JPH11284257A - Semiconductor laser excited solid laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid degradation of beam quality in high-output TEM00 mode by allowing high-output TEM00 mode at high efficiency and reducing thermal distortion of a solid laser medium due to high cooling efficiency, and to make position adjustment of a semiconductor laser easy at assembly or replacement of a semiconductor laser. SOLUTION: An LD optical transfer plate 2 which is transparent and about 1 mm thickness with its side surface tapered, and a solid laser medium 3 of disk or regular polygon wherein the thickness contacting to the LD optical transfer plate 2 is almost same with it while 3×3 mm or less or ϕ 3 mm or less in size are used, so that the component in vertical direction of the excitation light coming out of an LD1 is efficiently transferred in the solid laser medium through total reflection while light collected evenly to a width near TEM00 mode oscillation region to some extent in horizontal direction, for even excitation of a solid laser medium at high excitation density. The solid laser medium 3 is thin plate-like, contacting to a cooling plate 4 by surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solid-state laser device and, more particularly, to a semiconductor laser-excited solid-state laser device using a semiconductor laser as an excitation light source.

[0002]

2. Description of the Related Art In a conventional semiconductor laser-pumped solid-state laser (hereinafter referred to as an LD-pumped solid-state laser) of this kind, a pumping light emitted from a semiconductor laser (hereinafter referred to as an LD) is applied to an end face of a rod-shaped solid laser medium. An edge pumping method of irradiating and exciting, and a side-surface pumping method of exciting pump light from an LD from the side of a rod-shaped solid laser medium are generally used.

In a conventional LD-pumped solid-state laser, when a high-power TEMoo mode output is obtained, the end-pumping method is used to focus pumping light from a large number of LDs on the optical axis of a solid-state laser medium. A complicated optical system was used, or excitation light was coupled to an optical fiber and bundled.

In the side-pumping method, the pumping light from the LD is condensed linearly in the direction parallel to the axis of the rod by a cylindrical lens and irradiated from the side outer periphery of the rod-shaped solid laser medium to be excited. Alternatively, as disclosed in JP-A-9-18072, a method of uniformly exciting a solid-state laser medium by using a diffusion-propagation optical system for excitation light has been adopted.

[0005]

However, in the above-described conventional technique using the conventional end facet pumping method, first, in order to efficiently collect a plurality of LD lights in the TEMoo mode oscillation region of the solid-state laser medium, However, it is necessary to use a special optical system or use a bundle of LD light incident on a plurality of fibers, which makes the optical system complicated and expensive.

Second, since heat is concentrated locally in the end-pumping method, the thermal lens effect and the thermal birefringence of the solid-state laser medium increase with an increase in the pump input. Then the solid state laser output saturates,
Beam quality is reduced.

Further, as described in the above-mentioned Japanese Patent Application Laid-Open No. 9-18072, in the side-pumping method in which the solid-state laser medium is uniformly pumped by diffusing the pumping light, the TEMoo of the solid-state laser
Excitation is widely performed in areas other than the mode region, so that the ratio of spatial matching between the excitation light and the oscillation light decreases, and the oscillation threshold value also increases, so that the oscillation efficiency decreases.

An object of the present invention is to obtain a high-efficiency, high-power TEMoo mode with a simple optical system, a high cooling efficiency, a small thermal distortion of a solid-state laser medium, and therefore, an LD that does not degrade the beam quality at high power. An object of the present invention is to provide a pumped solid-state laser device.

Further, it is easy to adjust the position of the LD at the time of assembling the apparatus and exchanging the LD for excitation.

[0010]

SUMMARY OF THE INVENTION The present invention provides an array-type semiconductor laser for emitting excitation light for exciting a solid-state laser medium, and an incident end face having a width corresponding to the emission width of the semiconductor laser in the array direction. An emission end face having a width close to the width of the TEMoo mode oscillation region of the laser medium, an optical transmission plate having a thickness corresponding to the emission width in the direction perpendicular to the array direction of the semiconductor laser; and an emission end face of the optical transmission plate. A disk or regular prismatic solid-state laser medium having a thickness corresponding to the optical transmission plate and disposed in contact therewith.

According to the present invention, the excitation light of the array type LD is incident from the entrance end face of the optical transmission plate having a wide taper side corresponding to the width of the LD in the array direction, and the total reflection is repeated in the thickness direction of the optical transmission plate. In the horizontal direction, while being reflected by the tapered side surface, the light propagates so as to converge to the width of the emission end face having a width close to the width of the TEMoo mode oscillation region of the solid-state laser medium.
The emission end face of the D optical transmission plate contacts the side face of the solid-state laser medium,
Excitation light emitted from the LD excites the solid-state laser medium.
The pumping efficiency is good because the range of the width close to the width of the TEMoo mode region of the solid-state laser medium is uniformly excited.
The o mode is obtained with high efficiency. Also, to focus the excitation light from the array type LD, only an optical transmission plate with a thickness corresponding to the emission width in the direction perpendicular to the array direction of the semiconductor laser is used, and a special optical system or multiple fibers are used. To LD
The excitation light from the array type LD can be focused with a simple optical system without using a bundle of incident light.The solid laser medium has a high cooling effect due to its thin plate shape and has a high temperature gradient. Since it occurs in the thickness direction, the thermal lens effect and thermal distortion are reduced, and deterioration of beam quality can be prevented.

[0012]

Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1A is a plan view showing the configuration of the first embodiment of the present invention. Also,
FIG. 1B is a side view of the LD-pumped solid-state laser device of FIG.

An LD 1 for outputting an excitation light for exciting the solid-state laser medium 3 and an excitation light output from the LD 1 are
An LD light transmitter 2 that transmits light to a solid laser medium 3 and a solid laser medium 3 that is excited by excitation light are provided on a flat cooling plate 4.

The LD 1 is mounted on a cooling plate 4 and oscillates in an array type L which oscillates at a wavelength at which the solid-state laser medium 3 has good absorption.
D.

The LD light transmission plate 2 has a linear end face
And a plate-like optical transmission member having a thickness small enough to allow a light emission width in a direction perpendicular to the array direction to be incident and having a substantially uniform thickness. It is. Further, the LD light transmission plate 2 has a trapezoidal shape in which a pair of side surfaces is tapered, and the bottom side where the taper is widened faces the LD1 side as an incident end face, and the taper on the opposite side becomes narrow. The other side is provided in contact with the solid-state laser medium 3 as an emission end face. The emission end face is the T of the solid-state laser medium.
Although it is larger than the width of the EMoo mode oscillation region, it has a width close to it, for example, a width within about four times the TEMoo mode oscillation region. As a material of the LD light transmission plate 2, a material having a high transmittance with respect to the oscillation light of the LD 1 is used.

It is desirable that the thermal conductivity is good and the thermal expansion coefficient is close to that of the solid-state laser medium 3. The LD light transmission plate 2 is attached to the cooling plate 4 so as to maintain contact with the solid-state laser medium 3 which expands and contracts with temperature. The tapered side surface of the LD light transmission plate 2
A dielectric multilayer film or a metal film having a high reflectance with respect to the wavelength of the excitation light is coated by means such as vapor deposition.

The solid-state laser medium 3 is a disk-shaped laser medium having a thickness substantially equal to that of the LD light transmission plate 2, and has a diameter substantially equal to or slightly larger than the width of the emission end face of the LD light transmission plate 2.
The cooling plate 4 is installed on the same surface as the surface on which the LD light transmission plate 2 is installed. The surface of the solid-state laser medium 3 on the side of the cooling plate 4 is coated with a mirror coating that is highly reflective with respect to the output oscillation wavelength, and constitutes one of the laser resonators.

As shown in FIG. 1B, an output mirror 5 is provided on the side of the solid-state laser medium 3 opposite to the side in contact with the cooling plate 4.
Are arranged, and the mirror coating of the solid-state laser medium 3 and the output mirror 5 constitute a laser resonator.

The cooling plate 4 includes the laser medium 3, the LD,
1. The LD light transmission plate 2 is fixed, and each element that generates heat due to laser oscillation and absorption of laser light is cooled.

Excitation light emitted from the LD 1 is incident on the LD light transmission plate 2, is totally reflected in the vertical direction in the thickness direction of the LD light transmission plate 2, and is horizontally reflected by a high reflection coating applied to a tapered portion. The light converges at the emission end while being reflected. Excitation light that has propagated while converging in the LD light transmission plate 2 propagates to the solid-state laser medium 3 that is in contact at the emission end, and is uniformly excited. Due to this excitation, an inverted population of energy is formed in the solid-state laser medium 3. Solid laser medium 3
The surface on the side of the cooling plate 4 is mirror-coated so as to have a high reflection with respect to the oscillation wavelength, and forms a laser resonator with the output mirror 5, and TEMoo mode laser light oscillates.

The laser medium 3 has a very thin disk shape as described above, and is fixed on the cooling plate 4 in close contact with the entire bottom surface, so that the laser medium 3 is easily cooled, and has a thermal lens effect and a thermal effect. The effect of the birefringence is small and the deterioration of the beam quality is small.

Next, embodiments of the present invention will be described in detail. Solid laser medium 3 is φ3mm, thickness 0.5mm
Nd: YAG crystal. Even if the solid-state laser medium 3 is made thicker, the diameter of the output light is φ1 m in the TEMoo mode.
m and φ3mm from the point of efficiency because it does not become thick
Is preferred. LD1 has an oscillation output of 20 W, a light-emitting portion width of 10 mm, and an oscillation center wavelength of 809 nm, which is excellent in absorption of Nd: YAG crystal. The LD light transmission plate 2 uses a YAG crystal which has substantially the same refractive index as Nd: YAG and is not doped with active ions. The incident surface of the LD light transmission plate 2 is LD
The emission surface is slightly wider than the emission width of No. 1 and the emission surface is in contact with the side surface of the solid-state laser medium 3 by optical contact. LD
The tapered side surface of the optical transmission plate 2 has a wavelength of 809 nm of the excitation light.
, A dielectric multilayer film having high reflectance is deposited.
The surface of the solid-state laser medium 3 on the side of the cooling plate 4 is N
d: A mirror coating that provides high reflection for the oscillation wavelength of 1.06 μm of YAG is applied, and the output mirror 5 forms a laser resonator.

With this configuration, the output of the solid state laser is 5 to
In the end-pumping method, a temperature difference in the solid-state laser medium is usually about 30 ° C., but in this embodiment, it can be suppressed to about 10 ° C.

Next, a second embodiment of the present invention will be described with reference to FIGS.

FIG. 2 is a plan view of the second embodiment, and FIG. 3 is a sectional view of the LD-pumped solid-state laser of FIG.

In this embodiment, four sets of the LD 1 and the LD light transmission plate 2 in the first embodiment are radially arranged around the solid-state laser medium 3.

Each LD 1 is installed in parallel on a plane of the same height of the cooling plate 4.

Further, an LD optical transmission body 2 corresponding to each LD 1
Are also provided on the same surface of the cooling plate 4. Each L
The emission end of the D light transmission plate 2 has a width slightly smaller than the diameter of the solid-state laser medium, and the emission end of each LD light transmission plate 2 is located on the side surface of the solid-state laser medium 3 and adjacent to the LD light transmission plate. It is in contact with the body 2 by an optical contact from a direction different by 90 degrees.

As shown in FIG. 3, an output mirror 5 is disposed on the side of the solid-state laser medium 3 opposite to the side in contact with the cooling plate 4, and a mirror coating and an output mirror 5 are provided on the surface on the side of the cooling plate 4. A laser resonator is constituted by the above.

As a result, the excitation input is increased, and the TEMoo mode output can be easily increased in proportion to the increase in the number of LD1s. In addition, since a plurality of excitation lights are radiated at substantially equal intervals in the circumferential direction, not only a part of the side surface but also the entire side surface uniformly rises in temperature, and a temperature gradient mainly occurs in the thickness direction. The effect of the thermal birefringence is smaller than in the first embodiment. The number of irradiations with excitation light is 4
By installing the above output means around the solid-state laser medium 3, a higher output laser output can be obtained. In this case, the diameter of the solid-state laser medium 3 needs to be sufficiently larger than the emission end face so that the LD light transmission plates 2 do not interfere with each other. Alternatively, when the diameter of the solid laser medium 3 is made equal to the emission end face of the LD light transmission plate 2, the length of the solid laser medium 3 in the direction of the output light is doubled, and the LD light transmission for irradiating the upper part is performed. The cooling plate 4 is set so that the set of the plate 2 and the LD 1 and the set for irradiating the lower part are alternately set at different heights
It may be arranged above.

Further, the side surface of the solid-state laser medium 3 may be a regular polygon having the number of LDs 1 according to the shape of the emission end of the LD light transmission plate 2. Conversely, the shape of the emission end of the LD light transmission plate 2 may be a cylindrical surface according to the side surface shape of the solid-state laser medium 3. Thereby, the solid-state laser medium 3 and L
The contact property with the D light transmission plate 2 is improved, the transmission efficiency of the excitation light is improved, and high output can be achieved. Also one LD
, The solid-state laser medium 3 may be a regular polygonal prism.

Further, the taper angle of the LD light transmission body 2 is
When the angle is equal to or less than the predetermined angle, all the light incident from the LD 1 is totally reflected at a high reflectance on the side surface, so that a coating such as a dielectric multilayer film is not required, and the cost can be reduced.

In this case, a material having a large refractive index does not need to make the taper angle so small.
D The length of the light transmission plate can be shortened.
An anti-reflection coating may be applied to both the emission surface.

In any combination of a solid laser medium, a mirror coating, and an LD that oscillates at other wavelengths, the material of the LD light transmitting body is made of a material that transmits the wavelength at a high transmittance. The present invention also includes a coating provided with a coating that reflects the wavelength at a high reflectance.

[0035]

As described above, according to the present invention,
An LD optical transmission plate having a thickness of about 1 mm or less and having a tapered side surface is brought into contact with a solid laser medium having the same thickness as the LD optical transmission plate, and an array-type high-power LD is incident on the LD optical transmission plate. A simple optical system close to the edge enables highly efficient excitation of the solid-state laser medium, and a simple optical system enables TEM
High output in the oo mode can be realized with high efficiency.

In addition, since the LD light transmission plate makes the excitation light applied to the solid-state laser medium uniform in the horizontal direction, a local temperature rise unlike the end face excitation method does not occur.

Further, since a thin plate-shaped solid laser medium is used, the cooling effect is high, the optical loss inside the resonator due to the thermal lens effect and the thermal birefringence is small, and the beam quality of the solid laser is improved.

The combination of the LD 1 and the LD light transmission plate 2 is
By radially arranging a plurality of pieces around the solid-state laser medium 3, it becomes possible to increase the pumping input and to obtain a high output, and the temperature of the entire side surface is uniformly increased, so that the thermal lens effect and the thermal birefringence effect are small. Beam quality is improved.

In addition, the distance between the LD light transmission plate 2 and the LD 1 and the vertical, horizontal, and horizontal alignments are not affected by the effect on the excitation light emitted from the emission end of the LD transmission plate 2 even if positioning is not performed with high accuracy. Less than in assembly, L
It is easy to adjust the mounting position when replacing D.

Further, since the solid laser medium is thin and the distance between the mirrors constituting the laser oscillator can be shortened, when used for a Q-switched laser, the switch pulse can be shortened and a high-power pulsed laser can be output. Wear.

[Brief description of the drawings]

FIG. 1 is a diagram showing a structure according to a first embodiment of the present invention, wherein (a) is a plan view and (b) is a side view.

FIG. 2 is a plan view showing a structure according to a second embodiment of the present invention.

FIG. 3 is a sectional view of the LD-pumped solid-state laser device of FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 LD 2 LD light transmission plate 3 Solid-state laser medium 4 Cooling plate

Claims (6)

[Claims] 1. An array-type semiconductor laser for emitting excitation light for exciting a solid-state laser medium, an incident end face having a width corresponding to an emission width of the semiconductor laser in an array direction, and a TEMoo mode oscillation region of the solid-state laser medium. An optical transmission plate having an emission end face having a width close to the width and having a thickness corresponding to the emission width in the direction perpendicular to the array direction of the semiconductor laser; and the optical transmission plate installed in contact with the emission end face of the optical transmission plate A solid-state laser medium having a circular plate or a regular polygonal prism having a thickness corresponding to the above. 2. A plurality of array-type semiconductor lasers for emitting excitation light for exciting a solid-state laser medium, and a plurality of semiconductor lasers installed corresponding to the semiconductor lasers, the width corresponding to the emission width of the semiconductor lasers in the array direction. And an emission end face having a width close to the width of the TEMoo mode oscillation region of the solid-state laser medium having an emission end face having a thickness corresponding to an emission width in a direction perpendicular to the array direction of the semiconductor laser. A thickness corresponding to the emission width of the semiconductor laser in the array direction and the vertical direction, having a planar incident end face having a width corresponding to the width and an emitting end face having a width close to the width of the TEMoo mode oscillation region of the solid-state laser medium. A plurality of light transmission plates;
The plurality of the light transmission plates and the plurality of the semiconductor lasers are installed at substantially equal intervals radially around the solid-state laser medium and in contact with the emission end faces of the plurality of light transmission plates, and correspond to the light transmission plates. A semiconductor laser-excited solid-state laser device comprising: a solid disk medium having a thickness of a circular disk or a regular polygonal prism. 3. The semiconductor laser-excited solid-state laser device further comprises a single cooling plate for fixing and cooling all of the solid-state laser medium, the optical transmission plate, and the semiconductor laser. 3. The semiconductor laser-excited solid-state laser device according to 1 or 2. 4. The optical transmission plate according to claim 1, wherein the side surface of the optical transmission plate is coated with a dielectric multilayer film or a metal film having a high reflectance with respect to the wavelength of the excitation light by means such as vapor deposition. 4. The semiconductor laser-excited solid-state laser device according to any one of 1 to 3. 5. The semiconductor laser according to claim 1, wherein said optical transmission plate has a narrower interval toward an output end face at an angle for totally reflecting incident light from said input end face. Excitation solid-state laser device. 6. The semiconductor laser pumped solid-state laser device according to claim 1, wherein said optical transmission plate has a thickness of 1 mm or less, and said solid-state laser medium has a diameter of about 3 mm.