JP2544616B2 - Solid-state laser device - Google Patents

Description

The present invention relates to a solid-state laser device used for precision processing such as annealing mask repair.

[Conventional technology]

A typical conventional solid-state laser device is one in which a cylindrical laser active medium (hereinafter abbreviated as a laser medium) and an excitation lamp are arranged in parallel at each focal position of an ellipsoidal reflector. Is known,
In such a device, when the input energy increases, the output energy becomes unstable or the laser medium is destroyed due to the temperature difference between the center and the surface of the cylindrical (rod type) laser medium. However, there was a problem that the laser oscillation stopped. Therefore, in recent years slab (SLA
B) type [SPIE Vol 69 (1975) Laser Systems P38〜4
A surface-cooled, surface-pumped solid-state laser device called 4] has been developed and used.

This is a structure in which excitation lamps are arranged with a plate-shaped laser medium sandwiched between them, and a coolant such as cooling water or compressed air is flown between them. By repeating the total reflection on the surface, it passes through the zigzag optical path, and at that time, the low temperature part of the cooled main surface and the high temperature part of the center are alternately repeated. Propagation in the laser medium alleviates the drawbacks of the rod-type laser medium described above. FIG. 7 and FIG. 8 show a conventional example of such a slab type solid-state laser device. The outline thereof will be described. 1 is a laser medium, 2 is a holder for holding a laser medium 1, and 3 is the holder. Is a lamp housing for accommodating the container 2 and the excitation lamp 4, and the lamp housing 3 is composed of a pair of left and right housing bodies 3A and 3B that are opposed to each other with the retainer 2 interposed therebetween. Are formed with storage recesses 5A, 5B for storing the lamps 4, and two lamps 4 are respectively stored in the recesses 5A, 5B in the vertical direction and in parallel with the laser medium 1, and the recesses 5A are also disposed. The inner wall surfaces of 5B are curved in a circular arc shape and are plated with gold to reflect the light emitted from each lamp 4 and focus it on the main surfaces 1a, 1b of the laser medium 1, respectively. Forming 7. Each lamp 4 is surrounded by a cooling pipe 8. And each storage recess 5
The front openings of A and 5B are hermetically sealed by translucent glass substrates 9A and 9B, and cooling water 13 for cooling the lamp 4 is supplied to the inside through a pipe 10. It is configured. A holder 12 for holding the electrode lead-out portions 11 provided at both ends of each excitation lamp 4 is connected with a pipe 14 for supplying ion-exchanged water 15 (or cooling gas) to the cooling pipe 8. There is.

At the center of the upper surface of the lamp housing 3, a coolant supply member 1 for directly supplying a cooling gas 16 sent from a circulator (not shown) to the main surfaces 1a, 1b of the laser medium 1 is provided.
7 are provided. Cooling gas 16 is sent into the refrigerant passages 18A, 18B formed between the main surfaces 1a, 1b and the translucent glass substrates 9A, 9B, respectively, along the main surfaces 1a, 1b. The laser medium 1 flows downward to cool the laser medium 1, and the pipe 22 passes through the discharge passages 21A and 21B provided in the optical base 20 on which the lamp housing 3 is mounted and fixed.
Be led to. In this case, the cooling gas 16 and the cooling pipe 8
The ion-exchanged water 15 supplied to the above is cooled by the cooling water 13 that is circulated and supplied into each of the storage recesses 5A and 5B by the palup 10.

[Problems to be solved by the invention]

However, in such a conventional solid-state laser device, the temperature distribution on each of the main surfaces 1a and 1b of the laser medium 1 is different from that of the portion most strongly receiving the direct light of the excitation lamp 4, that is, the portion facing the lamp 4. Since the temperature is higher than that of the portion, the cooling medium 16 is flown in parallel to the main surfaces 1a and 1b of the laser medium 1 having such a non-uniform temperature distribution. On the other hand, since the cooling capacity is the same, it was impossible to sufficiently and effectively cool the high temperature portion of the laser medium 1. In particular, when the input energy from the excitation lamp 4 is rapidly repeated, the laser medium 1
9A shows a non-uniform temperature distribution as shown in FIG. 10A in the cross-sectional direction taken along the line AA, and only the temperature of the central portion of the laser medium 1 is in contact with the cooling gas 16. Main surface
Since the temperature is higher than that of 1a and 1b, there is a problem that thermal stress is generated and the laser medium 1 is destroyed.

Therefore, the present invention improves the above-mentioned drawbacks,
An object of the present invention is to provide a solid-state laser device capable of effectively cooling the main surface of a laser medium and preventing damage due to thermal stress.

[Means for solving problems]

In order to achieve the above-mentioned object, the solid-state laser device according to the present invention has an ejection port for blowing a refrigerant substantially vertically to at least a high temperature portion of a high temperature portion and a low temperature portion of a laser medium excited by an excitation lamp. And a coolant passage for allowing a coolant to flow from a high temperature portion to a low temperature portion of the laser medium.

[Action]

In the present invention, the cooling medium is blown almost vertically to the high temperature portion of the main surface of the laser active medium, so that the high temperature portion is effectively cooled and the temperature distribution on the entire main surface is made uniform.

〔Example〕

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

1 is a sectional view taken along the line I--I of FIG. 3 showing an embodiment of a solid-state laser device according to the present invention, FIG. 2 is a perspective view of one housing body, and FIG. 3 is an external perspective view of the same device. FIG. 4 is a sectional view taken along the line IV-IV in FIG. 3, in which the same components and parts as those in the conventional apparatus shown in FIGS. Omit it. The present embodiment shows an example in which one excitation lamp 4 is arranged in each of the housing recesses 5A, 5B of the housing bodies 3A, 3B. Further, as the laser medium 1, a phosphate laser glass LH containing 6% by weight of Nd ³⁺
G-5 (made by HOYA), width W = 15mm, flow L = 55mm, thickness t
It is processed into a thin plate of 4 mm, and light incident from the end surface processed to θ = 33 ° is formed so that total reflection is alternately repeated six times on the opposite main surfaces 1a and 1b parallel to each other. The excitation lamp 4 is a cylindrical Xe lamp using a vacuum container having an inner diameter of 6 mm and a wall thickness of 1 mm, and the excitation length is about 50 mm.

Now, the housing bodies 3A, 3B are screwed on the optical base 20 so as to face each other with the holder 2 for the laser medium 1 interposed therebetween.
The recesses 31A and 31B having a proper depth are formed in the central portions of the inner side surfaces which are fixed by 30, and are opposed to each other, and the lamp 4 is housed in the central portion of the inner bottom surface of each of the recessed portions 31A and 31B. Semicircular storage recesses 5A, 5B are formed in the longitudinal direction of the lamp 4. The inner wall surfaces of the storage recesses 5A, 5B are plated with gold to form reflectors 6, 7, respectively. Each of the storage recesses 5A, 5B is hermetically sealed by a translucent glass substrate 9A, 9B whose surface is made of pyrex glass or the like with a thickness of about 2 mm and precision-polished to prevent light scattering. The translucent glass substrates 32a and 32b and 33a, each of which has a pair of upper and lower sides, are also formed in the openings of the recesses 31A and 31B.
And 33b are arranged respectively. In this case, the translucent glass substrate 9A, 9B has a peripheral edge portion of each of the concave portions 31A, 31B.
It is brought into close contact with the inner bottom surface of the plate through an O-ring 34, and is pressed and fixed by a holding plate 35. The pressing plate 35 is fixed to the inner bottom surface of the recess by a set screw 36. Similarly, the translucent glass substrates 32a, 32b, 33a, 33b are also pressed and fixed by pressing plates 38 that are closely attached to the inner surfaces of the housing bodies 3A, 3B via O-rings 37 and fixed by screws. Has been done. The slit-shaped gaps formed between the translucent glass substrates 32a and 32b and 33a and 33b allow the cooling gas 16 serving as a coolant to be substantially applied to the main surfaces 1a and 1b of the laser medium 1. Refrigerant ejection ports 39A, 39B for vertically ejecting are formed.

These jet ports 39A, 39B are formed so as to correspond to the lamp 4, that is to say, the closest to the excitation lamp 4 of the main surfaces 1a, 1b and to receive the most direct light. There is.

In this case, in the present embodiment, the respective refrigerant ejection ports 39A, 39B are formed at equal intervals over the entire length by the two glass substrates 32a and 32b, 33a and 33b, but not limited to this, for example, FIG. Glass substrates 32a and 32b having shapes as shown in (a) and (b)
(The same applies to 33a and 33b) to increase the width of the jet port in the central portion, or as shown in FIG. 7 (c), the refrigerant jet port 39 is formed by a large number of small holes formed in one glass substrate 32. May be formed.

One end of each housing body 3A, 3B is located inside the housing body 3A, 3B.
A total of six refrigerant flow channels 41, 42, which are open to the outer side surfaces of A and 3B and communicate with the recessed portions 31A and 31B at the other end, are formed in three upper and lower two stages, one end of each of the passages 41 and 42. Pipes 43 are connected to the openings, respectively.

Refrigerant passages 18A, 18B for the cooling gas 16 are formed between the inner surfaces of the housing bodies 3A, 3B and the cage 2, and the passages 18A, 18B are provided in the optical base 20. The discharge passages 21A, 21B and the discharge passage 48 of the refrigerant discharge member 47 installed on the lamp housing 3 are respectively communicated with each other.

Next, cooling of the fixed laser device having the above configuration will be described. The cooling gas 16 (compressed air having a pressure of 0.5 kg / cm ² ) supplied from a cooling gas circulator (not shown) is supplied to the pipe 4
When it is guided to the coolant flow paths 41, 42 formed in the respective housing bodies 3A, 3B through 3 and flows into the recessed portions 31A, 31B, the main surface 1a of the laser medium 1 is discharged from the coolant ejection ports 39A, 39B. Sprayed almost vertically on 1b. At this time, since the portion of each main surface 1a, 1b to which the cooling gas 16 is blown is the high temperature portion that receives the most direct light of the excitation lamp 4 and is heated to the highest temperature, the heat energy of the high temperature portion is high. Efficiently moves to the cooling gas 16 and effectively lowers the temperature of the high temperature part.
On the other hand, the cooling gas 16 deprived of heat energy from the high temperature part
Is moved along the refrigerant passages 18A and 18B to the low temperature portion where the heat energy is relatively less accumulated because the excitation lamp 4 is located farther than the high temperature portion of the laser medium 1 while performing heat exchange, It is discharged to the discharge passages 21A and 21B of the optical base 20 and the discharge passage 48 of the refrigerant discharge member 47. Then, the cooling gas 16 discharged from these passages returns to the refrigerant circulator through the pipe 22.

On the other hand, the ion-exchanged water 15 supplied from the circulator of the ion-exchanged water 15 for cooling the respective excitation lamps 4 itself.
The ions that have flowed into the cooling pipe 8 through a flow path (not shown) formed in the electrode holding portion 12 and exchange heat by contacting with the outer wall of the lamp 4 to remove the heat energy. The exchanged water passes through the flow path formed in the other electrode holding portion 12 'and returns to the ion exchanged water circulator again.

Cooling water is stored in the storage recesses 5A, 5B of each housing body 13A, 13B.
13 is from the circulator Pipe 10 and housing body 13A, 13B
Is supplied through the passage 50 (FIG. 4) of the excitation lamp 4
Is cooled from the outside of the cooling pipe. Then, this cooling water 13 returns to the circulator through the passage 51 (FIG. 4) of the housing bodies 13A and 13B and the pipe 10 '.

Thus, according to the cooling structure using such a solid-state laser device, since the cooling gas 16 is intensively blown to the high temperature portion of the laser medium 1, the cooling effect is great, and the cutting is performed along the line AA in FIG. The temperature distribution in the cross section can be made almost uniform as shown in FIG. Therefore, the generation of thermal stress due to the temperature difference can be suppressed, and stable laser oscillation can be maintained. Further, in this embodiment, since the lamp housing 3 also serves as the flow path forming member for the cooling gas 16, the number of parts can be reduced and the number of assembling steps can be saved.

Although the above embodiment is applied to the slab type solid state laser device, it may be a rod type solid state laser device, and the refrigerant 16 is also N ₂ gas instead of compressed air, He gas, etc. The effect of is obtained.

Further, in the above embodiment, the cooling water 13 for cooling the refrigerant 16 and the ion-exchanged water 15 was circulated in the storage recesses 5A, 5B,
Cooling gas may be used instead of the cooling water. In that case, the translucent glass substrates 9A and 9B are removed, and together with the cooling medium 16 from the cooling medium jet ports 39A and 39B to the respective main surfaces 1a and 1b of the laser medium 1. You may spray.

Further, in the above embodiment, the main surfaces 1a and 1b of the laser medium 1 are
Although the cooling medium 16 is sprayed onto the lamp, if only one excitation lamp 4 is provided, then one injection port is provided corresponding to the lamp 4, and only one of the main surfaces needs to be cooled. Not only the main surface of the laser medium 1 but also the main surface on the opposite side, a sufficient cooling effect can be obtained when the plate thickness of the laser medium 1 is thin.

〔The invention's effect〕

As described above, the solid-state laser device according to the present invention,
Since the refrigerant is blown almost vertically to at least the high temperature portion of the high temperature portion and the low temperature portion of the laser active medium excited by the excitation lamp, the high temperature portion can be effectively cooled, The distribution can be made uniform. Therefore, it is possible to effectively prevent destruction of the laser active medium due to thermal stress, and to provide a solid-state laser device that performs stable oscillation operation.

[Brief description of drawings]

1 is a sectional view taken along the line I--I of FIG. 3 showing an embodiment of a solid-state laser device according to the present invention, FIG. 2 is a perspective view of a housing body, and FIG. 3 is an external perspective view of the same laser device. 4 is the third
FIG. IV-IV sectional view, FIGS. 5 (a), (b), and (c) are views showing other embodiments of the refrigerant outlet, FIG. 6 is a temperature distribution diagram of the laser medium, and FIG. Is a sectional view taken along line VII-VII of FIG. 8 showing a conventional example of a slab type solid-state laser device, FIG. 8 is an external perspective view of the same laser device, and FIG. 9 is a perspective view of a laser medium.
FIG. 10 is a temperature distribution diagram of the laser medium in the conventional device. 1 ... Laser active medium, 1a, 1b ... Main surface, 3 ... Lamp housing, 3A, 3B ... Housing body, 4 ... Excitation lamp, 16 ... Refrigerant, 18A, 18B ... Refrigerant passage, 39A , 39B
…… Refrigerant jet, 41, 42 …… Refrigerant flow path.

Claims (1)

(57) [Claims] 1. A solid-state laser device in which a laser medium and a pumping lamp are arranged substantially parallel to each other in at least a high temperature portion of a high temperature portion and a low temperature portion of the laser medium which is excited by the pumping lamp. A solid-state laser device, comprising: a jet port that blows a coolant substantially vertically through the cooling medium, and a coolant passage that circulates the coolant along a low-temperature portion from a high-temperature portion of the laser medium.