JP2936737B2 - Semiconductor-pumped solid-state laser - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor-pumped solid-state laser using a semiconductor laser as an excitation source, and more particularly to a semiconductor laser proximity solid-state laser for improving the oscillation efficiency and the beam mode. .

[0002]

2. Description of the Related Art FIG.
No., (1989), p. 287-290, schematically shows the configuration of a conventional semiconductor-pumped solid-state laser. In the figure, reference numeral 1 denotes a semiconductor laser, and 2 denotes a laser beam emitted from the semiconductor laser 1 and is hereinafter referred to as excitation light. Reference numerals 8 and 9 denote lenses, reference numeral 3 denotes a solid-state laser medium, reference numeral 6 denotes a laser beam output from the solid-state laser medium, and reference numeral 7 denotes a partial reflection mirror. The end face of the solid-state laser medium 3 is provided with a coating 32 that is totally reflective to the laser light 6 and a coating 33 that is non-reflective, and a laser resonator is formed between the coating 32 and the partial reflection mirror 7. Have been.

Next, the operation will be described. The excitation light 2 emitted by the semiconductor laser 1 is collimated by a lens 8 and condensed and incident on a solid-state laser medium 3 by a lens 9. The excitation light 2 is absorbed while spreading in the solid-state laser medium 3, and excites the solid-state laser medium 3. Part of the absorbed energy of the excitation light 2 is output to the outside as laser light 6.

[0004]

The conventional solid-state laser is constructed as described above. The spread of the excitation light 2 in the solid-state laser medium 3 is large, and the cross-sectional area of the excitation is substantially reduced. Was difficult. Therefore, the laser oscillation has a disadvantage that the threshold value of the laser oscillation is increased and the energy efficiency of the laser oscillation is small, and it is difficult for the laser beam 6 to have a mode of a high order and to obtain a beam of the fundamental mode with good convergence. .

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a semiconductor-excited solid-state laser which emits a high-quality beam having a high energy efficiency of laser oscillation and a stable output is provided. The purpose is to gain.

[0006]

A semiconductor-pumped solid-state laser according to the present invention has a thickness direction coincident with a vertical direction of an active layer of the semiconductor laser, and a solid-state laser medium of pumping light having the thickness extending in the vertical direction. The thickness is smaller than the width of the laser beam, and the photoexcitation area in the solid-state laser medium is
The thickness of the active layer so that it is equal in the vertical and parallel directions
A plate-shaped solid-state laser medium with a body, the excitation light incident end surface of the solid-state laser medium (hereinafter, referred to as incident end face) with applying a non-reflective coating, semiconductor laser - the distance between The an incident end face, the incident Placing the excitation light incident end face close to the semiconductor laser while maintaining a distance between the excitation light incidence end face and the semiconductor laser so that the reflected light from the end face does not change the oscillation wavelength of the semiconductor laser; In addition, the laser resonator,
The optical axis travels straight through the solid-state laser medium, and the beam diameter of the fundamental mode of the laser beam substantially matches the thickness of the solid-state laser medium.

The reflectivity of the antireflection coating applied to the excitation light incident end face to the excitation light is 2% or less, and the distance between the incident end face and the semiconductor laser is 100 μm to 500 μm.
It is good to set it between μm.

A semiconductor-pumped solid-state laser according to another aspect of the present invention has a thickness direction and a vertical direction of an active layer of the semiconductor laser that coincide with each other, and a solid-state laser medium of excitation light that spreads the thickness in the vertical direction. The thickness is smaller than the width of the laser beam, and the photoexcitation area in the solid-state laser medium is
The thickness of the active layer so that it is equal in the vertical and parallel directions
A solid laser medium in the form of a plate is placed close to the semiconductor laser, the optical axis of the excitation light is inclined from the normal to the end face of the excitation light, and the laser resonator is used to The axis of the laser beam travels straight through the solid-state laser medium, and the beam diameter of the fundamental mode of the laser beam substantially matches the thickness of the solid-state laser medium.

[0009]

According to the present invention, the thickness direction of the solid-state laser medium and the vertical direction of the active layer of the semiconductor laser are made to coincide with each other, and the thickness is smaller than the spread width of the excitation light spread in the vertical direction in the solid-state laser medium. And a solid ray
The light excitation region in the medium is parallel to the vertical direction of the active layer.
Since the thickness is made equal to the direction , the excitation light can be absorbed with being confined in a narrow area with a simple configuration, and the energy efficiency of laser oscillation can be improved. In addition, an anti-reflection coating is applied to the incident end face, and the excitation light incident end face and the semiconductor laser are arranged so that the distance between the semiconductor laser and the incident end face is reduced to such an extent that the reflected light from the incident end face does not change the oscillation wavelength of the semiconductor laser. The laser light is arranged close to the semiconductor laser while maintaining the distance between the lasers, or the optical axis of the excitation light is inclined from the normal to the incident end face, so that the excitation light reflected on the incident end face is Caused by being incident on a semiconductor laser,
Because it is not affected by so-called return light, the output is stable,
Efficient laser light with good beam quality can be generated. Further, the laser resonator is configured such that its optical axis goes straight through the solid-state laser medium and the beam diameter of the fundamental mode of the laser light substantially matches the thickness of the solid-state laser medium, so that the quality is good. A Gaussian beam can be output with high efficiency.

[0010]

[Embodiment 1] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing one embodiment of a semiconductor-pumped solid-state laser according to the present invention. In the figure, reference numeral 1 denotes a 1-W class semiconductor laser having a stripe width of 150 μm, for example. 2 is an excitation light emitted from the semiconductor laser 1, and 3 is a solid-state laser medium, for example, 5 mm long and 2 m wide.
m, 0.5 mm thick rectangular section Nd: YAG (Y3 _-xN
d _x Al ₅ O ₁₂ ) crystal, and the incident end face is set at a distance of 100 to 500 μm from the semiconductor laser 1. Reference numeral 4 denotes an optical adhesive, and reference numeral 5 denotes a metal block, for example, a rectangular parallelepiped gold-plated copper block having a length of 5 mm, a width of 4 mm, and a thickness of 3 mm. Reference numeral 32 denotes a coating formed on the end face of the solid-state laser medium 3, which is non-reflective for the excitation light 2 and totally reflected for the laser light 6, so that the reflectance for the excitation light 2 is 2% or less. I have to. 33 is a coating formed on the end face of the solid-state laser medium 3 and is non-reflective to the laser beam 6. 7 is a partial reflection mirror and 10 is a housing.

Next, the operation will be described. The excitation light 2 enters from the coating 32 on the end face of the solid-state laser medium 3.
The excitation light 2 emitted from the semiconductor laser 1 generally has a large spread. For example, the divergence angle is 60 ° in the vertical direction (hereinafter, simply referred to as the vertical direction) of the active layer of the semiconductor laser 1, and the parallel direction (hereinafter, simply the parallel direction). 20 ° (both full-angle) and anisotropic, but by arranging the semiconductor laser 1 and the solid-state laser medium 3 close to each other,
The excitation light 2 is effectively made incident on the laser medium 3. With this incident method, the excitation light 2 is repeatedly reflected internally on the upper and lower surfaces of the plate-shaped solid laser medium 3 having a thickness smaller than the spread width of the excitation light in the solid laser medium, and is confined in the solid laser medium 3. It is absorbed as it is and effectively excites it. By reflecting light spreading in the vertical direction of the semiconductor laser active layer on the upper and lower surfaces, the light excitation region in the solid-state laser medium can be reduced to about 0.5 mm in both directions parallel to the vertical direction. The heat generated in the solid-state laser medium 3 is efficiently radiated through the metal block 5 and the housing 10. A stable resonator is formed between the coating 32 and the partial reflection mirror 7. For example, when the coating 32 is a flat surface, the radius of curvature of the partial reflection mirror 7 is 2500 mm, and the resonator length is 10 mm, the beam diameter of the fundamental mode (Gaussian mode) is About 0.35mm
It is. For this reason, the fundamental mode cross-sectional area of the laser and the cross-sectional area in which the pumping light 2 is confined substantially coincide with each other, and a high-quality Gaussian beam can be output with high efficiency.

The distance between the incident end face and the semiconductor laser 1 must be set in consideration of efficiency and output stability. If it is too close, a small amount of reflected light from the incident end face of the excitation light 2 will be incident on the semiconductor laser 1, and the operation of the semiconductor laser 1 will be unstable due to the effect of so-called return light, that is, the output and emitted excitation The wavelength of light 2 fluctuates. On the other hand, the solid laser medium 3
When the semiconductor laser 1 and the semiconductor laser 1 are far apart, the pumping light 2 incident on the solid-state laser medium 3 decreases, and the laser output decreases.
In this embodiment, this problem is solved by setting the reflectance at the incident end face to 2% or less by the antireflection coating 32 and setting the distance between the incident end face and the semiconductor laser 1 to 100 μm to 500 μm.

Embodiment 2 FIG. In the above embodiment, 150 μm
For a 1 W class semiconductor laser having a stripe width of about m, the reflectance of the antireflection coating is set to 2% or less, and the distance between the semiconductor laser and the incident end face is set to 100 μm to 500 μm. By setting the reflectance of the non-reflective coating and the distance between the semiconductor laser and the incident end face to appropriate values according to the type, the same effects as in the above embodiment can be obtained.

Embodiment 3 FIG. In the above embodiment, the anti-reflection coating and the semiconductor laser were used.
Although the influence of the return light of the semiconductor laser 1 is avoided by setting the distance between the laser and the incident end face, the influence of the return light may be avoided by changing the reflection angle of the excitation light 2. FIG. 2 shows an embodiment in which the installation angle of the semiconductor laser 1 is inclined and the optical axis of the excitation light 2 is inclined from the normal line of the incident end face, and has the same effect as the above embodiment. A numerical example is shown below. The stripe width of the semiconductor laser is 150 μm, and the vertical opening angle (light intensity
The angle at which the degree becomes 1 / e ^{-2 of the} peak ) is 60 °. If the solid-state laser medium is YAG, the reflectivity of the end face in the case where the anti-reflection coating is not applied is about 9%. here,
Consider an effect when the vertical installation angle of the semiconductor laser is set to half the opening angle, that is, 30 °. The return light to the semiconductor laser is approximately proportional to the intensity of the excitation light in a region perpendicularly incident on the solid-state laser medium. When the installation angle is not inclined, the peak portion of the Gaussian intensity distribution contributes to the return light. On the other hand, when the installation angle is inclined by 30 ° while keeping the distance between the semiconductor laser and the incident end face the same, the intensity of the excitation light contributing to the return light is e ^-2 of the peak, that is, about 13.5%. As a result, by tilting the installation angle, almost the same effect as in the case of applying a non-reflective coating having a reflectance of about 1.2% (= 9% × 0.135) is obtained. Further, for example, when a 2% anti-reflection coating is applied to the incident end face, the influence of the return light is further reduced by inclining the installation angle, so that the distance between the semiconductor laser and the incident end face is reduced to reduce the oscillation efficiency. Improvement can be achieved. That is, when the installation angle is set to a half of the opening angle as described above, the return light is about 13.5% as compared with the case where the device is installed vertically. The amount of return light is 2 which is the distance between the semiconductor laser and the incident end face.
Assuming that the angle is almost inversely proportional to the power, the distance between the semiconductor laser and the incident end face can be reduced to almost 1/3 by inclining the installation angle. When the installation angle is set to 3/4 of the open angle, the intensity of the excitation light contributing to the return light is about 5%.
Becomes If the angle is too large, the excitation light leaks out of the incident end face, so that an appropriate installation angle is about ２〜 to ／ of the opening angle.

Embodiment 4 FIG. Further, in the above embodiment, the optical axis of the laser resonator and the pump light are substantially coincident, but a plurality of semiconductor lasers are arranged on the side of the laser medium, and the pump light is made incident from the side of the laser medium. The present invention can also be applied to a structure in which the optical axis is perpendicular to the excitation light.

Embodiment 5 FIG. In the above embodiment, the laser medium used was a plate-like material having a thickness smaller than the spread width of the excitation light in the solid-state laser medium. However, the laser medium was thinner than the spread width of the excitation light in the solid-state laser medium. A solid laser medium having a cross section having a thickness and a width, or having a diameter smaller than the spread width of the excitation light in the solid laser medium and having a substantially circular cross section may be used.

[0017]

As described above, according to the present invention, the thickness direction and the vertical direction of the active layer of the semiconductor laser are made to coincide with each other, and the width of the excitation light spreading in the vertical direction in the solid-state laser medium is increased. Thinner than solid
Photoexcitation region in the laser medium is parallel to the vertical direction of the active layer
Using a plate-shaped solid laser medium having a thickness equal to the direction , an anti-reflection coating is applied to the excitation light incident end face of the solid laser medium, and the distance between the semiconductor laser and the incident end face is set to the incident end face. The laser is disposed close to the semiconductor laser while maintaining the distance between the excitation light incident end face and the semiconductor laser so that the reflected light from the laser does not change the oscillation wavelength of the semiconductor laser. Since the laser resonator is configured so that its optical axis goes straight through the solid-state laser medium and the beam diameter of the fundamental mode of the laser light substantially matches the thickness of the solid-state laser medium, the laser resonator is simple. There is an effect that a semiconductor-pumped solid-state laser capable of stably outputting a high-quality Gaussian beam with high efficiency can be obtained.

More specifically, the reflectance of the non-reflection coating applied to the excitation light incident end face to the excitation light is 2% or less, and the distance between the incident end face and the semiconductor laser is 100 μm.
If the distance is set within a range from 500 μm to 500 μm, an efficient and stable laser can be obtained.

According to another aspect of the present invention, the thickness direction coincides with the vertical direction of the active layer of the semiconductor laser, and the width of the excitation light spreading in the vertical direction in the solid-state laser medium increases in the thickness. Thinner and solid
The photoexcitation region in the laser medium is aligned with the vertical direction of the active layer.
A plate-like solid-state laser medium having a thickness equal to the row direction is arranged close to the semiconductor laser, and
The optical axis of the excitation light is inclined from the normal to the excitation light incident end face, and the laser resonator is further configured so that its optical axis goes straight through the solid-state laser medium and the beam diameter of the fundamental mode of the laser light is reduced. Since it is configured so as to substantially match the thickness of the solid-state laser medium, a semiconductor-pumped solid-state laser capable of stably outputting a high-quality Gaussian beam with high efficiency and with a simple configuration is obtained. .

[Brief description of the drawings]

FIG. 1 is a sectional view showing a semiconductor-excited solid-state laser according to an embodiment of the present invention.

FIG. 2 is a semiconductor-excited solid-state laser showing another embodiment of the present invention.
FIG. 3 is a cross-sectional configuration diagram of the ther.

FIG. 3 is a configuration diagram showing a conventional semiconductor-excited solid-state laser.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor laser 2 Excitation light 3 Solid-state laser medium 6 Laser light 7 Partial reflection mirror 32 Coating

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-63-60578 (JP, A) JP-A-60-135913 (JP, A) JP-A-1-154010 (JP, A) JP-A-2- 1192 (JP, A) JP-A-64-23590 (JP, A) JP-A-2-122461 (JP, U) JP-A 63-50152 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01S 3/0941 H01S 3/16

Claims (3)

(57) [Claims] 1. A semiconductor laser that emits excitation light, and a non-reflective coating is applied to an excitation light incident end face, and a distance between the excitation light incident end face and the semiconductor laser is set to reflect from the excitation light incident end face. The laser is arranged close to the semiconductor laser while maintaining a distance between the excitation light incident end face and the semiconductor laser so that the light is small enough not to change the oscillation wavelength of the semiconductor laser. The direction is made to coincide with the vertical direction of the active layer of the semiconductor laser , and the thickness is smaller than the width of the excitation light spreading in the vertical direction in the solid laser medium.
The photoexcitation region inside is in the vertical direction and the parallel direction of the active layer.
A plate-shaped solid laser medium having a thickness so as to be equal ;
A laser beam is emitted from the solid-state laser medium, the optical axis of the laser beam travels straight through the solid-state laser medium, and the beam diameter of the fundamental mode of the laser beam substantially matches the thickness of the solid-state laser medium. Semiconductor-pumped solid-state laser comprising: 2. The reflectance of the antireflection coating applied to the excitation light incident end face to the excitation light is 2% or less, and the distance between the incident end face and the semiconductor laser is from 100 μm to 5 μm.
2. The semiconductor-excited solid-state laser according to claim 1, wherein said laser is set to be between 00 .mu.m. 3. A semiconductor laser that emits pump light and is disposed close to the semiconductor laser so that a thickness direction matches a vertical direction of an active layer of the semiconductor laser.
The thickness is set to be smaller than the width of the excitation light spreading in the vertical direction in the solid-state laser medium , and the solid-state laser medium
The photoexcitation region in the material is perpendicular to and parallel to the active layer.
In equal such thickness as the plate-shaped solid les - the laser medium, to emit a laser beam from the solid-state laser medium, the optical axis of the solid les - basic and straight The the medium, and the laser beam A laser resonator configured so that the beam diameter of the mode is substantially equal to the thickness of the solid-state laser medium, wherein the optical axis of the excitation light is adjusted from the normal to the excitation light incident end face of the solid-state laser medium. Semiconductor excited solid-state laser
The.