CN101043118A - Method and apparatus for liquid guided pump beam - Google Patents

Abstract

The invention relates to a method and a device for guiding a pump light beam by a liquid, which belong to the technical field of optics and laser optoelectronics. It contains pump light source, optical coupling device, liquid guiding device and optical fiber. Among them: the optical coupling device receives the pump light from the pump light source; the liquid nozzle, the pump beam coupled by the optical coupling device is coupled into the liquid column ejected from the liquid nozzle; the center line of the coolant collector is aligned with the liquid nozzle The center line of the liquid return pipe, the liquid inlet end communicates with the coolant collector; the radiator and the circulation pump are connected in series, the liquid inlet of the radiator is connected with the liquid outlet of the liquid return pipe, and the output end of the circulation pump It communicates with the lower end of the liquid nozzle; the liquid nozzle, the coolant collector, the liquid return pipe, the radiator and the circulating pump are connected in series to form a liquid guiding device. The invention solves the problem of high-power pumping in solid-state lasers and fiber lasers, can increase the average output power of the lasers, and ensures the stability and reliability of the laser system.

Description

Method and device for liquid guiding pump beam

technical field

The invention relates to a method and a device for guiding a light beam by a liquid, which can be used for a laser resonant cavity and a laser amplifier, and belongs to the technical field of optics and laser optoelectronics.

Background technique

In the field of solid-state lasers and fiber lasers, when high-power solid-state lasers and fiber lasers work, a large amount of pump light needs to be injected into the gain medium.

In the prior art of a fiber laser, as shown in FIG. 1 , it includes a pump source 1 , an optical system 2 , an optical fiber 3 and a heat sink 4 . After the pump beam is compressed and converged by the optical system 2, it is directly incident on the end face of the optical fiber 3 and is absorbed by the optical fiber. The heat distribution at the end of the optical fiber is concentrated, and the temperature is high. It must be cooled, otherwise it will cause the coating layer of the optical fiber to burn. Fiber end burst. Cooling of fiber ends is especially important in high power fiber lasers and high power fiber amplifiers. A commonly used cooling method in the prior art is to place the end of the optical fiber in the metal heat sink 4, and the heat at the end of the optical fiber is dissipated from the heat sink through contact conduction. In this heat dissipation method, the heat sink is only in contact with the side of the optical fiber, and can only perform conduction cooling on the side of the optical fiber, and the heat on the end face of the optical fiber is the most concentrated, so the heat dissipation effect is not good; at the same time, the side cooling also makes the optical fiber very uneven. The temperature distribution of the center, the hot edge of the center is cold, so that a large thermal gradient is formed on the end surface, and the large thermal effect generated by it causes the distortion of the laser beam and reduces the beam quality; the cooler outer part of the fiber restricts the hotter inner expansion. A large mechanical stress is generated in the fiber, which will lead to cracks in the fiber in severe cases. In addition, due to the small diameter of the optical fiber (less than 1mm), in order to ensure heat dissipation, the heat sink must be in close contact with the side of the optical fiber without being too tight to cause stress on the optical fiber, so the processing accuracy of the heat sink must be very high.

In the prior art of solid-state lasers, the pump beam is incident on the end face, side face or other pumping faces of the solid-state laser medium directly or after passing through the optical system. The heat distribution on the incident end surface is concentrated and the temperature is high. The solid laser medium must be cooled, otherwise the thermal effect caused by the temperature difference in the laser medium activation area will make the laser work unstable, the beam quality will decrease, and the thermal stress caused by the temperature difference will cause the crystal to deform. , overheating can easily cause the end film layer to burn easily, and the solid medium will burst in severe cases. Therefore, high-efficiency heat dissipation and reduction of thermal effects are usually the main factors considered when designing high average power systems. The commonly used cooling methods in the prior art include liquid cooling and conduction cooling, both of which cool the side of the crystal, which cannot solve the problem of overheating of the end face and the center of the crystal, so the heat dissipation effect is not good; at the same time, because the center is hot and the edges are cold, the crystal The temperature distribution is more uneven, and the thermal effect and thermal stress cannot be effectively reduced. As shown in Figure 2, 5 is a crystal, conduction cooling is to use the metal heat sink 4 in close contact with the solid laser medium, and realize heat dissipation through contact conduction, because in this heat dissipation method, the quality of the cooling joint surface between the heat sink and the solid laser medium is not Very high (especially the curved surface), so the heat dissipation effect is not good. In order to ensure heat dissipation, the processing accuracy of the heat sink must also be very high. As shown in FIG. 3 , liquid cooling is impossible for the cooling liquid 6 to sufficiently cool the few millimeters at the end of the crystal due to the volume covered by the O-ring 17 .

Contents of the invention

The purpose of the present invention is to propose a method and device for guiding the pump beam by liquid, which overcomes the heat dissipation problem of the pumped end face in the prior art, and adopts the method and device for guiding the pump beam by liquid to realize good heat dissipation of the pumped end face , effectively improving the thermal gradient at the end, reducing thermal effects and thermal stress, so that the original metal heat sink only needs to play a clamping role, which solves the contradiction between pump laser injection and mechanical clamping structure, and reduces the clamping structure. Processing accuracy requirements, thus solving the problem of high-power pumping in solid-state lasers and fiber lasers, ensuring the stability and reliability of the laser system.

One of the features of the present invention is that it contains a pumping light source, an optical coupling device 8, a liquid guiding device 9 and an optical fiber 3, wherein:

The optical coupling device 8 receives the pumping light emitted by the pumping light source;

The liquid nozzle 10, the pump beam coupled by the optical coupling device 8 is coupled into the liquid column 15 ejected by the liquid nozzle 10 through the transparent window at the front end of the liquid nozzle 10;

The coolant collector 11 is open at one end, the centerline of the coolant collector is aligned with the centerline of the liquid nozzle 10, and the outlet end of the coolant collector 11 is inserted into the input end of the optical fiber 3, and the liquid nozzle 10 The centerline of the ejected liquid column 15 is precisely aligned with the centerline of the optical fiber 3;

The liquid return pipe 12, the liquid inlet end communicates with the lower bottom of the coolant collector 11;

The radiator 14 and the circulation pump 13 are connected in series, the liquid inlet of the radiator 14 is connected with the liquid outlet of the liquid return pipe 12, and the output end of the circulation pump 13 is connected with the liquid return pipe 12 through the liquid return pipe 12. The liquid inlet at the lower end of the liquid nozzle 10 is connected;

The closed loop of the liquid column 15 formed by the liquid nozzle 10 , the cooling liquid collector 11 , the liquid return pipe 12 , the radiator 14 and the circulation pump 13 connected in series forms a liquid guiding device 9 .

The optical fiber 3 can be replaced by a laser crystal 16 completely immersed in the cooling liquid collector 11 .

The length of the liquid column 15 produced by the liquid nozzle 10 is between 1 time and 10000 times the diameter of the liquid column 15 .

The second feature of the present invention is that it contains: a pumping light source, an optical coupling device 8, a liquid guiding device 9 and an optical fiber 3, wherein:

The optical fiber 3 has a laser output port;

The liquid guiding device 9 contains: a cooling liquid cavity 17, a liquid return pipe 12, a radiator 14 and a circulating pump 13, wherein:

Cooling liquid cavity 17, the cavity is filled with cooling liquid 6, and one end where the optical fiber 3 input port is located passes through the axial side of the cooling liquid cavity 17 closed by the O-ring 7 and enters the cavity, and is fixed on the inner wall of the cavity , the other side of the cooling liquid chamber 17 along the axial direction is connected to the output port of the optical coupling device 8, the pumping light output by the pump light source is coupled into the cooling liquid 6 in the cavity after passing through the optical coupling device 8, and then along the The axial center line of the optical fiber 3 is incident on the port of the input port of the optical fiber 3, and enters the optical fiber 3;

The radiator 14 and the circulation pump 13 are connected in series with each other, the radiator 14 communicates with the bottom of the cooling liquid chamber 17 near the laser output port through the liquid return pipe 12, and the circulation pump 13 is connected to the cooling liquid chamber 17 near the optical fiber input through the liquid return pipe 12 The bottom of the mouth side is connected;

The closed loop of the cooling liquid 6 formed by the cooling liquid cavity 17 , the radiator 14 and the circulation pump 13 connected in series forms a liquid guiding device.

The optical fiber 3 can be replaced by a laser crystal 16 completely immersed in the cooling liquid cavity 17 .

The method and device for guiding the pumping light beam with liquid proposed by the present invention has the following advantages due to the adoption of the above technical scheme: the present invention uses liquid to cool the end surface, and the heat of the pumped end surface can be quickly taken away due to the good thermal conductivity of the liquid , the cooling effect is good, which solves the problem of heat dissipation in the prior art; due to the cooling of the entire end face, the problem of the cold edge of the middle heat is improved, the thermal gradient is reduced, and the thermal effect and thermal stress are reduced, and the beam quality is improved. The deformation of the end is reduced; due to the good heat dissipation of the liquid, the precision requirements for the mechanical clamping structure of the pumped medium are reduced, and the structural design and system installation are easier; the cooling liquid can play the role of refractive index matching , to reduce the reflection of the pump light on the end face, and also act as a filter to eliminate unnecessary pump radiation. The cooling method and device of the present invention are simple, and the implementation effect is remarkable, which solves the problem of high-power pumping in solid-state lasers and fiber lasers, can further improve the output average power of the laser, and ensure the stability and reliability of the laser system. . It has broad application prospects in many fields.

Description of drawings

FIG. 1 is a schematic diagram of a pumping and cooling device of an end-pumped fiber laser in the prior art.

Fig. 2 is a schematic diagram of a conduction cooling device for a solid-state laser in the prior art.

Fig. 3 is a schematic diagram of a liquid cooling device for a solid-state laser in the prior art.

Fig. 4 is a structural schematic diagram of the first embodiment of the method and device for guiding the pump beam with liquid according to the present invention.

FIG. 5 is a schematic structural diagram of a second embodiment of the method and device for guiding a pump beam with a liquid according to the present invention.

FIG. 6 is a structural schematic diagram of a third embodiment of the method and device for guiding a pump beam with a liquid according to the present invention.

FIG. 7 is a schematic structural diagram of a fourth embodiment of the method and device for guiding a pump beam with a liquid according to the present invention.

FIG. 8 is a schematic structural diagram of a fifth embodiment of the method and device for guiding a pump beam with a liquid according to the present invention.

Detailed ways

The present invention is described below in conjunction with accompanying drawing.

The first embodiment of the present invention is shown in FIG. 4 , the device of the present invention includes a coupling system 8 , a liquid guiding device 9 , and an optical fiber 3 for output. The liquid guiding device 9 is composed of a special liquid nozzle 10 , a coolant collector 11 , a liquid return pipe 12 , a circulating pump 13 and a radiator 14 . As shown in Figure 4, the feature of the present invention is that the pumping light through the coupling system 8 is coupled into the liquid column 15 ejected from the nozzle after passing through the special liquid nozzle 10 with a transparent window at the front end, and the center line of the liquid column 15 is accurate. Align the center line of the optical fiber 3, and seal the rear end of a tubular coolant collector 11 on the optical fiber 3. The front liquid inlet of the coolant collector 11 protrudes from the input end of the optical fiber 3 and is open. Align with the liquid nozzle 10, set a liquid return pipe 12 between the coolant collector 11 and the liquid inlet end of the liquid nozzle 10, and set a circulating pump 13 and radiator 14 on the liquid return pipe 12, so that the entire cooling system forms A cooling loop. When the device of the present invention is in operation, the pressure liquid ejected from the liquid nozzle 10 forms a section of liquid column 15, and the pumping light is totally internally reflected in the liquid column 15 and is guided to the input end of the optical fiber 3, and then continues to be transmitted by the optical fiber 3. The liquid sprayed to the input end of the optical fiber 3 is collected by the cooling liquid collector 11 , cooled by the radiator 14 , and returned to the input end of the liquid nozzle 10 through the circulation pump 13 to continue to circulate. The distance between the liquid nozzle 10 and the input end of the optical fiber 3, that is, the effective length of the stable liquid column 15 can be up to 10,000 times the diameter of the liquid column, and an appropriate length can be selected according to the actual situation. In this embodiment, during the process of guiding the pump beam to the end face of the optical fiber 3 through the liquid column 15, the higher the refractive index of the liquid column to the wavelength of the pump beam, the stronger the ability of the liquid column to guide the pump light; The smaller the absorption coefficient of the pump beam wavelength, the less the power of the pump light absorbed by the liquid column, and the higher the guided power; the greater the specific heat of the liquid column, the better the cooling effect of the liquid column on the end of the optical fiber 3 . Therefore, the liquid in the cooling liquid circuit can be a liquid with a relatively high refractive index (at least greater than 1), low absorption of the pump wavelength, and good cooling effect, such as water. In this embodiment, if the pump light is a laser with sufficient beam quality or other well-tuned beams, it can directly enter the nozzle 10 without the coupling system 8 and be directly coupled into the liquid column 15 .

Second Embodiment of the Present Invention As shown in FIG. 5 , the device of the present invention includes the coupling system 8 described in the first embodiment, the liquid guiding device 9 , and the branch optical fiber 3 in the optical fiber coupler. The device setting and working principle are the same as those described in the first embodiment.

The third embodiment of the present invention is shown in FIG. 6 , the device of the present invention includes the coupling system 8 described in the first embodiment, the liquid guiding device 9 , and the laser crystal 3 . The device setting and working principle are the same as those described in the first embodiment. In addition, the entire laser crystal is immersed in the cooling liquid collector 11 to realize liquid cooling by the cooling liquid 6, so that the side of the crystal 5 can also be cooled simply and effectively.

The fourth embodiment of the present invention is shown in FIG. 7 , the device of the present invention includes a coupling system 8 , a liquid guiding device 9 , and a laser crystal 16 . The liquid guiding device 9 is composed of a liquid return pipe 12 , a circulating pump 13 , a radiator 14 and a cooling liquid chamber 17 . The feature of the present invention is that the coupling system 8, the cooling liquid cavity 17 and the crystal 16 jointly form a closed cavity, which is filled with the cooling liquid 6, and the liquid return pipe 12 is arranged on the cooling liquid cavity 17, and a liquid return pipe 12 is provided with a The circulation pump 13 and the radiator 14 make the whole cooling system form a cooling circulation loop. The pump light is incident on the end face of the crystal 16 through the coupling system 8 and is absorbed by the crystal. Almost the entire laser crystal 16 is immersed in the cooling liquid 6 so that it can be cooled sufficiently effectively.

The fifth embodiment of the present invention is shown in FIG. 8 , the device of the present invention includes a coupling system 8 , a liquid guiding device 9 , and an optical fiber 3 . The liquid guiding device 9 is composed of a liquid return pipe 12 , a circulating pump 13 , a radiator 14 and a cooling liquid chamber 17 as described in the fourth embodiment. The feature of the present invention is that the coupling system 8 and the cooling liquid chamber 17 jointly form a closed chamber, which is filled with the cooling liquid 6, and the liquid return pipe 12 is arranged on the liquid return pipe 17, and a circulation pump 13 is arranged on the liquid return pipe 12 And radiator 14, make whole cooling system form a cooling circulation loop. The pump light is incident on the end face of the fiber through the coupling system 8 and absorbed by the fiber. The fiber ends are immersed in the cooling liquid so that they can be fully and effectively cooled.

Claims (5)

1, the system of liquid guided pump beam is characterized in that containing pump light source, optical couping device (8), liquid-conducting device (9) and optical fiber (3), wherein:

Optical couping device (8) is accepted the pump light that pump light source is sent;

Fluid injector (10), the pump beam of process optical couping device (8) coupling is coupled in the fluid column (15) of described fluid injector (10) ejection by the transparent window of fluid injector (10) front end;

Cooling fluid collector (11), one end is the opening shape, the center line of the center line alignment liquid nozzle (10) of this cooling fluid collector, and the port of export of this cooling fluid collector (11) has inserted the input of optical fiber (3), is accurately aimed at the center line of optical fiber (3) by the center line of the fluid column (15) of fluid injector (10) ejection;

Liquid back pipe (12), liquid feeding end is communicated with the lower bottom part of cooling fluid collector (11);

Radiator (14) and circulating pump (13), series connection mutually, the inlet of this radiator (14) links to each other with the liquid outlet of described liquid back pipe (12), and the output of circulating pump (13) is communicated with the inlet of opening in described fluid injector (10) lower end through liquid back pipe (12);

The closed circuit of the fluid column (15) that described fluid injector (10), cooling fluid collector (11), liquid back pipe (12), radiator (14) and circulating pump (13) serial connection constitute has formed a liquid-conducting device (9).

2, the system of liquid guided pump beam according to claim 1 is characterized in that, the available whole laser crystal (16) that is immersed in the cooling fluid collector (11) of described optical fiber (3) replaces.

3, the system of liquid guided pump beam is characterized in that containing pump light source, optical couping device (8), liquid-conducting device (9) and optical fiber (3), wherein:

Optical fiber (3) has a laser output;

Liquid-conducting device (9) contains: cooling sap cavity (17), liquid back pipe (12), radiator (14) and circulating pump (13), wherein:

Cooling sap cavity (17), be full of cooling fluid (6) in the cavity, one end at optical fiber (3) place, input port passes by a side vertically of the cooling sap cavity (17) of O RunddichtringO (7) sealing and enters in the cavity, and be fixed on the cavity inner wall, the opposite side vertically of cooling sap cavity (17) links to each other with the output port of optical couping device (8), be coupled to behind the pump light process optical couping device (8) of pump light source output in the cooling fluid (6) in the cavity, longitudinal center line along optical fiber (3) incides on the port of optical fiber (3) input port again, enters optical fiber (3);

Radiator (14) and circulating pump (13), series connection mutually, radiator (14) is communicated with the bottom of cooling sap cavity (17) near laser output one side by liquid back pipe (12), and circulating pump (13) is communicated with the bottom of cooling sap cavity (17) near optical fiber input port one side by liquid back pipe (12);

The closed-loop path of the cooling fluid (6) that described cooling sap cavity (17), radiator (14) and circulating pump (13) serial connection constitute has formed a liquid-conducting device.

4, the system of liquid guided pump beam according to claim 3 is characterized in that: the available whole laser crystal (16) that is immersed in the cooling sap cavity (17) of described optical fiber (3) replaces.

5, the system of liquid guided pump beam according to claim 1 is characterized in that: the length of the fluid column (15) that described fluid injector (10) produces is between 1 times to 10000 times of fluid column (15) diameter.

Images