Six-pass amplification high-power laser device crystal near-field center position deviation detection system

Abstract

The invention relates to a crystal near-field center position deviation detection system for a six-pass amplification high-power laser device, and belongs to the technical field of high-power laser device collimation. A pair of pyramids is used for calibrating the near-field position of a crystal, and two pairs of small light beams with overlapped near fields and separated far fields are used for calibrating the near-field center of a main light beam to serve as the near-field reference of the main light beam. A near-field camera is utilized to receive light spots of a near-field reference small light beam pair and a pyramid reflection light spot pair at the same time, and the center deviation of the two pairs of light spots is the deviation of the near-field center position of the crystal relative to a main light beam. And carrying out automatic collimation adjustment on the near-field position of the crystal by utilizing a feedback control system according to the deviation value. According to the invention, the problems of low image resolution and difficulty in center positioning and accurate adjustment due to the fact that the near-field position of the crystal and the deviation of the main light beam need to be observed by human eyes during crystal collimation are solved. The method improves the collimation efficiency and debugging precision of the crystal, and has the characteristics of simple equipment, easiness in adjustment and high precision.

Description

Technical Field

[0001] The invention belongs to the technical field of high-power laser device collimation, in particular to a six-pass amplified high-power laser device crystal near-field center position deviation detection system. Background Art

[0002] In the existing inertial confinement nuclear fusion research field at home and abroad, high-power laser devices play a vital role. These devices all rely on the precise near-field position alignment of the frequency-doubling crystal to achieve optimal performance. However, the current mainstream alignment adjustment technology still relies on manual operation. The specific process is: the operator observes the image of the laser beam at the crystal position with the naked eye, and manually adjusts a pair of reflectors located in front of the crystal accordingly, in order to achieve alignment between the center of the crystal and the center of the main laser beam.

[0003] However, this method is limited by the low resolution of human observation, which makes it difficult to accurately capture the center position of the crystal, thus affecting the accuracy and efficiency of adjustment. Therefore, this technical bottleneck not only increases the difficulty of operation, but also restricts the potential of high-power laser devices in inertial confinement fusion applications.

[0004] In view of this, a more efficient and accurate collimation adjustment solution is urgently needed to overcome the limitations of existing technologies and promote the further development of technologies in related fields. Summary of the invention

[0005] In order to overcome the above-mentioned deficiencies in the prior art, the present invention provides a system for detecting the near-field center position deviation of the crystal of a six-pass amplified high-power laser device. By placing a near-field reference beam and a corner cone, the near-field center of the main beam and the center of the crystal are located respectively, and the near-field center position deviation of the crystal is automatically detected. The crystal is adjusted to collimation according to the deviation value using a feedback system. The device has the characteristics of simple equipment, easy adjustment and high precision.

[0006] The technical solution of the present invention is as follows:

[0007] A six-pass amplification high-power laser device crystal near-field center position deviation detection system, which is characterized by including:

[0008] Two pairs of small beams are placed behind the adjustable reflectors to provide near-field references. The near-field positions of the two pairs of small beams coincide, but the far-field angles are different. The far-field directions of the beam pairs pass through different filter apertures of the transmission spatial filter respectively.

[0009] A pair of pyramids, which can be moved in and out in front of the crystal, are used to calibrate the near-field position of the crystal;

[0010] A reflector group, arranged in front of the corner cone, for adjusting the path of the light beam incident on the crystal;

[0011] A right-angle prism that can be moved behind different filter apertures of the transmission spatial filter to reflect the light beam to the near-field detection system;

[0012] A near-field detection system is used to obtain and image the near-field image of the main beam and the reflected light spots of the small beams and the corner cones;

[0013] Use the following steps to detect and adjust the crystal near-field center position deviation:

[0014] a) Using the small beam pairs after the transmission spatial filter with different filtering pinholes, adjust the near-field center of the main beam to coincide with the near-field center of the small beam pair, and determine the near-field reference of the main beam;

[0015] b) Using another small beam pair as a near-field position reference, after moving the right-angle prism to the corresponding filtering aperture, the beam is reflected to the near-field detection system for imaging;

[0016] c) Move a pair of pyramids into the main optical path, place them symmetrically in front of the crystal relative to the center line of the crystal, reflect the main laser to the near-field detection system for imaging, and obtain the center of the pyramid reflection spot;

[0017] d) Compare the deviation between the center of the near-field reference small beam spot and the center of the pyramid reflection spot, adjust the reflector group to adjust the deviation to within the predetermined error range, and realize the collimation of the near-field position of the crystal.

[0018] Furthermore, it also includes a feedback system for adjusting the reflector group according to the deviation between the center of the reflected light spot of the corner cone in the near-field camera and the center of the light spot of the near-field reference small beam, so that the center position deviation of the two pairs of light spots is adjusted to an error range.

[0019] Preferably, the near-field detection system comprises a focusing lens, a reflector, an imaging lens and a near-field detection camera which are sequentially arranged along the optical path, and the light beam is imaged to the near-field detection camera (35) through the focusing lens (31), the reflector (32) and the imaging lens (33, 34) to obtain the near-field image center of the main light beam and the imaging spot of the small light beam.

[0020] Furthermore, it also includes a transmission space filter, a cavity space filter, an amplifying medium, a reflector and a lens, which together constitute the optical path of the six-pass amplified high-power laser device.

[0021] The specific method of using the above system to detect the near-field center deviation of the crystal includes the following steps:

[0022] Step 1. Place two pairs of small beams behind the adjustment mirror RM1. The near-field positions of these two pairs of small beams coincide, but their far-field angles are different. The far-field directions of the beam pairs pass through hole #1 and hole #4 respectively, so we call them small beam pairs passing through hole #1 and small beam pairs passing through hole #4 to distinguish them.

[0023] Step 2. Determine the near-field reference of the main beam, and use the small beam pair through hole #4 to adjust the near-field center of the main beam to coincide with the near-field center of the small beam pair. The near-field reference position of the main beam is calibrated by the small beam pair through hole #4 placed behind the RM1 adjustment mirror.

[0024] The optical path of the main beam of the six-pass amplified high-power laser device is shown in the figure. The main beam coming out of the pre-amplifier is injected into the filter aperture #1 of the transmission space filter through the injection reflector, and becomes a parallel beam after passing through the transmission space filter lens TSF L1. After passing through the amplifying medium, it is reflected by the reflectors RM1 and P1, and then enters the cavity space filter. After four-pass amplification: after being converged by the cavity space filter focusing lens CSF L1, it passes through the cavity space filter aperture #1, and becomes parallel light after passing through CSF L2. It is amplified by the amplifying medium and reflected by the cavity reflector CM2. It passes through the amplifying medium, the cavity converging lens CSF L2, the cavity space filter aperture #2, the cavity converging lens CSF L1, and the polarization converter PEPC in sequence. Then the beam passes through the reflector P1, passes through the cavity space reflector CM1, the reflector P1, PEPC, and turns off PEPC. Then it passes through CSF L1, cavity space filter aperture #3, CSF L2, amplifying medium, CM2, amplifying medium, CSF L2, cavity space filter aperture #4, and CSF L1 in sequence. After the four-pass amplification, it is reflected by the reflector P1, passes through RM1, the amplifying medium, TSF L1, the transmission space filter aperture #4, the transmission space filter lens TSF L2, and is reflected by the reflectors TM1, TM2, TM3, and TM4 before being output to the terminal optical system where the crystal is located.

[0025] After the right-angle prism is moved to hole #4, the small beam pair placed after RM1 and passing through hole #4 passes through the amplifying medium and TSF L1 together with the main beam after four-pass amplification, passes through the filtering hole #4 of the transmission spatial filter, and is reflected to the near-field detection system by the right-angle prism. It is imaged to the near-field detection camera through the beam reduction lens, the reflector and the imaging lens to obtain the near-field image center of the main beam and the imaging spot of the small beam. The injection reflector in front of the amplifying system is adjusted to make the near-field image center of the main beam coincide with the center of the spot pair of the small beam pair passing through hole #4, so that the center of the small beam pair passing through hole #4 is used as the near-field reference of the main beam.

[0026] Step 3. The near-field positions of the small beam pair passing through hole #1 coincide with those of the small beam pair passing through hole #4, so the near-field center of the small beam pair passing through hole #1 also coincides with the near-field center of the main beam. Therefore, the center of the small beam pair passing through hole #1 is also used as the near-field reference of the main beam.

[0027] Step 4. After the right-angle prism is moved to hole #1, the small beam pair passing through hole #1 passes through the magnifying medium, TSF L1 and hole #1, and is reflected by the right-angle prism to the near-field detection system. After passing through the beam reduction lens, reflector and imaging lens, it is received by the near-field detection camera and imaged as a pair of small light spots. The center of the small light spot pair represents the reference center of the near-field beam position. The small beam pair passing through hole #1 is used as the near-field reference small beam of the main beam for subsequent detection and adjustment.

[0028] Step 5. At the other end, the position of the frequency doubling crystal in the terminal optical system is calibrated by a pair of target field cones, which can be moved in and out. Move the cone into the main optical path and place it symmetrically in front of the crystal relative to the center line of the crystal to calibrate the near-field position of the crystal. Before the main laser enters the terminal optical system, it will irradiate the cone and reflect. After the reflected light is reflected by TM4, TM3, TM2, and TM1, it enters the main amplifier system optical path: after passing through TSF L2, hole #4, TSF L1, and the amplifying medium, it is reflected by RM1 and P1. After four-pass amplification, it is reflected back by P1 and RM1, and then passes through the amplifying medium, TSF L1, and hole #1 again. It is reflected by the right-angle prism to the near-field monitoring system. After passing through the beam reduction lens, reflector, and imaging lens, the reflected light of the cone is received by the near-field camera. The center of the pair of cone spots represents the center of the crystal.

[0029] Step 6. The deviation between the center of the reflected light spot of the near-field camera and the center of the near-field reference small beam is the position deviation between the near-field center of the crystal and the near-field center of the main beam. The feedback system is used to adjust the crystal front reflectors TM3 and TM4 so that the deviation is adjusted to the error range, which means that the crystal near-field position is adjusted and collimated.

[0030] Step 7. After adjusting the collimation, move the cone out of the light path and turn off the near-field reference light source.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1) Through the precise placement of the near-field reference beam and the corner cone, the automatic detection and adjustment of the near-field center position of the crystal is achieved. Compared with the traditional manual adjustment method, this system can significantly reduce the adjustment time and improve the efficiency of crystal alignment. This is undoubtedly an important improvement for high-power laser devices that require frequent adjustment of the crystal position.

[0033] 2) The system uses a feedback system to precisely adjust the front reflector of the crystal, so that the deviation between the center of the pyramidal reflection spot and the center of the near-field reference small beam spot can be adjusted to a very small error range. This high-precision adjustment method ensures the accuracy of the near-field position of the crystal, thereby improving the debugging accuracy of the entire laser device. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1It is a schematic diagram of the optical path of the near-field center position deviation detection system of the crystal of the six-pass amplified high-power laser device of this embodiment.

[0035] Figure 2 It is the near-field image of the main beam in the near-field camera and the image of the small beam spot through the #4 hole

[0036] Figure 3 This is the detection image of the pyramid reflection spot and the small beam spot through hole #1 in the near-field camera.

[0037] Figure 1 Middle: 1-Near-field reference through hole #1 small beam pair 2-Near-field reference through hole #4 small beam pair 3, 4, 5-Injection reflector 6-Lens 7-Reflector 8-Right angle prism 9-Transmission space filter pinhole #1 hole 10-Transmission space filter pinhole #4 hole 11-Transmission space filter lens TSF L1 12-Amplification medium 13-Reflector RM1 14-Motor for controlling the movement of the reflector 15-Cavity reflector CM1 16-Reflector P1 17-Polarization converter PEPC 18-Cavity space filter lens CSF.L1 19-Cavity space filter pinhole #1 hole #2 hole #3 hole #4 hole 20-Cavity space filter lens CSF.L2 21-Amplification medium 22-Cavity reflector CM2 23-Transmission space filter lens TSF L224 - Reflector TM125 - Reflector TM226 - Reflector TM327 - Reflector TM428 - A pair of pyramids29 - Terminal optical system30 - Crystal31 - Beam reduction lens32 - Reflector33, 34 - Imaging lens35 - Near field detection camera DETAILED DESCRIPTION

[0038] The present invention is further described below in conjunction with the embodiments and drawings, but this should not limit the scope of protection of the present invention.

[0039] The six-pass amplified high-power laser device crystal near-field center position deviation detection system provided in this embodiment is intended to ensure that the crystal in the high-power laser device is accurately aligned with the main beam. The system can accurately locate the near-field center of the main beam and the center of the crystal through the clever placement of the near-field reference beam and the corner cone, and automatically detect the deviation between the two. Once the deviation is detected, the system will use the feedback system to adjust the crystal until it is fully collimated.

[0040] Please read first Figure 1 , Figure 1 1 is a schematic diagram of the optical path of the near-field center position deviation detection system of the six-pass amplified high-power laser device crystal of this embodiment. As shown in the figure, a six-pass amplified high-power laser device crystal near-field center position deviation detection system comprises:

[0041] Near-field reference beam: It is composed of two pairs of small beams 1 and 2 placed behind the adjustable reflector 13. These two pairs of small beams overlap in the near-field position, but have different far-field angles, and pass through the #1 hole 9 and #4 hole 10 of the transmission spatial filter respectively, so they are also called the small beam pair passing through the #1 hole and the small beam pair passing through the #4 hole.

[0042] Corner cones 28: A pair of target range corner cones 28 are placed in front of the crystal 30 to calibrate the near-field position of the crystal. The corner cones can be moved in and out for flexible use during testing and adjustment.

[0043] Reflector group 26, 27: located in front of the corner cone 28, used to adjust the path of the reflected light of the corner cone.

[0044] The right-angle prism 8 can be moved behind the filter holes #1 9 and #4 10 of the transmission space filter to change the path of the light beam so that it enters the near-field detection system.

[0045] Near-field detection system: It consists of a beam reduction lens 31, a reflector 32, imaging lenses 33, 34 and a near-field detection camera 35, and can obtain near-field images of the main beam and the reference beam and measure the deviation between them.

[0046] The method for detecting the near-field center deviation of a crystal using the above detection system comprises the following steps:

[0047] Step 1. Place the near-field reference beam: After adjusting the reflector 13, place two pairs of small beams 1 and 2 to ensure that they coincide in the near-field position and have different far-field angles. The far-field pointing of the beam pair passes through hole #1 9 and hole #4 10 respectively, so they are called small beam pair 1 through hole #1 and small beam pair 2 through hole #4 to distinguish them.

[0048] Step 2. Determine the near-field reference of the main beam: Use the small beam pair 2 through the #4 hole to adjust the main beam so that its near-field center coincides with the near-field center of the small beam pair. That is, the near-field reference position of the main beam is calibrated by the small beam pair 2 through the #4 hole placed behind the RM1 adjustment mirror 13.

[0049] The optical path of the main beam of the six-pass amplified high-power laser device is shown in the figure. The main beam from the pre-amplifier is injected into the filter pinhole #1 (9) of the transmission space filter through the injection reflectors (3, 4, 5), and becomes a parallel beam through the transmission space filter lens TSF L1 (11). After passing through the amplifying medium 12, it is reflected by the reflectors RM1 (13) and P1 (16), and then enters the cavity space filter. After four-pass amplification: after being converged by the cavity space filter focusing lens CSF L1 (18), it passes through the cavity space filter pinhole (19) #1 hole, passes through the cavity space filter lens CSF L2 (20) and becomes parallel light, is amplified by the amplifying medium 21, is reflected by the cavity reflector CM2 (22), and passes through the amplifying medium 21, the cavity converging lens CSF L2 (20), the cavity space filter pinhole (19) #2 hole, and the cavity converging lens CSF L3 (21) in sequence. L1 (18), polarization converter PEPC17, then the light beam passes through the reflector P1 (16), passes through the cavity space reflector CM1 (15), reflector P1 (16), PEPC (17) in sequence, closes PEPC, and then passes through CSF L1 (18), cavity space filter pinhole (19) #3 hole, CSF L2 (20), amplifying medium 21, CM2 (22), amplifying medium 21, CSF L2 (20), cavity space filter pinhole (19) #4 hole, CSF L1 (18) in sequence. After the four-pass amplification, it is reflected by the reflector P1 (16), passes through RM1 (13), amplifying medium 12, TSF L1 (11), transmission space filter pinhole #4 (10), transmission space filter lens TSF L2 (23), and is reflected by the reflectors TM1 (24), TM2 (25), TM3 (26), and TM4 (27) and then output to the terminal optical system 29 where the crystal 30 is located.

[0050] After the right-angle prism 8 is moved to the #4 hole (10), the small light beam pair (2) placed behind the RM1 (13) and passing through the #4 hole passes through the amplifying medium 12 and TSFL1 (11) together with the main light beam after four-pass amplification, passes through the filtering hole #4 hole (10) of the transmission space filter, and is reflected by the right-angle prism 8 to the near-field detection system, and is imaged to the near-field detection camera 35 through the beam reduction lens 31, the reflector 32 and the imaging lens (33, 34), so as to obtain the near-field image center of the main light beam and the imaging spot of the small light beam, and adjust the injection reflectors 3, 4, 5 in front of the amplifying system so that the near-field image center of the main light beam coincides with the center of the spot pair of the small light beam pair (2) passing through the #4 hole, so that the center of the small light beam pair (2) passing through the #4 hole is used as the near-field reference of the main light beam.

[0051] The near-field image of the main beam in the near-field camera and the image of the small beam spot through the #4 hole are as follows: Figure 2As shown. The gray part is the schematic diagram of the main laser near-field image, and the black circle represents the main laser near-field center. The white spot is the small beam spot pair passing through hole #4, and the center of the crosshairs is the center of the spot connection line. Adjust the injection reflectors 3, 4, and 5 to make the two centers coincide.

[0052] Step 3. Verify another reference beam: The near-field positions of small beam pair 1 passing through hole #1 coincide with those of small beam pair 2 passing through hole #4, so the near-field center of small beam pair 1 passing through hole #1 also coincides with the near-field center of the main beam. The center of small beam pair 1 passing through hole #1 also serves as the near-field reference of the main beam.

[0053] Step 4. Detecting the near-field reference small beam: After the right-angle prism 8 is moved to the #1 hole 9, the small beam pair 1 passing through the #1 hole passes through the amplifying medium 12, TSF L1 (11) and the #1 hole 9, and is reflected by the right-angle prism 8 to the near-field detection system. After passing through the beam reduction lens 31, the reflector 32 and the imaging lenses 32 and 34, it is received by the near-field detection camera and imaged as a pair of small light spots, as shown in FIG. Figure 3 As shown, the center of the small spot pair represents the reference center of the near-field beam position, and the small beam pair 1 passing through hole #1 is used as the near-field reference small beam of the main beam for subsequent detection and adjustment.

[0054] Step 5. Calibrate the crystal position: At the other end, the position of the frequency doubling crystal 30 in the terminal optical system 29 is calibrated by a pair of target field cones 28, which can be moved in and out. The cones 28 are moved into the main optical path and placed symmetrically in front of the crystal 30 relative to the crystal center line to calibrate the near-field position of the crystal. Before the main laser enters the terminal optical system 29, it will irradiate the corner cone 28 and reflect. After being reflected by a series of TM4 (27), TM3 (26), TM2 (25), and TM1 (24), the reflected light enters the main amplifier system optical path: after passing through TSFL2 (23), #4 hole (10), TSF L1 (11), and the magnifying medium 12, it is reflected by RM1 (13) and P1 (16). After four-pass amplification, it is reflected back by P1 (16) and RM1 (13), and then passes through the magnifying medium 12, TSF L1 (11), and #1 hole (9) again, and is reflected by the right-angle prism 8 to the near-field detection system. After passing through the beam reduction lens 31, the reflector 32, and the imaging lens (33, 34), the corner cone reflected light is received by the near-field camera 35. The center of the corner cone spot represents the center of the crystal, as shown in FIG. Figure 3 shown.

[0055] Step 6. Measurement deviation: The deviation between the center of the reflected light spot of the near-field camera and the center of the light spot of the near-field reference beamlet is the position deviation between the near-field center of the crystal and the near-field center of the main beam, such as Figure 3 shown. Figure 3 The two pairs of light spots in the middle are the pyramid reflection light spot pair and the near-field reference small beam light spot pair. The white circle and cross hairs represent the centers of the two pairs of light spots respectively.

[0056] Step 7. Adjust the crystal position: Use the feedback system to adjust the reflector group 26 and 27 in front of the crystal so that the center position deviation of the two pairs of spots is adjusted to the error range (so that the center of the corner cone reflection spot coincides with the center of the near-field reference small beam spot), which means that the near-field position of the crystal has been adjusted and collimated.

[0057] Step 8. Complete the test: After adjusting the collimation, move the corner cone out of the light path, turn off the near-field reference light source, and complete the test process.

[0058] This embodiment can detect the crystal center and the main beam center by placing the corner cone and the near-field reference beam, and automatically calibrate and adjust the crystal near-field center position deviation, thereby improving the crystal collimation efficiency and debugging accuracy. The system has the characteristics of simple equipment, easy adjustment and high accuracy.

Claims

1. A six-pass amplification high-power laser device crystal near-field center position deviation detection system, characterized in that: include: Two pairs of small beams are placed behind the adjustable reflectors to provide near-field references. The near-field positions of the two pairs of small beams coincide, but the far-field angles are different. The far-field directions of the beam pairs pass through different filter apertures of the transmission spatial filter respectively. A pair of pyramids, which can be moved in and out in front of the crystal, are used to calibrate the near-field position of the crystal; A reflector group, arranged in front of the corner cone, for adjusting the path of the light beam incident on the crystal; A right-angle prism that can be moved behind different filter apertures of the transmission spatial filter to reflect the light beam to the near-field detection system; A near-field detection system is used to obtain and image the near-field image of the main beam and the reflected light spots of the small beams and the corner cones; Use the following steps to detect and adjust the crystal near-field center position deviation: a) Using the small beam pairs after the transmission spatial filter with different filtering pinholes, adjust the near-field center of the main beam to coincide with the near-field center of the small beam pair, and determine the near-field reference of the main beam; b) Using another small beam pair as a near-field position reference, after moving the right-angle prism to the corresponding filtering aperture, the beam is reflected to the near-field detection system for imaging; c) Move a pair of pyramids into the main optical path, place them symmetrically in front of the crystal relative to the center line of the crystal, reflect the main laser to the near-field detection system for imaging, and obtain the center of the pyramid reflection spot; d) Compare the deviation between the center of the near-field reference small beam spot and the center of the pyramid reflection spot, adjust the reflector group to adjust the deviation to within the predetermined error range, and realize the collimation of the near-field position of the crystal.

2. The six-pass amplification high-power laser device crystal near-field center position deviation detection system according to claim 1 is characterized in that: It also includes a feedback system for adjusting the reflector group according to the deviation between the center of the reflected light spot of the corner cone pair in the near-field camera and the center of the light spot of the near-field reference small beam pair, so that the center position deviation of the two pairs of light spots is adjusted to an error range.

3. The six-pass amplification high-power laser device crystal near-field center position deviation detection system according to claim 1 or 2, characterized in that: The near-field detection system comprises a beam reduction lens, a reflector, an imaging lens and a near-field detection camera which are sequentially arranged along an optical path. The beam is imaged to the near-field detection camera (35) through the beam reduction lens (31), the reflector (32) and the imaging lens (33, 34) to obtain the near-field image center of the main beam and the imaging spot of the small beam.

4. The six-pass amplification high-power laser device crystal near-field center position deviation detection system according to claim 1 or 2, characterized in that: The device comprises a transmission space filter, a cavity space filter, an amplifying medium, a reflecting mirror and a lens, which together constitute an optical path of a six-pass amplified high-power laser device.

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