JPH08191164A - Solid-state laser - Google Patents

Abstract

PURPOSE: To prevent a solid-state laser from being overheated by effectively cooling the terminal electrodes of an exciting lamp, wherein the solid-state laser has such a structure that the exciting lamp is housed in a cavity equipped with an exciting light transmitting window on a solid-state laser medium side, and the exciting lamp is cooled down in a flow of medium introduced into the cavity. CONSTITUTION: Both end electrodes of exciting lamps 8 are separately or collectively are surrounded through the intermediary of empty gaps 100, and flow path guides 11 are provided inside the cavities 15a so as to restrain coolant which flows into the cavities 15a from flowing out of the cavities 15a without passing through either of the empty gaps 100.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser used in a laser processing apparatus or the like, and a solid-state laser medium is used as a laser medium for generating and amplifying laser light by receiving irradiation of excitation light. The excitation lamp for irradiating the is housed in a cavity having an inlet and an outlet for the refrigerant with an opening closed on the laser medium side by the excitation light transmitting window, and the excitation lamp is irradiating the excitation light in the flow of the refrigerant. It relates to a cooled solid-state laser.

[0002]

2. Description of the Related Art Conventionally, in this type of solid-state laser, a straight tube-shaped lamp has been used as an excitation lamp, and this lamp is arranged inside a tunnel-shaped reflector having a reflecting surface whose cross section is arcuate or semi-elliptical. , A rectangular solid laser medium with a transverse cross section, which is placed so that its longitudinal direction is parallel to the axial direction of the lamp, is irradiated with direct light from the lamp and reflected light from the reflector to apply light energy to the laser medium. It has a structure that absorbs and generates and amplifies laser light.
As the excitation lamp, a gas discharge lamp filled with a gas for light emission such as Xe or Kr is used in order to increase the ratio of light energy to the input energy, but still most of the energy consumed is generated by heat. Therefore, in order to cool the reflector and the lamp, a coolant such as pure water is flowed around the lamp and the inner surface of the reflector for cooling. FIG. 3 shows an example of the structure of a gas discharge type excitation lamp for pulsating a laser beam. A rod-shaped terminal electrode 4 is formed on each of the small diameter portions on both axial sides of a straight tubular discharge tube 1 made of quartz glass. And 5 are inserted, and both ends of the discharge tube 1 are welded to the anode terminal 2 and the cathode terminal 3 that draw these terminal electrodes 4 and 5 to the outside, so that the inside of the discharge tube 1 is kept airtight. The terminal electrodes 4 and 5 are composed of electrode cooling portions 4A and 5A and electrode tip portions 4B and 5B, respectively. However, during discharge, the electrode tip portions 4B and 5B generate a large amount of heat and become high in temperature. Part 4A, 5A
To the refrigerant through the small diameter portion of the discharge tube 1. In order to place the excitation lamp in the flow of the refrigerant, the excitation lamp and the reflector are housed in a cavity formed by a metal block having a vertically elongated deep recess and a lid plate closing the recess. . The metal block is formed with an inlet for introducing a refrigerant and an outlet for discharging a refrigerant, and
An opening is formed on the solid-state laser medium side, that is, on the bottom surface of the recess. This opening is closed by a pumping light transmitting window, and the pumping light transmitting window absorbs light having a wavelength that does not contribute to the generation of laser light to prevent unnecessary heating of the laser medium. Do not mix the refrigerant and the refrigerant on the excitation lamp side.

In the conventional solid-state laser configured as described above, in addition, in order to effectively conduct heat from the small diameter portion of the discharge tube 1, as shown in FIG. 4, the excitation lamp is made of straight-tube quartz glass. In the flow tube, the refrigerant flowing from the vicinity of the upstream side terminal 2 having a relatively low temperature is caused to flow near the excitation lamp due to the pressure difference between the upstream side and the downstream side,
The heat is taken away by the refrigerant.

[0004]

As described above, the conventional method using the flow tube for effectively cooling the electrode cooling portion has the following problems. (B) The thickness of the ring-shaped refrigerant layer between the flow tube and the excitation lamp cannot be set sufficiently large due to the size of the reflector, and therefore the temperature of the refrigerant easily rises and the downstream side of the excitation lamp. In this case, the temperature of the refrigerant rises considerably, the temperature difference with the downstream electrode cooling part becomes small, and the cooling of the downstream electrode cooling part is not performed effectively.On the other hand, between the electrode cooling part and the discharge tube small diameter part, Since the heat of the electrode cooling part is discharged to the outside through the discharge tube small-diameter portion, the gap cannot be large. Therefore, due to the thermal expansion of the electrode cooling part, the gap disappears and the discharge tube small-diameter portion is expanded. Force is applied and the discharge tube is easily broken.

(B) When the refrigerant flowing into the flow tube is vaporized around the high temperature electrode cooling section, the vapor of the refrigerant exists in the space between the flow tube and the excitation lamp on the downstream side along the excitation lamp, and this is the excitation lamp. As a result, the amount of refrigerant flowing into the flow tube is reduced, and the cooling effect particularly on the downstream electrode portion is further reduced, so that the discharge tube is more easily broken.

(C) Due to the surface reflection and absorption by the flow tube, the energy of the excitation light with which the solid-state laser medium is irradiated is reduced by about 10%, and the oscillation efficiency of the laser is reduced. (D) Miniaturization of the reflector is restricted because the flow tube is inserted. As a method of solving these problems, a method of increasing the discharge pressure of a pump that sends out the refrigerant is conceivable, but there are problems of pressure resistance of the cavity and cost increase due to an increase in size of the pump.

It is an object of the present invention to provide a solid-state laser having a cooling structure capable of supplying a sufficient amount of cooling medium to the pump lamp, especially around the both electrode cooling parts thereof, so that the temperature rise of the cooling medium is not a problem. .

[0008]

In order to solve the above problems, in the present invention, a solid-state laser having the structure described at the beginning, that is, a laser beam is generated by receiving excitation light irradiation,
An excitation lamp for irradiating a solid-state laser medium to be amplified is housed in a cavity having an inlet and an outlet for a refrigerant, which is provided with an opening on the laser medium side that is closed by an excitation light transmission window, and the excitation lamp during excitation light irradiation is a refrigerant. A solid-state laser that is cooled in a flow of a cavity, as described in claim 1, wherein both terminal electrode parts of the excitation lamp are individually or collectively enclosed in the cavity through a cavity, and a coolant inlet of the cavity is provided. The laser is provided with a flow path guide that does not allow any of the refrigerant flowing into the cavity from the inside of the cavity to pass through none of the voids and flow toward the refrigerant outlet.

In this case, it is preferable that the gap between the terminal electrode portion and the flow path guide is substantially constant in the circumferential direction of the terminal electrode portion. Further, the length of the inner circumferential surface of the void portion of the flow path guide that surrounds the terminal electrode portion via the void in the refrigerant flow direction covers the entire length of the terminal electrode portion in the refrigerant flow direction as described in claim 3. The length is preferable.

[0010]

In the present invention, the cooling effect when the object to be cooled is cooled in the flow of the refrigerant is determined by the mass flow of the refrigerant flowing along the object to be cooled, and the cavity is considered. The purpose of the invention is to form a cooling structure capable of flowing the refrigerant sent inward as much as possible along the terminal electrode portion. In the solid-state laser having the structure described at the beginning of the present invention, the coolant sent into the cavity is inevitably used in combination with the excitation lamp and the reflector to uniformly irradiate the light-receiving surface of the laser medium. However, in the present invention, since the laser loses its function when the excitation lamp is broken, the aim is to provide a cooling structure in which the entire amount of the refrigerant fed can be used to cool the terminal electrode portion. It was Even if the total amount of refrigerant is used to cool both terminal electrode parts first, the terminal electrode parts have a small mass,
Since the heat capacity is small, the temperature of the refrigerant after cooling does not rise so much, and the discharge tube body of the excitation lamp and the reflector can be sufficiently cooled. Therefore, as described in claim 1, this cooling structure encloses both terminal electrode parts of the excitation lamp in the cavity individually or collectively via a cavity, and a refrigerant flowing from the refrigerant inlet of the cavity into the cavity. Out of
When the cooling structure is provided with a flow path guide that does not pass the refrigerant toward the refrigerant outlet without passing through any of the gaps, the excitation lamp is formed in a straight tube shape, and the refrigerant inlet of the cavity is one of the longitudinal direction of the excitation lamp. When it is provided on the side, the refrigerant cools the upstream side terminal electrode portion-excitation lamp body, the reflector-downstream side terminal electrode portion in this order, and both terminal electrode portions in total amount. Further, when the refrigerant inlet of the cavity is provided at an intermediate position in the longitudinal direction of the excitation lamp, the refrigerant that has flowed in from the refrigerant inlet is divided into two directions in the cavity, and the length of the excitation lamp main body is about 1/2 of the longitudinal direction. The length of the reflector in the longitudinal direction of the excitation lamp is about 1 / 2-in the order of the terminal electrodes,
In addition, the total amount of both terminal electrode portions is halved, and the total amount of both terminal electrode portions cools the total amount of the refrigerant. on the other hand,
Looking at the temperature distribution in the refrigerant, the temperature is always high in the longitudinal range of the reflector on the excitation lamp side and the reflector reflection surface side, low in the middle, and the temperature distribution is valley-shaped, and the reflector is cooled in the cooling order. Even in the flow of the cooling medium that was previously cooled, the cooling medium introduced around the terminal electrode section of the excitation lamp is always directed toward the valley of the temperature of the terminal electrode section unless the radial width of the void is extremely small. Since the heat is transferred, the terminal cooling part can be effectively cooled. Further, when the excitation lamp is formed in a vertically long U-shape with a narrow interval between two opposite sides for the purpose of uniform irradiation of the solid-state laser light receiving surface, both terminal electrodes are upstream of the flow of the refrigerant. Since they are lined up in a horizontal row on the side, both the terminal electrode portions can be collectively cooled with the entire amount of the refrigerant.

When the cooling structure of the terminal electrode portion is formed as described above, the gap between the terminal electrode portion and the flow path guide is substantially constant in the circumferential direction of the terminal electrode portion as described in claim 2. Then, the thickness of the refrigerant layer around the terminal electrode portion becomes uniform, and when the flow rate of the refrigerant around the terminal electrode portion is constant,
Cooling of the terminal electrode portion is most often performed. Claim 3
As described, the length in the flow direction of the refrigerant of the cavity inner peripheral surface of the flow path guide that surrounds the terminal electrode portion through the void, and the length to cover the entire length of the flow direction of the refrigerant of the terminal electrode portion,
Even if the flow speed of the refrigerant is slow and it is not possible to make the flow along the terminal electrode part along the entire length of the terminal electrode part only by the inertia of the flow, the refrigerant is forced to the terminal in the same channel cross section. The cooling can be performed along the electrode portion, and the terminal electrode portion can be effectively cooled.

[0012]

FIG. 1 shows an example of the structure of a solid-state laser provided with a cooling structure for an excitation lamp terminal electrode portion according to an embodiment of the present invention. In this embodiment, the excitation lamp is a straight-tube gas discharge type excitation lamp for the purpose of pulse oscillation of laser light. The laser is, in this example, a solid-state laser medium 1 cut out from a YAG crystal in a slab shape and injected with Nd ^3+.
0, a light guide path 12 arranged on both sides in the longitudinal direction of the slab-shaped solid-state laser medium 10 to guide the laser light generated and amplified in the laser medium 10 in the vertical direction of the paper surface, and the laser medium 10 and the light guide path 12. A metal block 15 for holding, which has a long groove-shaped recess 15a formed in the vertical direction of the paper and an opening 15b formed on the bottom of the recess 15a, an excitation light transmitting window 9 for closing the opening 15b, and a metal block. 15
Lid plate 14 that closes the concave portion 15a of the hollow portion 15a to make the concave portion 15a a hollow space, and the excitation lamp 8 housed in the hollow space 15a.
A reflector 7, which is housed in the hollow space 15a and reflects the emitted light of the excitation lamp 8 toward the laser medium 10, and a flow path guide 11 which forms a terminal electrode cooling structure of the excitation lamp according to the present invention. It is organized as an element.
The lid plate 14 holds the terminals of the excitation lamp 8 and holds the excitation lamp 8 in the hollow space 15a.
Is attached.

When the laser light is pulsed, pure water is introduced as a refrigerant into the hollow space 15a from a refrigerant inlet (not shown) formed in the upper portion of the hollow space 15a in the plane of the drawing, and the refrigerant in which the laser medium 10 is located is located. While introducing pure water also into the flow path, a capacitor voltage is applied at a predetermined time interval between the anode terminal 2 and the cathode terminal 3 of the excitation lamp 8 so that each tip portion 4B of the terminal electrodes 4, 5 (FIG. 3). , 5B to generate a discharge, which excites the gas for light emission in the discharge tube 1 to generate a pulsed light. This light is directly reflected by the reflector and transmitted through the excitation light transmitting window 9 to irradiate the laser medium 10. The excitation light transmission window 9 is made of filter glass and absorbs ultraviolet light that does not contribute to the generation and amplification of the laser light to prevent unnecessary heating of the laser medium 10. The laser light generated in the laser medium 10 is the medium 1
In 0, while being totally reflected by the excitation light receiving surface of the medium 10, the laser light travels in a zigzag direction up and down on the paper surface, and the laser light traveling downward reaches the total reflection mirror (not shown) through the lower light guide path 12. Here, the light is totally reflected, passes through the light guide path 12 again, passes through the laser medium 10, and is amplified during the passage,
It reaches an output mirror (not shown) through the upper light guide path 12, a part of which penetrates the output mirror and is emitted to the outside as output light, and the rest is reflected and enters the upper light guide path 12 again.

Since the discharge in the excitation lamp 8 is continuously generated in a pulsed manner, the heat generated at the tip of the terminal electrode (FIG. 3) is transferred to the electrode cooling parts 4A and 5A one after another, and the temperature of the electrode cooling part is increased. Raise. As shown in FIGS. 1 and 2, the electrode cooling parts 4A and 5A are provided with a space 100 by the flow path guide 11.
The entire amount of the cooling water sent from the upper part of the figure into the cavity 15a passes through this void 100.
The flow path guide 11 includes electrode cooling parts 4A and 5A (see FIG. 3).
And a rectangular metal plate having a thickness equal to the length of the tunnel-shaped reflector 7 and the same contour shape as the cross-sectional shape of the tunnel-shaped reflector 7. At this time, a circular hole 11a centered on the central axis position of the excitation lamp 8 is formed. The circular hole 11a has a diameter larger than that of the main body of the discharge tube 1 (FIG. 3) of the excitation lamp 8. As a result, a space 100 is formed between the electrode cooling parts 4A and 5A and the hole 11a.

Pure water (hereinafter referred to as "cooling water") passing through the gap 100 first cools the upper electrode cooling portion 4A and enters the inside of the reflector 7, and the speed thereof is reduced in this inner space to slowly move the excitation lamp 8. The main body of the discharge tube 1 (FIG. 3) and the reflector 7 are cooled, and the entire amount of the cooling water again passes through the space 100 between the lower electrode cooling portion 5A and the hole 11a of the flow path guide 11, and the lower electrode cooling portion 5a. To cool the hollow space 15a
It flows out from the lower outlet. The electrode cooling part 4A tries to be heated to a high temperature by the heat transfer from the electrode tip part, but the heat is removed by a sufficient amount of cooling water to avoid the heating, and the electrode cooling part has a small size and a heat capacity. Since it is small, the temperature of the cooling water that has passed through the gap 100 around the upper electrode cooling portion 4A does not rise so much, and when this cooling water cools the excitation lamp 8 and the reflector 7, the excitation lamp 8 side The temperature of the cooling water does not rise so much in the middle, and the temperature of the cooling water does not rise so much in the middle, so that the temperature of the excitation lamp 8 side and the reflector 7 side increases.
The cooling water that has spread to the side collects again and the lower electrode cooling unit 5
Since the temperature difference between the lower electrode cooling part 5A and the cooling water when passing through the space around A does not become so small, the lower electrode cooling part 5A is also cooled to almost the same level as the upper electrode cooling part 4A. In FIG. 1, two hollow spaces 15a,
The flow passage cross section of each refrigerant inlet of 15a is made sufficiently larger than the flow passage cross section of each refrigerant outlet so that both cavity spaces 15a, 1
Refrigerant supply to 5a is performed in parallel to equalize the refrigerant flow rates in both spaces. Further, the cooling of the hollow spaces 15a, 15a and the cooling of the laser medium 10 are performed in different flow paths.

Although not shown in FIG. 1, the flow path guide 11 is fixed to both terminals of the reflector 7 in the vertical direction on the paper surface with screws. Therefore, when inserting both terminals 2 and 3 (FIG. 3) of the excitation lamp 8 into the current terminal 13 (FIG. 1) for sandwiching, the reflector 7 and the flow passage guide 11 are integrated with a screw, and then the excitation lamp 8 is inserted and pinched in the current terminal 13 through the hole 11a of the flow path guide 11. Since the discharge tube 1 (FIG. 3) of the excitation lamp 8 is made of quartz glass and is easily damaged by impact, the reflector 7 has a split structure in which the plane parallel to the paper surface of FIG. When it is desired to insert and pinch both terminals 2, 3 (FIG. 3) of 8 into the current terminal 13 (FIG. 1) and insert the excitation lamp 8 from both sides into the hollow space 15a, the flow path guide Reference numeral 11 also has two split structures in which a plane parallel to the paper surface of FIG. 1 is used as a split surface, and each of them is integrated with each piece of the reflector having the split structure.

[0017]

According to the present invention, as described in claim 1, the solid-state laser having the structure described at the beginning is enclosed in a cavity with both terminal electrodes of the excitation lamp individually or collectively via a gap. Of the refrigerant that has flowed into the cavity from the refrigerant inlet of the cavity, since a flow path guide that does not allow the refrigerant to go to the refrigerant outlet without passing through any of the voids is provided, the refrigerant sent into the cavity The entire terminal volume of the excitation lamp is cooled, and a large amount of heat in the terminal electrode section is carried away by the refrigerant, so that overheating of the terminal electrode section does not occur and destruction of the discharge tube of the excitation lamp due to thermal expansion of the terminal electrode section is prevented. As a result, the terminal electrode portion does not become a factor that determines the life of the excitation lamp, and the life of the lamp is dramatically extended. Moreover, the conventional flow tube is no longer required, the loss of excitation light energy is reduced, and the laser oscillation efficiency is improved. Furthermore, the reflector can be downsized, and the laser can be downsized to a small extent.

Further, as described in claim 2, the gap between the terminal electrode portion and the flow path guide is made substantially constant in the circumferential direction of the terminal electrode portion, so that the thickness of the refrigerant layer around the terminal electrode portion is uniform. Therefore, when the flow rate of the refrigerant around the terminal electrode portion is constant, the cooling of the terminal electrode portion is performed best, so that the efficiency of use of the refrigerant is maximized. Further, as described in claim 3, the length in the flow direction of the refrigerant of the inner peripheral surface of the void portion of the flow path guide that surrounds the terminal electrode portion via the void is covered by the entire length of the terminal electrode portion in the refrigerant flow direction. By making the length, the flow velocity of the refrigerant flow along the terminal electrode portion is small,
Even if it is not possible to make the refrigerant flow along the entire flow direction of the terminal electrode section in the same flow path cross-section only by the inertia of the flow, make the refrigerant flow along the same flow path cross section of the terminal electrode section in the flow direction of the refrigerant. It is possible to improve the utilization efficiency of the refrigerant.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a solid-state laser structure provided with a cooling structure for a terminal electrode portion of an excitation lamp according to the present invention.

2 is a sectional view taken along the line AA in FIG.

FIG. 3 is a sectional view showing a structural example of a straight tube excitation lamp.

FIG. 4 is a cross-sectional view showing an example of a conventional cooling structure for a straight tube excitation lamp.

FIG. 5 is a sectional view of an essential part for explaining how to cool an excitation lamp in a conventional general solid-state laser having no special cooling structure for a straight tube excitation lamp.

6 is a cross-sectional view of a main part for explaining how to cool an excitation lamp in a solid-state laser having the cooling structure shown in FIG.

[Explanation of symbols]

 1 Discharge Tube 2 Anode Terminal 3 Cathode Terminal 4 Terminal Electrode 4A Electrode Cooling Section 4B Electrode Tip 5 Terminal Electrode 5A Electrode Cooling Section 5B Electrode Tip 7 Reflector 8 Excitation Lamp 9 Excitation Light Transmission Window 10 Laser Medium 11 Flow Path Guide 11a Hole 14 Cover Plate 15 Metal Block 15a Recess (Cavity Space, Cavity) 15b Opening 100 Void

Claims (3)

[Claims] 1. An excitation lamp for irradiating a solid laser medium for generating and amplifying laser light upon receiving excitation light is provided with an opening closed on the laser medium side by an excitation light transmitting window, and an inlet and an outlet for a refrigerant. Housed in a cavity having and
In the solid-state laser in which the excitation lamp is cooled in the flow of the refrigerant during irradiation of the excitation light, both terminal electrodes of the excitation lamp are individually or collectively enclosed in the cavity through a gap, and the refrigerant inlet of the cavity The solid-state laser is provided with a flow path guide that does not allow a refrigerant, which does not pass through any of the voids and heads toward the refrigerant outlet, to exist in the refrigerant flowing into the cavity from. 2. The solid-state laser according to claim 1, wherein the gap between the terminal electrode portion and the flow path guide surrounding the terminal electrode portion is substantially constant in the circumferential direction of the terminal electrode portion. 3. The method according to claim 1 or 2, wherein
The solid-state laser characterized in that the length of the inner circumferential surface of the void portion of the flow path guide surrounding the terminal electrode portion through the void in the refrigerant flow direction is a length that covers the entire length of the terminal electrode portion in the refrigerant flow direction. .