the optical fiber amplifier 13 due to ASE (Amplified Spontanious Emission) can be further reduced as compared with the case where light in the 1480 nm band is used as the excitation light. This is the same for the optical fiber amplifier at the subsequent stage.

The m laser beams emitted from the splitter 14 are coupled to optical fibers 15-1 and 15-1 having different lengths.
5-2,..., 15-m, the planar waveguide type splitters 16-1 and 16- as the second optical branching elements, respectively.
, 16-m, and is branched into n laser beams having substantially the same intensity. n is an integer of 2 or more, and in this example, n = 32. The first light splitting element (1
4) and the second light splitting element (16-1 to 16-m) correspond to the light splitting means of the present invention. As a result, the laser beam LB1 emitted from the single-wavelength oscillation laser 11 is divided into nm (m in this example, 128) laser beams as a whole.

Then, the n laser beams LB3 emitted from the splitter 16-1 pass through optical fibers 17-1, 17-2,... Optical amplification unit 18-1,
, 18-n and amplified. The optical amplification units 18-1 to 18-n are single-wavelength oscillation lasers 1
Amplify the light in the same wavelength range (around 1.544 μm in this example) as the laser light LB1 generated from No. 1. Similarly, the n laser beams emitted from the other splitters 16-2 to 16-m also have optical fibers 17 having different lengths from each other.
The light enters the optical amplification units 18-1 to 18-n as optical amplification units at the subsequent stage via -1 to 17-n and is amplified.

M sets of optical amplification units 18-1 to 18-n
The laser light amplified by the optical amplifier unit 18
A predetermined substance in -1 to 18-n propagates through an extension of an exit end of an optical fiber (described later) doped with a predetermined substance, and these extensions constitute an optical fiber bundle 19. The lengths of the extension parts of the m sets of n optical fibers constituting the optical fiber bundle 19 are substantially the same. However, the optical fiber bundle 19 is formed by bundling m · n undoped optical fibers having the same length, and irradiating the laser light amplified by the optical amplification units 18-1 to 18-n with the corresponding undoped optical fibers. Optical fiber. The optical branching amplifier 4 is composed of members from the optical fiber amplifier 13 to the optical fiber bundle 19.

The laser beam LB4 emitted from the optical fiber bundle 19 enters a wavelength converter 20 having a non-linear optical element and is converted into a laser beam LB5 composed of ultraviolet light. ,
Alternatively, the light is emitted to the outside as inspection light. Each of the m sets of optical amplification units 18-1 to 18-n corresponds to the optical amplification unit of the present invention, but the optical amplification unit may include the optical fiber of the optical fiber bundle 19 in some cases.

As shown in FIG. 1B, the output end 19a of the optical fiber bundle 19 has mn (128 in this example) optical fibers in close contact with each other and has a circular outer shape. Are bundled together. Actually, the shape of the output end 19a and the number of optical fibers to be bundled are determined according to the configuration of the wavelength converter 20 at the subsequent stage, the usage conditions of the ultraviolet light generator of the present example, and the like. The cladding diameter of each optical fiber constituting the optical fiber bundle 19 is 12
Since the diameter is about 5 μm, the diameter d1 of the output end 19a of the optical fiber bundle 19 when 128 fibers are bundled in a circular shape can be set to about 2 mm or less.

In the wavelength converter 20 of this embodiment, the incident laser beam LB4 is converted into a laser beam LB having an eighth harmonic (having a wavelength of 1/8) or a tenth harmonic (having a wavelength of 1/10).
Convert to 5. Since the wavelength of the laser beam LB1 emitted from the single-wavelength oscillation laser 11 is 1.544 μm,
The wavelength of the second harmonic is 193n which is the same as that of the ArF excimer laser.
m, and the wavelength of the 10th harmonic is 154 nm, which is almost the same as the wavelength (157 nm) of the F ₂ laser (fluorine laser). To make the wavelength of the laser beam LB5 closer to the wavelength of the F ₂ laser beam, the wavelength converter 20 generates the 10th harmonic and the single-wavelength oscillation laser 11 emits a 1.57 μm laser beam. Should be generated.

In practice, the oscillation wavelength of the single-wavelength oscillation laser 11 is specified to be about 1.544 to 1.552 μm,
By converting to an eighth harmonic, ultraviolet light having substantially the same wavelength (193 to 194 nm) as the ArF excimer laser can be obtained. Then, the oscillation wavelength of the single-wavelength oscillation laser 11 is specified to be about 1.57 to 1.58 μm, and is converted into a tenth harmonic, thereby substantially the same wavelength (1) as the F ₂ laser.
57 to 158 nm). Therefore, it is possible to use these ultraviolet light generator as easy sources of each ArF excimer laser light source, and maintenance at low cost alternative to the F ₂ laser light source.

Incidentally, instead of finally obtaining ultraviolet light in a wavelength range close to an ArF excimer laser or an F ₂ laser or the like,
For example, an optimum exposure wavelength (for example, 160 nm) is determined from a pattern rule of a semiconductor device or the like to be manufactured. The harmonic magnification in the unit 20 may be determined.

Hereinafter, the present embodiment will be described in more detail. In FIG. 1A, as a single-wavelength oscillation laser 11 oscillating at a single wavelength, for example, an oscillation wavelength of 1.544
μm, a continuous wave output (hereinafter also referred to as “CW output”) and an InGaAsP structure DFB (Distribution) having an output of 20 mW.
(ted feedback: distributed feedback type) A semiconductor laser is used. Here, a DFB semiconductor laser is one in which a diffraction grating is formed in a semiconductor laser instead of a Fabry-Perot resonator having low longitudinal mode selectivity, and a single longitudinal mode oscillation can be performed under any circumstances. Is configured to do so. DF
Since the B semiconductor laser basically oscillates in a single longitudinal mode, its oscillation spectrum line width can be suppressed to 0.01 pm or less. In addition, as the single-wavelength oscillation laser 11,
A light source that generates a laser beam having a narrow band in a similar wavelength region, such as an erbium (Er) -doped fiber
Lasers and the like can also be used.

Further, it is desirable that the output wavelength of the ultraviolet light generator of this embodiment is fixed to a specific wavelength according to the application. Therefore, an oscillation wavelength control device for controlling the oscillation wavelength of the single-wavelength oscillation laser 11 as a master oscillator (Master Oscillator) to a constant wavelength is provided. When a DFB semiconductor laser is used as the single-wavelength oscillation laser 11 as in this example, the oscillation wavelength can be controlled by controlling the temperature of the DFB semiconductor laser, and the oscillation wavelength can be further stabilized by this method. It is possible to control to a constant wavelength or fine-tune the output wavelength.

Usually, a DFB semiconductor laser or the like is provided on a heat sink, and these are housed in a housing. Therefore, in this example, the single-wavelength oscillation laser 11 (DFB
A temperature adjusting unit 5 (for example, a heating element such as a heater, a heat absorbing element such as a Peltier element, and a temperature detecting element such as a thermistor) is attached to a heat sink attached to a semiconductor laser.
Is fixed, and the operation of the temperature adjusting unit 5 is controlled by the control unit 1 composed of a computer via the driver 3 to control the temperature of the heat sink and, consequently, the temperature of the single-wavelength oscillation laser 11 with high accuracy. Here, the temperature of a DFB semiconductor laser or the like can be controlled in units of 0.001 ° C. Further, the control unit 1 controls the power (driving current in the case of the DFB semiconductor laser) for driving the single-wavelength oscillation laser 11 via the driver 2 with high accuracy.

The oscillation wavelength of the DFB semiconductor laser is 0.1 n
Since the DFB semiconductor laser has a temperature dependence of about m / ° C., if the temperature of the DFB semiconductor laser is changed, for example, by 1 ° C., the wavelength of the fundamental wave (wavelength: 1544 nm) changes by 0.1 nm. Therefore, the wavelength of the eighth harmonic (193 nm) is 0.012.
The wavelength changes by 5 nm, and the wavelength of the 10th harmonic (157 nm) changes by 0.01 nm. The laser beam LB
In the case where 5 is used in an exposure apparatus, for example, in order to correct an error of an imaging characteristic due to a difference in atmospheric pressure in an environment where the exposure apparatus is installed, or an error due to a change in the imaging characteristic, the center wavelength of the exposure apparatus is adjusted. It is desirable to be able to change about ± 20 pm. For this purpose, the temperature of the DFB semiconductor laser may be changed by about ± 1.6 ° C. for the eighth harmonic and about ± 2 ° C. for the tenth harmonic, which is practical.

As the monitor wavelength for feedback control when controlling the oscillation wavelength to a predetermined wavelength,
The oscillation wavelength of the DFB semiconductor laser, or the harmonic output (2nd harmonic, 3rd harmonic) after wavelength conversion in the wavelength converter 20 described later.
It is sufficient to select a wavelength that gives the sensitivity required for performing the desired wavelength control from among the harmonics, the fourth harmonic and the like, and is the most easily monitored. For example, when a DFB semiconductor laser having an oscillation wavelength of 1.51 to 1.59 μm is used as the single-wavelength oscillation laser 11, the third harmonic of this oscillation laser light is 50
The wavelength ranges from 3 nm to 530 nm, and this wavelength band corresponds to a wavelength range in which absorption lines of iodine molecules exist densely.
Precise oscillation wavelength control can be performed by selecting an appropriate absorption line of iodine molecules and locking the wavelength. Therefore, in this example, a predetermined harmonic (preferably a third harmonic) in the wavelength conversion unit 20 is compared with an appropriate absorption line (reference wavelength) of iodine molecules, and the shift amount of the wavelength is fed back to the control unit 1. The controller 1 controls the temperature of the single-wavelength oscillation laser 11 so that the deviation amount becomes a predetermined constant value. Conversely, the controller 1 controls the single-wavelength oscillation laser 11
May be positively changed to make the output wavelength adjustable.

When the ultraviolet light generating apparatus of this embodiment is applied to, for example, an exposure light source of an exposure apparatus, according to the former, generation of aberration of the projection optical system due to wavelength fluctuation or fluctuation thereof is prevented.
Image characteristics during pattern transfer (optical characteristics such as image quality)
Will not change. According to the latter, the difference in elevation and pressure between the manufacturing site where the exposure apparatus is assembled and adjusted and the location where the exposure apparatus is installed (delivery destination), and the difference in the environment (atmosphere in the clean room) are also determined. The resulting fluctuations in the imaging characteristics (such as aberration) of the projection optical system can be offset, and the time required to start up the exposure apparatus at the delivery destination can be reduced. Furthermore, according to the latter, during the operation of the exposure apparatus, the irradiation of the exposure illumination light, and the aberration of the projection optical system caused by a change in the atmospheric pressure, the projection magnification, and the fluctuation of the focus position, etc., can be offset, and always. The pattern image can be transferred onto the substrate in the best image forming state.

The laser light LB1 composed of continuous light outputted from the single-wavelength oscillation laser 11 is converted into laser light composed of pulsed light by using a light modulation element 12 such as an electro-optic light modulation element or an acousto-optic light modulation element. Converted to LB2. In the present configuration example, as an example, a case will be described in which the light modulation element 12 modulates pulse light with a pulse width of 1 ns and a repetition frequency of 100 kHz (pulse period of 10 μs). As a result of performing such light modulation, the light modulation element 12
Has a peak output of 20 mW and an average output of 2 μW. Here, it is assumed that there is no loss due to the insertion of the light modulation element 12, but there is actually an insertion loss. For example, when the loss is −3 dB, the peak output of the pulse light is 10 mW, and the average output is 1 μW.

When an electro-optic modulation element is used as the light modulation element 12, the electrode structure has been subjected to chirp correction so as to reduce the wavelength spread of the semiconductor laser output due to chirp due to the change in refractive index with time. It is preferable to use an electro-optic modulator (for example, a two-electrode modulator). In addition, by setting the repetition frequency to about 100 kHz or more, the optical amplification units 18-1 to 18-1 to be described later.
ASE (Ampl) in the optical fiber amplifier within 18-n
ified Spontaneous Emission (spontaneous emission light) It is possible to prevent a decrease in amplification factor due to the influence of noise. Further, when the illuminance of the finally output ultraviolet light may be about the same as that of the conventional excimer laser light (pulse frequency is about several kHz), the pulse frequency is increased as in this example, and each pulse light is emitted, for example. By forming a set of 128 delayed pulsed lights, the energy per pulse can be reduced to 1/1000.
It can be reduced to about 1 / 10,000 and the fluctuation of the refractive index of the optical member (such as a lens) due to compaction or the like can be reduced. Therefore, it is desirable to have such a modulator configuration.

Further, in a semiconductor laser or the like, the output light can be pulse-oscillated by controlling the current. For this reason, in this example, the single-wavelength oscillation laser 11 (DF
It is preferable to generate pulsed light by using both the power control of a B semiconductor laser and the light modulation element 12 together. Therefore, by controlling the current of the single-wavelength oscillation laser 11, pulse light having a pulse width of, for example, about 10 to 20 ns is oscillated, and only a part of the pulse light is cut out from the pulse light by the light modulation element 12, that is, in this example, The pulse width is modulated to 1 ns.

As a result, compared with the case where only the light modulation element 12 is used, it is possible to easily generate pulse light having a narrow pulse width, and it is also possible to determine the oscillation interval of pulse light, the start and stop of the oscillation, and the like. Control becomes easier. In particular, when the extinction ratio is not sufficient even when the pulse light is turned off using only the light modulation element 12, it is desirable to use the power control of the single-wavelength oscillation laser 11 together.

The pulse light output obtained in this way is
Erbium-doped optical fiber amplifier 13
Then, optical amplification of 35 dB (3162 times) is performed. At this time
The pulse light has a peak output of about 63 W and an average output of about 6.3 m
W. In addition, instead of this optical fiber amplifier 13,
A plurality of stages of optical fiber amplifiers may be used. That
The output of the first-stage optical fiber amplifier 13 is connected to the splitter 1
4, four outputs of channels 0 to 3 (in this example, m =
4) Split in parallel. Each output of channels 0 to 3 is
Connected to optical fibers 15-1 to 15-4, each having a different length
By continuing, the output light from each optical fiber
A delay time corresponding to the optical fiber length is given. example
For example, in this embodiment, the propagation speed of light in the optical fiber is 2
× 10 ⁸m / s, and channels 0, 1, 2, and 3
0.1m, 19.3m, 38.5, 57.7m respectively
Are connected.
In this case, adjacent channels at the exit of each optical fiber
The light delay between them is 96 ns. In this case,
Optical fiber 15-1 used for delaying light
１５15-4 are conveniently referred to as “delay fibers”.

Next, the outputs of the four delay fibers are further divided in parallel into n (n = 32 in this example) outputs by the four splitters 16-1 to 16-4 (channel 0 in each splitter). ~ 31), and a total of 4.32 (= 128
Channels). And each splitter 16
Optical fibers (delay fibers) of different lengths are again provided at the output terminals of channels 0 to 31 of -1 to 16-4.
1-17-32, 3n between adjacent channels
s delay time. Thereby, the output of the channel 31 is given a delay time of 93 ns. On the other hand, between the first to fourth splitters 16-1 to 16-4, a delay time of 96 ns is given to each splitter at the time of input to each splitter by the delay fiber as described above. As a result, the output terminals of a total of 128 channels,
Pulse light having a delay time of 3 ns between adjacent channels can be obtained.

As a result, in this example, the spatial coherence of the laser beam LB4 emitted from the optical fiber bundle 19 is larger than that in the case where the sectional shape of the laser beam LB1 emitted from the single wavelength oscillation laser 11 is simply enlarged. Almost one
It drops on the order of / 128. Therefore, there is an advantage that the amount of speckle generated when the finally obtained laser beam LB5 is used as exposure light is extremely small.

By the above-described branching and delay, a pulse light having a delay time of 3 ns between adjacent channels is obtained at the output terminals of a total of 128 channels. At this time, the optical pulse observed at each output terminal is: The same 100 kHz as the pulse light modulated by the light modulation element 12 (pulse period 1
0 μs). Therefore, looking at the entire laser light generator, after generating 128 pulses at 3 ns intervals, 9.6 pulses are generated.
The repetition that the next pulse train is generated at intervals of 2 μs is performed at 100 kHz.

In this embodiment, an example has been described in which the number of divisions is 128 and a short delay fiber is used. 9.62 μs between each pulse train
However, by increasing the number of divisions m and n, or lengthening the delay fiber to an appropriate length, or using a combination thereof,
It is also possible to make the pulse intervals completely equal.

As described above, the splitter 14, the optical fibers 15-1 to 15-m, and the splitters 16-1 to 16-m of the present embodiment.
m and m sets of optical fibers 17-1 to 17-n are time division multiplexing (Time Division Multiplexing: T) as a whole.
DM) means. In this example, the time division multiplexing means is constituted by a two-stage splitter, but it may be constituted by three or more stages of splitters, or the number of divisions is reduced, but only by one stage of splitter. May be. Further, the splitters 14, 16-1 to 16-m of this example are of a flat-plate waveguide type, but other than that, for example, a fiber splitter or a beam splitter using a partially transmitting mirror can also be used.

Further, in this embodiment, the oscillation timing of the light source (pulse light), that is, the repetition wave number f can be adjusted by controlling the timing of the drive voltage pulse applied to the light modulation element 12. Further, when the output of the pulse light can fluctuate with the change of the oscillation timing, the magnitude of the drive voltage pulse applied to the light modulation element 12 is also adjusted at the same time to compensate for the output fluctuation. Good. At this time, the fluctuation of the output of the pulsed light may be compensated for only by the oscillation control of the single-wavelength oscillation laser 11 or in combination with the control of the light modulation element 12 described above.

In FIG. 1 (a), the laser beams passing through m sets of delay fibers (optical fibers 17-1 to 17-n) are incident on optical amplification units 18-1 to 18-n, respectively, and are amplified. Optical amplification unit 18-1 to 1 of this example
8-n is provided with an optical fiber amplifier. In particular, when high intensity light propagates in the optical fiber as in the last stage optical fiber amplifier, SPM (Self Phase Modulation) caused by the nonlinear effect of the optical fiber,
SRS (Stimulated Raman Scattering) and SBS
(Stimulated Brillouin Scattering) causes the wavelength width of propagating light to be widened. Therefore, in the following embodiment, a configuration example for reducing the influence of the nonlinear effect and suppressing the spread of the wavelength width will be described. Hereinafter, some configuration examples of the optical amplifying unit that can be used as the optical amplifying unit 18-1 will be described, but these can be similarly used as the other optical amplifying units 18-2 to 18-n.

FIG. 2 shows an optical amplification unit 1 of the first configuration example.
In FIG. 2, the optical amplification unit 18 is basically composed of two stages of erbium-doped fiber amplifiers (EDFAs).
The optical fiber amplifiers 22 and 25 are connected to each other. And the first stage optical fiber amplifier 2
Wavelength Division Multiplexing (WD) for coupling the excitation light
M) Elements (hereinafter referred to as “WDM elements”) 21A and 2
The excitation light EL1 from the semiconductor laser 23A and the excitation light from the semiconductor laser 23B as excitation light sources are respectively supplied to the optical fiber amplifier 22 from the front and rear by WDM elements 21A and 21B. Similarly, WDM elements 21C and 21D for coupling are also connected to both ends of the second-stage optical fiber amplifier 25, and the pump light from the semiconductor lasers 23C and 23D is supplied to the optical fiber amplifier 25 by the WDM elements 21C and 21D, respectively. It is supplied from around. That is, the optical fiber amplifiers 22 and 25 are both of a bidirectional pump type.

The optical fiber amplifiers 22 and 25 respectively receive the incident laser beam LB3 (wavelength 1.544 μm in this example).
For example, light in a wavelength range of about 1.53 to 1.56 μm including the wavelength of m) is amplified. Optical fiber amplifier 2
A narrow band filter 24A and an isolator IS3 for blocking return light are arranged between the WDM element 21B and the WDM element 21C, which is a boundary between the two, 25. As the narrow band filter 24A, a multilayer filter or a fiber Bragg grating (Fiber Bragg Grat) is used.
ing) can be used.

In this example, the laser beam LB3 from the optical fiber 17-1 in FIG. 1A enters the amplification optical fiber 22 via the WDM element 21A and is amplified.
The laser light LB amplified by the amplification optical fiber 22
3 enters the amplification optical fiber 25 via the WDM element 21B, the narrow band filter 24A, the isolator IS3, and the WDM element 21C, and is amplified again. The amplified laser light LB3 passes through the WDM element 21D in FIG.
The light propagates through one optical fiber (which may be an extension of the exit end of the amplification optical fiber 25) constituting the optical fiber bundle 19 of (a).

In this case, the two-stage amplification optical fiber 22
And 25 give an overall gain of about 46 dB as an example
(39810 times). Then, assuming that the total number of channels (mn) output from the splitters 16-1 to 16-m in FIG. The average power is about 6.4 mW. When the laser light of each channel is amplified by about 46 dB, each optical amplification unit 18-
The average output of the laser light output from 1 to 18-n is about 2 W each. If this is pulsed with a pulse width of 1 ns and a pulse frequency of 100 kHz, the peak output of each laser beam will be 20 kW. The average output of the laser beam LB4 output from the optical fiber bundle 19 is about 256W.

Here, the splitter 14 shown in FIG.
Although the coupling loss in 16-1 to 16-m is not considered,
If there is the coupling loss, the output of the laser light of each channel is made uniform to the above-mentioned value (for example, 20 kW peak power) by increasing at least one amplification gain of the optical fiber amplifiers 22 and 25 by the loss. be able to. The optical fiber amplifiers 22 and 25 shown in FIG.
The output of the single-wavelength oscillation laser 11 (the output of the fundamental wave) in FIG. 1A can be made larger or smaller than the above-mentioned value by changing the amplification gain due to.

In the configuration example shown in FIG.
4A shows the optical fiber amplifier 13 of FIG.
Generated by each optical fiber amplifier 22
(Amplified Spontanious Emission) By cutting the light and transmitting the laser light (wavelength width of about 1 pm or less) output from the single-wavelength oscillation laser 11 of FIG. This is a narrow band.
As a result, the ASE light is transmitted to the optical fiber amplifier 25 at the subsequent stage.
To reduce the amplification gain of the laser light. Here, the narrow band filter 24A preferably has a transmission wavelength width of about 1 pm.
Since the wavelength width of the E light is about several tens of nm, the ASE light can be cut to such an extent that there is no practical problem even if a narrow band filter having a currently available transmission wavelength width of about 100 pm is used.

Further, the single-wavelength oscillation laser 1 shown in FIG.
In the case where the output wavelength is positively changed, the narrow band filter 24A may be replaced according to the output wavelength. However, the variable width of the output wavelength (in an exposure apparatus, for example, about ± 20 pm described above). It is preferable to use a narrow band filter having a transmission wavelength width (at least as large as the variable width) according to the above.

Further, the influence of the return light is reduced by the isolator IS3. Further, in the configuration example of FIG.
Since the ASE noise is reduced by using the narrow-band filter 24A and the isolator IS3, another non-linear effect of the final stage optical fiber amplifier 25 is S.
RS (Stimulated Raman Scattering) and SBS (Sti
Since the influence of mulated brillouin scattering is also reduced, the spread of the wavelength width is suppressed. Optical amplification unit 18
Can be configured by connecting, for example, three or more stages of optical fiber amplifiers. In this case as well, a narrow band filter 2 is provided at all the boundaries between two adjacent optical fiber amplifiers.
It is desirable to insert 4A and isolator IS3.

In this embodiment, a large number of optical amplification units 18 are used.
It is desirable to make the distribution of the intensity of each output light uniform in order to use the bundled output lights. For this purpose, for example, W
A part of the laser light LB3 emitted from the DM element 21D is separated, and the separated light is photoelectrically converted to monitor the light quantity of the emitted laser light LB3. The output of the excitation light source (semiconductor lasers 23A to 23D) in each of the optical amplification units 18 may be controlled so as to be substantially uniform.

Next, an optical amplification unit 18A of a second configuration example will be described with reference to FIG. 3, parts corresponding to those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted. In FIG. 3, the optical amplification unit 18A is also configured by connecting two-stage optical fiber amplifiers 22 and 25, and the excitation light EL1 from the semiconductor laser 23A is supplied to the preceding amplification optical fiber 22 from the front via the WDM element 21A. Have been. Further, the WDM elements 21B are sequentially passed from the amplification optical fiber 22 to the amplification optical fiber 25,
The isolator IS3 and the WDM element 21C are connected, and a bypass optical fiber 30 is connected between the coupling WDM elements 21B and 21C.

In this embodiment, the incident laser beam LB3 is amplified by the amplification optical fiber 22, and then is
The light passes through S3 and is amplified by the amplification optical fiber 25.
At this time, the pumping light E that has passed through the amplification optical fiber 22 is
L1 passes through the amplifying optical fiber 25 in the subsequent stage via the bypass optical fiber 30, so that the amplifying optical fiber 2 has a simple configuration with a reduced number of excitation light sources.
5, a high amplification gain can be obtained. Also, isolator I
Since ASE can be reduced by using S3, SRS
And the effects of SBS are also reduced.

Next, an optical amplification unit 18B of a third configuration example will be described with reference to FIG. 4, parts corresponding to those in FIG. 3 are denoted by the same reference numerals, and detailed description thereof will be omitted. The optical amplification unit 18B of FIG. 4 is different from the optical amplification unit 18A of FIG.
The isolator IS3 between 2 and 25 is connected to a narrow band filter 2
4A. With this configuration, the ASE can be reduced. Furthermore, since the narrow band filter 24A blocks the light scattered by Raman scattering in the optical fiber, the scattered light is prevented from being coherently amplified, and the influence of SRS is reduced. Also in this example, the excitation light EL is transmitted through the bypass optical fiber 30.
1 is also supplied to the amplification optical fiber 25. In addition, as the narrow band filter 24A of FIG. 4, in order to reduce noise, in particular, a multilayer filter or a fiber filter is used.
Bragg gratings are preferred.

Next, an optical amplification unit 18C of a fourth configuration example will be described with reference to FIG. 5, parts corresponding to those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted. The optical amplification unit 18C in FIG. 5 is different from the optical amplification unit 18 in FIG. 2 in that the WDM elements 21B and 21C, the semiconductor lasers 23B and 23C for excitation, and the isolator I are used.
S3 is omitted. Further, in FIG. 5, the semiconductor laser 23 is provided on each end face of the optical fiber coupled to both end faces 24Aa and 24Ab of the narrow band filter 24A.
A highly reflective film that reflects the excitation light EL1 from A and the excitation light EL4 from the semiconductor laser 23D is coated. Since the amplification optical fibers 22 and 25 of this example are erbium-doped optical fibers, laser beams having a wavelength of 980 nm are used as the excitation lights EL1 and EL4. Therefore, the end faces of the optical fibers coupled to both ends of the narrow band filter are coated with a high reflection film for 980 nm light.

In this configuration example, the incident laser light LB3
Is a narrow band filter 24A from the optical fiber amplifier 22.
And further passes through the optical fiber amplifier 25. Also, after one pumping light EL1 passes through the optical fiber amplifier 22 from the front to perform pumping, the narrow band filter 24A
Reflected by the surface 24Aa of the optical fiber amplifier 22 again.
And the other excitation light EL4 passes through the optical fiber amplifier 25 from the rear to excite it, and is then reflected by the surface 24Ab to excite the optical fiber amplifier 25 again.
In the optical fiber amplifiers 22 and 25, high amplification gains can be obtained.

At this time, the use of the narrow band filter 24A reduces the ASE, thereby reducing the influence of the SRS. Further, in the configuration example of FIG. 5, it is not necessary to insert the WDM elements 21B and 21C for bypass as compared with the configuration example of FIG. 4, so that the configuration can be simplified and the insertion loss of the WDM element is also eliminated. Next, referring to FIG.
The optical amplifying unit 18D of the configuration example will be described. FIG.
In FIG. 2, the portions corresponding to FIG. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted. In the optical amplification unit 18D shown in FIG. 6, a coupling WDM element 21C and a narrow-band filter 24A are connected before and after the optical fiber amplifier 25, and the pump light EL3 from the semiconductor laser 23C is supplied to the optical fiber amplifier 25 via the WDM element 21C. Is supplied to Further, the narrow band filter 24A is provided with a wavelength division multiplexing (Wavelength Division Multiplexing) for coupling.
A pump light EL4 from a semiconductor laser 23D is supplied to an optical fiber amplifier 25 via a narrow band filter 24A. In this example, the exit end of the narrow-band filter 24A is connected to one undoped optical fiber 26 constituting the optical fiber bundle 19 of FIG. Although not shown,
The optical fiber amplifier 22 shown in FIG. 2 and a member for excitation thereof are connected to a stage preceding the WDM element 21C.

In FIG. 6, the incident laser beam LB3
Are amplified by the optical fiber amplifier 25 and then propagate through the optical fiber 26 via the narrow band filter 24A. At this time, the configuration is simplified since the narrow band filter 24A also serves as a WDM element. Further, the use of the undoped optical fiber 26
Since the influence of SRS (Stimulated Raman Scattering) in the inside is reduced, the spread of the wavelength width is suppressed as a whole.

Next, another embodiment of the present invention will be described with reference to FIG. 1, FIG. 2 and FIG. In the above embodiment, the pulse width of the laser light output from the light modulation element 12 in FIG. 1A is set to about 1 ns. If the peak output is increased when the pulse width is short, the SPM (Sequence) is increased especially in the optical fiber amplifier at the subsequent stage.
lf Phase Modulation) may increase the frequency spread. Therefore, in this example, the width of the output pulse from the light modulation element 12 is determined by the pulse width determined by the transfer limit of the required frequency width (about 1 ns in this example).
Several times, for example, about 2 ns to 5 ns,
The pulse waveform should be such that the pulse transient time is maximized.

FIG. 7 shows an example of the pulse waveform of each part of this embodiment. The intensity change of the laser beam LB2 output from the light modulation element 12 in FIG. 1A with respect to time t is shown in FIG. The waveform becomes like a solid waveform 28A. The pulse width ΔtA of the waveform 28A is set to be about twice the pulse width ΔtB of the waveform 28B indicated by a dotted line determined by the transfer limit of the frequency width of the desired laser light. In this case, the laser beam LB1 output from the single-wavelength oscillation laser 11 in FIG. 1A may be a CW wave as shown by a solid line in FIG. 7A, but is shown by a two-dot chain line waveform 27. So that the pulse width Δ
By making the pulse light wider than tA,
The utilization efficiency of laser light can be increased.

If the light amplification unit 18 of FIG. 2 is used as the light amplification unit 18-1 of FIG. 1A in this example, if the pulse width of the laser beam LB2 is widened as described above, In particular, while the influence of SPM is reduced in the final stage optical fiber amplifier 25, SBS (Stim)
The effect of ulated Brillouin Scattering) increases.
However, in the final stage of the optical fiber amplifier 25, bleaching of the gain occurs.
The pulse width of the laser beam LB3 output from the
As shown by the solid line waveform 29A in FIG.
The waveform is shorter than the dotted waveform 29B corresponding to the waveform 2 as it is. Therefore, the adverse effect of increasing the pulse width in the light modulation element 12 is reduced, and the wavelength width of the finally output ultraviolet light can be reduced as a whole.

In the above embodiment, a laser light source having an oscillation wavelength of about 1.544 μm is used as the single-wavelength oscillation laser 11, but instead, an oscillation wavelength of about 1.099 to 1.106 μm is used. A laser light source may be used. As such a laser light source, a DFB semiconductor laser or a ytterbium (Yb) -doped fiber laser can be used. In this case, as the optical fiber amplifier in the optical amplifier in the subsequent stage, an ytterbium (Yb) -doped optical fiber (YDF) for performing amplification in a wavelength range of about 990 to 1200 nm including that wavelength is used.
A) may be used. In this case, the wavelength conversion unit 20 shown in FIG. 1B outputs the seventh harmonic, so that the wavelengths 157 to 158n substantially the same as those of the F ₂ laser are output.
m ultraviolet light is obtained. Practically, the oscillation wavelength is set to 1.1.
By setting the thickness to about μm, ultraviolet light having substantially the same wavelength as that of the F ₂ laser can be obtained.

Further, the oscillation wavelength of the single-wavelength oscillation laser 11 may be set to around 990 nm, and the wavelength converter 20 may output the fourth harmonic of the fundamental wave. by this,
It is possible to obtain the same ultraviolet light having a wavelength of 248 nm as the KrF excimer laser. It should be noted that the last stage of the optical fiber amplifier having the high peak output (for example, the optical fiber amplifier 2 in the optical amplification unit 18 in FIG. 2) in the above embodiment.
In 5), in order to avoid an increase in the spectrum width of the amplified light due to the non-linear effect in the fiber, the fiber mode diameter is usually used in communication (5 to 6 μm).
It is desirable to use a larger mode diameter fiber, e.g.

Further, in order to obtain a high output in the final stage optical fiber amplifier (eg, the optical fiber amplifier 25 in FIG. 2), a double clad having a double fiber clad structure is used instead of the large mode diameter fiber. -A fiber may be used. In this optical fiber, ions contributing to the amplification of the laser light are doped in the core, and the amplified laser light (signal) propagates in the core. Then, the semiconductor laser for excitation is coupled to the first cladding surrounding the core. The first cladding is multi-mode and has a large cross-sectional area, so that it is easy to transmit a high-power excitation semiconductor laser light,
The semiconductor laser of multi-mode oscillation can be efficiently coupled, and the light source for excitation can be used efficiently. A second clad for forming a waveguide of the first clad is formed on the outer periphery of the first clad.

In addition, although a quartz fiber or a silicate fiber can be used as the optical fiber amplifier of the above embodiment, a fluoride fiber, for example, a ZBLAN fiber may be used. In this fluoride-based fiber, the erbium doping concentration can be increased as compared with quartz or silicate-based fibers, so that the fiber length required for amplification can be shortened. This fluoride fiber is desirably applied particularly to the final-stage optical fiber amplifier (the optical fiber amplifier 25 in FIG. 2). By shortening the fiber length, the spread of the wavelength width due to the nonlinear effect during the propagation of the pulsed light into the fiber is suppressed. For example, it is possible to obtain a light source in which the wavelength width required for an exposure apparatus is narrowed. In particular, the fact that this band narrowing light source can be used in an exposure apparatus having a projection optical system having a large numerical aperture is advantageous in designing and manufacturing a projection optical system, for example.

By the way, as described above, the output wavelength of the optical fiber amplifier having the double-structure clad is 1.51.
When using 1.59 μm, ytterbium (Y) in addition to erbium (Er) is added as ions to be doped.
Preferably, b) is co-doped. This is because there is an effect of improving the pumping efficiency by the semiconductor laser. That is, when both erbium and ytterbium are doped, the strong absorption wavelength of ytterbium is 91%.
A plurality of semiconductor lasers having wavelengths ranging from 5 to 975 nm and having different oscillation wavelengths at wavelengths close to each other are coupled by wavelength division multiplexing (WDM) and coupled to the first cladding, thereby forming the plurality of semiconductor lasers. Can be used as the excitation light, so that a large excitation intensity can be realized.

As for the design of the doped fiber of the optical fiber amplifier, in an apparatus (for example, an exposure apparatus) operating at a predetermined constant wavelength as in this example, the gain of the optical fiber amplifier at a desired wavelength becomes large. It is desirable to select the material as follows. For example, Ar
The same output wavelength as that of the F excimer laser (193 to 194n)
In the case of using an optical amplifier fiber in the ultraviolet laser device for obtaining m), a desired wavelength, for example, 1.5
It is desirable to select a material that increases the gain at 48 μm.

However, the communication fiber is designed to have a relatively flat gain in a wavelength region of several tens nm near 1.55 μm for wavelength division multiplexing communication. Therefore, for example, in a communication fiber having an erbium single-doped core as an excitation medium, a method of co-doping aluminum or phosphorus into a silica fiber is used to realize the flat gain characteristic. Therefore, in this type of fiber, the gain does not always increase at 1.548 μm. Further, aluminum as a doping element has an effect of shifting a peak around 1.55 μm to a longer wavelength side, and phosphorus has an effect to shift to a shorter wavelength side. Therefore, to increase the gain near 1.547 μm,
A small amount of phosphorus may be doped. Similarly, when an optical amplifier fiber (for example, the double clad type fiber) having a core doped with both erbium and ytterbium (co-doped) is used,
1.547 μm by adding a small amount of phosphorus to the core
Higher gain can be obtained in the vicinity.

Next, some examples of the configuration of the wavelength conversion section 20 in the ultraviolet light generator of the embodiment shown in FIG. 1 will be described. FIG. 8A shows a wavelength converter 20 which can obtain an eighth harmonic by repeating generation of the second harmonic.
In (a), the wavelength output from the output end 19a of the optical fiber bundle 19 is 1.544 μm (the frequency is ω
) Of the laser light LB4 is incident on the first-stage nonlinear optical crystal 502, where the second harmonic is generated, and the frequency 2ω (the wavelength is ２), which is twice the frequency ω of the fundamental wave.
(772 nm). The second harmonic wave enters the second-stage nonlinear optical crystal 503 through the lens 505, where the second harmonic is again generated, and the frequency is twice the frequency 2ω of the incident wave, ie, four times the fundamental wave. A fourth harmonic having 4ω (the wavelength is ４ of 386 nm) is generated. The generated fourth harmonic further proceeds to the third-stage nonlinear optical crystal 504 via the lens 506, where the second harmonic generation again causes the frequency to be twice the frequency 4ω of the incident wave, ie, eight times the fundamental wave. An eighth harmonic having a frequency of 8ω (the wavelength is 1/8
3 nm). This eighth harmonic is an ultraviolet laser beam LB
Injected as 5. That is, in this configuration example, the fundamental wave (wavelength: 1.544 μm) → the second harmonic wave (wavelength: 772 nm) →
4th harmonic (wavelength 386 nm) → 8th harmonic (wavelength 193 nm)
Are performed in this order.

As the nonlinear optical crystal used for the wavelength conversion, for example, a LiB ₃ O ₅ (LBO) crystal is used for the nonlinear optical crystal 502 for converting a fundamental wave to a second harmonic.
LiB ₃ O ₅ (LBO) crystal is used for the nonlinear optical crystal 503 for converting the harmonic wave to the fourth harmonic, and Sr ₂ Be ₂ B for the nonlinear optical crystal 504 for converting the fourth harmonic to the eighth harmonic.
₂ O ₇ (SBBO) crystal is used. Here, in the conversion from the fundamental wave to the second harmonic using the LBO crystal, a non-critical phase matching (NCPM) by adjusting the temperature of the LBO crystal is used for phase matching for wavelength conversion. The NCPM enables conversion to the second harmonic wave with high efficiency and generates the "Walk-off", which is an angle shift between the fundamental wave and the second harmonic wave in the nonlinear optical crystal, and does not occur. The second harmonic is advantageous because it does not suffer from beam deformation due to walk-off.

In FIG. 8A, it is desirable to provide a condenser lens between the optical fiber bundle 19 and the nonlinear optical crystal 502 in order to increase the efficiency of incidence of the laser beam LB4. At this time, the mode diameter (core diameter) of each optical fiber constituting the optical fiber bundle 19 is, for example, about 20 μm, and the size of the region having high conversion efficiency in the nonlinear optical crystal is, for example, about 200 μm. A microlens with a magnification of about 10 may be provided for each, and the laser light emitted from each optical fiber may be focused on the nonlinear optical crystal 50. This is the same in the following configuration examples.

Next, FIG. 8B shows a wavelength conversion section 20A capable of obtaining an eighth harmonic by combining the second harmonic generation and the sum frequency generation. In FIG. The fundamental wave of the laser light LB4 having a wavelength of 1.544 μm emitted from the output end 19a of the bundle 19 is LBO
The light enters the first-stage nonlinear optical crystal 507 made of crystal and controlled by the NCPM, and a second harmonic (wavelength: 722 nm) is generated by the generation of the second harmonic. Furthermore,
A part of the fundamental wave passes through the nonlinear optical crystal 507 as it is. Both the fundamental wave and the second harmonic wave pass through a wave plate (for example, a half-wave plate) 508 in a state of linear polarization, and only the fundamental wave is emitted with the polarization direction rotated by 90 degrees. The fundamental wave and the second harmonic wave pass through the lens 509 and pass through the lens 509, respectively.
The light is incident on the nonlinear optical crystal 510 of the stage.

In the nonlinear optical crystal 510, a third harmonic (wavelength 511) is generated from the second harmonic generated in the first-stage nonlinear optical crystal 507 and the fundamental wave transmitted without being converted.
5 nm). As the nonlinear optical crystal 510, LBO
A crystal is used, but the first-stage nonlinear optical crystal 507 is used.
It is used in the NCPM having a different temperature from (LBO crystal). The third harmonic obtained by the non-linear optical crystal 510 and the second harmonic transmitted without wavelength conversion are separated by the dichroic mirror 511, and the dichroic mirror 5
The third harmonic reflected by 11 is reflected by mirror M1, passes through lens 513, and the third stage β-BaB ₂ O ₄ (BBO)
The light enters a nonlinear optical crystal 514 made of a crystal. Here, the third harmonic becomes the sixth harmonic (wavelength 257n) due to the generation of the second harmonic.
m).

On the other hand, the second harmonic transmitted through the dichroic mirror enters the dichroic mirror 516 via the lens 512 and the mirror M2, and the sixth harmonic obtained by the nonlinear optical crystal 514 also passes through the lens 515 to the dichroic mirror.
The light enters the mirror 516, where the second harmonic and the sixth harmonic are combined coaxially and incident on the nonlinear optical crystal 517 made of the fourth stage BBO crystal. In the nonlinear optical crystal 517,
Eighth harmonic (wavelength 1) by sum frequency generation from sixth harmonic and second harmonic
93 nm). This eighth harmonic is generated by the ultraviolet laser beam LB5.
Injected as The fourth-stage nonlinear optical crystal 51
As CsLiB ₆ O ₁₀ (C
It is also possible to use (LBO) crystals. In the wavelength conversion unit 20A, the wavelength is changed in the order of fundamental wave (wavelength 1.544 μm) → second harmonic wave (wavelength 772 nm) → third harmonic wave (wavelength 515 nm) → sixth harmonic wave (wavelength 257 nm) → eighth harmonic wave (wavelength 193 nm). A conversion has been made.

As described above, in the configuration in which one of the sixth harmonic and the second harmonic enters the fourth-stage nonlinear optical crystal 517 through the branch optical path, the sixth harmonic and the second harmonic are respectively transmitted to the fourth stage. Lenses 515 and 5 for condensing and entering the nonlinear optical crystal 517
12 can be arranged in different optical paths. In this case, since the sixth harmonic generated in the third-stage nonlinear optical crystal 514 has an elliptical cross-sectional shape due to the Walk-off phenomenon, good conversion efficiency is obtained by the fourth-stage nonlinear optical crystal 517. For this purpose, it is desirable to perform beam shaping of the sixth harmonic. Therefore, as in this example, the lenses 515, 51
2 are arranged in separate optical paths, for example, the lens 5
For example, a cylindrical lens pair 15 can be used, and the beam shaping of the sixth harmonic can be easily performed. Therefore, the fourth-stage nonlinear optical crystal (BBO crystal)
It is possible to increase the overlap with the second harmonic at 517 to increase the conversion efficiency.

The second-stage nonlinear optical crystals 510 and 4
The configuration between the nonlinear optical crystal 517 of the stage and FIG.
However, the present invention is not limited to this.
Any configuration may be used as long as the optical path lengths of the sixth harmonic and the second harmonic are equal so that the sixth harmonic and the second harmonic are incident simultaneously. Further, for example, the third-stage and fourth-stage nonlinear optical crystals 514 and 517 are arranged on the same optical axis as the second-stage nonlinear optical crystal 510, and the third-stage nonlinear optical crystal 514 applies only the third harmonic wave to the second stage. It may be converted into a sixth harmonic by the generation of the second harmonic, and may be incident on the fourth-stage nonlinear optical crystal 517 together with the second harmonic that is not wavelength-converted. This eliminates the need to use the dichroic mirrors 511 and 516.

The average output of the eighth harmonic (wavelength: 193 nm) per channel for each of the wavelength converters 20 and 20A shown in FIGS. 8A and 8B was experimentally obtained. As described in the above embodiment, the output of the fundamental wave is the output terminal of each channel, and has a peak power of 20 kW, a pulse width of 1 ns, a pulse repetition frequency of 100 kHz, and an average output of 2 W. As a result, 8 per channel
The average output of the harmonic is 2 in the wavelength converter 20 in FIG.
29 mW, 38.3 in the wavelength converter 20A of FIG.
mW. Therefore, the average output from the bundle including all 128 channels is 29 W in the wavelength converter 20,
The wavelength converter 20A has a power of 4.9 W, and any of the wavelength converters 20 and 20A can provide ultraviolet light having a wavelength of 193 nm, which has a sufficient output as a light source for an exposure apparatus.

Note that, with the same configuration as the wavelength conversion units 20, 20A, a fundamental wave (wavelength: 1.544 μm) → a second harmonic wave (wavelength: 772 nm) → a fourth harmonic wave (wavelength: 386 nm) → a sixth harmonic wave (wavelength: 257 nm) → It is also possible to perform wavelength conversion in the order of the eighth harmonic (wavelength 193 nm). Furthermore, fundamental wave (wavelength 1.544 μm) → second harmonic wave (wavelength 772 nm) → third harmonic wave (wavelength 515 nm) → fourth harmonic wave (wavelength 386 nm) → seventh harmonic wave (wavelength 221 nm) → eighth harmonic wave (wavelength 193 nm) Can be converted in the order of the fundamental wave (wavelength 1.5).
44 μm) → 2nd harmonic (wavelength 772 nm) → 3rd harmonic (wavelength 515 nm) → 4th harmonic (wavelength 386 nm) → 6th harmonic (wavelength 257 nm) → 7th harmonic (wavelength 221 nm) → 8th harmonic (wavelength 193 nm) The eighth harmonic can also be obtained by wavelength conversion in the following order. Of these, it is desirable to use one having a high conversion efficiency and a simplified configuration.

In the above embodiment, FIG.
As can be seen, m sets of n optical amplification units 18-1
The wavelengths of the combined lights having outputs of 〜18-n are converted by one wavelength converter 20. However, instead, for example, m ′ (m ′ is an integer of 2 or more) wavelength conversion units are prepared,
Outputs of the m sets of optical amplification units 18-1 to 18-n are n ′
Each group is divided into m ′ groups, wavelength conversion is performed by one wavelength converter for each group, and the obtained m ′ (eg, m ′ = 4 or 5 in this example) ultraviolet light is synthesized. You may make it.

According to the ultraviolet light generator of the above-described embodiment, the diameter of the output end of the optical fiber bundle 19 shown in FIG. It is possible to perform wavelength conversion of all channels by several wavelength converters 20. Moreover, since the output end uses a flexible optical fiber, it is possible to arrange components such as a wavelength converter, a single-wavelength oscillation laser, and a splitter separately, and the degree of freedom in arrangement is extremely high. . Therefore, according to the ultraviolet light generator of this example,
It is possible to provide an inexpensive and compact ultraviolet laser device having a single wavelength and low spatial coherence.

The laser device of the present invention can be used not only for an exposure device, but also for a laser repair device used for cutting a part (such as a fuse) of a circuit pattern formed on a wafer. it can. Further, the laser device according to the present invention can also be applied to an inspection device using visible light or infrared light. In this case, it is not necessary to incorporate the above-mentioned wavelength converter into the laser device. That is, the present invention is effective not only for an ultraviolet light generating device but also for a laser device that generates a fundamental wave in the visible or infrared region and has no wavelength conversion unit.

It is to be noted that the present invention is not limited to the above-described embodiment, but can take various configurations without departing from the gist of the present invention.

[0111]

According to the present invention, since an optical fiber amplifier is used, it is possible to provide a laser device that is small in size and easy to maintain. Etc. can be used. Further, the spread of the wavelength width due to the nonlinear effect of the optical element used can be suppressed.

Further, there is further provided a light branching means for branching the laser light generated from the laser light generating section into a plurality of laser lights, and an optical amplifying section is provided independently for each of the plurality of branched laser lights. By performing wavelength conversion on the bundle of laser beams output from the plurality of optical amplifiers, the oscillation frequency of the output light can be increased, the spatial coherence can be reduced, and the oscillation spectrum line width as a whole can be reduced. Can be reduced with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an ultraviolet light generating device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating optical amplification units 18-1 to 18-n in FIG.
FIG. 2 is a diagram showing a first configuration example of FIG.

FIG. 3 is a diagram illustrating a second configuration example of the optical amplification units 18-1 to 18-n.

FIG. 4 is a diagram illustrating a third configuration example of the optical amplification units 18-1 to 18-n.

FIG. 5 is a diagram illustrating a fourth configuration example of the optical amplification units 18-1 to 18-n.

FIG. 6 is a diagram illustrating a fifth configuration example of the optical amplification units 18-1 to 18-n.

FIG. 7 is a diagram showing a waveform of a laser beam of each part according to another example of the embodiment of the present invention.

8A is a diagram illustrating a first configuration example of the wavelength conversion unit 20 in FIG. 1, and FIG. 8B is a diagram illustrating a second configuration example of the wavelength conversion unit 20.

[Explanation of symbols]

11: single wavelength oscillation laser, IS1 to IS3: isolator, 12: optical modulator, 13: optical fiber amplifier,
14 splitter, 15-1 to 15-m, 17-1 to 1
7-n: Optical fiber (delay element), 16-1 to 16-
m: Splitter, 18-1 to 18-n: Optical amplification unit, 18, 18A to 18D: Optical amplification unit, 19: Optical fiber bundle, 20: Wavelength conversion unit, 20A to 2
0C: wavelength conversion unit, 22, 25: optical fiber amplifier,
24A ... narrow band filter

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Shu Namiki 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. F-term (reference) 2H097 BB02 CA13 CA17 GB01 LA10 LA12 2K002 AA04 AB12 CA02 HA20 5F046 AA07 BA04 CA03 CA08 DA30 5F072 AB09 AK06 QQ02 RR05 YY09

Claims (16)

[Claims] 1. A laser device for generating a single-wavelength ultraviolet light, comprising: a laser-light generating unit for generating a single-wavelength laser light within a wavelength range from an infrared region to a visible region; A plurality of stages of optical fiber amplifiers for sequentially amplifying the laser light generated from the unit, an optical amplification unit having a narrow band filter and an isolator disposed between the plurality of stages of optical fiber amplifiers, and an optical amplifier amplified by the optical amplification unit A wavelength conversion unit for converting the wavelength of the laser light into ultraviolet light using a nonlinear optical crystal. 2. The laser device according to claim 1, wherein the narrow-band filter and the isolator reduce noise having a wavelength corresponding to a phonon sideband. 3. The laser device according to claim 1, wherein the plurality of optical fiber amplifiers are provided in at least three stages, and a narrow band filter and an isolator are provided between the optical fiber amplifiers. 4. The laser device according to claim 1, further comprising a gate element for temporally removing ASE (Amplified Spontanious Emission) between the plurality of optical fiber amplifiers. . 5. A laser device for generating a single-wavelength ultraviolet light, comprising: a laser light generator for generating a single-wavelength laser light within a wavelength range from an infrared region to a visible region; A plurality of stages of amplification optical fibers for sequentially amplifying the laser light generated from the section, an excitation light generation light source for generating excitation light for at least one stage of the amplification optical fibers of the plurality of stages of amplification optical fibers, and An optical amplifier having a narrow band filter or isolator disposed between the amplification optical fibers, and a bypass member for passing the pump light in parallel with the narrow band filter or isolator; and an amplifier amplified by the optical amplifier. A wavelength conversion unit for converting the wavelength of the laser light into ultraviolet light using a nonlinear optical crystal. 6. A laser device for generating a single-wavelength ultraviolet light, comprising: a laser-light generator for generating a single-wavelength laser light within a wavelength range from an infrared region to a visible region; A plurality of stages of optical fiber amplifiers for sequentially amplifying the laser light generated from the section, a plurality of excitation light generating light sources for generating excitation light for each of the plurality of stages of optical fiber amplifiers, and the plurality of stages of optical fiber amplifiers. A narrow-band filter disposed in the optical amplifier, a light-amplifying unit having a reflection film for reflecting excitation light formed at ends of optical fibers coupled to both sides of the narrow-band filter; A wavelength conversion unit for converting the wavelength of the laser light into ultraviolet light using a nonlinear optical crystal. 7. A laser device for generating ultraviolet light of a single wavelength, comprising: a laser light generator for generating a laser light of a single wavelength within a wavelength range from an infrared region to a visible region; An optical modulator for converting a laser beam generated from the optical modulator into a pulse light having a predetermined width at a predetermined repetition frequency; an optical amplifier having an optical fiber amplifier for amplifying the laser beam passing through the optical modulator; A wavelength conversion unit that converts the wavelength of the laser light amplified by the unit into ultraviolet light using a non-linear optical crystal, wherein the width of the pulse light converted by the light modulation unit is predetermined by the finally generated ultraviolet light. Wherein the pulse width is set to be wider than a pulse width for obtaining the wavelength width. 8. The laser device according to claim 7, wherein the width of the pulse light converted by the light modulator is 2 to 5 ns. 9. A laser device for generating ultraviolet light of a single wavelength, comprising: a laser light generator for generating a laser light of a single wavelength within a wavelength range from an infrared region to a visible region; An optical fiber amplifier that amplifies the laser light generated from the section, a transmission optical fiber that propagates the laser light amplified by the optical fiber amplifier, and a narrow band filter disposed between the optical fiber amplifier and the transmission optical fiber. 1. A laser device comprising: a light amplifying unit having: a wavelength conversion unit configured to convert a laser beam amplified by the light amplifying unit into ultraviolet light using a nonlinear optical crystal. 10. The apparatus according to claim 1, wherein said narrow-band filter is also used as a wavelength division multiplexing element for multiplexing for supplying pumping light to said optical fiber amplifier.
2. The laser device according to 1. 11. The optical fiber amplifying unit is an erbium-doped optical fiber amplifier, and uses laser light having a wavelength of (980 ± 10) nm as pumping light for the amplifier. The laser device according to claim 1. 12. The laser device according to claim 1, wherein a multilayer filter or a fiber Bragg grating is used as said narrow band filter. 13. A single-wavelength oscillating laser for generating a single-wavelength laser beam within a wavelength range from an infrared region to a visible region, and a laser beam for generating a laser beam having a constant wavelength. The laser device according to any one of claims 1 to 14, further comprising an oscillation wavelength control unit for controlling the laser beam. 14. The laser device, further comprising: a light branching unit that branches the laser light generated from the laser light generating unit into a plurality of light beams, wherein the light amplifying unit is independent of each of the plurality of laser light beams. The laser device according to any one of claims 1 to 13, wherein the wavelength converter is provided, and the wavelength converter collectively converts the wavelength of the bundle of laser lights output from the plurality of optical amplifiers. 15. The laser light generating section having a wavelength of 1.5
a single-wavelength laser light having a wavelength of about 1.5 μm, and the wavelength conversion section converts the fundamental wave having a wavelength of about 1.5 μm output from the optical amplification section into eight-fold or ten-fold harmonic ultraviolet light. The laser device according to claim 1, wherein the laser device outputs the converted laser beam. 16. The laser light generating section has a wavelength of 1.1.
a wavelength of about 1 μm, and the wavelength conversion section converts the fundamental wave of about 1.1 μm outputted from the optical amplification section into a 7th harmonic ultraviolet light and outputs the fundamental wave. The laser device according to claim 1, wherein: