JP2000277837A - Solid state laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently excite a solid state laser medium by placing a plurality of luminous elements for emitting exciting light applied to the solid state laser medium in the direction perpendicular to the length of the solid state laser medium, and controlling the length of placement of the luminous elements to a value equal to or less than the diameter of the solid state laser medium. SOLUTION: For example, eight exciting light sources 14-21 are placed on the periphery of a tube for YAG cooling. For these exciting light sources 14-21 a plurality of semiconductor lasers (LD) are linearly placed in the direction of the length of an Nd: YAG rod 1 to form an LD bar 22, and the LD bar 22 is so formed that the length of the LD bar is equal to or less than the diameter of the Nd: YAG rod 1. With this constitution, LD light can be launched into the Nd: YAG rod with less loss of the LD light due to angle of divergence without need for an optical system such as a collimator lens even if the distance between the LD and the Nd: YAG rod 1 is increased. Therefore, the Nd: YAG rod 1 can be excited at high density and laser light can be oscillated with efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state laser device that optically excites a solid-state laser medium using a semiconductor laser (hereinafter, referred to as an LD) as an excitation light source and outputs laser light.

[0002]

2. Description of the Related Art FIGS. 9A and 9B are schematic structural views of a solid-state laser device. FIG. 9A is a side view seen from a direction perpendicular to the optical axis direction, and FIG. FIG.

As a solid-state laser medium, for example, Nd: YAG
The rod 1 is disposed in an optical resonator (not shown).
The Nd: YAG rod 1 is disposed in a YAG cooling flow tube 2, and a YAG cooling water 3 is provided between the YAG cooling flow tube 2 and the Nd: YAG rod 1.
Is flowing to cool the Nd: YAG rod 1.

On the outer peripheral side of the YAG cooling flow tube 2, for example, four excitation light sources 4 to 7 are arranged. Each of these excitation light sources 4 to 7 is provided with a plurality of LDs.
d: YAG rod 1 arranged linearly along the longitudinal direction, in other words, a plurality of LDs arranged linearly so as to be parallel to the laser optical axis. A linear arrangement of these LDs (light emitting element group) is called an LD bar.

In such a solid-state laser device, when LD light is emitted as excitation light from each LD of each of the excitation light sources 4 to 7 and irradiates the side surface of the Nd: YAG rod 1, the Nd: YAG rod 1 1 is excited from the side, amplified by the optical resonance of the optical resonator, and oscillated and outputs a laser beam.

However, in the LD bar, the divergence angle of the LD light in the direction in which the LDs are arranged is as small as 10 degrees in full width, and the divergence angle in the direction perpendicular to the direction in which the LDs are arranged is 40 degrees. It is getting bigger.

Therefore, as described above, a plurality of LDs are arranged so as to be parallel to the laser optical axis and the Nd: YAG rod 1
In the configuration in which the LD is excited from the side, it is necessary to dispose the LD near the Nd: YAG rod 1. However, Nd: YA
Even if LDs are arranged in the vicinity of the G rod 1, the number of LDs to be arranged can be limited, and it becomes difficult to perform high-density excitation that is advantageous for laser oscillation efficiency.

On the other hand, Nd: YAG rod 1 and LD
When the distance is large, the collimator lens is used to
The spread angle of the D light must be corrected. However, when a collimator lens is used, a loss of 15 to 20% occurs due to the reflection of the collimator lens or the like.

As described above, Nd: Y is obtained by using a plurality of LDs.
It was difficult to excite the AG rod 1 at high density and efficiently.

On the other hand, as an excitation light source for optically exciting a solid-state laser medium such as an Nd: YAG rod 1, for example, an arc lamp, a flash lamp or an LD is known.
Recently, LDs capable of outputting excitation light of a predetermined wavelength absorbed by a solid-state laser medium as described above have been used frequently. This makes it possible to efficiently perform light excitation of the solid-state laser medium.

As a solid-state laser device using such an LD, for example, as described in JP-A-8-181368, a solid-state laser medium is inserted and held in a flow tube for flowing a cooling medium such as water. Then, the inner surface of the flow tube is held in a light collector formed on the diffuse reflection surface. An LD as an excitation light source for exciting the solid-state laser medium is arranged outside the condenser, and LD light output from the LD enters the condenser through an opening formed in the condenser. It has become. Therefore, the LD light is multiply reflected by the diffuse reflection surface to optically excite the solid-state laser medium.

In such a solid-state laser device, since the LD light incident into the condenser is multiply reflected by the diffuse reflection surface to optically excite the solid-state laser medium, the aperture formed in the condenser is formed. By reducing the size of the portion and reducing the size of the portion, it is attempted to prevent the LD light that is multiply reflected inside the light collector from escaping outside the light collector.

However, since the LD light is multiple-reflected inside the condenser, the intensity of the LD light is reduced each time it is reflected, so that the efficiency of laser oscillation cannot be increased so much.

Another technique for optically pumping a solid-state laser medium is disclosed in Japanese Patent Application No. 10-81845, for example, in a thick flow tube having a function of suppressing the convex lens effect. To excite the solid-state laser medium inserted in the flow tube by an excitation light source arranged on the outer periphery of the flow tube. At this time, since a reflecting mirror is disposed in a portion facing the excitation light source, the LD light transmitted through the solid-state laser medium is reflected by the reflecting mirror and re-enters the solid-state laser medium, so that it is efficiently performed. The solid-state laser medium can be excited.

However, since the LD having the linear light emitting region in the direction parallel to the longitudinal direction of the solid-state laser medium is used as the excitation light source, the loss due to Fresnel reflection on the surface of the solid-state laser medium is large. In addition, since the collimating microlenses are mounted in each of the plurality of linear light emitting regions, the excitation distribution in the solid-state laser medium becomes non-uniform.

[0016]

As described above, a plurality of Ls
D is arranged so as to be parallel to the laser optical axis, and Nd: YA
In a configuration in which excitation is performed from the side surface of the G rod 1, Nd: YAG
It was difficult to efficiently excite the rod 1 with high density.

As a technique for exciting a solid-state laser medium, Japanese Patent Laid-Open Publication No. Hei 8-181368 discloses that the LD light is reflected multiple times inside the condenser, so that the intensity of the LD light decreases every time it is reflected. Oscillation efficiency cannot be made very high.

As another technique for optically exciting a solid-state laser medium, Japanese Patent Application No. 10-81845 proposes that the loss due to Fresnel reflection on the surface of the solid-state laser medium increases, and that a plurality of linear Since the collimating microlenses are mounted in each of the light emitting regions, the excitation distribution in the solid-state laser medium becomes non-uniform.

Accordingly, an object of the present invention is to provide a solid-state laser device capable of efficiently exciting a solid-state laser medium.

[0020]

According to a first aspect of the present invention, there is provided a solid-state laser which optically excites a solid-state laser medium disposed in an optical resonator, generates optical resonance in the optical resonator, and outputs laser light. In the device, a plurality of light-emitting elements that emit excitation light for irradiating the solid-state laser medium are arranged in a direction perpendicular to the longitudinal direction of the solid-state laser medium, and the arrangement length of these light-emitting elements is set to be equal to or less than the diameter of the solid-state laser medium. A solid-state laser device.

According to a second aspect of the present invention, in the solid-state laser device according to the first aspect, the length of the plurality of light-emitting elements in the direction perpendicular to the longitudinal direction of the solid-state laser medium is set to be equal to or less than the diameter of the solid-state laser medium. A light emitting element group is formed by linearly arranging the light emitting element groups, and a plurality of light emitting element groups are arranged along the longitudinal direction of the solid-state laser medium.

According to a third aspect of the present invention, in the solid-state laser device according to the first aspect, the divergence angle of the excitation light in a direction in which the light emitting elements are linearly arranged is smaller than a predetermined angle, and The divergence angle of the excitation light in the direction in which the light emitting element groups are arranged is larger than a predetermined angle.

According to a fourth aspect of the present invention, there is provided a solid-state laser device which optically excites a solid-state laser medium disposed in an optical resonator, generates optical resonance in the optical resonator, and outputs laser light. A linear excitation light source in which a plurality of light emitting elements that emit excitation light to irradiate are arranged in a direction perpendicular to the longitudinal direction of the solid-state laser medium, and are provided at positions symmetrical to the excitation light source through the solid-state laser medium, A reflection member that reflects the excitation light output from the excitation light source and transmitted through the solid-state laser medium.

According to a fifth aspect of the present invention, there is provided the solid-state laser device according to the fourth aspect, wherein a cylindrical surface lens for collimating the excitation light emitted from the excitation light source and irradiating the collimated excitation light to the solid-state laser medium is provided.

According to a sixth aspect of the present invention, in the solid-state laser device according to the fifth aspect, the diameter of the solid-state laser medium is 5 to 5.
10 mm, the emission width of the excitation light source is 8 to 12 mm
And the focal length of the cylindrical lens is 20-40 mm
It is formed in the range of.

[0026]

(1) Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. The same parts as those in FIG. 9 are denoted by the same reference numerals.

FIG. 1 is a configuration diagram of a solid-state laser device.

A pair of opposed resonator mirrors 1
An optical resonator is formed by 0 and 11, and an LD excitation module 12 is included in the optical resonator.

The LD pumping module 12 is used to optically pump, for example, an Nd: YAG rod 1 as a solid-state laser medium. FIG. 2 is a schematic configuration diagram of the LD pumping module 12, and FIG. FIG. 4B is a side view as viewed from a direction perpendicular to the axial direction, and FIG. 5B is a cross-sectional view as viewed from the optical axis direction. FIG. 3 shows an external view of the LD excitation module 12.

The Nd: YAG rod 1 is disposed in a YAG cooling flow tube 2, and YAG cooling water 3 flows between the YAG cooling flow tube 2 and the Nd: YAG rod 1 so that the Nd: YAG rod 1 is being cooled. The temperature of the YAG cooling water 3 is controlled by the cooler 13.

On the outer peripheral side of the YAG cooling flow tube 2, for example, eight excitation light sources 14 to 21 are arranged. These excitation light sources 14 to 21
d: One LD that is linearly arrayed (arrayed) in the longitudinal direction of the YAG rod 1, that is, in the direction perpendicular to the laser optical axis.
The bar 22 is formed, and as shown in FIG.
Is formed to be equal to or less than the diameter of the Nd: YAG rod 1. The excitation light sources 14 to 21 have a plurality of sets of LD bars 22 stacked in parallel along the longitudinal direction of the Nd: YAG rod 1.

The stacked height of the LD bars 22 is shorter than the length of the excitable portion of the Nd: YAG rod 1 excluding the cooling water allowance.

The divergence angle of the LD light emitted from each of the excitation light sources 14 to 21 in the direction in which the LD bar 22 is arranged (the direction of the laser optical axis) is as small as about 10 degrees in full angle (FWHM), and the LD light is The divergence angle of the bar 22 in the direction in which the LDs are arranged (the direction perpendicular to the laser optical axis direction) is as large as about 40 degrees.

The excitation light sources 14 to 21 are connected to the LD driver 23 to emit light.

Next, the operation of the above-configured device will be described.

When LD light is emitted as excitation light from each LD of each of the excitation light sources 14 to 21 and irradiates the side surface of the Nd: YAG rod 1, this Nd: YAG rod 1 is excited from the side surface and the optical resonator is excited. Amplified by the optical resonance of each of the resonator mirrors 10 and 11 and laser light is oscillated and output.

At the time of this laser oscillation operation, each excitation light source 1
LD light emitted from 4 to 21 has a divergence angle in the laser optical axis direction as small as about 10 degrees in full angle (FWHM) and a divergence angle in the direction perpendicular to the laser optical axis direction as large as about 40 degrees. Further, since the direction of each LD bar 22 is perpendicular to the laser optical axis direction, when viewed from a direction perpendicular to the laser optical axis direction as shown in FIG. By making the Nd: YAG rod 1 sufficiently long, the LD light can be efficiently incident on the Nd: YAG rod 1 even if the distance between the LD and the Nd: YAG rod 1 is increased.

When viewed from the laser beam axis direction as shown in FIG. 2B, the spread angle of the LD light is small.
Even if the distance between the LD and the Nd: YAG rod 1 is increased, the LD light can be efficiently incident on the Nd: YAG rod 1.

As described above, in the first embodiment, the length of the LD bar 22 in the direction perpendicular to the longitudinal direction of the Nd: YAG rod 1 is set to Nd: YAG.
Since the plurality of sets of the LD bars 22 are formed along the longitudinal direction of the Nd: YAG rod 1, the LD bars 22 are formed to have a diameter equal to or less than the diameter of the rod 1, and thus no optical system such as a collimator lens is required. Even if the distance to the rod 1 is increased, the loss of the LD light due to the spread angle is reduced, and Nd: Y
The laser beam can be incident on the AG rod 1 and can excite the Nd: YAG rod 1 with high density to efficiently oscillate and output laser light.

The first embodiment of the present invention may be modified as follows.

For example, in the first embodiment, the excitation light is incident from the side surface of the solid-state laser medium using the rod-shaped Nd: YAG rod 1, but the solid-state laser medium is made of the same material. The present invention is not limited to the shape, the excitation method, and the same operation and effects as those of the first embodiment can be obtained as long as the medium and the excitation method can perform laser oscillation.

In the first embodiment, the LD and the N
d: The water cooling method is used for cooling the YAG rod 1. However, as long as the cooling can be performed without affecting the performance of the solid-state laser device, the same operation and effect as those of the first embodiment can be obtained by using any cooling method. Can be played.

Each of the excitation light sources 14 to 21 is an LD bar 2
Although the two are stacked, the same operation and effects as those of the first embodiment can be obtained if the configuration is the same even if the two are not stacked.

Although the LD bar 22 is arranged in the direction perpendicular to the laser optical axis, the same effect can be obtained even if the LD bar is installed obliquely as long as the LD light can be incident.

(2) Next, a second embodiment of the present invention will be described with reference to the drawings.

4 and 5 are structural views of the solid-state laser device. FIG. 4 is a side view as viewed from a direction perpendicular to the laser optical axis direction, and FIG. 5 is a cross-sectional view as viewed from the optical axis direction. .

The end plate 30 is provided with rod holders 31 and 32, and these rod holders 31 and 32 are
For example, 8 m in diameter as a solid-state laser medium via 3, 34
m Nd: YAG rod 35 is fixed. Further, a water passage 36 for flowing cooling water for cooling the Nd: YAG rod 35 is provided in the end plate 30.

On the outer peripheral side of the Nd: YAG rod 35, a cooling sleeve 37 made of, for example, a thick glass material is used.
Is provided. The cooling sleeve 37 has an outer diameter of 30 mm and an inner diameter of 12 mm, for example. And
A cylindrical mirror 38 is arranged on the outer peripheral side of the cooling sleeve 37, and the cylindrical mirror 38 has slits 39 to 41 formed in portions that divide the circumference into approximately three equal parts. The cylindrical mirror 38 is, for example, provided with a total reflection dielectric film.

On the front surfaces of these slits 39 to 41, single cylindrical lenses 42 to 44 for collimation are provided, respectively.
, The respective excitation light source units 45 to 47 are arranged. Each of the excitation light sources 45 to 47 includes a single excitation light source 45a to 45d, 46a to 46d, and 47a to 47d arranged along the longitudinal direction of the Nd: YAG rod 35. 46a-46
d, 47a to 47d respectively set a plurality of LDs to Nd: Y
A single light emitting region (LD bar) 48 is formed by linearly arraying (arraying) the longitudinal direction of the AG rod 35, that is, the direction perpendicular to the laser optical axis.

By arranging the LD bars 48 in a direction perpendicular to the longitudinal direction of the Nd: YAG rod 35 in each of the excitation light source sections 45 to 47, the LD light incident on the Nd: YAG rod 35 is p-polarized. It becomes.

Next, the operation of the device configured as described above will be described.

Each LD bar 48 of each excitation light source section 45 to 47
, LD light is emitted as excitation light from each of these, the LD light passes through each of the cylindrical lenses 42 to 44, passes through each of the slits 39 to 41, passes through the cooling sleeve 37, and Nd:
The light is irradiated on the side surface of the YAG rod 35. At this time, since the LD bars 48 of the excitation light sources 45 to 47 are arranged in a direction perpendicular to the longitudinal direction of the Nd: YAG rod 35, the LD light incident on the Nd: YAG rod 35 is P-polarized light. Become. The irradiation of the LD light excites the Nd: YAG rod 35, is amplified by the optical resonance of each resonator mirror, and oscillates and outputs laser light.

Here, each single cylindrical lens 42-44
LD light efficiently using only Nd: YAG
The function that can be incident on the rod 35 will be described with reference to the schematic diagram of the optical path of LD light shown in FIG. The figure shows the tracking results of LD light on the assumption that a dielectric film of total reflection is provided on the outer periphery of the cooling sleeve 37.

Each LD bar 48 of each excitation light source section 45-47
, The LD light as the excitation light is output at a typical spread angle (full width at half maximum) of 16 degrees. The LD light is collimated by each of the cylindrical lenses 42 to 44 having a focal length of 30 mm, is collected by a cooling sleeve 37 having an outer diameter of 30 mm and an inner diameter of 12 mm, and efficiently and uniformly irradiates an Nd: YAG rod 35 having a diameter of 8 mm. Is done.

Further, the Nd: YAG rod 35 has a P-polarized L
The operation of incident D light will be described with reference to FIG.
The figure shows a case where the LD bar is formed horizontally in the longitudinal direction (axial direction) of the Nd: YAG rod 35, that is, a case where the polarization direction of the LD light is S-polarized with respect to the Nd: YAG rod 35,
Nd: LD perpendicular to the longitudinal direction of YAG rod 35
When a bar is formed, that is, the polarization direction of the LD light is Nd:
LD in case of P-polarized light for YAG rod 35
This shows the transmittance dependence on the incident angle of light.

As can be seen from the figure, the LD light is Nd: Y
In the case of S-polarized light with respect to the AG rod 35, the transmittance is 91%.
On the other hand, by using P-polarized light, the transmittance becomes 97.
%.

As described above, in the second embodiment, the LD bars 48 in the respective excitation light source sections 45 to 47 are arranged in the direction perpendicular to the longitudinal direction of the Nd: YAG rod 35, LD of P polarization for 35
Since the light was irradiated, the Nd: YAG rod 35 was used.
Since the loss due to Fresnel reflection on the surface can be reduced, and the cylindrical mirror 38 is arranged in a symmetrical portion from each of the excitation light source sections 45 to 47 via the axis of the Nd: YAG rod 35, Nd: YAG The Nd: YAG rod 35 can be more efficiently excited by reflecting the LD light transmitted through the rod 35 and transmitting the reflected light again into the Nd: YAG rod 35.

Further, the LD bar 4 of each of the excitation light source sections 45 to 47 is provided.
Since the LD light in which the cylindrical lenses 42 to 44 are arranged on the front surface of the Nd 8 is condensed, a uniform excitation distribution can be formed in the Nd: YAG rod 35.

Further, since the cylindrical mirror 38 such as a dielectric film is provided on the outer peripheral side of the cooling sleeve 37 as a reflecting member, the overall configuration of the apparatus can be made compact.

Further, the diameter of the Nd: YAG rod 35 is 5 to 10 mm, and the LD bar 48 of each excitation light source section 45 to 47 is provided.
Are formed in the range of 8 to 12 mm and the focal length of each of the cylindrical lenses 42 to 44 is in the range of 20 to 40 mm.
d: The YAG rod 35 can be efficiently excited, and a more uniform excitation distribution can be formed.

The second embodiment may be modified as follows.

For example, instead of the cylindrical mirror 38 of the second embodiment, instead of the cylindrical mirror 38 of the second embodiment, the entire length of the Nd: YAG rod 35 in the longitudinal direction of the Nd: YAG rod 35 is provided as shown in FIG. The reflection film 50 and the antireflection film 51 may be formed. The reflection film 50 and the anti-reflection film 51 are provided with a predetermined interval in the circumferential direction of the outer peripheral surface of the cooling sleeve 37 so as to reflect the LD light that cannot be absorbed by the Nd: YAG rod 35, and to reflect the Nd again. : Absorbed by the YAG rod 35.

With this configuration, it is needless to say that the same operation and effect as those of the second embodiment can be obtained, and it is possible to eliminate the need to provide a reflecting mirror outside the cooling sleeve 37.
The number of parts can be reduced and the overall configuration can be made compact.

[0064]

As described above, according to the present invention, a solid-state laser device capable of efficiently exciting a solid-state laser medium can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a solid-state laser device according to the present invention.

FIG. 2 is a configuration diagram of an LD excitation module in the apparatus.

FIG. 3 is an external view of an LD excitation module in the apparatus.

FIG. 4 is a configuration diagram showing a second embodiment of the solid-state laser device according to the present invention.

FIG. 5 is a cross-sectional view of the same device as viewed from the optical axis direction.

FIG. 6 is a schematic diagram showing an optical path of LD light by a cylindrical lens.

FIG. 7 is a diagram showing transmittance with respect to an incident angle when P-polarized LD light is incident on an Nd: YAG rod.

FIG. 8 is a configuration diagram showing a modified example of the device.

FIG. 9 is a schematic configuration diagram of a conventional solid-state laser device.

[Explanation of symbols]

 1: Nd: YAG rod, 2: YAG cooling flow tube, 3: YAG cooling water, 10, 11: resonator mirror, 12: LD excitation module, 13: cooler, 14-21: excitation light source, 22: LD Bar, 23: LD driver, 30: End plate, 31, 32: Rod holder, 33, 34: O-ring, 35: Nd: YAG rod, 36: Water path, 37: Cooling sleeve, 38: Cylindrical mirror, 39- 41: slit, 42 to 44: cylindrical lens, 45 to 47: excitation light source section, 48: light emitting area (LD bar).

Claims (6)

[Claims] 1. A solid-state laser device that optically excites a solid-state laser medium disposed in an optical resonator, generates optical resonance in the optical resonator, and outputs laser light, wherein the excitation light is applied to the solid-state laser medium. A plurality of light-emitting elements that emit light are arranged in a direction perpendicular to the longitudinal direction of the solid-state laser medium, and the arrangement length of these light-emitting elements is set to be equal to or less than the diameter of the solid-state laser medium. . 2. A light emitting element group is formed by arranging a plurality of the light emitting elements linearly in a direction perpendicular to a longitudinal direction of the solid state laser medium so as to have a length equal to or less than a diameter of the solid state laser medium, and 2. The solid-state laser device according to claim 1, wherein a plurality of the light-emitting element groups are arranged along a longitudinal direction of the solid-state laser medium. 3. The light emitting device according to claim 1, wherein a spread angle of the excitation light in a direction in which the light emitting devices are linearly arranged is smaller than a predetermined angle, and the spread of the excitation light in a direction in which the light emitting device groups are arranged. 2. The solid-state laser device according to claim 1, wherein the angle is larger than a predetermined angle. 4. A solid-state laser device that optically excites a solid-state laser medium disposed in an optical resonator, generates optical resonance in the optical resonator, and outputs laser light, wherein the excitation light is applied to the solid-state laser medium. A linear excitation light source in which a plurality of light-emitting elements that emit light are arranged in a direction perpendicular to the longitudinal direction of the solid-state laser medium; provided at a position symmetrical to the excitation light source through the solid-state laser medium; A reflection member that reflects the excitation light output from the light source and transmitted through the solid-state laser medium. 5. The solid-state laser device according to claim 4, further comprising a cylindrical lens for collimating said excitation light emitted from said excitation light source and irradiating said solid-state laser medium with said excitation light. 6. The solid-state laser medium has a diameter of 5 to 10 m.
m, the emission width of the excitation light source is formed to 8 to 12 mm, and the focal length of the cylindrical lens is 20 to 40 m.
The solid-state laser device according to claim 5, wherein the solid-state laser device is formed in a range of m.