A UV laser

Abstract

The present invention relates to an ultraviolet laser, comprising a substrate, an optical cavity mounted on the substrate, a pump source and an ultraviolet laser generating mechanism, wherein the ultraviolet laser generating mechanism is arranged in the optical cavity, and a first cooling unit for cooling the optical cavity is arranged on the substrate; the ultraviolet laser generating mechanism is also equipped with a Q-switched driver, the Q-switched driver and the pump source are both mounted on the substrate, located outside the optical cavity and connected to the ultraviolet laser generating mechanism, and a second cooling unit for cooling the Q-switched driver and the pump source is arranged on the substrate. In the present invention, the Q-switched driver and the pump source are arranged outside the optical cavity, which can achieve thermal isolation of the optical cavity from other heat sources, reduce the thermal effects of these heat sources on the optical cavity, effectively improve the working stability of the ultraviolet laser generating mechanism, and help to improve the application range of air-cooled ultraviolet lasers; the optical cavity, the Q-switched driver and the pump source can be zoned for temperature control, which can save energy consumption.

Description

Technical Field

[0001] The invention belongs to the technical field of lasers, and in particular relates to an ultraviolet laser. Background Art

[0002] The semiconductor laser end-pumped ultraviolet laser has the characteristics of good beam quality and high peak energy, and is widely used in laser processing fields such as marking and PCB cutting. There are mainly two types of ultraviolet lasers: water-cooled lasers and air-cooled lasers, among which:

[0003] Water-cooled UV lasers are large in size and have the risk of cooling medium leakage, so they cannot be used in high-end applications such as medical and semiconductors where leakage needs to be avoided. Although air-cooled UV lasers do not have this leakage risk, the power of most air-cooled UV lasers will drift with changes in ambient temperature and cannot be used in processing that requires high power stability. Summary of the invention

[0004] The invention relates to an ultraviolet laser, which can at least solve some defects of the prior art.

[0005] The present invention relates to an ultraviolet laser, comprising a substrate, an optical cavity, a pump source and an ultraviolet laser generating mechanism.

[0006] The optical cavity is mounted on the substrate, the ultraviolet laser generating mechanism is arranged in the optical cavity, and a first cooling unit for cooling the optical cavity is arranged on the substrate;

[0007] The ultraviolet laser generating mechanism is also equipped with a Q-switched driver. The Q-switched driver and the pump source are both mounted on the substrate, located outside the optical cavity and connected to the ultraviolet laser generating mechanism. A second cooling unit for cooling the Q-switched driver and the pump source is provided on the substrate.

[0008] As one of the embodiments, the first cooling unit includes a first semiconductor refrigerator and a first radiator, the first semiconductor refrigerator is sandwiched between the optical cavity and the first radiator, and the cold end and the hot end of the first semiconductor refrigerator are respectively facing the optical cavity and the first radiator.

[0009] As one of the implementation modes, the second cooling unit includes a second radiator, and the Q-switched driver and the pump source are both mounted on the second radiator.

[0010] As one of the embodiments, the second cooling unit further includes a second semiconductor refrigerator, which is sandwiched between the pump source and the second radiator, and the cold end and the hot end of the second semiconductor refrigerator are respectively facing the pump source and the second radiator.

[0011] As one of the embodiments, the ultraviolet laser also includes a collimator extension tube, which is located outside the optical cavity, connected to the side wall of the optical cavity and located on the ultraviolet light emission path of the ultraviolet laser generating mechanism, and a collimator is provided in the collimator extension tube.

[0012] As one of the implementation modes, the light incident end of the beam expander is configured as a concave mirror.

[0013] As one of the implementation modes, the distance between the light input end of the beam expander and the ultraviolet light output end of the ultraviolet laser generating mechanism is 160-300 mm.

[0014] As one of the implementation modes, the Q-switched driver and the pump source are located on the same side of the optical cavity and are arranged on both sides of the collimator extension tube.

[0015] As one of the implementation modes, a mounting plate is formed by extending outwardly from the periphery of the optical cavity, and the mounting plate has a mounting area connected to the base and a stress release groove between the mounting area and the optical cavity.

[0016] As one of the implementation modes, the ultraviolet laser further includes an internal air circulation purification device, wherein the internal air circulation purification device is located outside the optical cavity and the two are connected via a gas circulation pipeline.

[0017] The present invention has at least the following beneficial effects:

[0018] In the present invention, the Q-switched driver and the pump source are arranged outside the optical cavity, which can achieve thermal isolation of the optical cavity from other heat sources, reduce the thermal impact of these heat sources on the optical cavity, and effectively improve the working stability of the ultraviolet laser generating mechanism; when the ultraviolet laser is an air-cooled laser, it is beneficial to improve the application range of the air-cooled ultraviolet laser. In addition, the optical cavity, the Q-switched driver and the pump source can be zoned for temperature control, which can save energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 A schematic diagram of the structure of an ultraviolet laser provided in an embodiment of the present invention;

[0021] Figure 2A schematic diagram of a partial explosion structure of an ultraviolet laser provided in an embodiment of the present invention;

[0022] Figure 3 A schematic diagram of the structure of an ultraviolet laser generating mechanism provided in an embodiment of the present invention;

[0023] Figure 4 A schematic diagram of the structure of an optical cavity provided by an embodiment of the present invention;

[0024] Figure 5 A schematic diagram of the installation of a beam expander extension tube provided in an embodiment of the present invention;

[0025] Figure 6 A side view of an ultraviolet laser provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] like Figure 1-Figure 6 The embodiment of the present invention provides an ultraviolet laser, comprising a substrate 7, an optical cavity 1, a pump source 5 and an ultraviolet laser generating mechanism 3,

[0028] The optical cavity 1 is mounted on the base 7, the ultraviolet laser generating mechanism 3 is arranged in the optical cavity 1, and a first cooling unit for cooling the optical cavity 1 is arranged on the base 7;

[0029] The ultraviolet laser generating mechanism 3 is also equipped with a Q-switched driver 6. The Q-switched driver 6 and the pump source 5 are both mounted on the base 7, located outside the optical cavity 1 and connected to the ultraviolet laser generating mechanism 3. A second cooling unit for cooling the Q-switched driver 6 and the pump source 5 is provided on the base 7.

[0030] The Q-switched driver 6 can be an acousto-optic Q-driver, whose normal operating temperature can reach about 60°C and is insensitive to changes in ambient temperature. The connection between the Q-switched driver 6 and the ultraviolet laser generating mechanism 3 is a conventional technology in the art and will not be described in detail here.

[0031] The above-mentioned pump source 5 can be a semiconductor pump source 5, which is generally connected to the ultraviolet laser generating mechanism 3 through the pump fiber 2-1, and couples the pump light into the resonant cavity of the ultraviolet laser generating mechanism 3. Correspondingly, a pump fiber connector 2 is set on the optical cavity 1.

[0032] In this embodiment, the Q-switched driver 6 and the pump source 5 are arranged outside the optical cavity 1, which can achieve thermal isolation of the optical cavity 1 from other heat sources, reduce the thermal impact of these heat sources on the optical cavity 1, and effectively improve the working stability of the ultraviolet laser generating mechanism 3; when the above-mentioned ultraviolet laser is an air-cooled laser, it is beneficial to improve the application range of the air-cooled ultraviolet laser. In addition, the optical cavity 1, the Q-switched driver 6 and the pump source 5 can be zoned for temperature control, which can save energy consumption.

[0033] In one embodiment, if Figure 2 The first cooling unit includes a first semiconductor refrigerator 12 and a first radiator 9. The first semiconductor refrigerator 12 is sandwiched between the optical cavity 1 and the first radiator 9. The cold end and the hot end of the first semiconductor refrigerator 12 face the optical cavity 1 and the first radiator 9 respectively.

[0034] The first radiator 9 is provided with a cooling fan 13 , and the first radiator 9 may further be an air-cooled radiator.

[0035] The first semiconductor refrigerator 12 may include one or more semiconductor cooling sheets. When there are multiple semiconductor cooling sheets, each semiconductor cooling sheet is laid flat on the first heat sink 9. In one embodiment, the maximum cooling capacity of the semiconductor cooling sheet used is 108W. When actually used, the cooling capacity of a single sheet is about 30W, which is in a relatively high efficiency range of the refrigerator.

[0036] The first heat sink 9 is fixedly mounted on the base 7, and the optical cavity 1 can be mounted on the first heat sink 9. The optical cavity 1 and the first heat sink 9 / base 7 are preferably connected in a detachable manner, including but not limited to screw fixing, etc. Furthermore, a heat insulating pad can be provided at the screw installation location for heat insulation treatment.

[0037] The first semiconductor refrigerator 12 cooperates with the first heat sink 9 to reliably cool the optical cavity 1 and take away the heat of the optical cavity 1 .

[0038] In one embodiment, if Figure 2 and Figure 6 The second cooling unit includes a second radiator 8 , and the Q-switched driver 6 and the pump source 5 are both mounted on the second radiator 8 .

[0039] The second radiator 8 is provided with a cooling fan 13 , and the second radiator 8 may further be an air-cooled radiator.

[0040] The second radiator 8 is fixedly mounted on the base 7 , and a detachable connection is preferably used between the Q-switching driver 6 and the second radiator 8 , and between the pump source 5 and the second radiator 8 , including but not limited to screw fixing and the like.

[0041] Further preferably, the second cooling unit also includes a second semiconductor refrigerator, which is sandwiched between the pump source 5 and the second radiator 8, and the cold end and the hot end of the second semiconductor refrigerator are respectively facing the pump source 5 and the second radiator 8.

[0042] The second semiconductor refrigerator may include one or more semiconductor cooling sheets. When there are multiple semiconductor cooling sheets, each semiconductor cooling sheet is laid flat on the second heat sink 8. In this embodiment, one semiconductor cooling sheet can better control the temperature of the pump source 5. In one embodiment, the maximum cooling capacity of the semiconductor cooling sheet is 108W. In actual use, the cooling capacity of a single cooling sheet is about 30W, which is in a relatively high efficiency range of the refrigerator.

[0043] The Q-switched driver 6 and the pump source 5 are located on the same side of the optical cavity 1 , so that they can share a second heat sink 8 .

[0044] In one embodiment, if Figure 3 , shows an optical path diagram of an ultraviolet laser generating mechanism 3, but is obviously not limited to the ultraviolet laser generating mechanism 3 of this composition. The ultraviolet laser generating mechanism 3 includes:

[0045] A first collimating lens 3-1, used for collimating the pump light;

[0046] A second collimating lens 3-2, used to further collimate the light emitted by the first collimating lens 3-1;

[0047] The first resonant cavity reflector 3-3, which serves as a reflector of the resonant cavity, can transmit the pump light and reflect the 1064nm light;

[0048] Nd:YVO4 crystal 3-4, used for radiating 1064nm light by being excited by 878nm light from a pump source;

[0049] Q-switched crystals 3-5, used to generate optical pulses;

[0050] Turning reflectors 3-6 are used to fold the resonant cavity and reduce the volume of the laser;

[0051] The sum frequency crystal 3-7 is used to convert the 1064nm light and the 532nm light into 355nm light;

[0052] Frequency doubling crystals 3-8, used to convert 1064nm light into 532nm light by frequency doubling;

[0053] The second resonant cavity reflector 3-9, the first resonant cavity reflector 3-3 and the turning reflector 3-6 form a resonant cavity for reflecting 1064nm light and 532nm light.

[0054] Among them, the first resonant cavity reflector 3-3, the turning reflector 3-6 and the second resonant cavity reflector 3-9 form a resonant cavity with a folded optical path; the 1064nm light in the resonant cavity generates 355nm ultraviolet light after passing through the frequency doubling crystal 3-8 and the sum frequency crystal 3-7, and the sum frequency crystal 3-7 is provided with a suitable cutting angle. Due to the different refractive indices of the 1064, 532 and 355nm lights in the resonant cavity, the 355nm ultraviolet light is separated and emitted.

[0055] Among them, the output surface of the sum frequency crystal 3-7 constitutes the ultraviolet light output end of the ultraviolet laser generating mechanism 3;

[0056] The Q-switched driver 6 is connected to the Q-switched crystal 3 - 5 .

[0057] In one embodiment, if Figure 1 , Figure 2 and Figure 5 The ultraviolet laser also includes a collimator extension tube 10, which is located outside the optical cavity 1, connected to the side wall of the optical cavity 1 and located on the ultraviolet light emission path of the ultraviolet laser generating mechanism 3, and a collimator 11 is provided in the collimator extension tube 10.

[0058] Preferably, the ultraviolet light beam emitted by the ultraviolet laser generating mechanism 3 is coaxial with the beam expander extension tube 10 .

[0059] Preferably, the beam expander extension tube 10 is detachably connected to the optical cavity 1, which can facilitate disassembly, assembly and maintenance.

[0060] The collimator extension tube 10 is preferably a sealed tube. For example, the laser emitting end (i.e., the end away from the optical cavity 1) of the collimator extension tube 10 is sealed. Transparent glass can also be used to seal the connection between the collimator extension tube 10 and the optical cavity 1. This ensures the stability of the working environment such as the gas pressure in the optical cavity 1.

[0061] The ultraviolet light emitted from the ultraviolet laser generating mechanism 3 (corresponding to the ultraviolet light emitted from the above-mentioned sum frequency crystal 3-7) has a certain divergence angle. In this embodiment, an external collimator extension tube 10 is used to increase the distance between the collimator 11 and the ultraviolet light emitting end of the ultraviolet laser generating mechanism 3, which can increase the beam radius R1 hitting the first lens 11-1 of the collimator 11 (obviously, the first lens 11-1 refers to the lens that first contacts the laser), and the energy density on the lens will be reduced accordingly (the reduction value is the square of the increase in the beam radius), which can significantly extend the service life of the first lens 11-1 of the collimator 11.

[0062] In addition, based on the above scheme, the collimator extension tube 10 is connected to the side wall of the optical cavity 1, which will not adversely affect the optical installation in the optical cavity 1 (that is, the installation of the ultraviolet laser generating mechanism 3); moreover, the collimator extension tube 10 can be manufactured separately at a lower cost.

[0063] In addition, based on the above scheme, the collimator extension tube 10 is placed externally, which not only achieves the purpose of laser beam expansion, but also reduces the heat exchange surface area and heat capacity of the optical cavity 1, which can not only improve the thermal stability of the optical cavity 1, but also reduce the power consumption of temperature control.

[0064] Preferably, the beam expander 11 is disposed at the laser emitting end of the beam expander extension tube 10 , so that the distance between the beam expander 11 and the ultraviolet light emitting end of the ultraviolet laser generating mechanism 3 can be further increased.

[0065] In one embodiment, the distance between the light input end of the beam expander 11 and the ultraviolet light output end of the ultraviolet laser generating mechanism 3 is 160-300 mm, preferably controlled at about 200 mm.

[0066] In a specific embodiment, when the collimator extension tube 10 is not provided, the distance between the light input end of the collimator 11 and the ultraviolet light output end of the ultraviolet laser generating mechanism 3 is 130 mm; when the collimator extension tube 10 is provided, the distance between the light input end of the collimator 11 and the ultraviolet light output end of the ultraviolet laser generating mechanism 3 is 200 mm; the light with a spot radius of 0.2 mm emitted from the sum frequency crystal 3-7 has a spot radius of 0.33 mm and 0.4 mm at 130 mm and 200 mm, respectively, and the spot area ratio of the two places is 0.4 2 / 0.33 2 =1.47. It can be seen that after the collimator extension tube 10 is provided, the radius of the light beam hitting the first lens 11-1 of the collimator 11 can be increased, and the energy density on the lens is reduced accordingly.

[0067] Preferably, the light incident end of the collimator 11 is set as a concave mirror, that is, the first lens 11-1 of the collimator 11 is a concave mirror. After the light beam passes through the concave mirror, the divergence angle is larger, and the risk of subsequent lenses of the collimator 11 being damaged and failing due to ultraviolet light is lower, thereby effectively extending the service life of the collimator 11.

[0068] Preferably, if Figure 1 and Figure 2 The Q-switched driver 6 and the pump source 5 are located on the same side of the optical cavity 1 and are arranged on both sides of the collimator extension tube 10. While reducing the thermal impact on the optical cavity 1, the compactness of the structural layout of the laser can be improved, and the setting of the collimator extension tube 10 will not increase the overall volume of the laser.

[0069] In one embodiment, if Figure 4 The periphery of the optical cavity 1 extends outward to form a mounting plate, and the mounting plate has a mounting area 1-1 connected to the base 7 and a stress release groove 1-2 located between the mounting area 1-1 and the optical cavity 1.

[0070] In the case where the optical cavity 1 is mounted on the first heat sink 9, the mounting plate is connected to the first heat sink 9, for example, threaded holes are provided in the mounting area 1-1.

[0071] By setting a stress release groove 1-2 between the installation area 1-1 and the optical cavity 1, when the first heat sink 9 / substrate 7 / external installation structure is deformed due to changes in ambient temperature, the deformation of the optical cavity 1 will be concentrated at the stress release groove 1-2, so that the stress release groove 1-2 can isolate the influence of the heat sink deformation on the optical cavity 1, greatly reducing the interference of the optical cavity 1 with external deformation, and ensuring the working stability and reliability of the ultraviolet laser generating mechanism 3.

[0072] In traditional designs, the control means for laser power stability generally include whether the heat dissipation power is sufficient, whether the temperature control temperature is stable, and whether the temperature control structure and related algorithms are reasonable; in this embodiment, unlike the traditional control means, the stability of the laser power is improved by setting the above-mentioned stress release grooves 1-2. The method is simple and reliable, easy to control and implement, and the effect of improving the stability of the laser power is very obvious: in actual tests, when the ambient temperature changes from 10°C to 40°C, under the same other conditions, when the above-mentioned stress release grooves 1-2 are not used, the laser power fluctuates by about 15%, while when the above-mentioned stress release grooves 1-2 are used, the laser power fluctuates by about 3%. In particular, combined with the above-mentioned traditional control means, the stability of the laser power can be significantly improved.

[0073] In one embodiment, if Figure 1The ultraviolet laser also includes an air internal circulation purification device 4, which is located outside the optical cavity 1 and the two are connected through a gas circulation pipeline, so that the gas in the optical cavity 1 can be filtered and purified, thereby extending the life of components such as crystals and lenses in the ultraviolet laser generating mechanism 3. Among them, the gas circulation pipeline preferably uses a dust-free Teflon air pipe to reduce adverse effects on the components in the optical cavity 1.

[0074] In a specific embodiment, a semiconductor laser with a pump power of about 30W is used, and an end-pumped Nd:YVO4 crystal 3-4 is used. The crystal doping concentration is 0.2-0.3at%, and the output 355nm laser power is about 5W after LBO and BBO frequency doubling. The electro-optical conversion efficiency of the semiconductor laser is about 50%, and the waste heat is about 30W; the waste heat of the Q-switched driver 6 is about 20W; the waste heat of the frequency doubling temperature control device is about 20W, and the total waste heat is about 105W. The first semiconductor refrigerator 12 uses 4 semiconductor cooling plates, and the second semiconductor refrigerator uses 1 semiconductor cooling plate. The maximum cooling capacity of a single semiconductor cooling plate is 108W. In actual use, the single cooling capacity is about 30W, which is in a relatively high efficiency range of the refrigerator.

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An ultraviolet laser, characterized in that: It includes a substrate, an optical cavity, a pump source and an ultraviolet laser generating mechanism. The optical cavity is mounted on the substrate, the ultraviolet laser generating mechanism is arranged in the optical cavity, and a first cooling unit for cooling the optical cavity is arranged on the substrate; The ultraviolet laser generating mechanism is further provided with a Q-switched driver, the Q-switched driver and the pump source are both mounted on the substrate, outside the optical cavity and connected to the ultraviolet laser generating mechanism, and a second cooling unit for cooling the Q-switched driver and the pump source is provided on the substrate; The ultraviolet laser also includes a collimator extension tube, which is located outside the optical cavity, connected to the side wall of the optical cavity and located on the ultraviolet light emission path of the ultraviolet laser generating mechanism. A collimator is provided inside the collimator extension tube, and the collimator is arranged at the laser emission end of the collimator extension tube; the distance between the light input end of the collimator and the ultraviolet light emission end of the ultraviolet laser generating mechanism is 160~300mm.

2. The ultraviolet laser according to claim 1, characterized in that: The first cooling unit includes a first semiconductor refrigerator and a first radiator. The first semiconductor refrigerator is sandwiched between the optical cavity and the first radiator. The cold end and the hot end of the first semiconductor refrigerator face the optical cavity and the first radiator respectively.

3. The ultraviolet laser according to claim 1, characterized in that: The second cooling unit includes a second radiator, and the Q-switched driver and the pump source are both mounted on the second radiator.

4. The ultraviolet laser as claimed in claim 3, characterized in that: The second cooling unit further includes a second semiconductor refrigerator, which is sandwiched between the pump source and the second radiator, and the cold end and the hot end of the second semiconductor refrigerator are respectively facing the pump source and the second radiator.

5. The ultraviolet laser according to claim 1, characterized in that: The light incident end of the beam expander is arranged as a concave mirror.

6. The ultraviolet laser according to claim 1, characterized in that: The Q-switched driver and the pump source are located on the same side of the optical cavity and are arranged on both sides of the beam expander extension tube.

7. The ultraviolet laser according to claim 1, characterized in that: The periphery of the optical cavity extends outward to form a mounting plate, and the mounting plate has a mounting area connected to the base and a stress release groove located between the mounting area and the optical cavity.

8. The ultraviolet laser according to claim 1, characterized in that: It also includes an air internal circulation purification device, which is located outside the optical cavity and the two are connected through a gas circulation pipeline.

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