JP2003309309A - High-density and high-output laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical system device which can obtain high density and high output laser using simple, efficient, and direct irradiation and injection of a beam emitted from a multi-mode semiconductor laser as the excitation light to a clad pumping laser fiber. <P>SOLUTION: The device has a lens for condensing a direction of fast axis in the light emission region of the multi-mode semiconductor laser and a convex lens 11, through which the end face of the clad pumping laser fiber 13 is irradiated directly with the beam shaped by the condensing lens. Reflecting films 17, 17' reflecting the wavelength of a single mode laser to be emitted from the clad excitation laser fiber 13 are provided on the clad pumping fiber side of the convex lens 11 or on the end face of the clad pumping laser fiber. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is a means for obtaining a high-density and high-power single-mode laser by exciting a multi-mode laser emitted by combining one or more multi-mode semiconductor laser outputs. More specifically, the present invention relates to a means capable of obtaining high density and high output single mode laser output by enhancing the output even in a low output multimode laser device.

[0002]

2. Description of the Related Art In order to meet the demand for high output and high output of laser light, various laser light sources have been advanced in high density and high output. Among them, semiconductor lasers and cladding pumped laser fibers are attracting attention. Conventionally, there have been the following two methods of coupling the multimode semiconductor laser light and the cladding pumped laser fiber to obtain high output and high density.

1. Optical Component Coupling Method As shown in FIG. 1, this method uses a large number of lens sets 102 for adjusting the multimode fiber end of the laser diode bar 101 with a multimode fiber to the incident index of the cladding pumped laser fiber. Deploy. Fiber laser mirrors 104, 104 are provided on both end faces of the cladding pumped laser fiber 103.

According to this method, a high-density and high-power laser can be obtained from a cladding pumped laser fiber with a multimode semiconductor laser bar.
No. 02 and the fiber laser mirror 104 are required, and it is extremely difficult to manufacture and assemble the optical components, resulting in a high cost.

2. Fiber coupling method This method uses a multimode semiconductor laser with a multimode fiber and a cladding pumped laser fiber.
As shown in FIG. 2, the multimode semiconductor laser 105 is coupled to a multimode fiber 106 having a core diameter of 200 μ and an aperture ratio (NA) of 0.12 to 0.5 as shown in FIG. The tip of the multimode fiber 106 is thinned to about 50 to 80 microns to form a tapered fiber, which is connected in series to a clad pump laser fiber 108 having Bragg grating filters 107 at both ends.

Although this method is characterized in that the output can be coupled by a fiber component, the production of the tapered fiber and the coupling of the tapered fiber and the clad pump laser fiber are mechanically performed, which causes a failure. However, there was a problem in that the usage was difficult and the reliability was extremely low. Also, in order to increase the emission energy from this device, it is important to increase the excitation energy injected into the cladding pumped laser fiber, but in this method, it can be injected only from one end of the cladding pumped laser fiber. Laser fiber performance 1
There was a problem that it could not be used at 100%.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a first object thereof is to make a beam emitted from a multimode semiconductor laser into a cladding pumped laser fiber. It is an object of the present invention to provide an optical system device capable of obtaining a high-density and high-power laser by directly irradiating and injecting excitation light easily and efficiently.

A second object of the present invention is to reduce the beam energy emitted from a multimode semiconductor laser,
An object of the present invention is to provide an optical system device capable of simply and injecting near the limit of a cladding pumped laser fiber.

The device of the present invention is for exciting a single crystal laser,
Wide range of fields such as attenuated optical signal amplification reproduction for high-density wavelength division multiplexing (DWDM) communication, two-dimensional bar code writing, precision painless tooth cutting, cosmetic surgery, ophthalmic treatment, ultra-precision machining equipment such as trimmer Available for

[0010]

In order to achieve the above object, the first invention of the present invention is to arrange light emitted from a multimode semiconductor laser in a substantially concentric circle around a core doped with a rare earth element. A device for irradiating a clad pumped laser fiber having at least a double clad and emitting a single mode laser from a central core on the other end face of the cleaved surface, the device being a device for emitting light in an emission region of the multimode semiconductor laser. It has a lens for focusing in the fast axis direction and a convex lens for directly irradiating the end face of the cladding pumped laser fiber with a beam shaped by the lens, and the cladding lens is provided on the cladding pumped fiber side of the convex lens or on the end face of the cladding pumped laser fiber. Single-mode laser firing from a pump laser fiber It is characterized in that a reflective film that reflects wavelengths.

With this configuration, the multimode semiconductor laser is not destroyed by the high density single mode laser, and the aperture ratio is 0.05 to 0.15, for example.
From the core diameter of about 5 to 7 microns, it becomes possible to emit laser light with a high efficiency of about 50 to 70% of the energy of the multimode semiconductor laser irradiated for pumping the cladding pumped laser fiber.

A second aspect of the invention is a lens for converging the light in the first axis direction of the light emitting region of the multimode semiconductor laser, and a convex lens 1 for condensing the beam shaped by the lens.
1, a multimode fiber having an aperture ratio of 0.05 to 0.7 and being irradiated with a beam from the convex lens, a core doped with a rare earth element, and at least a double clad arranged around the core in a substantially concentric pattern. And a cladding pumped laser fiber having, wherein the multimode fiber has a side surface fused to the innermost cladding of the cladding pumped laser fiber so that pumping light can be injected, and the end of the multimode fiber is a multimode fiber. It has a semiconductor laser reflection film, and one end face of the cladding pumped laser fiber is provided with a film that reflects a single mode wavelength emitted from the core in the central portion.

According to the second aspect of the invention, the end face of the cladding pumped laser fiber is not directly irradiated and pumped, but is once received by the multimode fiber, and pumping light is injected into the cladding pumped laser fiber from the side surface of the multimode fiber. However, since the densified laser light is emitted only from a predetermined end face of the clad pumped laser fiber, the aperture ratio is, for example, 0.05 to 0.15, and the core diameter is approximately 5 to 7 microns, although the structure is simple. From about 50 of the multimode semiconductor laser energy applied to pump the cladding pumped laser fiber.
It is possible to emit laser light with a high efficiency of -80%. Moreover, the excitation energy can be significantly increased by fusing multiple multimode fibers,
As a result, the single mode laser light can be increased to the limit value.

In the first and second aspects of the present invention, the clad at the innermost periphery of the clad pumped laser fiber having a core doped with a rare earth element and at least double clads arranged substantially concentrically around the core has three or more sides. Preference is given to using those which have a polygonal cross section. When this configuration is adopted, the light is incident at a right angle on the polygonal surface, so that high density can be obtained.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 3 shows a first embodiment of the present invention. Reference numeral 2 denotes a multimode semiconductor laser mounted on the heat sink 1, and both the heat sink 1 and the heat sink 1 are attached to a housing 6 having a heat radiation effect. On the optical axis of the multimode semiconductor laser 2, a cylindrical lens 3 and a flat-cylindrical lens 4 having a flat emitter side and a cylindrical opposite side are arranged. On the optical axis of the cylindrical lens 4, a total reflection mirror or a prism 5 for reflecting the beam in a right angle direction (see reference numeral 8) is arranged. The heat sink 1, the multimode semiconductor laser 2, the cylindrical lens 3, the flat-cylindrical lens 4 and the total reflection mirror or prism 5 are included.

A plurality of units U (four in this example) including the heat sink 1, the multimode semiconductor laser 2, the cylindrical lens 3, the flat-cylindrical lens 4, and the total reflection mirror or the prism 5 are arranged in a line in the slow axis direction. Has been. The mirrors or prisms 5 are arranged with their phases shifted so that their reflected lights are substantially parallel.

The multimode semiconductor laser 2 is, for example,
The emitter size is 1 micron x 100 microns, the fast axis divergence half-value angle is 47 degrees, and the slow axis divergence half-value angle is 12 degrees.
A material having a characteristic of 15 nm is used. The laser light emitted from the emitter is first focused and shaped by the cylindrical lens 3 in the fast axis direction, and then the slow axis direction is focused by the flat-cylindrical lens 4 having a flat emitter side and the opposite side of a cylindrical shape. Shape. The cylindrical lens 3 has a diameter of 0.5 mm, for example.
It is desirable that the focal length is 0.2 mm and the flat-cylindrical lens 4 has, for example, a lens diameter of 2 mm and a focal length of 8 mm. The beam is reflected at a right angle by a total reflection mirror or prism 5.

The casing 6 is made of a non-translucent material in a highly airtight state, and a transparent plate 7 such as quartz or sapphire glass 7 is provided in the optical axis direction of the total reflection mirror or prism 5. Is fixed. A case 14 is provided adjacent to the case 6, and a condenser lens 11 is arranged on the beam optical axis so as to face the translucent plate 7 in the case 14.
On the optical axis of this is the cladding pumped laser fiber 13
The housing 14 has a connector 12 for fixing the cladding pumped laser fiber 13 so as to be positioned at the focal point of the condenser lens 11. Condensing lens 11
Has a focal length of 4.5 mm, for example.

On the cladding pumped laser fiber side of the condenser lens 11, in order to prevent the single mode laser from irradiating the multimode semiconductor laser 2, a reflection film 17 having a similar oscillation wavelength to the emitted light is coated. It is provided. The reflective film 17
′ May be provided on the end face of the pumping light incident surface 15 of the clad pumping laser fiber 13, or may be provided on both the pumping light incident surface 15 and the clad pumping laser fiber side of the condenser lens 11.

As described above, each beam reflected by the total reflection mirror or prisms 5 and 5 in the orthogonal direction is shown in FIG.
As shown in (b), the beam shapes (9) are densely arranged. The shape of each beam is 0.5 mm x 2.0
mm, which is a densely arranged and synthesized beam,
It is 2.0 mm × 2.0 mm.

The cladding pumped laser fiber 13 is
As shown in FIG. 3C, the core 1 doped with a rare earth element
5-1 has a central portion 5-1 around which the innermost clad (or pump guide) 15-2 for guiding the pumping multimode semiconductor laser light and the second clad 15-3
And a film 15-4 for protecting it. The innermost clad 15-2 has a polygonal cross section to enhance the reflection efficiency.

Specific specifications of the clad pumped laser fiber 13 are as follows: core: ytterbium-doped laser core diameter 7 μ, NA approximately 0.12, innermost clad or pump guide: average diameter 125 μm,
NA is about 0.50 and the second clad has an average diameter of 150 microns. In this case, the cladding pumped laser fiber 13 has an outer diameter of approximately 250 μm.

The combined beam transmitted through the light transmitting plate 7 is condensed by the condenser lens 11 and irradiated on the innermost clad 15-2 at the end face of the clad pumping laser fiber 13.
As a result, a single mode laser with an oscillation wavelength of about 1060 nm and an output of about 4 W is emitted from the ytterbium-doped core laser on the other end surface 16 of the cladding pumped laser fiber 13.

FIG. 4 shows a second embodiment of the present invention.
The basic configuration of this embodiment is the same as that of the first embodiment and the housing 14.
The fiber is the same as that of the first embodiment except that the fiber to be inserted in is not the cladding pump laser fiber 13 but the multimode optical fiber 18. In the second embodiment, the condenser lens 11 is arranged on the optical axis of the beam, and the multi-mode optical fiber 18 is arranged so as to be located at the focal portion thereof to collect the light. The multimode optical fiber 18 has, for example, an NA of approximately 0.42 and a core diameter of 125 microns.

The multimode optical fiber 18 has a core part 18-1 and a clad 18-2, is curved with an appropriate curvature, and the side surface of an arbitrary part is in a state in which light can be transmitted to a part of the clad pumped laser fiber 13. Joined by.
That is, the core part 1 of the multimode optical fiber 18
8-1 is fused to the innermost clad 15-2 of the clad pumped laser fiber 13. Reference numeral 19 indicates a fused portion.

A reflection film 22 of the multimode semiconductor laser is provided at the tip of the multimode optical fiber 18, and the end face of the cladding pumped laser fiber 13 is
A reflection film 20 that efficiently reflects the oscillation wavelength of the single mode laser is provided. As a result, a single mode laser with an oscillation wavelength of approximately 1060 nm and an output of approximately 4 W is emitted from the other end surface 21 of the cladding pumped laser fiber 13, that is, the ytterbium doped core laser.

The present invention includes fusing a plurality of core portions 18-1 of the multimode fiber 18 to the innermost cladding 15-2 of the cladding pumped laser fiber 13. That is, a plurality of devices indicated by reference numeral A are arranged, and the core portion 18-1 of the multimode fiber 18 in each of the devices A and A is fused to the innermost clad 15-2 of the cladding pumped laser fiber 13. Is. The fusion bonding position is arbitrary such as the same cross-sectional position and the displaced position, and by doing so, the pumping energy can be injected to the limit of the cladding pumping laser fiber 13.

What is shown is merely an example of the present invention, and the present invention is not limited thereto. The cylindrical lens 4 for beam-shaping in the slow axis direction in the embodiment may be omitted. Further, the number of units U is not limited. The reflection films 15, 20, and 22 are concepts including a Bragg grating filter. Instead of this, the convex lens 11 may be a concave mirror.

[0029]

According to claim 1 of the present invention described above, the light emitted from the plurality of multi-mode semiconductor lasers 2 is condensed by the convex lens 11 and at least 2 is provided on the outer periphery of the core doped with the rare earth element. The end face of the clad pumped laser fiber 13 having a heavy clad is directly irradiated and excited, a single mode laser is emitted from the core of the other end face, and the clad pumped fiber side of the convex lens 11 or the end face of the clad pumped laser fiber is clad pumped. Since the reflection film 17 that reflects the wavelength of the single mode laser emitted from the laser fiber 13 is provided, the multimode semiconductor laser 2 is not damaged and high density and high output can be obtained efficiently. As a result, an excellent effect is obtained that, for example, a single mode laser beam having a diameter of 7 μm and NA = 0.12 can be obtained inexpensively and reliably with an output of 5 to 30 watts.

According to the second and third aspects, the lens for condensing the first axis direction of the light emitting region of the multimode semiconductor laser, the convex lens 11 for condensing the beam shaped by the lens, and the aperture ratio of 0. The multi-mode fiber 18 having a diameter of 05 to 0.7 and being irradiated with the beam from the convex lens 11, a core doped with a rare earth element, and a clad pump laser fiber 13 having at least double clads arranged substantially concentrically around the core. The side surface of the multimode fiber 18 is fused to the innermost clad 15-2 of the clad pumping laser fiber 13 so that pumping light can be injected, and the end of the multimode fiber 18 is It has a reflective film 22 of a multimode semiconductor laser, and one end surface of the cladding pumped laser fiber 13 is Since the film 20 that reflects the single mode wavelength emitted from the central core is provided, the degree of pumping of the cladding pumped laser fiber 13 can be easily set by selecting the fusion number of the multimode fiber 18. Yes, clad pumped laser fiber 1
Injection energy up to the limit of 3 and high density
The excellent effect that a high output single mode laser can be obtained is obtained.

According to the fourth aspect, since the light is reflected by the polygonal surface at a right angle and enters the light, an excellent effect that a reliable high density can be obtained can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a conventional polarization coupling method.

FIG. 2 is an explanatory diagram showing a conventional fiber coupling method.

3A is a longitudinal side view showing the first embodiment of the present invention, FIG. 3B is an explanatory view showing a beam shape downstream of the convex lens in FIG. 3A, and FIG. 3C is pumping light of a clad pumping laser fiber. FIG. 3D is an enlarged cross-sectional view of the entrance end, and FIG. 3D is an enlarged view of the single-mode laser emission end of the cladding pumped laser fiber.

FIG. 4A is a longitudinal side view showing a second embodiment of the present invention, and FIG. 4B is an enlarged cross-sectional view of the fusion-bonded portion of the multimode fiber and the cladding pumped laser fiber in FIG.

[Explanation of symbols]

2 multimode semiconductor laser 11 condensing lens 13 multimode optical fiber 15-1 core 15-2 innermost clad or pump guide 15-3 second clad 17, 17 'reflective film 18 multimode fiber 19 multimode fiber and clad pumping Fusion point with laser fiber 20 Reflective film 22 Reflective film

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[Procedure amendment]

[Submission date] April 19, 2002 (2002.4.1)
9)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Explanation of code

[Correction method] Change

[Correction content]

[Description of Reference Signs] 2 multimode semiconductor laser 11 condensing lens 13 clad pump laser fiber 15-1 core 15-2 innermost clad or pump guide 15-3 second clad 17, 17 'reflective film 18 multimode fiber 19 Fusion point of multimode fiber and cladding pumped laser fiber 20 Reflective film 22 Reflective film

Claims (4)

[Claims] 1. Light emitted from a multi-mode semiconductor laser is irradiated to a clad pumped laser fiber having a core doped with a rare earth element and at least double clads arranged substantially concentrically around the core, and the light is cut off. A device for emitting a single-mode laser from a central core of an end face, the device including a lens for focusing in the fast axis direction of the emission region of the multimode semiconductor laser and a beam shaped by the lens. It has a convex lens 11 that directly irradiates the end face of the clad pumped laser fiber 13, and reflects the wavelength of the single mode laser emitted from the clad pumped laser fiber 13 to the clad pumped fiber side of the convex lens 11 or to the end face of the clad pumped laser fiber 13. Reflective film 1
High-density, high-power laser device characterized by having 7, 17 '. 2. A lens which collects light in a fast axis direction of a light emitting region of a multimode semiconductor laser, a convex lens 11 which collects a beam shaped by the lens, and an aperture ratio of 0.
The multi-mode fiber 18 having a diameter of 05 to 0.7 and being irradiated with the beam from the convex lens 11, a core doped with a rare earth element, and a clad pump laser fiber 13 having at least double clads arranged substantially concentrically around the core. The side surface of the multimode fiber 18 is fused to the innermost clad 15-2 of the clad pumping laser fiber 13 so that pumping light can be injected, and the end of the multimode fiber 18 is A high density characterized in that it has a reflection film 22 for a multimode semiconductor laser, and one end surface of the cladding pumped laser fiber 13 is provided with a film 20 for reflecting a single mode wavelength emitted from the core in the central portion. -High power laser device. 3. The high-density and high-power laser device according to claim 2, wherein the cladding-pumped laser fiber 13 includes a plurality of multimode fibers 18 fused to the side surface thereof. 4. A clad pumped laser fiber having a core doped with a rare earth element and at least double clads arranged substantially concentrically around the core has a polygonal cross section with three or more sides. The high-density and high-power laser device according to any one of claims 1 to 3, which is a clad pumping fiber.