A YAG optical system with stable splitting ratio

Abstract

The present invention discloses a YAG optical path system with a stable light splitting ratio, comprising a YAG laser, a quarter-wave plate, a beam splitter, a reflector, a light-limiting aperture, and a turntable reflection system; the reflector comprises a first reflector and a second reflector; the light-limiting aperture comprises a first light-limiting aperture and a second light-limiting aperture; the turntable reflection system comprises multiple reflectors for adjusting the direction of the optical path; the quarter-wave plate 1 is disposed at the end of the YAG laser; laser light emitted by the YAG laser sequentially passes through the quarter-wave plate, the beam splitter, the first reflector, the second reflector, the first light-limiting aperture, the second light-limiting aperture, and the turntable reflection system. The present invention achieves precise shot-by-shot energy monitoring of the YAG laser and enables full-sky scanning of the output beam with a 360° azimuth angle and a 90° elevation angle. The absolute value deviation of the ratio measurement is less than 2%, meeting the technical specifications for YAG laser calibration.

Description

Technical Field

[0001] The present invention relates to the field of YAG lasers, and in particular to a YAG optical path system with a stable light splitting ratio. Background Art

[0002] The High Altitude Cosmic Ray Observatory (LHAASO) is a major national scientific infrastructure focused on cosmic ray observation and research. Its core scientific objectives are to study the origin, acceleration, and propagation mechanisms of cosmic rays within and beyond the Milky Way, high-energy physics processes in compact objects such as black holes and neutron stars, the search for dark matter particles, and the discovery of new physics. The Wide Field Cherenkov Telescope Array (WFCTA) is one of its four main detectors. Its primary physical objective is to accurately measure the single-component energy spectrum of cosmic rays in the 30 TeV-1 EeV range through a phased array layout, using multiple parameters and energy bands. Cosmic ray energy spectrum measurements are primarily calculated based on the number of detected photons, necessitating absolute calibration of the number of photons received by the telescope. During the LHAASO-WFCTA absolute calibration and atmospheric monitoring process, multiple factors, including laser beam stability, laser rotation accuracy, slow control system, and telescope, influence the calibration results. The laser provides the light source for calibration, and its energy stability and directivity directly determine the quality of the calibration.

[0003] A YAG laser is a solid-state laser based on a yttrium aluminum garnet crystal. It typically consists of a laser rod, a pump lamp, a concentrator, and a resonant cavity. If a YAG laser is used directly as a light source for photon count calibration without prior processing, its laser energy resolution (energy resolution measured as Sigma / Mean) will be too high to meet the required performance. Furthermore, as a precision laboratory instrument, the laser has stringent environmental requirements, and six-monthly maintenance is essential for long-term stable operation. Its operation requires constant temperature and low humidity. Ambient temperature fluctuations exceeding 25°C can cause drastic fluctuations in laser energy. With YAG lasers experiencing energy fluctuations approaching 100%, this fluctuation cannot meet experimental calibration requirements. Furthermore, large temperature fluctuations can severely reduce the laser's lifespan and performance. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a YAG optical path system with a stable light splitting ratio.

[0005] The object of the present invention is achieved through the following technical solutions:

[0006] A YAG optical path system with a stable light splitting ratio comprises a YAG laser, a quarter-wave plate, a beam splitter, a reflector, a light-limiting hole and a turntable reflection system; the reflector comprises a first reflector and a second reflector; the light-limiting hole comprises a first light-limiting hole and a second light-limiting hole; the turntable reflection system comprises a plurality of reflectors for adjusting the direction of the optical path; the quarter-wave plate is arranged at the end of the YAG laser; laser light emitted by the YAG laser passes through the quarter-wave plate, the beam splitter, the first reflector, the second reflector, the first light-limiting hole, the second light-limiting hole and the turntable reflection system in sequence.

[0007] Furthermore, the YAG laser, quarter wave plate, beam splitter, first reflector, second reflector, first light limiting hole and second light limiting hole are all placed in a temperature control box.

[0008] Furthermore, an insulation layer and an acrylic plate are sequentially placed under the temperature control box. When working, the temperature inside the box is set to 23°C.

[0009] Furthermore, the beam splitter is a 50% beam splitter, and the light beam passing through the beam splitter is incident on the first reflector with the reflected light serving as the reference beam and the transmitted light serving as the calibration beam.

[0010] Furthermore, the turntable reflection system includes a first turntable reflector, a second turntable reflector, a third turntable reflector, a fourth turntable reflector and a fifth turntable reflector. The light beam guided by the first reflector and the second reflector passes through the first light limiting hole and the second light limiting hole after being adjusted, and then passes through the first turntable reflector, the second turntable reflector, the third turntable reflector, the fourth turntable reflector and the fifth turntable reflector in sequence.

[0011] Furthermore, the turntable reflection system is arranged on a laser turntable which consists of a lifting platform, a horizontal rotation platform and a pitch rotation platform from bottom to top; the first turntable reflector is fixed to the bottom end of the lifting platform, the second turntable reflector and the third turntable reflector are fixed to the table surface of the lifting platform, and the laser is guided to couple with the horizontal rotation axis through the second turntable reflector and the third turntable reflector; the third turntable reflector is on the central axis of the horizontal rotation platform, and the fourth turntable reflector is arranged at the center of the horizontal rotation platform; the fifth turntable reflector is arranged on the pitch rotation platform, and the fourth turntable reflector and the fifth turntable reflector guide the laser to couple with the pitch rotation axis, and the final laser is emitted from the fifth turntable reflector.

[0012] Furthermore, the first turntable reflector, the second turntable reflector and the third turntable reflector are kept fixed; the fourth turntable reflector rotates 360 degrees in azimuth along with the horizontal turntable; and the fifth turntable reflector rotates 180 degrees in pitch along with the pitch turntable.

[0013] Furthermore, the first light-limiting hole and the second light-limiting hole are both light-limiting apertures, which are used to restore the laser to the original light position.

[0014] Furthermore, it also includes an energy meter, which is used to measure the energy of the reference beam reflected by the spectrometer and the beam emitted by the fifth turntable reflector.

[0015] The beneficial effects of the present invention are as follows: the present invention reduces the influence of the optical path distance on the technical indicators, and places the spectrometer at the end position of the optical path to improve the stability of the ratio value; a stable working environment is provided for the laser by being placed in a temperature-controlled box, thereby ensuring the stability of the laser emitted by the laser and improving the service life of the equipment; the entire optical path design realizes precise shot-by-shot energy monitoring of the YAG laser and realizes full-sky scanning of the output light beam at 360° azimuth angle and 90° elevation angle. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. 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 the structures shown in these drawings without paying any creative work.

[0017] Figure 1 It is a system principle diagram of the present invention.

[0018] Figure 2 This is an experimental test result graph showing how the minute mean of ratio changes over time.

[0019] Figure 3 This is the test result chart of the half-hour average value simulating the actual situation on the evening of the 24th.

[0020] Figure 4 This is the test result chart of the half-hour average value simulating the actual situation on the evening of the 25th.

[0021] Explanation of the reference numerals: 1-quarter wave plate; 2-beam splitter; 3-first reflector; 4-second reflector; 5-first light-limiting hole; 6-second light-limiting hole; 7-first turntable reflector; 8-second turntable reflector; 9-third turntable reflector; 10-fourth turntable reflector; 11-fifth turntable reflector. DETAILED DESCRIPTION

[0022] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0023] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0024] In this embodiment, the YAG laser contains precision optical components that require shockproofing and temperature control. However, the laser turntable has limited space, and the tube connecting the laser head and the water cooling system is heavy, which can easily drag the laser head. Therefore, this solution redesigns the YAG laser optical path. The laser is fixed to the optical platform, and the YAG laser pulse is guided by a reflector on the turntable and rotates with the turntable. Figure 1 As shown, a YAG optical path system with a stable splitting ratio includes a YAG laser, a quarter-wave plate 1, a beam splitter 2, a reflector, a light-limiting hole and a turntable reflection system; the reflector includes a first reflector 3 and a second reflector 4; the light-limiting hole includes a first light-limiting hole 5 and a second light-limiting hole 6; the quarter-wave plate is arranged at the end of the YAG laser to convert linearly polarized light into circularly polarized light; the laser light emitted by the YAG laser passes through the quarter-wave plate 1, the beam splitter 2, the first reflector 3, the second reflector 4, the first light-limiting hole 5, the second light-limiting hole 6 and the turntable reflection system in sequence, and the beam splitter 2 is located at the end of the optical path (before passing through the reflector).

[0025] In this embodiment, the YAG laser, the quarter-wave plate 1, the beam splitter 2, the first reflector 3, the second reflector 4, the first light-limiting aperture 5 and the second light-limiting aperture 6 are all placed in a temperature-controlled box to provide a stable working environment.

[0026] The temperature control box is padded with an insulation layer and an acrylic plate in sequence; when working, the temperature inside the temperature control box remains stable at about 23°C.

[0027] The beam splitter allows a portion of the light to pass through the lens and reflects the remaining light. In this embodiment, a 50% beam splitter 2 is used (i.e., it splits the laser light at a 50:50 ratio). The reflected light from the beam passing through beam splitter 2 serves as a reference beam, which can be used to monitor the energy of each transmitted laser pulse, thereby more accurately analyzing the telescope's laser imaging. The transmitted light serves as a calibration beam and is emitted into first reflector 3.

[0028] The laser beam is split to obtain reference and calibration beams. The single pulse energy measured by the reference and calibration optical paths all originate from the same pulse. In addition, because the beam splitting ratio of the beam splitter has a constant value under the same polarization and angle, the emitted and transmitted laser energies are positively correlated, and this ratio is independent of the fluctuation of the laser's output pulse energy. Although the laser's output pulse energy is affected by various factors at high altitude, resulting in large fluctuations in the output pulse energy, we can still accurately calculate the energy of the emitted laser by monitoring the energy of the reference beam, which is of great significance for the accurate calibration of the telescope's absolute photon count. However, this places high demands on the precise measurement of the splitting ratio (the absolute value change is less than 2%). Previous experiments were interfered with by various factors (the ratio is calculated using the energy values ​​measured by the two beams of light, and the source of the deviation is related to the splitting ratio of each light emission, the reflectivity, and the error of the probe; the ratio is mainly used when the calibration light energy cannot be measured (the calibration light is emitted to calibrate the telescope), and the calibration light energy is calculated by multiplying the reference light by the ratio. Deviations in the ratio will lead to errors in the calibration light energy calculation). Experimental results show that the absolute value deviation of the ratio measurement is greater than 2%.

[0029] To address this result, in this embodiment, beam splitter 2 is positioned at the end of the optical path (before the reflector). Testing has shown that this arrangement effectively improves the stability of the ratio. Furthermore, to study the effect of temperature on the polarization of the output laser light, a polarizer (quarter-wave plate) was added to the optical path to enhance the polarization of the output laser light.

[0030] In this embodiment, the turntable reflection system includes a first turntable reflector 7, a second turntable reflector 8, a third turntable reflector 9, a fourth turntable reflector 10 and a fifth turntable reflector 11. The light beam guided by the first reflector 3 and the second reflector 4 passes through the first turntable reflector 7, the second turntable reflector 8, the third turntable reflector 9, the fourth turntable reflector 10 and the fifth turntable reflector 11 in sequence after being adjusted by the first light limiting hole 5 and the second light limiting hole 6.

[0031] Among them, the turntable reflection system is arranged on a laser turntable which consists of a lifting platform, a horizontal rotation platform and a pitch rotation platform from bottom to top; the first turntable reflector 7 is fixed at the bottom end of the lifting platform, the second turntable reflector 8 and the third turntable reflector 9 are fixed on the table surface of the lifting platform, and the laser is guided to couple with the horizontal rotation axis through the second turntable reflector 8 and the third turntable reflector 9; the third turntable reflector 9 is on the central axis of the horizontal rotation platform, and the fourth turntable reflector 10 is arranged at the center of the horizontal rotation platform; the fifth turntable reflector 11 is arranged on the pitch rotation platform, and the fourth turntable reflector 10 and the fifth turntable reflector 11 guide the laser to couple with the pitch rotation axis, and the final laser is emitted from the fifth turntable reflector 11.

[0032] Among them, the first turntable reflector 7, the second turntable reflector 8 and the third turntable reflector 9 remain fixed; the fourth turntable reflector 10 rotates 360 degrees in azimuth along with the horizontal turntable; and the fifth turntable reflector 11 rotates 180 degrees in pitch along with the pitch turntable.

[0033] The first light-limiting hole 5 and the second light-limiting hole 6 are both light-limiting apertures, which are used to restore the laser to its original light position.

[0034] In summary, this solution improves the stability of the system, reduces the influence of temperature, adds a polarizer in the optical path to enhance the polarization of the laser, and moves the beam splitter backward, effectively improving the deviation of the ratio value. The ratio value is tested continuously throughout the night, and the test results are as follows: Figure 2 As shown, if the ratio is plotted against time and calculated according to the peak-to-peak value based on the data average required by the identification, the deviation is less than 1.9%. If the half-hour data average required by the indicator is measured and (Meanratio30-Meanratioall) / Meanratioall is plotted, even if the peak-to-peak value is calculated, the deviation is less than 0.9% (24 days, Figure 3 ), 1% (25th, Figure 4 ), fully met the acceptance standards and satisfied the technical index requirements of YAG laser.

[0035] The present invention achieves precise, shot-by-shot energy monitoring of YAG lasers through optical path design, and enables full-sky scanning of the emitted light beam with a 360° azimuth angle and a 90° elevation angle. In the optical path design, the design of the beam splitter improves the stability of laser energy monitoring from 5% to 2%. Components 1, 3, 4, and 7-11 reflectors adjust the direction of the optical path, and the optical path can be adjusted according to actual conditions to accommodate more observation needs. Components 1-6 are located in a custom-made temperature-controlled box to provide a stable operating environment for the laser. Component 7 is fixed to the laser turntable. After being guided by component 6, the laser is then coupled to the laser turntable's lifting and lowering motion by component 7. After being guided by components 8 and 9, the laser is coupled to the turntable's azimuth axis. Finally, components 10 and 11 guide the movement in the elevation direction and the final laser emission.

[0036] The structures, functions, and connection forms disclosed herein may be implemented in other ways. For example, the embodiments described above are merely illustrative, and multiple components may be combined or integrated into another component. In addition, the functional components in the various embodiments herein may be integrated into a single functional component, or each functional component may exist physically separately, or two or more functional components may be integrated into a single functional component.

[0037] The foregoing description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein and should not be construed as excluding other embodiments. Rather, the present invention can be used in various other combinations, modifications, and environments and can be modified within the scope of the concept described herein through the above teachings or techniques or knowledge in the relevant field. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention are intended to be protected by the appended claims.

Claims

1. A +YAG optical system with a stable splitting ratio, characterized in that: The invention comprises a YAG laser, a quarter-wave plate (1), a beam splitter (2), a reflector, a light-limiting hole and a turntable reflection system; the reflector comprises a first reflector (3) and a second reflector (4); the light-limiting hole comprises a first light-limiting hole (5) and a second light-limiting hole (6); the turntable reflection system comprises a plurality of reflectors for adjusting the direction of the light path; the quarter-wave plate 1 is arranged at the end of the YAG laser; the laser light emitted by the YAG laser passes through the quarter-wave plate (1), the beam splitter (2), the first reflector (3), the second reflector (4), the first light-limiting hole (5), the second light-limiting hole (6) and the turntable reflection system in sequence; The YAG laser, the quarter-wave plate (1), the beam splitter (2), the first reflector (3), the second reflector (4), the first light-limiting hole (5) and the second light-limiting hole (6) are all placed in a temperature-controlled box; The first light-limiting hole (5) and the second light-limiting hole (6) are both light-limiting apertures, used to restore the laser to its original light position; The turntable reflection system comprises a first turntable reflector (7), a second turntable reflector (8), a third turntable reflector (9), a fourth turntable reflector (10) and a fifth turntable reflector (11); the light beam guided by the first reflector (3) and the second reflector (4) passes through the first light-limiting hole (5) and the second light-limiting hole (6) for adjustment, and then passes through the first turntable reflector (7), the second turntable reflector (8), the third turntable reflector (9), the fourth turntable reflector (10) and the fifth turntable reflector (11) in sequence; The turntable reflection system is arranged on a laser turntable which is composed of a lifting platform, a horizontal rotating platform and a pitch rotating platform from bottom to top; the first turntable reflector (7) is fixed on the bottom end of the lifting platform, the second turntable reflector (8) and the third turntable reflector (9) are fixed on the table surface of the lifting platform, and the laser is guided to couple with the horizontal rotation axis through the second turntable reflector (8) and the third turntable reflector (9); the third turntable reflector (9) is on the central axis of the horizontal rotating platform, and the fourth turntable reflector (10) is arranged at the center of the horizontal rotating platform; the fifth turntable reflector (11) is arranged on the pitch rotating platform, and the fourth turntable reflector (10) and the fifth turntable reflector (11) guide the laser to couple with the pitch rotation axis, and the final laser is emitted from the fifth turntable reflector (11).

2. The YAG optical system with a stable splitting ratio according to claim 1, characterized in that: The temperature control box is padded with an insulation layer and an acrylic plate in sequence. When working, the temperature inside the box is set to 23°C.

3. The YAG optical system with a stable splitting ratio according to claim 1, characterized in that: The beam splitter (2) is a 50% beam splitter, and the light beam passing through the beam splitter (2) is incident on the first reflector (3) with the reflected light serving as a reference light beam and the transmitted light serving as a calibration light beam.

4. The YAG optical system with a stable splitting ratio according to claim 1, characterized in that: The first turntable reflector (7), the second turntable reflector (8) and the third turntable reflector (9) are kept stationary; the fourth turntable reflector (10) rotates 360 degrees in azimuth along with the horizontal turntable; and the fifth turntable reflector (11) rotates 180 degrees in pitch along with the pitch turntable.

5. The YAG optical system with a stable splitting ratio according to claim 1, characterized in that: It also includes an energy meter, which is used to measure the energy of the reference beam reflected by the beam splitter (2) and the beam emitted by the fifth turret reflector (11).

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