High-energy output single longitudinal mode oscillation system of pulse laser for laser shock

Abstract

The invention discloses a high-energy output single longitudinal mode oscillation system of a pulse laser for laser shock, which belongs to the technical field of pulse lasers and comprises a resonant cavity structure, an electro-optical driver, a PIN laser pulse waveform detector and a xenon lamp. The laser is characterized in that the resonant cavity structure comprises a total reflection mirror, an analyzer, an electro-optic Q-switched crystal, a polarizer, a crystal rod, a small-hole diaphragm and an output mirror which are arranged along an optical line, the distance between the output mirror and the total reflection mirror is equal to the length of the resonant cavity, the crystal rod is fixed in the metal light-gathering cavity, and the xenon lamp is driven by a rotation driving mechanism to rotate around the total reflection mirror. The xenon lamp rotates around the crystal rod in the metal light-gathering cavity, the xenon lamp pumps in the circumferential direction of the crystal rod in a side pump working mode, and the crystal rod generates polarized light. According to the high-energy output single longitudinal mode oscillation system, the xenon lamp rotates around the crystal rod, the xenon lamp works in a side pump mode, and the mode of pumping in the circumferential direction of the crystal rod is adopted, so that the energy utilization rate is improved, high-energy output of the single longitudinal mode oscillation system is ensured, the size of the whole laser can be reduced, and the size of the laser can be reduced. Optical components are greatly reduced, the quality stability of light beams is improved, and meanwhile, the manufacturing and subsequent debugging difficulty of the whole laser is greatly reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of pulse lasers, and in particular to a high-energy output single longitudinal mode oscillation system of a pulse laser for laser shock. Background Art

[0002] The pulse laser technology used for laser shock strengthening is very complex and difficult. During long-term operation, there are high requirements for the stability of the energy, pulse width, and frequency of the laser output. Shock strengthening lasers must meet the following technical conditions at the same time: high energy (10-50J), short pulses (10-30ns), repetitive frequency (0.5-10Hz), and adjustable and controllable pulse width. These technical conditions are related to the oscillation system of the pulsed laser. In the oscillation system, there is multi-mode oscillation without any restrictions, and the output laser mode is multi-mode, and the output laser energy is relatively large. Single longitudinal mode output requires that there is only one mode oscillation output in the laser oscillation system, and other modes are suppressed or lost in competition, which causes a large amount of energy loss and the output energy is extremely small. In addition, in the single longitudinal mode output mode, it is possible to become multi-mode output during a long period of work, and the control conditions for single longitudinal mode output are very high.

[0003] Among the current finished products of pulsed solid-state lasers, the output of single longitudinal mode mainly adopts seed light injection mode. The energy output by the seed light source is very small, only a few millijoules. Taking LSPT's product Procudo@200 as an example, its oscillation stage is a small single longitudinal mode pulsed solid-state laser with an output laser energy of 3mJ. To achieve a high-energy laser output of 10J, it needs to be amplified by about 3333 times, which requires many levels of subsequent laser energy amplification. The size of the entire laser will be very large, and the number of optical components will increase exponentially, resulting in a decrease in the stability of the beam quality. At the same time, it increases the difficulty of manufacturing and subsequent debugging of the entire laser.

[0004] Under given pulse laser power supply conditions, there is an inverse relationship between the energy and frequency of the pulse laser, that is, if the laser output energy is large, the frequency will decrease, and if the output energy is small, the frequency can be increased accordingly. Therefore, to ensure high energy output at high repetition frequency, it is necessary to provide a laser power supply with high energy and high charging efficiency. However, the energy utilization rate of pulse lasers is relatively low, at 2%-3%. The remaining electrical energy is converted into heat energy and accumulated in the focusing cavity, causing heat accumulation problems. Therefore, how to improve the energy utilization rate of pulse lasers is a core technical issue for large-energy single longitudinal mode oscillation systems. Summary of the invention

[0005] The object of the present invention is to provide a high energy output single longitudinal mode oscillation system of a pulsed laser for laser shock.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: The invention discloses a high-energy output single longitudinal mode oscillation system of a pulsed laser for laser shock, comprising a resonant cavity structure, an electro-optical driver, a PIN laser pulse waveform detector and a xenon lamp. The resonant cavity structure comprises a total reflection mirror, an analyzer, an electro-optical Q-switched crystal, a polarizer, a crystal rod, a small aperture and an output mirror arranged along an optical line. The distance between the output mirror and the total reflection mirror is the length of the resonant cavity. The crystal rod is fixed in a metal focusing cavity. The xenon lamp rotates around the crystal rod in the metal focusing cavity under the drive of a rotating drive mechanism. The xenon lamp is pumped along the circumferential direction of the crystal rod in a side pump working mode, and the crystal rod generates polarized light. The polarizer, the electro-optical Q-switched crystal and the analyzer constitute a photoelectric Q-switched switch. The polarization axis of the analyzer is parallel to the polarization axis of the polarizer. The polarized light generated by the crystal rod is converted into linear polarized light in a specific direction by the polarizer. When the electro-optical driver applies a half-wave voltage to the electro-optical Q-switched crystal, the linear polarized light is converted into linear polarized light in a specific direction by the polarizer. After passing through the electro-optical Q-switched crystal, the vibration direction rotates 90°, and the linearly polarized positive light cannot pass through the subsequent analyzer. The photoelectric Q-switched switch is closed. When the voltage on the electro-optical Q-switched crystal is instantly removed, it is equivalent to the photoelectric Q-switched switch being turned on. The electro-optical driver controls the opening and closing of the photoelectric Q-switched switch at different times to select a single longitudinal mode, so that the resonant cavity structure outputs a single longitudinal mode laser. The electro-optical driver controls the pulse width and energy of the laser by changing the refractive index of the electro-optical Q-switched crystal medium in the photoelectric Q-switched switch. When the linearly polarized positive light passes through the analyzer, the reflected laser enters the PIN laser pulse waveform detector, which is used to detect the shape of the laser pulse waveform and the time when the pulse is established. When the photoelectric Q-switched switch is turned on, the linearly polarized positive light is emitted through the analyzer and then reflected back through the total reflection mirror, passes through the photoelectric Q-switched switch and enters the crystal rod. The laser after the crystal rod gain is selected through the pinhole aperture and then emitted from the output mirror.

[0007] Furthermore, the rotary drive mechanism includes a servo motor, a driving gear, an outer gear ring and an annular rotating frame, wherein the outer gear ring is installed at one end of the metal focusing cavity through a bearing, and the annular rotating frame is fixedly connected to the end face of the outer gear ring. The two xenon lamps are distributed on both sides of the crystal rod and fixed on the annular rotating frame. The outer gear ring is meshed with the driving gear, and the driving gear is installed on the output shaft of the servo motor.

[0008] Furthermore, the cavity wall of the metal focusing cavity is a sandwich structure, and a spiral water cooling channel is provided in the sandwich structure. One end of the spiral water cooling channel is connected to the cooling water inlet on the outer wall of the metal focusing cavity, and the other end of the spiral water cooling channel is connected to the cooling water outlet on the outer wall of the metal focusing cavity. The cooling water absorbs the heat of the metal focusing cavity during the flow in the spiral water cooling channel to regulate the temperature inside the metal focusing cavity.

[0009] Furthermore, the laser working material of the crystal rod is Nd:YAG crystal.

[0010] Furthermore, both ends of the crystal rod are coated with a 1064nm anti-reflection film.

[0011] Furthermore, the polarizer adopts a Brewster angle polarizer.

[0012] Furthermore, the total reflection mirror is coated with a 1064nm total reflection film.

[0013] Furthermore, the total reflection mirror is a concave spherical total reflection mirror with a curvature radius of 4m.

[0014] Furthermore, the crystal rod has a length of 240 mm and a diameter of 12 mm.

[0015] Furthermore, the electro-optical Q-switched crystal is an RTP crystal. The performance of the RTP crystal is mainly reflected in the very high threshold of its piezoelectric ringing effect.

[0016] The beneficial effects of the present invention are: The high energy output single longitudinal mode oscillation system of the present invention adopts a xenon lamp rotating around a crystal rod. The xenon lamp works in a side pumping mode and pumps along the circumferential direction of the crystal rod, thereby improving energy utilization. It not only ensures the high energy output of the single longitudinal mode oscillation system, but also reduces the size of the entire laser, greatly reduces the number of optical components, improves the stability of the beam quality, and greatly reduces the difficulty of manufacturing and subsequent debugging of the entire laser.

[0017] The present invention adopts a spiral water cooling channel on the metal focusing cavity. The cooling water absorbs the heat of the metal focusing cavity during the flow of the spiral water cooling channel to regulate the temperature in the metal focusing cavity, thereby solving the problem of heat accumulation in the focusing cavity. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention is further described with the aid of the accompanying drawings, but the embodiments in the accompanying drawings do not constitute any limitation to the present invention. A person skilled in the art can obtain other accompanying drawings according to the following drawings without creative work: Figure 1 It is a structural schematic diagram of the present invention; Figure 2 for Figure 1 Schematic diagram of the structure of the metal focusing cavity and the rotation drive mechanism shown.

[0019] In the figure: 1. electro-optic driver; 2. PIN laser pulse waveform detector; 3. xenon lamp; 4. total reflector; 5. analyzer; 6. electro-optic Q-switched crystal; 7. polarizer; 8. crystal rod; 9. pinhole aperture; 10. output mirror; 11. metal focusing cavity; 12. rotation drive mechanism; 13. anti-reflection film; 14. servo motor; 15. driving gear; 16. outer ring gear; 17. annular rotating frame; 18. bearing; 19. spiral water cooling channel; 20. cooling water inlet; 21. cooling water outlet. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present application and the features therein can be combined with each other without conflict.

[0021] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper surface", "lower surface", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "forward", "reverse", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0022] like Figure 1 As shown, a high-energy output single longitudinal mode oscillation system of a pulsed laser for laser shock includes a resonant cavity structure, an electro-optical driver 1, a PIN laser pulse waveform detector 2 and a xenon lamp 3. The resonant cavity structure includes a total reflector 4, an analyzer 5, an electro-optical Q-switched crystal 6, a polarizer 7, a crystal rod 8, a small aperture 9 and an output mirror 10 arranged along the optical line. The distance between the output mirror 10 and the total reflector 4 is the length of the resonant cavity. The crystal rod 8 is fixed in a metal focusing cavity 11. The xenon lamp 3 rotates around the crystal rod 8 in the metal focusing cavity 11 under the drive of a rotating drive mechanism 12. The xenon lamp 3 pumps along the circumferential direction of the crystal rod 8 in a side pumping mode, and the crystal rod 8 generates polarized light. The laser working material of the crystal rod 8 is Nd:YAG crystal. Both ends of the crystal rod 8 are coated with a 1064nm anti-reflection film 13. The length of the crystal rod 8 is 240mm and the diameter is 12mm. The analyzer 5 uses a Brewster angle polarizer. The total reflection mirror 4 is plated with a 1064nm total reflection film, and the total reflection mirror 4 is a concave spherical total reflection mirror with a curvature radius of 4m.

[0023] The advantages of Nd:YAG crystal can be summarized as follows: (1) Its matrix material YAG is easy to grow large-sized high-performance crystals, the processing and manufacturing process is mature, the mechanical properties are high, and the thermal conductivity is good; (2) The crystal is an isotropic cubic crystal structure, the charge is balanced, and it is easy to obtain a narrow fluorescence spectrum; (3) The crystal has a large stimulated emission cross section, the generated fluorescence lifetime is long, the ability to resist strong light damage is strong, and the fluorescence quantum efficiency is greater than 99.5%. The laser working material of the crystal rod is Nd:YAG crystal.

[0024] The polarizer 7, the electro-optical Q-switched crystal 6 and the analyzer 5 constitute a photoelectric Q-switched switch. The polarization axis of the analyzer 5 is parallel to the polarization axis of the polarizer 7. The polarized light generated by the crystal rod 8 is converted into linear polarized light in a specific direction by the polarizer 7. When the electro-optical driver 1 applies a half-wave voltage to the electro-optical Q-switched crystal 6, the vibration direction of the linear polarized light rotates 90° after passing through the electro-optical Q-switched crystal. The linearly polarized positive light cannot pass through the subsequent analyzer 5, and the photoelectric Q-switched switch is closed. When the voltage on the electro-optical Q-switched crystal 6 is instantly removed, it is equivalent to that the photoelectric Q-switched switch is turned on. The electro-optical driver 1 controls the opening and closing of the photoelectric Q-switched switch at different times to select a single longitudinal mode. , so that the resonant cavity structure outputs single longitudinal mode laser, and the electro-optical driver 1 controls the pulse width and energy of the laser by changing the refractive index of the electro-optical Q-switched crystal 6 medium in the photoelectric Q-switched switch; when the linearly polarized positive light passes through the analyzer 5, the reflected laser enters the PIN laser pulse waveform detector 2, and the PIN laser pulse waveform detector 2 is used to detect the laser pulse waveform shape and the time when the pulse is established; when the photoelectric Q-switched switch is turned on, the linearly polarized positive light is emitted through the analyzer 5 and then reflected by the total reflection mirror 4, passes through the photoelectric Q-switched switch and enters the crystal rod 8, and the laser after gain of the crystal rod 8 is selected by the pinhole aperture 9 for the fundamental transverse mode and then emitted from the output mirror 10.

[0025] The electro-optical Q-switched crystal is an RTP crystal. The performance of the RTP crystal is mainly reflected in the very high threshold of its piezoelectric ringing effect.

[0026] like Figure 2 As shown, the rotary drive mechanism 12 includes a servo motor 14, a driving gear 15, an outer gear ring 16 and an annular rotating frame 17. The outer gear ring 16 is installed at one end of the metal focusing cavity 11 through a bearing 18. The annular rotating frame 17 is fixedly connected to the end face of the outer gear ring 16. The two xenon lamps 3 are distributed on both sides of the crystal rod 8 and fixed on the annular rotating frame 17. The outer gear ring 16 is meshed with the driving gear 15, and the driving gear 15 is installed on the output shaft of the servo motor 14.

[0027] The cavity wall of the metal focusing cavity is a sandwich structure, in which a spiral water cooling channel 19 is provided. One end of the spiral water cooling channel 19 is connected to a cooling water inlet 20 on the outer wall of the metal focusing cavity 11, and the other end of the spiral water cooling channel 19 is connected to a cooling water outlet 21 on the outer wall of the metal focusing cavity 11. The cooling water absorbs the heat of the metal focusing cavity 11 during the flow in the spiral water cooling channel 19 to regulate the temperature inside the metal focusing cavity 11.

[0028] Working principle: The high energy output single longitudinal mode oscillation system of the present invention adopts a xenon lamp rotating around the crystal rod. The xenon lamp works in a side pumping mode and pumps along the circumferential direction of the crystal rod. The laser working material of the crystal rod is Nd:YAG crystal. Nd:YAG crystal is formed by adding Nd3+ activation ions to replace Y3+ in the yttrium aluminum garnet matrix material. It has good optical quality and high thermal conductivity and is a commonly used gain medium. The atomic ratio of Nd3+ replacing Y3+ is about 1%, and the crystal color is light purple. The energy level system of Nd:YAG belongs to a four-level system. Under pumping conditions, the neodymium ion (Nd3+) absorbs energy and is pumped from the base energy level to the high energy level, and then immediately reaches the metastable 4F3 / 2 energy level through a non-radiative transition. The 4F3 / 2 energy level has a long lifetime and is used as the upper energy level of the laser. The 4F3 / 2 energy level spontaneously radiates to the lower energy level to produce fluorescence. The xenon lamp rotates around the crystal rod, which enables the energy emitted by the xenon lamp to be fully absorbed by the neodymium ions (Nd3+) distributed in the crystal rod, thereby improving energy utilization and reducing heat energy formation.

[0029] Under room temperature conditions, Nd:YAG crystal can achieve more than 30 different spectral lines, among which 946nm, 1064nm, and 1319nm are more obvious, especially the 1064nm line has the largest area value, that is, the 1064nm line is more susceptible to excitation output than the 946nm and 1319nm lines. Therefore, in order to obtain a single spectral line 1064nm output, a 1064nm anti-reflection film 13 is plated on both ends of the crystal rod 8.

[0030] In order to output high energy, the high energy output single longitudinal mode oscillation system of the present invention adopts two xenon lamps for energy output and pumping the crystal rod, which can reduce the size of the entire laser, greatly reduce the optical components, improve the stability of the beam quality, and greatly reduce the difficulty of manufacturing and subsequent debugging of the entire laser.

[0031] In addition, lasers with a single spectral line output often contain multiple longitudinal modes within the width of the gain curve. If no intervention is made, multiple longitudinal modes oscillate simultaneously, and the output is a multi-longitudinal mode laser beam. The multi-longitudinal mode beam has obvious dispersion effect, and there will be problems such as light field distortion and increased width during transmission inside and outside the laser cavity. Moreover, the quality of the multi-longitudinal mode beam is poor, and large defocus or deviation occurs during beam focusing and transmission. This does not meet our requirements for controllable laser impact quality. Therefore, the high-energy output single longitudinal mode oscillation system of the laser of the present invention selects a single longitudinal mode by controlling the opening and closing of the photoelectric Q-switching switch at different times through the electro-optical driver 1, thereby realizing the regulated output of the single longitudinal mode beam.

[0032] In addition, those skilled in the art may combine and combine the different embodiments or examples and the features of the different embodiments or examples described in this specification without contradiction. Although the embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. Those skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A high energy output single longitudinal mode oscillation system of a pulsed laser for laser shock, comprising a resonant cavity structure, an electro-optical driver, a PIN laser pulse waveform detector and a xenon lamp, characterized in that: The resonant cavity structure includes a total reflection mirror, an analyzer, an electro-optical Q-switched crystal, a polarizer, a crystal rod, a small aperture and an output mirror arranged along the optical line. The distance between the output mirror and the total reflection mirror is the length of the resonant cavity. The crystal rod is fixed in the metal focusing cavity. The xenon lamp rotates around the crystal rod in the metal focusing cavity under the drive of the rotation drive mechanism. The xenon lamp is pumped along the circumferential direction of the crystal rod in a side pump working mode, and the crystal rod generates polarized light; the polarizer, the electro-optical Q-switched crystal and the analyzer constitute a photoelectric Q-switched switch. The polarization axis of the analyzer is parallel to the polarization axis of the polarizer. The polarized light generated by the crystal rod is converted into linear polarized light in a specific direction by the polarizer. When the electro-optical driver applies a half-wave voltage to the electro-optical Q-switched crystal, the linear polarized light rotates 90° in vibration direction after passing through the electro-optical Q-switched crystal, and the linearly polarized positive light cannot pass through the electro-optical Q-switched crystal. The analyzer after the photoelectric Q-switching is closed. When the voltage on the electro-optical Q-switching crystal is instantly removed, it is equivalent to that the photoelectric Q-switching switch is turned on. The electro-optical driver controls the opening and closing of the photoelectric Q-switching switch at different times to select a single longitudinal mode, so that the resonant cavity structure outputs a single longitudinal mode laser. The electro-optical driver controls the pulse width and energy of the laser by changing the refractive index of the electro-optical Q-switching crystal medium in the photoelectric Q-switching switch. When the linearly polarized positive light passes through the analyzer, the reflected laser enters the PIN laser pulse waveform detector, which is used to detect the shape of the laser pulse waveform and the time when the pulse is established. When the photoelectric Q-switching switch is turned on, the linearly polarized positive light is emitted through the analyzer and then reflected back through the total reflection mirror, passes through the photoelectric Q-switching switch and enters the crystal rod. The laser after the gain of the crystal rod is selected through the pinhole aperture and then emitted from the output mirror.

2. The high energy output single longitudinal mode oscillation system of the pulsed laser for laser shock according to claim 1, characterized in that: The rotary drive mechanism comprises a servo motor, a driving gear, an outer gear ring and an annular rotating frame. The outer gear ring is installed at one end of the metal focusing cavity through a bearing. The annular rotating frame is fixedly connected to the end face of the outer gear ring. The two xenon lamps are distributed on both sides of the crystal rod and fixed on the annular rotating frame. The outer gear ring is meshed with the driving gear, and the driving gear is installed on the output shaft of the servo motor.

3. The high energy output single longitudinal mode oscillation system of the pulsed laser for laser shock according to claim 1, characterized in that: The cavity wall of the metal focusing cavity is a sandwich structure, and a spiral water cooling channel is provided in the sandwich structure. One end of the spiral water cooling channel is connected to the cooling water inlet on the outer wall of the metal focusing cavity, and the other end of the spiral water cooling channel is connected to the cooling water outlet on the outer wall of the metal focusing cavity. The cooling water absorbs the heat of the metal focusing cavity during the flow in the spiral water cooling channel to regulate the temperature inside the metal focusing cavity.

4. The high energy output single longitudinal mode oscillation system of the pulsed laser for laser shock according to claim 1, characterized in that: The laser working material of the crystal rod is Nd:YAG crystal.

5. The high energy output single longitudinal mode oscillation system of the pulsed laser for laser shock according to claim 4, characterized in that: Both ends of the crystal rod are plated with a 1064nm anti-reflection film.

6. The high energy output single longitudinal mode oscillation system of the pulsed laser for laser shock according to claim 1, characterized in that: The polarizer is a Brewster angle polarizer.

7. The high energy output single longitudinal mode oscillation system of a pulsed laser for laser shock according to claim 1, characterized in that: The total reflection mirror is plated with a 1064nm total reflection film.

8. The high energy output single longitudinal mode oscillation system of the pulsed laser for laser shock according to claim 7, characterized in that: The total reflection mirror is a concave spherical total reflection mirror with a curvature radius of 4m.

9. The high energy output single longitudinal mode oscillation system of a pulsed laser for laser shock according to claim 4, characterized in that: The crystal rod has a length of 240 mm and a diameter of 12 mm.

10. The high energy output single longitudinal mode oscillation system of a pulsed laser for laser shock according to claim 1, characterized in that: The electro-optical Q-switched crystal is an RTP crystal.

Images