JP3472471B2 - Polarization-maintaining self-compensating reflector, laser resonator and laser amplifier - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarization-maintaining self-compensating reflecting device for compensating the tilt of a reflecting mirror and preserving and reflecting the polarization of incident light, and a laser resonator and a laser amplifier using the same. In particular, the present invention relates to a solid-state laser reflector mounted on a flying body such as an artificial satellite or an aircraft.

[0002]

2. Description of the Related Art Conventionally, as this type of reflecting device, ones shown in FIGS. 8 to 10 have been known. 8 to 10 show Walter Koechner, "Splid-State Laser Engine".
ergin "4th Ed, Springer Series in Optical Sciences,
3 shows a roof prism used as a reflecting device in a laser oscillator described on page 227 of Vol. 1 (Springer, Germany, 1995). Figure 8
In the above, reference numeral 100 denotes a roof prism, 101 to 105 each surface constituting the prism 100, and 106 a ridgeline where the surfaces 102 and 103 intersect.

Further, the conventional prism 100 will be described in detail with reference to FIG. For each slope of the prism 100, the angle formed by the surface 101 with the surface 102 is 45 degrees, the angle formed with the surface 103 is 45 degrees, and the surface 102 is the surface 103.
Is 90 degrees, and the surfaces 104 and 105 are
Are configured to make an angle of approximately 90 degrees with each of the surfaces 101 to 103.

Next, the operation of the prism 100 will be described with reference to FIGS. In FIG. 8, the ridge line 106
Is the x-axis, and the direction perpendicular to the x-axis in the plane perpendicular to the traveling direction of the input light incident on the roof prism 100 is the y-axis, and the input light is incident on the surface 101 substantially perpendicularly.

Input light that has entered the surface 101 of the roof prism 100 substantially vertically enters the surface 102 at an incident angle θ ₁₀ . Input light is reflected from the surface 102, enters the surface 103 at an incident angle θ ₁₁ , is reflected from the surface 103, and is emitted from the surface 101 as output light.

The reflection direction of the laser light incident on the roof prism 100 will be described with reference to FIG. In FIG. 9, L1 is an optical path of incident input light, and L2 is an optical path of output light reflected by the roof prism 100. Face 10
Since 2 and the surface 103 are fixed at 90 degrees to each other, the angle θ ₁₀ formed by the surface 101 and the optical path L1 and the angle θ ₁₁ formed by the surface 101 and the optical path L1 are approximately 45 degrees, respectively, and the angles θ ₁₀ and θ ₁₁ are The sum is 90 degrees.

The input light that has traveled along the optical path L1 and is incident on the roof prism 100 is incident on the surface 102 by approximately 90 degrees.
3 gives an angle change of almost 90 degrees, and the total angle change given to the input light by the two surfaces is 180 degrees in total. That is, the optical path L2 of the output light reflected by the roof prism 100 is parallel to the optical path L1.

Next, with reference to FIG. 10, the reflection direction of the laser light incident when the roof prism 100 is inclined by the angle β with the axis parallel to the x-axis as the rotation axis will be described. Figure 10
As shown in, when the input light is incident on the roof prism 100, the angle change given by the surface 102 by the input light is (90 + 2β) degrees, and the angle change given by the surface 103 by the input light reflected from the surface 102 is (90-2β) degrees, and the angle formed by the optical paths L1 and L2 is 180 degrees in total. Therefore, the roof prism 100 has the ridge 106
The roof prism 1
00 reflects incident input light as output light parallel to the incident input light and traveling in the opposite direction. for that reason,
The roof prism 100 acts as a self-compensating reflection device that compensates for alignment misalignment with an axis parallel to the x-axis as a rotation axis.

Next, consider the polarization state of the output light reflected from the roof prism 100. When light is reflected from one plane, a polarization component in the direction perpendicular to the plane containing the input light and the output light is S-polarized, and is oscillated in the plane containing the input light and the output light.
A polarization component in a direction perpendicular to S-polarized light is called P-polarized light. For example, on the surface 101, the polarization component of the input light in the x-axis direction is S-polarized light, and the polarization component in the y-axis direction is P-polarized light. On the total reflection surface in the prism, the S polarized component has a δ (θ) phase advance and the P polarized component has a δ (θ) phase delay with respect to the input light having an incident angle θ. Here, δ (θ) is expressed by the following formula [Formula 1] using the refractive index n of the prism material.

[0010]

[Equation 1]

When the polarized light of the input light is separated into a component Ex in the x-axis direction and a component Ey in the y-axis direction, the polarized light of the arbitrary input light can be expressed by the following equation [Equation 2].

[0012]

[Equation 2]

The phase change J102 on the surface 102 and the phase change J103 on the surface 103 are expressed by the following equations [Equation 3] and [Equation 4] using the Jones matrix.

[0014]

[Equation 3]

[0015]

[Equation 4]

Therefore, the Jones matrix J100, which represents the total amount of change in the phase of the light that has passed through the prism 100, is expressed by the following equation (Equation 5).

[0017]

[Equation 5]

According to [Equation 5], the x-axis component and the y-axis component of the output light have a phase difference of 2 (δ (θ ₁₀ ) + δ (θ ₁₁ )). When the polarization of the input light has both the x-axis component and the y-axis component, δ (θ) has a non-zero value in a normal optical material, and therefore the polarization states of the input light and the output light change.

[0019]

However, in the above-described conventional reflecting device, as shown in [Equation 5], different phase changes occur in the x-axis component and the y-axis component of the polarization of the input light. When the polarization of the input light has the x-axis component and the y-axis component, there is a problem that the polarization states of the input light and the output light change. Specifically, in order to hold and reflect the polarized light in the reflection mirror or the folding mirror of the laser resonator or the laser amplifier, the polarization component of the input light needs to be only the x-axis component or the y-axis component. There was a problem that the optical system became complicated.

The present invention has been made in order to solve the above-mentioned conventional problems. It self-compensates for the misalignment of the reflection device, does not require an optical component for adjusting the polarization direction, and has a small number of optical components. It is an object of the present invention to provide a polarization-maintaining self-compensating reflection device, a laser resonator, and a laser amplifier, in which an input light having an arbitrary polarization is preserved and reflected by an optical system.

[0021]

A polarization-maintaining self-compensating reflecting device according to the present invention as defined in claim 1 reflects input light in a direction substantially parallel to the input light and outputs it, and is a plane perpendicular to the input light. The difference between the phase change amount of the polarized light in the first axis direction in the above and the phase change amount of the polarized light in the second axis direction perpendicular to the first axis in the plane perpendicular to the input light is π. And a quarter wave plate arranged so that the axial direction thereof coincides with the first axis or the second axis, and the input light is
/ 4 wavelength plate is incident and transmitted, then is incident on the prism
It is reflected, re-enters the quarter-wave plate, passes through, and exits.
It is output as force light .

The laser resonator according to the present invention described in claim 2 is substantially parallel to the reflected and polarization-maintaining self-compensating reflector according, the output light of the polarization maintaining self-compensating reflector as an input light in claim 1 And a reflective element arranged to
A laser medium arranged on an optical path formed by said polarization maintaining self-compensating reflector and the reflective element, is obtained by so and a pump light source that pumps the laser <br/> laser medium.

In the laser resonator according to the present invention as defined in claim 3, a corner cube is used as the reflecting element. A laser resonator according to a fourth aspect of the present invention reflects input light in a direction substantially parallel to the input light and outputs the reflected light, and a phase change of polarization in a first axis direction in a plane perpendicular to the input light. The difference between the phase change amount of the polarized light in the second axis direction perpendicular to the first axis in the plane perpendicular to the input light is π, and has a ridge line in the first axis direction. 1 prism and the axial direction is the first axis or the second
And a first quarter-wave plate arranged so as to coincide with the axis of the input light, the input light is incident on the first quarter-wave plate and transmitted.
Then, it is incident on the first prism and is reflected, and then is again incident on the first quarter-wave plate and transmitted therethrough, and is output as output light.
A first polarization-maintaining self-compensating reflector for output and an input light reflected in a direction substantially parallel to the input light for output, and a phase change amount of polarization in a third axis direction in a plane perpendicular to the input light. And a difference in the amount of phase change of the polarized light in the direction of the fourth axis perpendicular to the third axis in the plane perpendicular to the input light is π,
A second prism having a ridge line in a third axial direction, and a second quarter-wave plate arranged so that the axial direction coincides with the third axis or the fourth axis, the input light is provided. Is the second
The light enters the quarter-wave plate and is transmitted therethrough, and then is transmitted to the second prism.
It is incident, reflected, and re-enters the second quarter-wave plate.
The second polarization-maintaining light that is transmitted through and is output as output light.
A self-compensating reflector, which is arranged so as to reflect the output light of the first polarization-maintaining self-compensating reflector as input light substantially in parallel, and the first axis direction of the first prism, and A second polarization-maintaining self-compensating reflector which is arranged such that the directions of the third axes of the second prisms are orthogonal to each other; the first polarization-maintaining self-compensating reflector; and the second
And a pumping light source for pumping the laser medium.

According to a fifth aspect of the present invention, there is provided a laser amplifier, which comprises a polarizer for injecting light, and the polarizer.
Of the laser medium disposed in the optical path, the excitation light source for exciting the laser medium, a polarization maintaining self-compensating reflector device according to claim 1, arranged to reflect incident light from the laser medium, the and a polarization rotation element disposed between the laser medium and the polarization maintaining self-compensating reflector, before
The polarization rotator enters the polarization rotator and transmits it.
Laser light is reflected by the polarization-maintaining self-compensating reflector.
Is emitted, is incident on the polarization rotation element again, and is output,
The polarization direction of the incident laser light and the polarization of the output laser light
The light directions are mutually perpendicular in the plane perpendicular to the direction of travel of the laser light.
It is arranged so as to be orthogonal to .

According to a sixth aspect of the laser amplifier of the present invention, a ¼ wavelength plate is used as the polarization rotation element, and a fast axis or a slow axis is formed at an angle of 45 degrees with respect to the polarization direction of the incident light. the way form is obtained to arrange the quarter-wave plate.

According to a seventh aspect of the laser amplifier of the present invention, a Faraday rotator that rotates the polarized light by 45 degrees in one pass is used as the polarization rotating element.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings and FIGS. 1 to 7. 1 is a diagram showing a configuration of a polarization-maintaining self-compensating reflector in Embodiment 1 of the present invention, FIG. 2 is an explanatory diagram of a prism constituting the polarization-maintaining self-compensating reflector shown in FIG. 1, and FIG. FIG. 4 is an explanatory view of a polarization direction in the polarization maintaining self-compensating reflecting device shown in FIG. 4, FIG. 4 is a view showing a configuration of a laser resonator according to a second embodiment of the present invention, and FIG. 5 is a configuration of a laser resonator according to a third embodiment of the present invention. FIG. 6 is a diagram showing a configuration of a laser resonator according to a fourth embodiment of the present invention, and FIG. 7 is a diagram showing a configuration of a laser amplifier according to the fifth embodiment of the present invention.

Embodiment 1. First, the configuration of the polarization-maintaining self-compensating reflecting device according to the first embodiment of the present invention will be described with reference to FIGS. 1 and 2. In FIG. 1, 1 is a wave plate for adjusting the amount of phase change (described later), 3 is a polarization-maintaining self-compensating reflecting device, and 10 is an x-axis direction (first axis direction) in a plane perpendicular to the input light. The prism is configured so that the difference between the phase change amount of polarization and the phase change amount of polarization in the y-axis direction (second axis direction) perpendicular to the x-axis in a plane perpendicular to the input light is π. . Further, in FIG. 2, 11 to 15
Are respective surfaces constituting the prism 10.

The wave plate 1 advances the phase of the polarized light component in the fast axis direction, and slows (s) perpendicular to the fast axis.
low) has the effect of delaying the phase of the polarization component in the axial direction. In the wave plate 1, the difference between the amount of phase change given to the fast axis and the amount of phase change given to the slow axis is 2α = π / 2 + mπ (m
Is an integer) and is arranged such that the fast axis or the slow axis coincides with the x axis or the y axis.

The prism 10 will be described with reference to FIG. Each slope has an angle of 90 degrees between the surface 11 and the surface 13, and an angle between the surface 12 and the surface 11 of 45 degrees and the surface 13.
The angle between the surface 14 and the surface 11 is 90 degrees.
And the angle formed with the surface 13 is 135 degrees, and the surface 15 is the surface 11.
The angle formed with is 90 degrees, and the angle formed with the surface 14 is 90 degrees.

Input light incident on the prism 10 is reflected by the surface 11
To the surface 12 at an angle of incidence θ1 and is reflected. The input light reflected by the surface 12 enters the surface 14 at an incident angle θ2 and is reflected. The input light reflected by the surface 14 enters the surface 15 at an incident angle θ3 and is reflected. The input light reflected by the surface 15 is incident on the surface 12 again at the incident angle θ4, is reflected, and is output from the surface 11 as output light.

The polarization component of the input light incident on the prism 10 in the x-axis direction is P-polarized light on the surface 12, and the polarization component in the y-axis direction is S-polarized light on the surface 12, so that the Jones matrix on the surface 12 is obtained. J12 is represented by the following equation [Equation 6].

[0033]

[Equation 6]

Similarly, for surfaces 14 and 15,
The polarization component in the x-axis direction is S polarization, and the polarization component in the y-axis direction is P polarization.
Since it becomes polarized light, the Jones matrix J14-15 of reflection on the surfaces 14 and 15 is expressed by the following [Equation 7].

[0035]

[Equation 7]

Here, it was taken into consideration that the electric field direction which is symmetrical to the ridgeline formed by the surfaces 14 and 15 is reversed. further,
Since the light is reflected again by the surface 12, the Jones matrix of the prism 10 from the incidence to the emission is expressed by the following equation [Equation 8].

[0037]

[Equation 8]

Since θ1 to θ4 are all 45 degrees, δ (θ1) = δ (θ2) = δ (θ3) = δ (θ
4), and the [Equation 8] becomes the following [Equation 9].

[0039]

[Equation 9]

Next, a Jones matrix when the wave plate 1 and the prism 10 are combined will be considered with reference to FIG. In FIG. 3, 2 is a fast axis of the wave plate 1.
The wave plate 1 gives different phase changes to the polarized light component in the fast axis direction and the polarized light component in the direction perpendicular to the fast axis (slow axis). The angle between the fast axis and the x axis is φ, and the difference in phase change given to the polarization components of the fast axis and the slow axis is 2
Assuming α, the Jones matrix of the wave plate 1 is expressed by the following equation [Equation 10].

[0041]

[Equation 10]

Angle φ formed between the fast axis of the polarizing plate 1 and the x axis
Is φ = nπ / 2 (n is an integer), and the difference 2α in phase change given to the fast axis and the slow axis is 2α = π / 2 + mπ, the light enters the wave plate 1, passes through the prism 10, and
The Jones matrix J from the entrance to the exit when the light is again emitted from the wave plate 1 is expressed by the following equation [Equation 11].

[0043]

[Equation 11]

Therefore, since the same phase change is given to the polarization component in the y-axis direction and the polarization component in the x-axis direction, the polarization state is maintained and output even for the input light of any polarization state. It is emitted as light.

Further, as described above, the roof prism shape formed by the surface 14 and the surface 15 of the prism 10 serves as a self-compensating reflecting device for compensating the alignment deviation about the axis parallel to the x-axis as the axis of rotation. To do. According to the above description, a polarization-maintaining self-compensating reflection device that compensates for misalignment about an axis parallel to the x-axis as a rotation axis and reflects input light of an arbitrary polarization state while maintaining the polarization state You can

Embodiment 2. First, with reference to FIG. 4, a configuration of a self-compensation type laser resonator (hereinafter referred to as a laser resonator) in the second embodiment of the present invention will be described. Figure 4
In FIG. 1, 1 is a wave plate, 3 is a polarization-maintaining self-compensating reflecting device similar to that shown in FIG. 1, 4 is a laser medium, 5 is an excitation light source, 6 is a reflecting element, and 10 is a prism.

Next, the operation of the laser resonator according to the second embodiment of the present invention will be described with reference to FIG. The reflecting element 6 is arranged so as to reflect the output light from the polarization-maintaining self-compensating reflecting device 3 substantially in parallel, and constitutes a laser resonator in which the laser light is confined in the device. The laser medium 4 is arranged on the optical path of the laser light and is excited by the excitation light source 5. When the laser light confined in the device passes through the laser medium, the laser light is amplified and operates as a laser oscillator.

The polarization-maintaining self-compensating reflection device 3 compensates for alignment deviation about the axis parallel to the x-axis of the reflection element 6 and the optical component arranged in the optical path. Also, for example, 1
When the laser medium has polarization dependency such that polarized light in one axial direction easily oscillates, the reflection by the polarization-maintaining self-compensating reflection device 3 preserves the polarization, so that the free direction in accordance with the polarization dependency of the laser medium is maintained. It is possible to generate laser oscillation with polarized light.

Further, the pumping distribution of the laser medium 4 by the pumping light source 5 often occurs especially when pumping is performed from the side surface of the laser medium 4, but it may be asymmetrical with respect to the optical axis. When the excitation distribution is asymmetric, an asymmetric intensity distribution is generated in the laser light as well. The polarization-maintaining self-compensating reflector 3 reflects the input light with an intensity distribution that is line-symmetric with respect to the ridgeline of the prism. Therefore, when the laser resonator goes around, it is folded back with respect to the x-axis. , And the shape is close to axisymmetric about the optical axis.

With the above operation, it is possible to oscillate in a free polarization direction according to the polarization dependence of the laser medium, and a stable laser resonator having a self-compensating function for misalignment is constructed. can do. Further, even if the excitation distribution of the laser medium has asymmetry, it is possible to obtain a laser output having a shape close to axial symmetry.

Embodiment 3. First, with reference to FIG. 5, a configuration of a self-compensation type laser resonator (hereinafter referred to as a laser resonator) in the third embodiment of the present invention will be described. Figure 5
In FIG. 1, 1 is a wave plate, 3 is a polarization-maintaining self-compensating reflecting device similar to that shown in FIG. 1, 4 is a laser medium, 5 is an excitation light source, 7 is a corner cube reflector, and 10 is a prism.

Next, the operation of the laser resonator according to the third embodiment of the present invention will be described with reference to FIG. The corner cube reflector 7 is arranged so as to reflect the output light from the polarization-maintaining self-compensating reflecting device 3 substantially in parallel, and constitutes a laser resonator in which the laser light is confined in the device. The laser medium 4 is arranged on the optical path of the laser light and is excited by the excitation light source 5. The laser light trapped inside the device is amplified when passing through the laser medium, and operates as a laser oscillator.

The corner cube reflector 7 is constructed so that the three reflecting surfaces form an angle of 90 degrees with each other, and the input light incident on one of the reflecting surfaces forming the corner cube reflector 7 is regarded as the input light. It is reflected as output light that is parallel and has opposite traveling directions. Therefore, the corner cube reflector 7 compensates the inclination of the optical path of the laser light due to the misalignment of the polarization-maintaining self-compensating reflecting device 3 in the y-axis direction and the misalignment of the optical components arranged in the optical path.
It is possible to construct a stable laser resonator.

Further, the pumping distribution of the laser medium 4 by the pumping light source 5 often occurs especially when pumping is performed from the side surface of the laser medium 4, but it may be asymmetrical with respect to the optical axis. When the excitation distribution is asymmetric, an asymmetric intensity distribution is generated in the laser light as well. The polarization-maintaining self-compensating reflection device 3 reflects the input light with an intensity distribution that is line-symmetric with respect to the ridgeline of the prism 10, and the corner cube reflector folds and reflects the intensity distribution at the ridgeline formed by the three surfaces. When the resonator circulates, the intensity distribution of the laser light is folded back in a plurality of directions, and the shape becomes close to axial symmetry about the optical axis.

With the above operation, a stable self-compensation type laser resonator having a function of self-compensating for misalignment can be constructed. Further, even if the excitation distribution of the laser medium has asymmetry, it is possible to obtain a laser output having a shape close to axial symmetry.

Fourth Embodiment First, with reference to FIG. 6, a configuration of a self-compensation type laser resonator (hereinafter referred to as a laser resonator) in the fourth embodiment of the present invention will be described. Figure 6
1a and 1b are wave plates, and 3a and 3b are shown in FIG.
A polarization-maintaining self-compensating reflector similar to that shown in 4 is a laser medium, 5 is an excitation light source, and 10a and 10b are prisms.

Next, the operation of the laser resonator according to the fourth embodiment of the present invention will be described with reference to FIG. The polarization maintaining self-compensating reflector 3b is a polarization maintaining self-compensating reflector 3a.
Is arranged so as to reflect the output light from (the output optical path is the third axis) substantially in parallel, and to rotate 90 degrees about the reflected optical path (the reflection optical path is the fourth axis) as the central axis. , A laser resonator configured so that laser light is confined in the device. The first axis and the second axis are arranged so as to be orthogonal to each other. The laser medium 4 is arranged on the optical path of the laser light and is excited by the excitation light source 5. When the confined laser light passes through the laser medium, the laser light is amplified and operates as a laser oscillator.

The polarization-maintaining self-compensating reflector 3b compensates for the polarization deviation of the polarization-maintaining self-compensating reflector 3a and the optical components arranged in the optical path about the axis parallel to the y-axis, and maintains the polarization-maintaining self-compensating reflection. The device 3a compensates for misalignment about the axis parallel to the x-axis of the polarization-maintaining self-compensating reflecting device 3b and the optical components arranged in the optical path. In addition, when the laser medium has polarization dependency, for example, polarized light in one axial direction is likely to oscillate, the reflection by the polarization-maintaining self-compensating reflectors 3a and 3b preserves the polarization. Laser oscillation can be generated by the combined polarized light in free directions.

Further, the pumping distribution of the laser medium 4 by the pumping light source 5 often occurs particularly when pumping is performed from the side surface of the laser medium 4, but it may be asymmetrical with respect to the optical axis. When the excitation distribution is asymmetric, an asymmetric intensity distribution is generated in the laser light as well. Since the polarization-maintaining self-compensating reflectors 3a and 3b reflect the input light with a line-symmetric intensity distribution centered on the ridgeline of the prism,
When the laser resonator circulates, it is reflected back a plurality of times with respect to the x-axis and the y-axis, so that the intensity distribution of the laser light has a shape that is nearly axisymmetric about the optical axis.

With the above operation, it is possible to oscillate in a free polarization direction according to the polarization dependence of the laser medium, and a stable laser resonator having a function of self-compensating for misalignment is constructed. be able to.
Further, even if the excitation distribution of the laser medium has asymmetry, it is possible to obtain a laser output having a shape close to axial symmetry.

Embodiment 5. First, the configuration of the laser amplifier according to the fifth embodiment of the present invention will be described with reference to FIG. In FIG. 7, 1 is a wave plate, 3 is a polarization-maintaining self-compensating reflecting device similar to that shown in FIG. 1, 4 is a laser medium, 5 is an excitation light source, 8 is a polarizer, 9 is a polarization rotation element, and 1
0 is a prism.

Next, the operation of the laser amplifier according to the fifth embodiment of the present invention will be described with reference to FIG. Polarizer 8
Reflects polarized light in a first axial direction and transmits polarized light in a second axial direction perpendicular to the first axis in a plane perpendicular to the optical path. The laser light incident in the polarization direction that is reflected by the polarizer 8 is amplified when passing through the laser medium 4 excited by the excitation light source 5. The laser light emitted from the laser medium 4 passes through the polarization rotation element 9 and enters the polarization maintaining self-compensating reflection device 3. The laser light is reflected by the polarization-maintaining self-compensating reflection device 3 substantially in parallel with the incident direction, and then enters the polarization rotation element 9 again. Polarization rotator 9
Has the action of rotating the polarization directions in directions orthogonal to each other before and after entering the polarization maintaining / reflecting device 3. The laser light is again amplified by the laser medium 4, passes through the polarizer 8 and is output to the outside. The polarization-maintaining self-compensating reflection device 3 compensates for misalignment about the axis parallel to the x-axis of the polarization rotator 9 and the optical components arranged in the optical path.

The polarization rotation element 9 is, for example, 1/4.
There is a method of using a wave plate (not shown). The fast axis or slow axis is 4 with respect to the polarization direction of the incident laser light.
If the quarter-wave plate is arranged so as to form an angle of 5 degrees, the laser light before entering the polarization-maintaining self-compensating reflector 3 becomes circularly polarized light, and the polarization-maintaining self-compensating reflector 3 maintains the polarization state. Is reflected. The circularly polarized laser light that has entered the quarter-wave plate again is converted into linearly polarized light that is perpendicular to the polarization direction of the incident laser light, and is output from the quarter-wave plate. Therefore, the quarter-wave plate arranged such that the fast axis or the slow axis forms an angle of 45 degrees with respect to the polarization direction of the incident laser light operates as the polarization rotation element 9.

A Faraday rotator (not shown) may be used as the polarization rotation element 9. The Faraday rotator has the function of rotating the polarized light by a certain angle regardless of the polarization state of the input light. When a Faraday rotator having a polarization rotation angle of 45 degrees is arranged as the polarization rotator 9, the laser light passes through the Faraday rotator twice, and thus operates as the polarization rotator 9. In the laser amplifier using the Faraday rotator as the polarization rotator 9, since the Faraday rotator does not have the axis as in the wave plate 1, the adjustment is not necessary and the adjustment becomes easy.

Further, the excitation distribution of the laser medium 4 by the excitation light source 5 may be asymmetric with respect to the optical axis. When the excitation distribution is asymmetric, an asymmetric intensity distribution is generated in the laser light as well. The polarization-maintaining self-compensating reflector 3 reflects the input light with an intensity distribution that is line-symmetric with respect to the ridge of the prism 10, so that the intensity distribution of the laser light is folded back with respect to the x-axis, so that the output light has the optical axis. The shape is close to the axial symmetry about the center.

With the above operation, the present embodiment can construct a stable laser amplifier having a function of self-compensating for misalignment. In addition, even if the excitation distribution of the laser medium has asymmetry,
It is possible to obtain a laser output having a shape close to axial symmetry. Furthermore, when the Faraday rotator is used as the polarization rotator 9, a laser amplifier that can be easily adjusted can be obtained.

[0067]

The polarization-maintaining self-compensating reflecting device according to the first aspect of the present invention is configured as described above, and in particular has a roof prism shape to compensate for misalignment about one axis. In addition, since the same phase change is given to the polarization components in the x-axis direction and the y-axis direction, the polarization state is completely retained and reflected even for input light with arbitrary polarization. It can be output as light. Therefore, for example, when it is used as a reflecting mirror of a laser resonator or a folding mirror of a laser amplifier, an optical component for adjusting the polarization direction is not required, and a stable optical system can be configured with a simple configuration and a small number of optical components. You can

The laser resonator according to any one of claims 2 to 4 is a polarization maintaining self-compensating reflecting device according to claim 1 and a reflecting element, a corner cube reflector or a second reflecting means, respectively. By using the polarization-maintaining self-compensating reflector, it is possible to obtain a stable laser resonator having the function of self-compensating for misalignment, and the reflection from the polarization-maintaining self-compensating reflector retains the polarized light. Therefore, when the laser light circulates, even if the excitation distribution of the laser medium has asymmetry, it is possible to obtain a laser output having a shape close to axial symmetry.

Further, in the laser resonator according to the invention described in any one of claims 2 to 4, when a laser medium having polarization dependency is used, oscillation occurs in a free polarization direction matched with the polarization dependency of the laser medium. It is possible to

Further, the laser amplifier according to the invention described in claims 5 to 7 uses the polarization maintaining self-compensating reflection device and the polarization rotating element according to claim 1 to compensate for the alignment deviation. A self-compensation type laser amplifier can be constructed, and even if the pumping distribution of the laser medium is asymmetric, it is possible to obtain a laser output having a shape close to axial symmetry.

Further, in the laser amplifier according to the invention described in claim 7, since the Faraday rotator is used as the polarization rotation element 9, a laser amplifier which can be easily adjusted can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a polarization maintaining self-compensating reflecting device according to a first embodiment of the present invention,

2 is an explanatory view of a prism that constitutes the polarization-maintaining self-compensating reflecting device shown in FIG. 1,

3 is an explanatory view of polarization directions in the polarization-maintaining self-compensating reflecting device shown in FIG. 1,

FIG. 4 is a diagram showing a configuration of a self-compensation type laser resonator according to a second embodiment of the present invention,

FIG. 5 is a diagram showing a configuration of a self-compensation type laser resonator according to a third embodiment of the present invention,

FIG. 6 is a diagram showing a configuration of a self-compensation type laser resonator according to a fourth embodiment of the present invention,

FIG. 7 is a diagram showing a configuration of a laser amplifier according to a fifth embodiment of the present invention,

FIG. 8 is a diagram showing a configuration of a conventional self-compensating reflecting device,

FIG. 9 is an explanatory view illustrating a reflection direction of a conventional self-compensating reflection device,

FIG. 10 is an explanatory diagram illustrating a reflection direction when an alignment shift occurs in a conventional self-compensating reflection device.

[Explanation of symbols]

1 wave plate, 2 fast axis of wave plate, 3 polarization maintaining self-compensating reflection device, 4 laser medium, 5 excitation light source, 7 corner cube reflector, 6 reflection element, 8 polarizer, 9 polarization rotation element, 10 prism, 11 to 11 15 faces, 100 roof prism,
101-105 faces, 106 ridges.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-8-222792 (JP, A) JP-A-7-162065 (JP, A) JP-A-9-321367 (JP, A) JP-A-5- 102618 (JP, A) JP 52-149996 (JP, A) JP 55-146992 (JP, A) JP 54-124694 (JP, A) JP 57-75486 (JP, A) Actual Development Sho 60-116262 (JP, U) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01S 3/00-3/30

Claims (7)

(57) [Claims] 1. An input light is reflected in a direction substantially parallel to the input light and output, and a phase change amount of polarization in a first axis direction in a plane perpendicular to the input light and a plane perpendicular to the input light. A prism configured such that the difference in the amount of phase change of polarized light in the second axis direction perpendicular to the first axis of is equal to π, and the axial direction matches the first axis or the second axis. And a 1/4 wavelength plate disposed at the input side of the 1/4 wavelength plate.
And then enters and is reflected by the prism.
A polarization-maintaining self-compensating reflection device characterized in that it is incident on a long plate again, is transmitted therethrough, and is output as output light. [2 claim] and polarization maintaining self-compensating reflector according to claim 1, and a reflective element arranged to reflect substantially parallel output light of the polarization maintaining self-compensating reflector as the input light, the polarization retention a laser medium arranged on an optical path formed by the self-compensation reflector and the reflective element, the laser resonator characterized by comprising a pump light source that pumps the <br/> laser medium. 3. The laser resonator according to claim 2, wherein a corner cube is used as the reflecting element. 4. An input light is reflected in a direction substantially parallel to the input light and output, and a phase change amount of polarization in a first axis direction in a plane perpendicular to the input light and a plane perpendicular to the input light. A first prism having a ridgeline in the first axial direction and having a difference in the amount of phase change of polarized light in the second axial direction perpendicular to the first axis of A first quarter-wave plate arranged to coincide with the one axis or the second axis ,
The input light enters the first quarter-wave plate and is transmitted therethrough,
Is incident on and reflected by the serial first prism, the first 1 /
It is incident on the four-wave plate again, transmitted, and output as output light.
And a first polarization-maintaining self-compensating reflection device for reflecting the input light in a direction substantially parallel to the input light and outputting the same, and a phase change amount of the polarization in the third axis direction in a plane perpendicular to the input light and the input The fourth perpendicular to the third axis in the plane perpendicular to the light
A second prism having a ridgeline in the third axial direction, which is configured so that the difference in the amount of phase change of the polarized light in the axial direction is π;
A second quarter-wave plate arranged so that its axial direction coincides with the third axis or the fourth axis, and input light is applied to the second quarter-wave plate. incident and transmitted, the second pre
Incident on the second quarter wave plate and reflected again.
The second polarized light that is incident once, transmitted, and output as output light.
A holding self-compensating reflecting device, arranged to reflect the output light of the first polarization-maintaining self-compensating reflecting device as substantially parallel light as input light, and a direction of a first axis of the first prism, A second polarization-maintaining self-compensating reflector which is arranged such that the directions of the third axes of the second prisms are orthogonal to each other; the first polarization-maintaining self-compensating reflector; and the second polarization-maintaining A laser resonator comprising: a laser medium arranged on an optical path formed by a self-compensating reflection device; and a pumping light source for pumping the laser medium. 5. A polarizer for injecting light, and the polarized light
A laser medium arranged on an optical path from the child, an excitation light source for exciting the laser medium, a polarization maintaining self-compensating reflector device according to claim 1, arranged to reflect incident light from the laser medium , and a polarization rotation device arranged between the laser medium and the polarization maintaining self-compensating reflector, the polarization rotation element is incident on the polarization rotation element
The transmitted laser light is transmitted to the polarization maintaining self-compensating reflector.
More reflected and then re-incident on the polarization rotator and output
The output laser is the polarization direction of the incident laser light
In the plane where the polarization direction of the light is perpendicular to the direction of travel of the laser light
A laser amplifier characterized by being arranged so as to be orthogonal to each other . As claimed in claim 6, wherein the polarization rotation element, using a 1/4-wavelength plate, and arranging the quarter-wave plate at an angle of 45 degrees fast axis or slow axis with respect to the polarization direction of the incident light The laser amplifier according to claim 5, wherein: 7. The laser amplifier according to claim 5, wherein a Faraday rotator that rotates polarized light by 45 degrees in one pass is used as the polarization rotation element.