JP2001085770A - Solid laser device, its manufacturing, method and laser diode array used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid laser medium having a high output power and a high excitation efficiency, and provide a laser diode array using the same, by so setting the pitching interval between the adjacent linear light emitting regions to each other of the laser diode array as not to generate any thermal destruction of the solid laser medium caused by the input of the excitation beams of the laser diode array. SOLUTION: When the thermal destruction limit of a laser rod 11 is 300 W/cm, it is assumed that the power of the excitation beams obtained from linear light emitting regions 17 of a laser diode array is 40 W, and the incident directions of the excitation beams to the laser rod 11 are three, and further, the ratio of the power reaching the laser rod 11 to the total power of the excitation beams emitted from a housing 16 of the laser diode array is temporarily 0.9. In this case, an equal pitching interval 18 between the adjacent linear light emitting regions 17 to each other of the housing 16 of the laser diode array can be set to 0.36 cm. Thereby, a solid laser device having a high output power and a high excitation efficiency can be formed without generating in the laser rod 11 any thermal destruction caused by the input of the excitation beams.

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 for generating a laser beam by exciting a solid-state laser medium with light from a semiconductor laser (laser diode: LD), a method of manufacturing the same, and a laser diode array used for the same.

[0002]

2. Description of the Related Art In general, a solid-state laser device (which represents a concept including a solid-state laser oscillation device and a solid-state laser amplification device) has a laser rod as a solid-state laser medium, and laser light is excited by optically exciting the laser rod. Is to occur. Therefore, if the laser rod is arranged in the optical resonator, the laser light generated from the laser rod is amplified inside the optical resonator, and the final laser light is output.

As an excitation light source that optically excites the laser rod, an arc lamp, a flash lamp, a laser diode, and the like are known. Recently, an excitation light having a predetermined wavelength to be absorbed by the laser rod is output. Laser diodes that can be used are increasingly used in particular. With the advent of this laser diode, it has become possible to efficiently excite the laser rod with light.

Conventionally, as such a solid-state laser device, Japanese Patent Application Laid-Open No. 9-260754 discloses a laser rod that is inserted and held in a flow tube through which a cooling medium such as water flows, and the flow tube itself. In some cases, the inner surface was held in a light collector formed on a diffuse reflection surface. Then, outside the light collector, as an excitation light source for exciting the laser rod from the side surface, an array is formed so as to have a linear light emitting region so that the linear light emitting region is parallel to the laser medium. A plurality of laser diodes (laser diode arrays) are arranged.

Further, the present applicant has filed Japanese Patent Application No. 10-81845.
In the solid-state laser device disclosed in the specification, a laser rod inserted into a thick flow tube having a function of suppressing a convex lens effect is disposed on the outer periphery of the flow tube and a solid-state laser medium is disposed. A plurality of laser diodes (laser diode arrays) arranged in an array so as to have a linear light-emitting region in a direction parallel to the axial direction of the laser are excited as an excitation light source. At this time, the light emitting regions of these laser diode arrays are radially arranged at equal intervals from the periphery of the solid-state laser medium.

Further, the applicant of the present invention has disclosed Japanese Patent Application No. 11-77430.
The solid-state laser device disclosed in the specification also includes a plurality of laser diodes (laser diode arrays) having a linear light-emitting region around the solid-state laser medium in a direction perpendicular to the axial direction of the solid-state laser medium. The excitation suppresses the Fresnel reflection loss on the rod surface and increases the efficiency of laser oscillation.

[0007]

In the solid-state laser device, if the power of the pumping light is increased, a high output operation becomes possible, and furthermore, an oscillation operation in an energy region higher than the oscillation threshold becomes possible. Therefore, a highly efficient oscillation operation can be performed. However, when excitation light having high power is applied to the solid-state laser medium, there is a problem that the laser medium is thermally destroyed by the power of the excitation light.

In the technology described in Japanese Patent Application Laid-Open No. 9-260754 and Japanese Patent Application No. 10-81845, a laser diode array in which a linear light emitting region is oriented in parallel with a laser medium is arranged. The power of the excitation light is limited by changing the number of laser diodes arranged on a plane (array). However, in this method, the excitation distribution may be asymmetric inside a laser medium such as a laser rod, and the non-uniformity of the heat generated by the excitation may cause a distortion in the solid-state laser medium, and the output laser light may be distorted. It can have a negative impact. Further, Fresnel reflection on the side surface of the laser rod is large, and there is a possibility that the power of the excitation light incident on the laser rod is lost.

In the technique described in Japanese Patent Application No. 11-77430, a plurality of linear light-emitting regions having a linear light-emitting region around the solid-state laser medium and substantially perpendicular to the axial direction of the solid-state laser medium are provided. By arranging laser diode arrays and exciting by these laser diode arrays, loss of power of excitation light incident on the laser rod due to Fresnel reflection on the surface of the laser rod is suppressed, and oscillation efficiency is increased. However, since the laser diode array, which is the mainstream in the current market, has a high mounting density, when a large number of laser diode arrays are symmetrically arranged around the laser medium, the power of the excitation light is reduced by the solid-state laser medium. Above the thermal breakdown limit, the laser medium can be damaged. Further, even when damage is not caused, the amount of the thermal lens may be increased and the performance of the resonator may be deteriorated.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and according to the present invention, it is arranged in a direction substantially perpendicular to the axial direction of the solid-state laser medium. Solid-state laser device that irradiates excitation light emitted from a laser diode array having a plurality of formed linear light-emitting regions from a side surface of the solid-state laser medium to excite the solid-state laser medium to generate laser light from the solid-state laser medium Wherein the laser diode array is set at an interval between the linear light emitting regions such that the laser medium is not destroyed by the input of the excitation light. .

According to a second aspect of the present invention, the solid-state laser medium has a cylindrical body surrounding the solid-state laser medium, and the cylindrical body has a cooling medium between the solid-state laser medium and the solid-state laser medium. The solid-state laser medium can be cooled by flowing.

According to a third aspect of the present invention, an odd number of the laser diode arrays are arranged at substantially equal intervals along a circumferential direction of an outer peripheral portion of the cylindrical body. According to a fourth aspect, a lens having a cylindrical surface for converging the excitation light is disposed between the laser diode array and the solid-state laser medium.

According to a fifth aspect of the present invention, the solid-state laser is provided at an outer peripheral portion of the cylindrical body at a position symmetrical to the laser diode array via an axis of the solid-state laser medium and output from the laser diode array. Reflecting means for reflecting the excitation light transmitted through the medium.

According to a sixth aspect, a columnar rod material is used as the solid-state laser medium. According to claim 7, a plate-shaped slab material is used as the solid-state laser medium.

According to an eighth aspect of the present invention, in the laser diode array, an interval between the linear light emitting regions is d (cm), and an output obtained per one linear light emitting region is P.
(W), assuming that the direction of the laser diode array placed around the laser medium is m (location) and the ratio of the power of the emitted pump light reaching the solid-state laser medium is η, 95 ≦ P × m It is characterized in that it is configured so that the relationship of × η / d ≦ 500 is satisfied.

According to a ninth aspect, Nd: YAG is used as the solid-state laser medium. According to a tenth aspect, there is provided a step of arranging a laser diode array having a plurality of linear light-emitting regions arranged in a direction substantially perpendicular to the axial direction of the solid-state laser medium along a side surface of the solid-state laser medium. A method of manufacturing a solid-state laser device, comprising a step of setting the laser diode array to an interval between the linear light-emitting regions so that the laser medium is not broken by the input of the excitation light. Is provided.

According to an eleventh aspect, a laser diode array having a plurality of linear light-emitting regions which are arranged to be excited in a direction substantially perpendicular to the axial direction of the solid-state laser medium while receiving excitation light from the side surface of the solid-state laser medium. In the above, there is provided a laser diode array, wherein an interval between the linear light-emitting regions is such that the solid-state laser medium is not broken by the input of the excitation light.

According to the solid-state laser device and the like as described above,
Using a laser diode array in which the distance between the linear light emitting regions is adjusted so that the power of the excitation light input from the laser diode array to the solid-state laser medium is equal to or less than the destruction limit of the solid-state laser medium, A high efficiency and high output solid-state laser device can be obtained without breaking the medium.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 and FIG. 2 are configuration diagrams of an excitation portion of a laser diode array housing 16 constituting a solid-state laser device. FIG. 1 is a longitudinal sectional view of the exciting portion, and FIG. 2 is a sectional view of the exciting portion taken along line AA 'in FIG. FIG. 3 shows a linear light emitting region 17 in the laser diode array case 16.
Only the laser rod 11 (an example of a solid laser medium) is extracted to show the positional relationship between the two. Here, in the present embodiment, the laser diode array case 16
, Which contains the assembled laser diode array.

In the embodiment described below, a rod (cylinder) type solid laser medium is used. However, the present invention is not limited to this, and a slab (plate) type solid laser medium may be used. Good. This is because the present invention has a problem of alleviating the effect of the thermal stress given to the solid-state laser medium by the excitation light.

Here, each configuration of this embodiment will be described. First, the cooling sleeve 1 is provided on the outer circumference of the laser rod 11.
2. Further, a cylindrical mirror 13 is arranged on the outer periphery. The cylindrical mirror 13 is provided with a slit 14 (which is not actually visible in FIG. 2 but is indicated by a dotted line corresponding to the cylindrical mirror 13), and the front surface of the slit 14 (the traveling direction of the excitation light).
A cylindrical lens 15 for converging and collimating the excitation light
And a laser diode array housing 16 having a plurality of laser diodes arranged in an array. The laser diode array housing 16 is provided with a plurality of linear light emitting regions 17 at a predetermined pitch interval 18, and excitation light is emitted from these light emitting regions 17 to the side surfaces of the laser rod 11.

The sleeve 12 and the cylindrical mirror 13
Are fixed to each other by an end plate 19, and the laser diode array housing 16 is fixed to the end plate 19 so as to face the laser rod 11. Generally, an odd number of laser diode array housings 16 are provided to provide the cylindrical mirror 13 and appropriately reflect the excitation light to the laser rod. The laser rod 11 is also fixed to the end plate 19 via the rod holder 20. In addition, a water passage 21 through which a cooling medium (here, cooling water) for cooling the laser rod 11 passes is provided in the end plate 19, and the cooling water is used to cool the laser rod 11. The cooling water is O-ring 22
Sealed by

Further, the linear light emitting area 17 of the laser diode array case 16 is formed in a direction perpendicular to the axial direction of the laser rod 11. By adopting such a configuration, it becomes possible to input the excitation light emitted from the laser diode array housing 16 to the laser rod 11 while making the laser beam 11 into the P-polarized light, so that the laser rod 11 has a cylindrical surface. Fresnel reflection at the laser rod 11 is reduced. Therefore, it becomes possible to input the excitation light to the laser rod 11 while increasing the oscillation efficiency of the laser rod 11. When a slab (plate) type solid laser medium is used instead of the laser rod 11, the incident surface does not have a curved surface and the influence of Fresnel reflection is small. Excitation light can be input without consideration.

Next, a description will be given of the linear light emitting region 17 in which a plurality of laser diode array housings 16 are formed, focusing on the respective pitch intervals. First, a main factor that limits the power of the excitation light emitted from the laser diode array housing 16 and input to the laser rod 11 is thermal destruction of the laser rod 11 caused by injection of the excitation light. That is, the thermal destruction of the laser rod 11 is caused by heat input (heating) accompanying the input of excitation light to the laser rod 11.
The main cause is the thermal stress caused by the distortion of the laser rod 11 caused by the above. The ratio of heat input by the excitation light to the laser rod 11 is 30 to 40 of the power of the excitation light emitted from the laser diode array housing 16.
%.

The breaking limit of the laser rod 11 is determined by the thermal stress generated inside the laser rod 11 by being heated by the excitation light and the surface condition (surface roughness, etc.) of the laser rod 11, and the breaking limit is set. The amount of heat Pa (W) is represented by the following equation.

[Equation 1]: P _a / L = 8πR where R = {K × (1-ν) × σ _max } / (α × E)

Here, R is a thermal shock parameter (W / c)
m), and the value differs depending on the base material of the laser medium (here, the laser rod 11). The standard of the value is “1” for glass (quartz), “7.9” for YAG, and “100” for sapphire. L (cm) is the length of the excited portion of the laser rod 11, and K (W / cm ·
K) is a heat transfer coefficient indicating the ratio of the amount of heat flowing perpendicularly in a unit time through the unit area of the isothermal surface through the unit area of the laser rod 11 to the temperature gradient in this direction. The Poisson ratio indicates the ratio of the contraction per unit length in the lateral direction to the elongation per unit length. Σ _max (kg / cm ² ) is the value of laser rod 1
1 is the maximum stress that is the force per unit area received immediately before breaking, α (° C. ⁻¹ ) is the thermal expansion coefficient indicating the degree of thermal expansion per unit length of the laser rod 11, and E is the laser rod 1
It is a Young's modulus (kg / cm ² ) representing a ratio of stress to strain obtained by elongation deformation given to 1.

According to this [Equation 1], the laser rod 11
Is Nd: YAG, the critical heat input per unit length (cm) is about 200 (W / cm). In addition, `` Solid-State Laser Engine
ering ^4th edition, Springer-Verlag 1996, P391-426 ''
According to the empirical estimate, the limit heat input per unit length in the laser rod 11 of Nd: YAG is 11
5 (W / cm), which is markedly different (changes about three times) in the surface state of the laser rod 11.

The limit of the power of the pumping light emitted from the laser diode array housing 16 that can be input to the laser rod 11 is considered to be as follows from the above examination. That is, the laser diode array housing 16
Given that the laser beam 11 is not broken by thermal stress under the condition that about 40% of the power of the pump light emitted from the laser beam is converted into heat, the limit of this power is [Equation 1]. 500 (W / c
m), which is 290 (W /
cm). Furthermore, considering that the limit heat input to the laser rod 11 changes about three times due to the state of the surface of the laser rod 11, the laser diode array housing 16 corresponding to the breaking limit of the laser rod 11 is considered. The power of the excitation light emitted from the light source is 95 to 500 (W
/ Cm).

Therefore, the laser diode array housing 16
The pitch interval between the linear light emitting regions 18 at d is
(Cm), the power of the excitation light obtained from one of the linear light-emitting regions 18 and emitted from the laser diode array housing 16 is P (W), and the laser diode array housing arranged around the laser rod 11. Assuming that the input direction of the excitation light to the laser rod 16 by the body 16 is m (location), and that the ratio of the power P of the excitation light emitted from the laser diode array housing 16 reaching the laser rod 16 is η. , The following relational expression holds.

[Equation 2] 95 ≦ (P × m × η) / d ≦ 500

Therefore, the solid-state laser device of the present invention (and the method of manufacturing the solid-state laser device and the laser diode array)
According to the above, according to the surface state of the laser rod 11, each pitch interval 18 of the linear light emitting regions 17 formed in the laser diode array housing 16 is set to a numerical value obtained from [Equation 2]. Thereby, a solid-state laser device with high output and high excitation efficiency can be supplied without causing breakage of the laser rod 11.

The above description will be specifically described with reference to, for example, a solid-state laser device having the configuration of the embodiment shown in FIG. The breaking limit of the laser rod 11 is 30
In the case of 0 (W / cm), the power of the excitation light obtained from these linear light-emitting regions 17 is 40 (W), and the directions in which these excitation lights are incident on the laser rod 11 are three places.
Here, of the power of the excitation light emitted from the laser diode array housing 16, the proportion of the power reaching the laser rod 11 is temporarily assumed to be 90%.

Then, based on [Equation 2], the pitch interval 18 between the linear light emitting regions 17 of the laser diode array case 16 can be set to 0.36 (cm). By doing so, it is possible to configure a solid-state laser device with high output and high pumping efficiency without causing thermal destruction by the input of pumping light in the laser rod 11.

[0035]

As described in detail above, the present invention relates to a laser diode array having a plurality of linear light-emitting regions arranged in a direction substantially perpendicular to the axial direction of a solid-state laser medium; The spacing between these linear light emitting regions is adjusted so that the power of the excitation light emitted from the laser diode array to the solid-state laser medium is equal to or less than the breaking limit of the solid-state laser medium due to thermal stress. According to the present invention, a high-power and high-efficiency solid-state laser device, a method of manufacturing the same, and a laser diode array used for the same can be provided.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an excitation part in a solid-state laser device of the present invention.

FIG. 2 is a cross-sectional view taken along line A-A ′ of FIG.

FIG. 3 is a perspective view showing a positional relationship between a solid-state laser medium and a laser diode array housing arranged opposite thereto.

[Explanation of symbols]

11 laser rod, 12 cooling sleeve, 13 cylindrical reflector, 14 slit 15 cylindrical lens, 16 laser diode array housing, 17 light emitting area 18 pitch pitch of light emitting area, 19 end plate, 20 ‥ rod holder, 21 ‥ waterway 22 ‥ O-ring

Claims (11)

[Claims] An excitation light emitted from a laser diode array having a plurality of linear light-emitting regions arranged in a direction substantially perpendicular to the axial direction of the solid-state laser medium is irradiated from a side surface of the solid-state laser medium. In a solid-state laser device that excites a solid-state laser medium and generates laser light from the solid-state laser medium, the laser diode array includes the linear light-emitting region such that the laser medium does not break down due to the input of the excitation light. A solid-state laser device which is set at intervals. 2. A solid body in which the solid-state laser medium is accommodated inside the solid-state laser medium, wherein the cylindrical body flows a cooling medium between the solid-state laser medium and the solid-state laser medium,
The solid-state laser device according to claim 1, wherein the solid-state laser medium can be cooled. 3. The laser diode array according to claim 1, wherein an odd number of the laser diode arrays are arranged at substantially equal intervals along a circumferential direction of an outer peripheral portion of the cylindrical body. Solid state laser device. 4. A lens according to claim 1, wherein a lens having a cylindrical surface for converging the excitation light is disposed between the laser diode array and the solid-state laser medium. The solid-state laser device according to claim 1. 5. An outer peripheral portion of the cylindrical body is provided at a position symmetrical to the laser diode array via an axis of the solid-state laser medium, and is output from the laser diode array and transmitted through the solid-state laser medium. The solid-state laser device according to claim 1, further comprising: a reflection unit configured to reflect the excitation light. 6. The solid-state laser device according to claim 1, wherein a cylindrical rod material is used as the solid-state laser medium. 7. The solid-state laser device according to claim 1, wherein a plate-shaped slab material is used as said solid-state laser medium. 8. The laser diode array, wherein the distance between the linear light emitting regions is d (cm), the output obtained per one linear light emitting region is P (W), and the laser diode array is arranged around the laser medium. Assuming that the direction of the placed laser diode array is m (location) and the ratio of the power of the emitted pump light reaching the solid-state laser medium is η, the relationship of 95 ≦ P × m × η / d ≦ 500 is established. The solid-state laser device according to claim 1, wherein the solid-state laser device is configured as described above. 9. A solid-state laser medium comprising: Nd: Y
6. The method according to claim 1, wherein AG is used.
The solid-state laser device according to any one of the above. 10. A solid-state device comprising a step of disposing a laser diode array having a plurality of linear light-emitting regions arranged in a direction substantially perpendicular to the axial direction of the solid-state laser medium along a side surface of the solid-state laser medium. A method of manufacturing a laser device, comprising the step of: setting the laser diode array to an interval between the linear light-emitting regions so that the laser medium is not broken by the input of the excitation light. Production method. 11. A laser diode array having a plurality of linear light-emitting regions which are incident on a side surface of a solid-state laser medium and which are arranged in a direction substantially perpendicular to an axial direction of the solid-state laser medium. The laser diode array, wherein the diode array has an interval between the linear light-emitting regions so that the solid-state laser medium is not broken by the input of the excitation light.