GB2310313A

GB2310313A - Solid state laser apparatus

Info

Publication number: GB2310313A
Application number: GB9709783A
Authority: GB
Inventors: Kazuki Kuba; Akira Ishimori; Masaki Seguchi; Takashi Yamamoto
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 1993-09-24
Filing date: 1994-01-18
Publication date: 1997-08-20
Anticipated expiration: 2014-01-18
Also published as: GB2310532A; GB9709648D0; GB9709783D0; GB9710392D0; GB2310532B; GB2310313B; GB2310077B; GB2310077A

Description

2310313 - 1 SOLID STATE LASER APPARATUS is The present invention relates

to enhancement of beam quality, oscillation efficiency, and reliability of a slab solid state laser apparatusi and to enhancement of a performance of a laser machining apparatus by using the slab solid state laser apparatus.

Figs. 31 and 32 show a solid state laser apparatus including an exciting system and a cooling system for a conventional laser medium disclosed in, for example, Japanese Patent Application No. 64-84680 in addition to a conventional solid state laser apparatus disclosed in, for example, Japanese Patent Application Laid-Open No. 63-188980.

In Figs. 31 and 32, reference numeral 1 means a slab solid state laser medium (hereinafter referred to as slab) including a pair of opposing smooth surfaces 11, a pair of side surfaces 12, and a pair of end surfaces 13 serving as an entrance surface and an exit surface for a laser beam. The slab is made of, for example, Nd:YAG (Yttrium Aluminum Garnet) obtained by doping Nd. Reference numeral 5 means a supporter disposed on the slab side surface 12, 2 means a lamp to perform light excitation of the slab 1, and 21 is the excitation light.

Reference numeral 7 means a frame integrally containing the slab 1 and the supporter 5, and an opening portion 711 is provided in the frame 7 to extend over substantially an entire surface of the smooth surface 11 of the slab as shown in Fig. 33. Reference numeral 70 means a sealant to seal water 41 serving as a coolant for the slab, and the sealant 70 extends over an entirely peripheral length of a plane formed by the slab surface (the smooth surface) 11 and the supporters 5 disposed on the side surface as shown in Fig.3+. Reference numeral 3 means a condenser to condense the excitation light for irradiation of the slab 1, and 81 and 82 are housings containing the condensers 3. Reference numeral 40 means a partition plate to form a flow path 4 of the slab cooling water 41, and the partition plate 40 is transparent with respect to the excitation light.

A description will now be given of the operation.

The slab 1 absorbs the excitation light 21 emitted from the lamp 2 to form inverted population. Energy of the inverted population is derived externally to the medium as a laser beam 100 which is propagated between the pair of opposing smooth surfaces 11 of the slab in a zigzag fashion while repeating internally total reflection. However, 50 % or more excitation light energy absorbed by the slab becomes thermal energy in the slab, and finally flows out of the slab into the coolant 41 which is filled to contact the opposing smooth surfaces 11 of the slab. At this time, as shown in Fig. 3 5, there are generated the square temperature distribution having a hot center portion, and the square refractive index distribution along with the square temperature distribution in a thickness direction of the slab. The laser beam 100 in the slab, however, follows a zigzag optical path so that an effect of the square refractive index distribution can be canceled, and no laser beam is distorted. The coolant 41 is sealed by the sealants 70 on the opposing smooth surfaces 11 of the slab and the supporters 5 disposed on the side surfaces so as not to be externally leaked. The sealant 70 also serves as a supporter of the slab 1 to the frame 7.

In an ideal condition of slab laser, a laser medium can be uniformly excited in a width direction, and heat can also be uniformly generated in the width direction. Further, the slab can uniformly be cooled from only the slab surfaces (the opposing smooth surfaces) 11, onedimensional square temperature distribution can be established in the thickness direction, and a uniform temperature distribution can be established in the width direction. For purpose of the ideal condition, the condenser 3 is employed such that the slab 1 can be irradiated with the most uniform and the most efficient excitation light 21 possible. For cooling, the coolant 41 uniformly flows on the slab surface 11, and the supporters 5 are adhered on the side surfaces 12 and are made of glass (having thermal conductivity K of 0.012 W/CM2 deg), fluorocarbon resin (having thermal conductivity K of 0.0025 W/CM2 deg), or siliconcrubber (having thermal conductivity K of 0.0015 W/CM2 deg) which has a higher heat insulation property than that of the laser medium (i.e., YAG having thermal conductivity K of 0.12 W/CM2 deg).

A conventional laser oscillator is constructed as set forth above. There are problems in that heat insulating materials 5 on the slab side surfaces 12 and adhesives absorb the excitation light to generate heat, and generate a temperature distribution having hot side surfaces in a width direction and a concave lens-like optical distortion along with the hot temperature distribution on the side surface as shown in Fig. 36, resulting in degradation of beam quality and laser output. Further, there is another problem in that the beam quality varies according to an output level since the optical distortion depends upon excitation intensity.

In case reflectance of the supporter 5 with respect 4 to the excitation lluht 2 1 is low, the excitation light 271 passes from the slab side surfaces 12 to the supporters 5 as shown in Fig. 37. Hence, there are other drawbacks in that a sufficient oscillation effect can not be provided, and uniform excitation can not be achieved due to degraded excitation intensity in the vicinity of the side surfaces.

Substances having high reflectance may be employed as the supporter 5 in order to provide more enhanced oscillation efficiency. Most substances of this kind, however, have extremely poor adhesive properties, and it Is typically difficult to provide compatibility of the heat insulating properties with water-tightness for the slab side surface 12 even if such substances are used.

It would be desirable to be able to provide a compact solid state laser apparatus at a lower cost, having higher efficiency, excellent beam quality and output stability, and higher reliability.

The present invention provides a solid state laser apparatus comprising:

a laser medium having a rectangular plate form including upper and lower smooth surfaces extending substantially parallel to each other, opposed side surfaces extending substantially perpendicular to said smooth surfaces, and end surfaces for entrance/exit of a laser beam, a pair of supporters disposed on the opposed sides of said laser medium, a frame containing said supporters., a light source for exciting said laser medium., a condenser to condense excitation liaht from said lieht source for irradiation of said laser medium., and coolinu means for cooling said laser medium via at least one of said smooth surfaces.' wherein a said supporter is made of a plurality of different materials.

As stated above, in a solid state laser apparatus according to the present invention, the supporter is made of a composite material containing a plurality of different materials. It is thereby possible to optimize a thermal boundary condition between a slab side surface and the supporter, and prevent temperature distributions from occurring in a slab width direction and in a longitudinal direction and optical distortion from occurring along with the temperature distribution.

The support may be contacted with the side surface of the laser medium with pressure. It is thereby possible to further stabilize an effect obtained by forming the supporter from a plurality of materials, that is, an effect to optimize a thermal boundary condition between a laser medium side surface and the supporter and to improve watertiehtness.

The invention will more fully appear from the following detailed description when the same is read in connection with the accompanying drawing. It is to be expressly understood, however, that the drawings are for purpose of illustration only and are not intended as a definition of the limits of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1. is a front sectional view showing one embodiment of a laser apparatus, Fig. 2 is a side sectional view; Fig. 3 is a perspective view showing a configuration of a laser medium and supporters; Fig. 4 is an enlarged view showing the configuration of the supporter., Figs. 5A and B are diagrams showing an optical distortion distribution in a laser medium width direction; Fies. 6A and B are diagrams showing a configuration of a resonator used with the laser apparatus; Fie. 7 is a diagram showing an output characteristic of the laser apparatus.

Fig. 8 is a perspective view showing another configuration of supporters., Fie. 9 is an enlarged sectional view showing another configuration of a supporter; supporter., supporter., apparatus', Fig. 10 is an enlarged perspective view showing another configuration of a Fie. 11 is an enlarged perspective view showing another configuration of a Fie 12 is a front sectional view showine another embodiment of a laser 6 Fie 13 is a sectional view illustrating a temperature distribution of the laser apparatus taken along the thickness and longitudinal directions of the laser medium, Fig. 14 is a perspective view illustrating a temperature distribution of the laser apparatus in a width direction of the laser medium,, Fig. 15 is a top view showing one configuration of supporters of the laser apparatus, Fig. 16 is a top view showing another configuration of supporters; Fig. 17 is a top view showing another configuration of supporters; Figs. 18a to c are views taken along a thickness-width direction of the laser medium, illustrating temperature distributions of the laser apparatus.' Fig. 19 is a front sectional view showing another configuration of a supporter; Fig. 20 is a front sectional view showing another configuration of a supporter; Fig. 21 is a perspective view showing another configuration of a supporter,- Fig. 22 is a perspective view showing another configuration of a supporter; Fig. 23A is a top view showing a configuration of supporters of one embodiment of a laser apparatus according to the present invention., Fig. 23)B is a top view showing a configuration of supporters of another embodiment of the laser apparatus according to the present invention; Fig. 24 shows a top view and a side view illustrating a resonator applied to a laser apparatus; Fig. 25 shows a top view and a side view illustrating another resonator applied to a laser apparatus; Figs. 26A and B are a top view and a side view illustrating a resonator and an amplifier applied to a laser apparatus; Figs. 27A and B are a top view and a side view illustrating a resonator applied to a laser apparatus; Figs. 28A and B are a top view and a side view illustrating a resonator and an amplifier applied to a laser apparatus; Fig. 29 is a side view showing one embodiment of a laser machining apparatus, Fie. 30 is a side,,.iew showing another embodiment of a laser machining apparatus, 7 Flu, 3 1 Is a front sectional view sho,k.inú! a conventional laser apparatus, Fig. 32 Is a side sectional view showing the conventional laser apparatus, - Fia, 33 is a top view showing a laser medium, supporters, and a frame containinu the laser medium and the supporters of the conventional laser apparatus, Fla. 34 is a top view showing the laser medium and the supporters of the conventional laser apparatus.' Fig. 3) 5 Is a view showing a temperature distribution in a thickness direction of a laser medium, a ziaza. optical path, and an equivalent optical path; Ficr. 36 is a view a temperature distribution and a heat optical distortion in a width direction of the laser medium of the conventional laser apparatus; and Fig. 37 Is a view an excitation intensity distribution in a width direction of the laser medium of another conventional laser apparatus.

Preferred embodiment of laser apparatus will now be described in detail referring to the accompanying drawings. It is to be noted that embodiments 1 to 4 are not in accordance with the present invention.

Embodiment 1 Referrincr now to Figs. 1 to 7, a description will be given of one embodiment of a solid state laser apparatus. Fig. 1 is a front sectional view showing the embodiment, Fie. 2 is a side sectional view thereof, Fig. 3 is a perspective view of a laser medium and supporters, and Fig. 4 is a partially enlarged view of Fig. 3.

In Figs. 1 and 2, reference numeral 1 denotes a solid state laser medium (hereinafter referred to as slab) including pair of upper and lower smooth surfaces 11 extending parallel to each other, a pair of opposed side surface 12 extending vertically, and a pair of end surfaces 1 J3) 13 serving as an entrance/exit surface for a laser beam. Reference numeral 5 means a supporter disposed along the side surface 12 of the slab 1. Reference numeral 7 means a frame integrally containing the slab 1 and the supporters 5, and 70 is a sealant to seal water 41 serving as a coolant for the slab. The sealant 70 extends over an entirely peripheral portion of the slab 1 and the respective supporters 5 along a plane perpendicular to a longitudinal direction (i.e., back and forth directions) of the slab 1. Reference numeral 2 means a lamp for light excitation of the slab 1, and 21 is the excitation light. Reference numeral 3 means a condenser to condense the excitation light 21 for irradiation of the slab 1, and 8 is a housing to contain the condensers 3. Reference numeral 40 means a partition plate to form a flow path 4 of the slab cooling water 41, and the partition plate 40 is transparent with respect to the excitation light 21.

In the embodiment, a plurality of vertical grooves 52 are provided in the supporters 5 at inner surfaces 51 opposed to the side surfaces 12 of the slab 1 to extend in a thickness direction (a vertical direction) of the slab at predetermined pitches as shown in Figs. 3 and 4. Thereby, the inner surface 51 has an irregular construction.

A description will now be given of the operation. A basic operation is identical with the operation of a conventional apparatus, and descriptions thereof are omitted. Thus, a description will now be given of the operation and a detailed embodiment of the supporters 5 having the vertical grooves 52 disposed on the slab side surfaces 12.

Problems in the conventional solid state laser apparatus are an increased temperature due to absorption 9 is of the excitation light 21 or heat generation in the supporter 5, and the side surfaces of the slab 1 having a hot temperature distribution in a width direction (i.e., in a lateral direction) along with the increased temperature. In the embodiment, the vertical cooling grooves 52 are provided in the slab facing/contacting surfaces 51 of the supporters 5 in order to overcome the problems. The water 41 serving the coolant for the slab 1 infiltrates into the vertical grooves 52 so that the interfaces 51 of the supporters can be cooled. It is thereby possible to reduce optical distortion by optimizing the temperature distribution in the width direction of the slab 1. In this case, since a substance infiltrating the grooves 52 is water, there is little absorption or heat generation of the excitation light 21, and a cooling effect more increases as a groove width 522 is more extended.

In actuality, for YAG slab having a thickness of 6 mm, a width of 25 mm, and an excitation length of 150 mm, TeflonAresin (Spectralon) was employed as the supporter 5 to measure optical distortion (heat lens) in the slab width direction. As a result, in case electrical input for the excitation lamp was 30 kW with no groove, an intensive concave lens distribution was exhibited at side ends as shown by the curve c in Fig. 5. Further, in case the groove width 522 was set at 0.5 mm, and the pitch 521 was set at 1 mm, and a groove depth 523 was set at 0.2 mm, an intensive convex lens distribution was exhibited at side ends as shown by the curve a in Fig. 5. Subsequently, the groove width 521 was varied while the pitch 521 and the depth 523 were left as they were. Consequently, for the groove width of 0.1 mm and the pitch of 1 mm, it was possible to provide a condition having substantially no heat lens as shown by the curve b to is in Fig. 5.

In addition, oscillation experiments were performed under the respective conditions by using a stable resonator as shown in Fig. 6. Fig. 7 shows output characteristics for the respective conditions. While a laser output substantially proportionally increased to the electrical input of 30 kW under the optimized condition b, large output saturation was observed at the electrical input of 20 kW or later under conditions a and c having the optical distortion.

The embodiment is characterized by thermal boundary conditions of the slab side surface 12 which are optimized by only variation in the width 522 of the groove 52 provided in the supporter 5, an extremely simple construction, and the optimal condition which can invariably be found. Heat lens refracting power under the optimized condition is equal to 0.1 mm-1 or less for the electrical input of 30 kW and the laser output of 1 kW or more. Absolute value of the heat lens refracting power is smaller than heat lens refracting power of 2 m-' in a rod YAG, and has smaller electrical input dependency than that of the rod YAG.

The embodiment as shown in Figs. 1 and 2 has been discussed with reference to a case where, as the coolant infiltrating groove 52, the groove extends parallel to the slab thickness direction. However, the same effect can be provided by grooves extending parallel to the longitudinal direction of the slab as shown in Figs. 8 and 9, or by finely irregular constructions as shown in Figs. 10 and 11.

Embodiment 2 Referring now to Figs. 12 to 15, a description will be given of snoz;wi embodiment.

11 In a slab laser, a rod-like lamp 2 and a rod-like condenser 3 are employed so as to provide the most uniform excitation/heat generation possible in a longitudinal direction as well as a width direction. In actuality, excitation intensity, however, is more reduced at ends of an excitation length than would be in the vicinity of a longitudinal intermediate portion, resulting in a temperature distribution as shown in Fig. 13. The heat generation on slab facing surfaces 51 of supporters 5 is more reduced toward the ends. Accordingly, the ends are too cooled under the same cooling condition as that at the intermediate portion so that the optical distortion in the width direction exhibits a concave lens distribution at the longitudinal ends as shown in Fig. 14. Hence, in the embodiment, groove widths 522 have more thin forms in a direction closer to the longitudinal ends of the slab as shown in Fig. 15 so as to reduce a cooling effect, and minimize the optical distortion even in the vicinity of the ends.

As set forth above, according to the embodiment, it is possible to provide the optimal thermal boundary condition at any desired position in the longitudinal direction the slab side surfaces 12 as well as in the lateral direction of the slab 1 so as to provide more uniform and higher quality laser beam.

In the embodiment, the cooling condition is varied by reducing only the width 522 while keeping the groove depth 523 and the pitch 521 constant. However, it is also possible to vary the cooling condition by varying the pitch and the groove depth as shown in Figs. 16 and 17.

Further, the embodiment has been described with reference to a case where there is the intensive lz excitation intensity at the longitudinally intermediate portion. However, it must be noted that the optical distortion may be minimized by adjusting the pitch, the width, and the depth of the groove at the respective longitudinal positions even if, for example, the. intensive excitation intensity is generated at the longitudinal ends.

Embodiment 3 Referring now to Figs. 18 to 20, a description will be given of another embodiment.

The embodiments 1 and 2 have been described with reference to a constant thermal boundary condition (a cooling condition) of slab side surfaces 12 in a thickness direction. In the embodiment, a distribution is generated in the thermal boundary condition in the thickness direction. A slab 1 is cooled through both ends (smooth surfaces) 11 thereof so that the slab 1 exhibits the square temperature distribution whose center portion in the thickness direction is hot. In case the slab side surfaces 12 are completely insulated to cause no heat generation, the temperature distribution should become uniform in a width direction as shown in Fig. 18(a) (at an upper stage). In actuality, however, temperature distributions as shown in Figs. 18(b) (at a middle stage) and 18(c) (at a lower stage) are generated due to thermal conduction and heat generation of a supporter.

Hence, in the embodiment, a distribution is provided for a groove configuration in the thickness direction as shown in Figs. 19 and 20 such that a slab facing surface 51 of the supporter 5 can have the same square temperature distribution in the thickness direction as 2 1 that under an ideal condition for the slab. It is thereby possible, even in material having the heat generation and the thermal conduction to some extent, to provide the same temperature distribution as that of a completely insulated medium generating no heat. Further, it is possible to enhance quality of a laser beam by optimizing the thermal boundary condition in the slab thickness direction.

Embodiment 4 Referring now to Figs. 21 and 22, a description will be given of another embodiment.

In the embodiment, in order to provide the optimal thermal boundary condition at any desired positions in longitudinal and thickness directions of a slab side surface 12, grooves 52 are provided in a supporter 5 in both the longitudinal and thickness directions as shown in Fig. 21 so as to have distributions in a depth, a width, and a pitch. As a result, there is an effect in that optical distortion can further be reduced.

It is also possible to provide the same effect by providing circular concave portions 52 having different radii in a slab facing surface of the supporter 5 as shown in Fig. 22 with a distribution of the circular concave portions.

Embodiment 5 Referring now to Figs. 23 and 24, a description will be given of one embodiment according to the present invention.

The embodiment 4 has been described with reference to a case where a thermal boundary condition of a slab side surface 12 is optimized by fine concave portions 52 which is provided in a slab facing surface 51 of a supporter 5. However, as shown in Fig. 23A. materials 501 and 502 having different thermal conductivity, absorptivity, and heat rates may be alternately laminated in a slab longitudinal direction to form a composite material. Further, a pitch, a thickness, and the material (i.e., the thermal conductivity, and the absorptivity and the heat rate) of the composite material may be optimized so as to optimize macroscopic thermal conductivity. Thereby, it is also possible to reduce temperature distributions in a width direction and a longitudinal direction of the slab 1, and generation of optical distortion.

For example, Spectralon (resin) and macerite (ceramic) may be employed as the.materials 501 and 502 for the composite material. In addition, it must be noted that a laminating direction of the respective materials should not be limited to the longitudinal direction of the slab 1, the composite material may have another construction in which the materials are laminated in a thickness direction of the slab 1, or in both the longitudinal and thickness directions. It is also possible to further optimize the thermal boundary condition by varying, for example, a width, a pitch of the lamination according to an exothermic distribution in the longitudinal direction of the slab 1.

Alternatively, a construction as shown in Fig. 23ES may also be carried out in another embodiment according to the present invention. In the construction, grooves are provided in a supporter 501 made of ceramic having relatively high thermal conductivity, the grooves are filled with a transparent siliconerubber 502, and the silicontrubber 502 is adhered to the slab 1.

/,:5' In Ficr-Lre 24- a hybrid resonator serving as a symmetrically positive branch unstable resonator in a width direction and as a stable resonator in a thickness direction is applied to a slab laser med Ium 1 having little optical distortion described in the eiments 1 to 5. The resonator includes a cylindrical concave surface mirror 61 having curvature only In a slab width direction, a cylindrical convex surface mirror 62, and a convex lens 63 having refracting power only in the slab thickness direction. Reflection reducing coating in applied to both exids 622 of the cylindrical convex mirror 62, and a laser beam 100 is outputted f rom both the 9 622.

Since the slab laser medium 1 in provided with a rectangular section having a high aspect ratio, laser oscillation by using a typical stable resonator causes a higher-order transverse mode In the range of tens order to hundreds order in a width direction to provide a larger opening, and causes a divergent angle of t millimeters rad. It Is thereby impossible to provide a high focusing performance. On the other hand, the laser oscillation causes a transverse abode of about tenth order in a thickness direction to provide a smaller opening, and causes a divergent angle of several millimeters red, resulting in another problem of anisotropy in the focusing performance.

Hence, In this arrangement, there is f ormed a onedimensional symmetrically positive branch unstable resonator in the width direction to provide the larger opening so as to provide a beam having a higher focusing performance which is several times diffraction limit. Further, there is formed a lower-order stable resonator in the thickness direction so as to reduce the anisotropy in the focusing performance of the beam. It is generally possible to provide a beam having an excellent focusing performance even in the larger opening by using the unstable resonator. However, the unstable resonator can provide lower tolerance for optical distortion in the resonator such as heat. lens than that of the higherorder stable resonator. In this arrangement., consctions an described In the embodiments 1 to 5 are employed to reduce the optical distortion in a slab width direction in case the unstable resonator Is employed. It is thereby possible to realize unstable type oscillation which becomes stable even in a high output area, and provide a beam having a higher focusing performance and excellent isotropy.

In - F1qure 2-5 cylindrical concave surface mirrors 61 and 61 having curvature in a slab width direction are provided to form a single side negative branch unstable resonator. In a one- dimensional symmetrically unstable resonator describedwith reference to 1 Y F.Lgure 2. -4-, beams are separately outputted from both ends in a slab width direction. On the other hand, in the single side negative branch unstable resonator, a solid type beam 100 is outputted from a mirror cut- out portion 622 on the single side in the slab width direction, resulting in a more improved focusing performance. Further, the negative branch unstable resonator can provide higher tolerance for optical distortion than that of the positive unstable resonator - shown in Figure 2-4-, thereby realizing a more stable operation.

In rigs.26 A and B, a slab laser medium 1 is employed as an amplif ier of a laser beam. In the slab. 1-aser medium 1, optical distortion is reduced by constructions described in the embodiments 1 to. 5. A laser apparatus serving as an oscillator shown on the left side in Figs.26A" B is an oscillator including a stable resonator shown in Fig. 6. Another laser apparatus serving as the amplifier shown on the right side is combined with no resonator. The laser apparatus on the right side amplifies a beam 100 outputted from the oscillator on the left side as an input beam so as to generate a high power output beam 1000.

In the laser beam amplifying operation, in case the amplifier has optical distortion with an aberration component while the input beam 100 has a high focusing performance, the resultant output beam is affected by theoptical distortion so that the focusing performance is degraded. In tnis arrangement, the optical distortion of 1 s/ the slab medium serving as the amplifying medium is reduced by methods discussed in the above embodiments. It is thereby possible to amplify the input beam without degradation of the focusing performance of the Input beam, and provide the high power output beam.

In Pigs. 27A and B, optical distortion of a slab laser medium 1 is reduced by constructions discussed in the above embodiments 1 to 5, and a rectangular prism 69 Is used together with the slab laser medium 1 to form a stable resonator having an optical path which is folded by the rectangular prism 69 in a width direction. By folding the optical path, It Is possible to compress an equivalent section in the width direction of the medium 1, and provide a laser been which in excellent in a focusing performance and isotropy even in a typical stable oscillator which is rotationally symmetric with respect to the optical path formed by a spherical total reflection mirror 61 and a spherical partial reflection mirror 62. In this case, In the folded optical path, an effect due to the optical distortion is superimposed proportional to the number of folding. Accordingly, in order to realize a stable laser operation, there is no other choice to considerably reduce the optical distortion of the laser medium 1 as described. - 9 In Figs. 26.k and B, a laser beam 100 having an excellent focusing performance and excellent isotropy is outputted from a slab laser oscillator including a hybrid resonator shown in -Ficrure 25. Then, the laser beam 100 is amplified by a slab laser apparatus having the same folded optical path as that 9 In Frgi=es27A and 58B so as to provide a high power beam 1000 which Is excellent in the focusing performance and isotropy. Tl,-,is a--rangement is characterized in that the input beam 100 and an amplifying medium have equivalent sections which are matched in a width direction as well as in a slab thickness direction, and highly efficient amplification can be made.

In 'F-1gure 2.13 a laser beam 100 is generated from a solid state laser apparatus whose optical distortion is reduced by constructions described in the above emb<>d:lments 1 to 5. The laser beam 100 is transferred in the atmosphere, and is condensed by a condensing lens 801 after a direction of the laser beam is changed by a reflection mirror 601. The condensed laser beam is used for machining a work piece 800.

Inthis arrancemert the laser beam to be condensed is generated from the slab laser medium 1 whose optical distortion is reduced, and the laser beam is excellent in stability and has a high focusing performance. Therefore, the beam at a condensing position can have an extremely small spot diameter and a deep depth of focus is so as to realize high quality laser machining for the work piece in high efficiency. In particular, the focusing performance of the laser beam in the embodiment Is constant irrespective of output. This eliminates the need for adjustment of a condensing lens position for each output level which is conventionally required, and considerably reduces a time required for maintenance.

The embodiment has been described with reference to the solid state laser apparatus employing the laser oscillator including a stable resonator described in the odiment 1. However, it Is possible to provide higher performance machining by using a solid state laser apparatus described in another embodiment which is more excellent in a beam focusing performance.

In Figure 3 0 - a laser beam 100 Is. generated f rom a solid state lasex apparatus whose optical distortion is reduced by constructions described In the above eiments 1 to 5. The laser beam 100 enters an end 6021 of an optical fiber 602 through a condensing lens 603, and is transferred through the fiber.

Thereafter, the beam exits an exit end 6022, and is condensed by condensing lens 604 and 801. The condensed laser beam is used for machining a work piece 800.

In this- arrangement, the laser beam to be condensed is generated from the slab laser medium 1 whose optical distortion is reduced, and is excellent in stability and has a high focusing performance, and the laser beam enterg the fiber end surface. Therefore, the beam at a condensing position of the fiber entrance end surface can 1 have an extremely small spot diameter and a deep depth of focus so as to stably and efficiently perform connection of the beam to the fiber and maintain high beam quality even after fiber transmission. As set forth above, the laser beam even after being emitted from the fiber has the high focusing performance, the beam at the condensing position for laser machining has the extremely small spot diameter and the deep depth of focus, and high quality laser machining for the work piece can be realized in high efficiency. In particular, the focusing performance of the laser beam in the embodiment is constant Irrespective of output. This eliminates the need for adjustment of a machining lens position for each output level which is conventionally required, and considerably reduces a time required for maintenance.

The enbodiment has been described with reference to the solid state laser apparatus employing a laser oscillator including a stable resonator described in the embodiment 1. However, It In possible to provide higher performance machining by using a solid state laser apparatus described in another eizent which in wore excellent in a beam focusing performance.

is -)l

Claims

1. A solid state laser apparatus comprising.

a laser medium having a rectangular plate form including upper and lower smooth surfaces extendiniz substantially parallel to each other, opposed side surfaces extending substantially perpendicular to said smooth surfaces, and end surfaces for entrance/exit of a laser beam., a pair of supporters disposed on the opposed sides of said laser medium, a frame containing said supporters.

a light source for exciting said laser medium., a condenser to condense excitation light from said light source for irradiation of said laser medium, and coolin means for cooling said laser medium via at least one of said smooth 9 surfaces., wherein a said supporter is made of a plurality of different materials.

2. A solid state laser apparatus as claimed in claim 1, in which the said different materials are laminated in the longitudinal direction of the laser medium.

A solid state laser apparatus as claimed in claim 1, in which the said different materials are laminated in the thickness direction of the laser medium.

4. A solid state laser apparatus substantially as described with reference to, and as shown in, Fl!zure 23A or Figure 23B of the accompanyina drawin n g s.