CN114188807A - YAG optical path system with stable light splitting ratio - Google Patents

Abstract

The invention discloses a YAG light path system with stable light splitting ratio, which comprises a YAG laser, a quarter-wave plate, a light splitter, a reflector, a light limiting hole and a turntable reflecting system, wherein the light splitting ratio of the light splitter is stable; the reflector comprises a first reflector and a second reflector; the light limiting holes comprise a first light limiting hole and a second light limiting hole; the turntable reflecting system comprises a plurality of reflecting mirrors used for carrying out pointing adjustment on the light path; the quarter-wave plate 1 is arranged at the tail end of the YAG laser; the YAG laser device emits laser which sequentially passes through the quarter-wave plate, the spectroscope, the first reflector, the second reflector, the first light limiting hole, the second light limiting hole and the rotary table reflection system. The invention realizes the precise gradual energy monitoring of the YAG laser, realizes the whole day area scanning of the outgoing beam with 360-degree azimuth angle and 90-degree pitch angle, has the absolute value deviation of the ratio measurement less than 2 percent, and meets the technical index for calibrating the YAG laser.

Description

YAG optical path system with stable light splitting ratio

Technical Field

The invention relates to the field of YAG lasers, in particular to a YAG optical path system with a stable light splitting ratio.

Background

The high-altitude cosmic ray observation station (LHAASO) is a national important scientific and technological infrastructure taking cosmic ray observation research as a core, and the core scientific aim is to research the origin, acceleration and propagation mechanism of cosmic rays inside and outside a galaxy system, compact celestial body high-energy physical processes such as black holes, neutron stars and the like, the search of dark matter particles and the discovery of new physics. The wide-angle Cherenkov telescope array (WFCTA) is one of four main detectors, and the main physical target is to accurately measure the cosmic ray single-component energy spectrum of 30 TeV-1 EeV through a staged array layout and multi-parameter energy-division section. The measured cosmic ray energy spectrum is mainly obtained by calculating the number of detected photons, so that the number of photons received by a telescope needs to be absolutely calibrated. In the absolute calibration and atmosphere monitoring process of LHAASO-WFCTA, a plurality of factors such as laser beam stability, laser rotation precision, a slow control system, a telescope and the like comprehensively influence the calibration result. The laser provides a light source for calibration, and the energy stability, the directivity and the like of the laser directly determine the quality of the calibration.

YAG laser is a solid laser with YAG crystal as matrix, and is composed of laser rod, pump lamp, condenser and resonant cavity. YAG laser is used as a light source for calibrating photon number, and if the YAG laser is directly used without treatment, the laser energy resolution (the energy resolution is Sigma/Mean) is too large to meet the use requirement. Meanwhile, the laser is used as a precision instrument for experiments, the requirement on the environment is strict when the laser is used, and the maintenance once in 6 months is also a basic requirement for long-time stable work. Its operation must be constant in temperature, constant in humidity and small. When the change of the environmental temperature reaches 25 ℃, the laser energy is changed violently, the energy change of the YAG laser is close to 100 percent, the requirement of experimental calibration cannot be met, and the service life and the performance index of the laser are seriously reduced by large temperature difference.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a YAG optical path system with stable light splitting ratio.

The purpose of the invention is realized by the following technical scheme:

a YAG optical path system with stable light splitting ratio comprises a YAG laser, a quarter-wave plate, a light splitter, a reflector, a light limiting hole and a turntable reflecting system; the reflector comprises a first reflector and a second reflector; the light limiting holes comprise a first light limiting hole and a second light limiting hole; the turntable reflecting system comprises a plurality of reflecting mirrors used for carrying out pointing adjustment on the light path; the quarter-wave plate is arranged at the tail end of the YAG laser; the YAG laser device emits laser which sequentially passes through the quarter-wave plate, the spectroscope, the first reflector, the second reflector, the first light limiting hole, the second light limiting hole and the rotary table reflection system.

Furthermore, the YAG laser, the quarter-wave plate, the spectroscope, the first reflector, the second reflector, the first light limiting hole and the second light limiting hole are all arranged in the temperature control box.

Furthermore, a heat insulation layer and an acrylic plate are sequentially arranged below the temperature control box, and the temperature in the box is set to be 23 ℃ during operation.

Furthermore, the beam splitter is a 50% beam splitter, and the light beam passing through the beam splitter takes the reflected light as a reference light beam and the transmitted light as a calibration light beam to enter the first reflecting mirror.

Furthermore, the turntable reflecting system comprises a first turntable reflecting mirror, a second turntable reflecting mirror, a third turntable reflecting mirror, a fourth turntable reflecting mirror and a fifth turntable reflecting mirror, and light beams guided by the first reflecting mirror and the second reflecting mirror pass through the first turntable reflecting mirror, the second turntable reflecting mirror, the third turntable reflecting mirror, the fourth turntable reflecting mirror and the fifth turntable reflecting mirror after being adjusted by the first light limiting hole and the second light limiting hole.

Furthermore, the rotary table reflection system is arranged on a laser rotary table which sequentially comprises a lifting table, a horizontal rotary table and a pitching rotary table from bottom to top; the first rotary table reflector is fixed at the bottom end of the lifting table, the second rotary table reflector and the third rotary table reflector are fixed at the table top of the lifting table, and the laser is guided by the second rotary table reflector and the third rotary table reflector to be coupled with the horizontal rotating shaft; the third rotary table reflector is positioned on the central shaft of the horizontal rotary table, and the fourth rotary table reflector is arranged at the center of the horizontal rotary table; the fifth rotary table reflector is arranged on the pitching rotary table, the fourth rotary table reflector and the fifth rotary table reflector guide laser to be coupled with the pitching rotary shaft, and the final laser is emitted from the fifth rotary table reflector.

Further, the first, second and third turntable mirrors are held stationary; the fourth rotary table reflector rotates with the horizontal rotary table at an azimuth angle of 360 degrees, and the fifth rotary table reflector rotates with the pitching rotary table at a pitching angle of 180 degrees.

Furthermore, the first light limiting hole and the second light limiting hole are both light limiting diaphragms and are used for restoring the laser to the original light ray position.

And further, the optical system also comprises an energy meter which is used for measuring the energy of the reference beam reflected by the optical splitter and the beam emitted by the fifth turntable reflecting mirror.

The invention has the beneficial effects that: the invention reduces the influence of the distance of the light path on the technical index, and improves the stability of the ratio value by placing the spectroscope at the tail end of the light path; a stable working environment is provided for the laser through the temperature control box, the stability of the laser emitted by the laser is ensured, and the service life of the equipment is prolonged; the whole light path design realizes the accurate gradual energy monitoring of the YAG laser, and realizes the whole day area scanning of the emergent light beam with 360-degree azimuth angle and 90-degree pitch angle.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.

FIG. 1 is a system schematic of the present invention.

FIG. 2 is a graph of experimental test results of the ratio minute mean as a function of time.

Fig. 3 is a graph of the test results of the half-hour mean simulation in the evening of 24 days.

Fig. 4 is a graph of the test results of the 25-day half-hour-late mean simulation.

Description of reference numerals: 1-a quarter wave plate; 2-a spectroscope; 3-a first mirror; 4-a second mirror; 5-a first light limiting hole; 6-a second light limiting hole; 7-a first turntable mirror; 8-a second turret mirror; 9-a third turret mirror; 10-a fourth turret mirror; 11-fifth turntable mirror.

Detailed Description

It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In this embodiment, the YAG laser contains accurate optical member, need take precautions against earthquakes and accuse temperature, and laser revolving stage space is limited, and the pipe of connecting laser head and water cooling system is heavier, pulls the laser head easily, therefore this scheme has redesigned YAG laser light path. The laser is fixed to the optical platform and the YAG laser pulses are directed by a mirror to travel over and rotate with the turntable. As shown in fig. 1, a YAG optical path system with stable beam 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 comprises a first reflector 3 and a second reflector 4; the light limiting holes comprise a first light limiting hole 5 and a second light limiting hole 6; the quarter-wave plate is arranged at the tail end of the YAG laser to convert linearly polarized light into circularly polarized light; the YAG laser emits laser which sequentially passes through a quarter-wave plate 1, a spectroscope 2, a first reflector 3, a second reflector 4, a first light limiting hole 5, a second light limiting hole 6 and a turntable reflection system, and the spectroscope 2 is positioned at the tail end of a light path (not before the reflector).

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 hole 5, and the second light limiting hole 6 are all disposed in the temperature control box to provide a stable working environment.

An insulating layer and an acrylic plate are sequentially padded under the temperature control box; when the temperature control box works, the temperature in the temperature control box is kept stable and is about 23 ℃.

The beam splitter enables a part of light to transmit through the lens and reflects the rest of light. In this embodiment, a 50% beam splitter 2 (i.e. the light beam equally divides the laser light at a ratio of 50: 50) is used, and the reflected light passing through the beam splitter 2 is used as a reference beam, so as to monitor the energy of each transmitted pulse laser, and thus analyze the laser image of the telescope more accurately; the transmitted light is incident as a calibration beam on the first mirror 3.

And splitting the light beam of the laser to obtain a reference light beam and a calibration light beam. The single pulse energies measured by the reference and calibration optical paths are all from the same pulse, and furthermore, since the beam splitting ratio of the beam splitter has a constant value under the same polarization and angle, the emitted and transmitted laser energies have a positive correlation, and this ratio (ratio) is independent of the fluctuation of the laser outgoing pulse energy. Although the output pulse energy of the laser is influenced by various factors at high altitude, so that the fluctuation of the output pulse energy is large, the energy of the emergent laser can be accurately calculated by monitoring the energy of the reference light, and the method has important significance for accurately calibrating the absolute photon number of the telescope. However, this places high demands on the precise measurement of the fractional light (ratio) (less than 2% change in absolute value). In the previous experiment, the Ratio is interfered by various factors (the Ratio is calculated by energy values measured by two beams, the deviation source is related to the light splitting Ratio, the reflectivity and the error of a probe of each light-emitting part; the Ratio is mainly used for calculating the calibrated light energy by a method of multiplying the reference light by the Ratio under the condition that the calibrated light energy cannot be measured (the calibrated light is emitted out of a calibrated telescope), the deviation generated by the Ratio can cause the error generated by the calculation of the calibrated light energy), and the experiment result shows that the deviation of the measured absolute value of the Ratio is more than 2%.

In view of the above, in the embodiment, the spectroscope 2 is located at the end of the optical path (not before the mirror), and tests show that this arrangement can effectively improve the stability of the ratio value. Meanwhile, in order to research the influence of temperature on the polarization of the laser emergent light, a polarizer (a quarter wave plate) is added into a light path, so that the polarization of the emergent laser light is enhanced.

In this embodiment, the turntable reflecting system includes a first turntable reflecting mirror 7, a second turntable reflecting mirror 8, a third turntable reflecting mirror 9, a fourth turntable reflecting mirror 10, and a fifth turntable reflecting mirror 11, and the light beams guided by the first reflecting mirror 3 and the second reflecting mirror 4 pass through the first turntable reflecting mirror 7, the second turntable reflecting mirror 8, the third turntable reflecting mirror 9, the fourth turntable reflecting mirror 10, and the fifth turntable reflecting mirror 11 in sequence after being adjusted by the first light limiting hole 5 and the second light limiting hole 6.

The rotary table reflection system is arranged on a laser rotary table which consists of a lifting table, a horizontal rotary table and a pitching rotary table from bottom to top in sequence; the first rotary table reflector 7 is fixed at the bottom end of the lifting table, the second rotary table reflector 8 and the third rotary table reflector 9 are fixed at the table top of the lifting table, and laser is guided to be coupled with the horizontal rotary shaft through the second rotary table reflector 8 and the third rotary table reflector 9; the third rotary table reflector 9 is positioned on the central shaft of the horizontal rotary table, and the fourth rotary table reflector 10 is arranged at the center of the horizontal rotary table; the fifth rotary table reflector 11 is arranged on the pitching rotary table, the fourth rotary table reflector 10 and the fifth rotary table reflector 11 guide the laser to be coupled with the pitching rotary table, and the final laser is emitted from the fifth rotary table reflector 11.

Wherein the first, second and third turntable mirrors 7, 8, 9 are held stationary; the fourth rotary table reflector 10 rotates with the horizontal rotary table at an azimuth angle of 360 degrees; the fifth rotary table mirror 11 performs a 180-degree tilting rotation along with the tilting rotary table.

The first light limiting hole 5 and the second light limiting hole 6 are both light limiting diaphragms and are used for restoring laser to the original light ray position.

In conclusion, the scheme improves the working stability of the system, reduces the influence of temperature, adds the polarizer in the light path to enhance the laser polarization, moves the beam splitter backwards and effectively improves the deviation of the ratio value. And testing the ratio value continuously all night, wherein the test result is shown in figure 2, the ratio value is measured according to the average value of the data required by identification, the ratio value is plotted against the time, and the deviation is calculated according to the peak value and is less than 1.9 percent. If measured according to the half-hour data average of the index requirement, the (Meanratio 30-Meanratio all)/Meanratio all graph, even if the calculated deviation of the peak value is less than 0.9% (24 days, figure 3) and 1% (25 days, figure 4), the acceptance standard is completely achieved, and the technical index requirement of the YAG laser is met.

The YAG laser device realizes accurate gradual emission energy monitoring of the YAG laser device through light path design, and realizes full-day area scanning of an emergent light beam with 360-degree azimuth angle and 90-degree pitch angle. In the light path design, the stability of laser energy monitoring is improved from 5% to 2% by the design of a spectroscope, the light path is directionally adjusted by the elements 1, 3, 4 and 7-11 through the reflecting mirrors, the light path can be adjusted according to actual conditions to meet more observation requirements, wherein the parts of the elements 1-6 are positioned in a self-made temperature control box to provide a stable working environment for the laser, the element 7 is fixed on a laser turntable, the laser is guided by the element 7 to be coupled with the lifting action of the laser turntable after being guided by the element 6, the guided laser is coupled with an azimuth rotating shaft of the turntable through the elements 8 and 9, and finally the action in the pitching direction and the final laser emission are finished through the guidance of the elements 10 and 11.

The structures, functions, and connections disclosed herein may be implemented in other ways. For example, the embodiments described above are merely illustrative, e.g., multiple components may be combined or integrated with another component; in addition, functional components in the embodiments herein may be integrated into one functional component, or each functional component may exist alone physically, or two or more functional components may be integrated into one functional component.

The foregoing is illustrative of the preferred embodiments of this invention, and it is to be understood that the invention is not limited to the precise form disclosed herein and that various other combinations, modifications, and environments may be resorted to, falling within the scope of the concept as disclosed herein, either as described above or as apparent to those skilled in the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (9)

1. The YAG optical path system with stable light splitting ratio is characterized by comprising a YAG laser, a quarter-wave plate (1), a light splitter (2), a reflector, a light limiting hole and a turntable reflecting system; the mirrors comprise a first mirror (3) and a second mirror (4); the light limiting holes comprise a first light limiting hole (5) and a second light limiting hole (6); the turntable reflecting system comprises a plurality of reflecting mirrors used for carrying out pointing adjustment on the light path; the quarter-wave plate 1 is arranged at the tail end of the YAG laser; the YAG laser device emits laser which sequentially passes through a quarter-wave plate (1), a spectroscope (2), a first reflector (3), a second reflector (4), a first light limiting hole (5), a second light limiting hole (6) and a rotary table reflection system.

2. The YAG optical path system with stable splitting ratio as claimed in claim 1, wherein 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 arranged in a temperature control box.

3. The YAG optical path system with stable light splitting ratio as claimed in claim 2, wherein an insulating layer and an acrylic plate are sequentially arranged under the temperature control box, and the temperature in the box is set to 23 ℃ during operation.

4. YAG optical path system with stable splitting ratio as claimed in claim 1, characterized in that the beam splitter (2) is a 50% beam splitter, and the beam passing through the beam splitter (2) uses the reflected light as the reference beam and the transmitted light as the calibration beam to enter the first reflector (3).

5. A spectrally proportion-stabilized YAG optical path system according to claim 1, characterized in that, the turntable reflection system comprises a first turntable mirror (7), a second turntable mirror (8), a third turntable mirror (9), a fourth turntable mirror (10) and a fifth turntable mirror (11); the light beams guided by the first reflector (3) and the second reflector (4) pass through the first rotary table reflector (7), the second rotary table reflector (8), the third rotary table reflector (9), the fourth rotary table reflector (10) and the fifth rotary table reflector (11) in sequence after being adjusted by the first light limiting hole (5) and the second light limiting hole (6).

6. The YAG optical path system with stable beam splitting ratio as claimed in claim 5, wherein the turntable reflection system is arranged on a laser turntable which comprises a lifting platform, a horizontal rotating platform and a pitching rotating platform in sequence from bottom to top; the first rotary table reflector (7) is fixed at the bottom end of the lifting table, the second rotary table reflector (8) and the third rotary table reflector (9) are fixed at the table top of the lifting table, and laser is guided to be coupled with the horizontal rotating shaft through the second rotary table reflector (8) and the third rotary table reflector (9); the third rotary table reflector (9) is positioned on the central shaft of the horizontal rotary table, and the fourth rotary table reflector (10) is arranged at the center of the horizontal rotary table; the fifth rotary table reflector (11) is arranged on the pitching rotary table, the fourth rotary table reflector (10) and the fifth rotary table reflector (11) guide laser to be coupled with the pitching rotary shaft, and finally the laser is emitted from the fifth rotary table reflector (11).

7. A spectrally proportion-stabilized YAG optical path system according to claim 6, characterized in that the first (7), second (8) and third (9) turntable mirrors are held stationary; the fourth rotary table reflector (10) rotates with the horizontal rotary table at an azimuth angle of 360 degrees; and the fifth rotary table reflector (11) rotates in a pitching mode by 180 degrees along with the pitching rotary table.

8. The YAG optical path system with stable splitting ratio as claimed in claim 1, wherein the first light limiting hole (5) and the second light limiting hole (6) are both light limiting diaphragms for restoring the laser to the original light position.

9. A beam splitting ratio stabilized YAG optical path system according to claim 1, characterized by further comprising an energy meter for measuring the energy of the reference beam reflected by the beam splitter (2) and the beam emitted from the fifth turntable mirror (11).

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