CN116565676A - 1 ns-level pulse width single-frequency pulse laser and control method - Google Patents
1 ns-level pulse width single-frequency pulse laser and control method Download PDFInfo
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- H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
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- H01S3/11—Mode locking; Q-switching; Other giant-pulse techniques, e.g. cavity dumping
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/11—Mode locking; Q-switching; Other giant-pulse techniques, e.g. cavity dumping
- H01S3/1123—Q-switching
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Abstract
The invention belongs to the technical field of solid lasers, and discloses a 1 ns-level pulse width single-frequency pulse laser and a control method thereof.A reflecting device is fixed at the lower end of pumping laser, a thin film polaroid is fixed at one side of the reflecting device, a crystal is fixed at one side of the thin film polaroid, and an acousto-optic switch, an absorption crystal and an output lens are arranged at the rear end of the thin film polaroid for outputting; the pumping laser and the reflecting device are fixed in the protective shell, the left side of the protective shell is fixed with a continuous single-frequency seed light source, piezoelectric ceramics is arranged on the upper right side of the protective shell, and a photoelectric detector is arranged on the lower right side of the protective shell. The piezoelectric ceramics and the photoelectric detector are linearly connected with a CPLD controller, the CPLD controller is linearly connected with an acousto-optic switch, and the acousto-optic switch is an acousto-optic Q switch. The seed light is injected twice in the driven laser resonant cavity through a thin film type polarization beam splitter (TFP), and meanwhile, the length of the resonant cavity is finely adjusted through piezoelectric ceramics (PZT), so that injection locking is realized.
Description
Technical Field
The invention belongs to the technical field of solid lasers, and particularly relates to a 1 ns-level pulse width single-frequency pulse laser and a control method thereof.
Background
Currently, single frequency pulse lasers are mainly used in wind lidar, differential absorption radar and synthetic aperture lidar. Synthetic aperture lidar (Synthetic Aperture Ladar, SAL), laser SAL for short.
In 1995, the Marcus team in lincoln laboratories in the united states used a continuous laser test system to perform two-bit SAL images on military targets. The system has the emission power of 5mW, and adopts a mode that a light source is not moved but a target moves to perform synthetic aperture imaging. This is also the first time that imaging is achieved using synthetic aperture. In 2002, the united states naval laboratory uses a single longitudinal mode tunable laser from New Focus to image the target. The theoretical distance resolution of the experimental system is 168 mu m, the azimuth resolution is 75 mu m, and the actual resolution is estimated to be 170 mu m from the obtained speckle, and the azimuth resolution is 90 mu m. The phase information is processed by wavelength compensation and synthetic aperture algorithm to obtain an image.
In 2011, the team performed SAL experiments on ground targets using an airborne method, resulting in high resolution SAL images. The airborne experimental platform is located at 3600 feet high altitude, the strabismus angle is 45 degrees, and the distance between the platform and the target is about 1.6km. A1550 nm optical-fiber laser and a 1.5WEDFA are used together as a transmitting source, and the pulse repetition frequency of the transmitting waveform is 100kHz. The system adopts an internal phase coding mode to transmit pulse waveforms, and the method can increase the frequency modulation bandwidth to 7GHz, which corresponds to a distance of 2cm and high resolution. After the synthetic aperture algorithm is adopted, the azimuth resolution is improved by more than 30 times.
In 2008, the research institute of Shanghai optical engine institute Liu Li reports the special problem of SAL related technology, and the key problems of synthetic aperture laser radar hardware implementation, software algorithm and the like are respectively and deeply studied. The SAL key technology search was then conducted by the university of western security criminal Meng Daojiao teaching team and Zeng Xiaodong teaching team affiliates. SAL-based rotating platform target imaging was also reported in 2009.
In 2011, the Shanghai ray machine institute Liu Liren team developed a system for near SAL imaging in the laboratory. The system incorporates optics in the SAL that enable it to produce near-geometrical projections of the emerging beam at close distances and a sufficiently large heterodyne receive field of view.
At the end of 2011, institute of science electronics, wu Jin, liu Guo et al have also developed and realized laboratory imaging of SAL. In order to solve the problem of poor nonlinearity of a linear frequency modulation signal, a compensation scheme of distance nonlinear degradation is provided, and the cause of the nonlinear problem and the distance nonlinear degradation problem caused by spectrum broadening are theoretically analyzed. The experimental system uses 1550nm laser as a light source, the distance between a target and the light source is 2.4 meters, the distance and the directional size of the target are 6.8cm, and the azimuth size is 10cm:
synthetic aperture lidar has an increasingly important role in the future, and SAL related technology is also being studied more and more intensively. To date, SAL technology has not become a practical technology, and for this reason, device performance has not yet reached the practical application requirement, making a very important bottleneck.
Recent SAL studies in China reported Wu Shudong of the institute of science electronics, wu Jin, et al in 2016 as an imaging experiment based on focused pattern SAL on both synthetic and non-cooperative targets. In the experiment, the light emitted by the light source is divided into a heterodyne signal channel, a frequency modulation nonlinear error compensation channel and an initial wavelength compensation channel. The acquired echo signals are preprocessed, phase errors of the signals are compensated, then the model distances of the signals are compressed, then the directions of the signals are subjected to Fourier transformation to obtain SAL signals after matched filtering, and finally the gradient sub-focusing algorithm is used for imaging.
The light source required by the synthetic aperture radar is single-frequency pulse laser. Currently, single frequency pulse lasers are realized by a seed injection locking technology. The most widely used seed injection technology is that seed light is single-frequency continuous laser through acousto-optic Q-switch diffraction order injection and annular cavity injection, and seed light is injected into a driven laser resonant cavity through Bragg diffraction or Raman Ness diffraction of an acousto-optic Q-switch, so that seed light injection is realized.
However, with the acousto-optic Q-switch injection technology in the prior art, due to the influence of the acousto-optic Q-switch device, the pulse width is usually above tens of nanoseconds, and it is difficult to achieve the compression of the pulse width to the level of 1ns. This reduces its resolution for synthetic aperture lidar.
By adopting a passive Q-switching mode, the pulse width can be compressed to 1ns through the initial light transmittance of the saturated absorber and the pumping speed of the laser crystal.
In the seed injection laser having the ring structure, since the optical axis of the oscillation light in one direction is required as the seed injection optical axis, only the seed light and the oscillation light of the slave laser can pass through the gain medium at one time.
Through the above analysis, the problems and defects existing in the prior art are as follows:
(1) Because of the influence of diffraction order injection efficiency, the power of the seed light is required to be certain, and the manufacturing difficulty of the seed light is greatly improved.
(2) Since the optical axis of the oscillation light in one direction needs to be injected as a seed into the optical axis, only the seed light and the oscillation light of the slave laser can pass through the gain medium once.
Disclosure of Invention
Aiming at the problems existing in the prior art, the invention provides a 1 ns-level pulse width single-frequency pulse laser and a control method.
The invention is realized in such a way that a 1 ns-level pulse width single-frequency pulse laser is provided with:
pumping laser; the pumping light is an optical fiber coupling 808nm semiconductor laser and is used for pumping Nd: YAG crystals.
The lower end of the pumping laser is fixed with a reflecting device, one side of the reflecting device is fixed with a film polaroid, one side of the film polaroid is fixed with a crystal, and the rear end is provided with an acousto-optic switch, an absorption crystal and an output lens for output; the pumping laser and the reflecting device are fixed in the protective shell, the left side of the protective shell is fixed with a continuous single-frequency seed light source, piezoelectric ceramics is arranged on the upper right side of the protective shell, and a photoelectric detector is arranged on the lower right side of the protective shell.
Further, the piezoelectric ceramics and the photoelectric detector are linearly connected with a CPLD controller, the CPLD controller is linearly connected with an acousto-optic switch, and the acousto-optic switch is an acousto-optic Q switch.
Further, the reflecting device is provided with a first reflecting device, a second reflecting device and a third reflecting device, wherein the first reflecting device is arranged between the continuous single-frequency seed light source and the first film vibration sheet, the second reflecting device is arranged at the lower end of the piezoelectric ceramic, the third reflecting device is arranged at one side of the pumping laser, and the first reflecting device, the second reflecting device and the third reflecting device are 45-degree reflecting mirrors.
Further, the pumping laser is 808nm laser, the pumping laser is vertically installed, and the position where the central line of the pumping laser coincides with the central line of the continuous single-frequency seed light source is the central point of the first reflecting device.
Further, the film polaroid is a 45-degree film polaroid, the film polaroid is provided with a first film polaroid and a second film polaroid, the first film polaroid is arranged on the left side of the crystal, and the second film polaroid is arranged on the right side of the crystal.
Further, a first half-wave plate is arranged between the first reflecting mirror and the first thin film polaroid, a second half-wave plate is arranged between the crystal and the second thin film polaroid, and the first half-wave plate and the second half-wave plate are 1.06 mu m half-wave plates.
Another object of the present invention is to provide a method for controlling the 1 ns-level pulse width single frequency pulse laser, where the method for controlling the 1 ns-level pulse width single frequency pulse laser includes: the seed light continuous single-frequency seed light source is a single-frequency continuous light source, sequentially passes through the pump laser, the first half wave plate and the first film vibration plate, is input into the crystal by adjusting the rotation angle of the first half wave plate, and then the rest seed light sequentially passes through the second film vibration plate, the second reflecting mirror, the third reflecting mirror 10 and the first film vibration plate to be injected into the crystal again by adjusting the angle of the second half wave plate; the length of the resonant cavity is finely adjusted through piezoelectric ceramics, so that the maximum resonance point is realized in the resonant cavity by injecting seed light into the resonant cavity, a resonant signal is monitored by a photoelectric detector, after the resonant point is reached, a CPLD controller releases a control signal of an acousto-optic switch, the control signal is conducted, seed injection is realized, fluorescence generated by laser crystal oscillation is enabled to obtain higher gain in a wave band of 1.06 mu m, and therefore, the oscillation light crossing mode in the resonant cavity competes, and a longitudinal mode closest to the seed light frequency is realized;
after seed injection, the p polarization state of laser generated by the crystal passes through the second half wave plate to form an s polarization state, and then sequentially passes through the second reflecting mirror, the third reflecting mirror and the first film vibration plate to pass through the laser crystal again, so that a double-pass gain is formed; the laser amplified by the double-pass gain passes through a second half wave plate, the polarization state of the laser is changed into p-polarization state, and single-frequency pulse laser is formed by a second film vibration plate, an acousto-optic switch, a saturated body output lens and an output coupling lens.
Further, the two-time crystal injection process of the seed light of the control method of the 1 ns-level pulse width single-frequency pulse laser is represented as a first reflecting mirror of the graph:
the injected seed light is adjusted to a P polarization state through a half-wave plate, then is injected into a driven laser resonant cavity from a first film vibration plate, and is changed into an S polarization state after passing through a second half-wave plate, so that the seed light is reflected by the second film vibration plate, then passes through a second half-wave plate, a third mirror and the first film vibration plate, and then passes through a half-wave plate second half-wave plate again, and after passing through the half-wave plate second half-wave plate for the second time, the S polarization state is changed into the P polarization state. The seed light is injected into the slave laser cavity in two different polarization states.
In addition, after YAG is injected by seed light, the generated P-polarized oscillating light is changed into S-polarized state after passing through a second half-wave plate, then sequentially passes through a second reflecting mirror, a third reflecting mirror and a first film vibrating plate, and then passes through the crystal again to obtain the double-pass gain, and after passing through the second half-wave plate for the second time, the oscillating light is changed into P-polarized state from S-polarized state and is emitted from the second film vibrating plate.
In combination with the technical scheme and the technical problems to be solved, the technical scheme to be protected has the following advantages and positive effects:
first, aiming at the technical problems in the prior art and the difficulty in solving the problems, the technical problems solved by the technical proposal of the invention are analyzed in detail and deeply by tightly combining the technical proposal to be protected, the results and data in the research and development process, and the like, and some technical effects brought after the problems are solved have creative technical effects. The specific description is as follows:
according to the invention, seeds are directly injected into the driven laser resonant cavity, seed light is injected into the driven laser resonant cavity twice through a thin film type polarization beam splitter (TFP), and meanwhile, the length of the resonant cavity is finely adjusted through piezoelectric ceramics (PZT), so that injection locking is realized.
Secondly, the technical scheme is regarded as a whole or from the perspective of products, and the technical scheme to be protected has the following technical effects and advantages:
in order to realize high-gain pulse laser output, a driven laser with a TFP structure is designed to enable pulse oscillation light which is injected and locked in a resonant cavity to pass through a crystal in two polarization states to obtain a twice-gain optical path.
An acousto-optic Q switch and a Saturated Absorber (SA) are adopted to form a composite Q switch. When the acousto-optic Q switch is opened, the passive Q-switched laser resonant cavity formed by SA can realize passive Q-switched output. After outputting the single-frequency pulse laser, the acousto-optic Q switch is closed, and the next trigger signal is waited to realize the output of the next pulse laser. The SA initial transmittance is designed to be 40% -50%, so that 1 ns-level single-frequency pulse laser output is realized. The structure utilizes the characteristic of short pulse of passive Q-switching, and simultaneously utilizes the advantages of a polarized double-pass gain resonant cavity formed by TFP, so that single-frequency 1 ns-level pulse laser output can be realized. Can be used as a light source of a synthetic aperture laser radar, thereby obtaining a high-resolution image.
Thirdly, as inventive supplementary evidence of the claims of the present invention, the following important aspects are also presented:
(1) The expected benefits and commercial values after the technical scheme of the invention is converted are as follows:
the technology of the invention mainly provides a laser light source capable of realizing high resolution for the synthetic aperture laser radar. The synthetic aperture laser radar has clearer image because the wavelength is far smaller than Yu Weibo wave band. The laser output by the single-frequency pulse laser designed based on the invention can be used for imaging the synthetic aperture laser radar. Synthetic aperture lidar imaging is one of the most advanced lidars in the world at present, and only developed countries in the united states and europe have been publicly reported in China at present. Is the only optical means for realizing centimeter-level ultrahigh resolution, and has wide application prospect in the remote sensing field.
(2) The technical scheme of the invention fills the technical blank in the domestic and foreign industries:
the invention provides a solid laser resonant cavity structure with high-efficiency seed injection, which can provide a high-efficiency seed injection mode. Meanwhile, single-frequency pulse laser output with the pulse width of 1ns is realized by utilizing an acousto-optic Q switch and a passive Q-switched crystal. The 1ns single-frequency pulse laser output obtained by the invention fills the blank of the domestic synthetic aperture laser radar light source in the aspect of 1ns pulse width laser.
Drawings
FIG. 1 is a schematic diagram of a 1 ns-level pulse width single frequency pulse laser according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a seed two-shot slave laser according to an embodiment of the present invention;
FIG. 3 is a graph of the gain of a crystal oscillator in two passes provided by an embodiment of the present invention;
FIG. 4 is a schematic diagram of a pulsed output laser message provided by an embodiment of the present invention; (a) a Q-switched frequency (b) a Q-switched output pulse waveform;
FIG. 5 is a schematic diagram of a single frequency pulse output verified and obtained through experimentation provided by an embodiment of the present invention; (a) outputting test results by time domain pulses; (b) post-FFT frequency domain results;
in the figure: 1. pumping laser; 2. a first mirror; 3. a first half-wave plate; 4. a first film vibrating plate; 5. a crystal; 6. a second half-wave plate; 7. a second film vibrating plate; 8. a second mirror; 9. piezoelectric ceramics; 10. a third mirror; 11. an acousto-optic switch; 12. an absorption crystal; 13. an output lens; 14. a photodetector; 15. a CPLD controller; 16. a continuous single frequency seed light source.
Detailed Description
The present invention will be described in further detail with reference to the following examples in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
As shown in fig. 1 to 3, a 1 ns-level pulse width single frequency pulse laser provided by an embodiment of the present invention is provided with: the laser device comprises a pump laser 1, a first reflecting mirror 2, a first half wave plate 3, a first film vibration plate 4, a crystal 5, a second half wave plate 6, a second film vibration plate 7, a second reflecting mirror 8, piezoelectric ceramics 9, a third reflecting mirror 10, an acousto-optic switch 11, an absorption crystal 12, an output lens 13, a photoelectric detector 14, a CPLD controller 15 and a continuous single-frequency seed light source 16.
The lower end of the pump laser 1 is fixed with a reflecting device, one side of the reflecting device is fixed with a thin film polaroid, one side of the thin film polaroid is fixed with a crystal 5, and the rear end is provided with an acousto-optic switch 11, an absorption crystal 125 and an output lens 13 for outputting; the pump laser 1 and the reflecting device are fixed in a protective shell, a continuous single-frequency seed light source 16 is fixed on the left side of the protective shell, piezoelectric ceramics 9 is arranged on the upper right side of the protective shell, and a photoelectric detector 14 is arranged on the lower right side of the protective shell.
The piezoelectric ceramic 9 and the photoelectric detector 14 are linearly connected with a CPLD controller 15, the CPLD controller 15 is linearly connected with an acousto-optic switch 11, and the acousto-optic switch 11 is an acousto-optic Q switch.
The reflection device is provided with a first reflection device, a second reflection device and a third reflection device, wherein the first reflection device is arranged between the continuous single-frequency seed light source 16 and the first film vibration sheet 4, the second reflection device is arranged at the lower end of the piezoelectric ceramic 9, the third reflection device is arranged at one side of the pumping laser 1, and the first reflection device, the second reflection device and the third reflection device are 5-degree reflection mirrors of the crystal of the first film vibration sheet 4.
The pump laser 1 is 8nm laser of a second reflecting mirror 80, the pump laser 1 is vertically arranged, and the position where the central line of the pump laser 1 coincides with the central line of the continuous single-frequency seed light source 16 is the central point of the first reflecting device.
The film polaroid is a 5-degree film polaroid of a crystal of the first film polaroid 4, the film polaroid is provided with a first film polaroid and a second film polaroid, the first film polaroid is arranged on the left side of the crystal 5, and the second film polaroid is arranged on the right side of the crystal 5.
A first half-wave plate 3 is arranged between the first reflecting mirror 2 and the first thin film polaroid, a second half-wave plate 6 is arranged between the crystal 5 and the second thin film polaroid, and the first half-wave plate 3 and the second half-wave plate 6 are half-wave plates of pumping laser 1.0 mu m and the second half-wave plate 6 mu m.
The invention is used when: the seed light continuous single-frequency seed light source 16 is a single-frequency continuous light source, sequentially passes through the pump laser 1, the first half-wave plate 3 and the first film vibration plate 4, is input into the crystal 5 by adjusting the rotation angle of the first half-wave plate 3, and then sequentially passes through the second film vibration plate 7, the second reflecting mirror 8, the third reflecting mirror 10 and the first film vibration plate 4 to be injected into the crystal 5 again by adjusting the angle of the second half-wave plate 6. The length of the resonant cavity is finely adjusted through the piezoelectric ceramic 9 to enable the seed light to be injected into the resonant cavity to achieve the maximum resonance point, the resonance signal is monitored by the photoelectric detector 14, after the resonance point is achieved, the CPLD controller 15 releases the control signal of the acousto-optic switch 11 to conduct the control signal, so that seed injection is achieved, and the fluorescence crossing mode of the laser crystal 5 is enabled to compete to achieve the same longitudinal mode as the seed light.
After seed injection, the p-polarization state of the laser generated by the crystal 5 passes through the second half-wave plate 6 to form an s-polarization state, and then passes through the second reflecting mirror 8, the third reflecting mirror 10 and the first thin film vibration plate 4 again through the laser crystal 5 in sequence, so that a double-pass gain is formed. The laser amplified by the double-pass gain passes through the second half-wave plate 6, the polarization state of the laser is changed into p-polarization state, and the laser passes through the second film vibration plate 7, the acousto-optic switch 11, the saturated body output lens 13 and the output coupling lens output lens 13, so that single-frequency pulse laser is formed.
The seed light twice-injected into the crystal 5 process can be represented as the first mirror 2:
the injected seed light is adjusted to the P polarization state through a half-wave plate, then is injected into the driven laser resonant cavity from the first film vibration plate 4 (TFP), and is changed into the S polarization state after passing through the second half-wave plate 6 (half-wave plate), so that the seed light is reflected by the second film vibration plate 7 (TFP), then passes through the half-wave plate second half-wave plate 6 after passing through the second reflecting mirror 8, the third reflecting mirror 10 and the first film vibration plate 4, and is changed into the P polarization state from the S polarization state after passing through the half-wave plate second half-wave plate 6 for the second time. Thereby realizing that the seed light is injected into the slave laser resonant cavity in two different polarization states.
The oscillating light double-pass gain of the crystal 5 is shown as a first half wave plate 3:
YAG is injected into the laser crystal 5Nd by seed light, the generated P-polarized oscillation light is changed into S-polarized state after passing through the second half-wave plate 6, then sequentially passes through the second reflecting mirror 8, the third reflecting mirror 10 and the first film vibration plate 4, passes through the crystal 5 again, thereby obtaining double-pass gain, and after passing through the second half-wave plate 6 for the second time, the oscillation light is changed into P-polarized state from the S-polarized state, and is emitted from the second film vibration plate 7.
Crystal 5. Essential features of the invention
The (pump laser 1) seed light is injected into the crystal 5 twice, greatly increasing the seed injection efficiency. The injection locked laser passes through the crystal 5 twice as well to obtain a higher gain.
(first mirror 2) the gain is obtained twice for Nd: YAG oscillation light, and the gain of Nd: YAG crystal 5 is improved.
(first half wave plate 3) the acousto-optic Q switch 11 and the saturation absorption crystal 125 in the invention form a compound Q-switch. The acousto-optic Q switch can control the repetition frequency of the laser, and the pulse width-pumping laser 1ns level laser output is realized through the characteristic of the YAG saturated absorber.
In order to prove the inventive and technical value of the technical solution of the present invention, this section is an application example on specific products or related technologies of the claim technical solution.
The invention has been experimentally verified to be practical.
The invention firstly obtains the condition that the simple Q pulse width is near 3ns by calculating a rate equation, wherein the rate equation is as follows:
always, phi is the intra-cavity photon number density, n is the gain medium inversion particle number density, L is the gain medium length, sigma is the stimulated cross-sectional area of the medium, R is the output lens reflectivity, L is the total cavity length of the resonant cavity, t r For the transit time of photons in the resonant cavity to and fro a circle, c is the speed of light, l c For the optical length of the cavity, γ is the inversion factor, where γ=1, τ c Is the energy level lifetime on the gain medium.
| Sigma gain medium emission cross-sectional area | 2.8×10 -19 cm -2 |
| loss of resonant cavity | 0.005cm -1 |
| c speed of light | 3.0×10 10 cm·s -1 |
| Energy level lifetime at τc | 240μs |
| nat doped particle number concentration | 1.2×10 20 cm -3 |
| Frequency of nup pump light | 3.71×10 14 Hz |
| Sigma s pump light corresponding absorption cross section | 8.2×10 -19 cm 2 |
Bringing the parameters described in table 1 and the parameters for the designed cavity into the above equation, or alternatively, pulsing the laser information as follows: as shown in fig. 4;
the output passive Q-switched pulse width is 3-5 ns. This is because the designed cavity outputs pulses that include the pulse width established by the time taken for mode competition. The seed light is injected into the passive Q-switched resonant cavity, and the obtained pulse width is reduced to-1 ns.
The invention has proved through experiment and obtained single frequency pulse output: as shown in fig. 5;
the output pulse of which is heterodyned by a high sensitivity detector to obtain a beat frequency time domain image, as shown in figure 5 a. The output result corresponds to a time domain signal with a pulse width of 1.5ns, and the pulse width is 5MHz after FFT conversion.
The foregoing is merely illustrative of specific embodiments of the present invention, and the scope of the invention is not limited thereto, but any modifications, equivalents, improvements and alternatives falling within the spirit and principles of the present invention will be apparent to those skilled in the art within the scope of the present invention.
Claims (10)
1. A 1 ns-level pulse width single frequency pulse laser, characterized in that the 1 ns-level pulse width single frequency pulse laser is provided with:
pumping laser;
the lower end of the pumping laser is fixed with a reflecting device, one side of the reflecting device is fixed with a film polaroid, one side of the film polaroid is fixed with a crystal, and the rear end is provided with an acousto-optic switch, an absorption crystal and an output lens for output; the pumping laser and the reflecting device are fixed in the protective shell, the left side of the protective shell is fixed with a continuous single-frequency seed light source, piezoelectric ceramics is arranged on the upper right side of the protective shell, and a photoelectric detector is arranged on the lower right side of the protective shell.
2. The 1 ns-level pulse width single-frequency pulse laser according to claim 1, wherein the piezoelectric ceramic and the photoelectric detector are linearly connected with a CPLD controller, the CPLD controller is linearly connected with an acousto-optic switch, and the acousto-optic switch is an acousto-optic Q switch.
3. The 1ns pulse width single frequency pulse laser of claim 1, wherein the reflecting means is provided with a first reflecting means, a second reflecting means and a third reflecting means, the first reflecting means being mounted between the continuous single frequency seed light source and the first thin film vibrating plate.
4. A 1ns pulse width single frequency pulse laser according to claim 3, wherein the second reflecting device is mounted at the lower end of the piezoelectric ceramic, the third reflecting device is mounted at one side of the pump laser, and the first, second and third reflecting devices are 45 degree mirrors.
5. The 1ns pulse width single frequency pulse laser of claim 1, wherein the pump laser is 808nm laser, and the pump laser is vertically mounted.
6. A 1ns pulse width single frequency pulse laser as defined in claim 3, wherein the position where the pump laser center line coincides with the continuous single frequency seed light source center line is the first reflecting device center point;
the thin film polaroid is provided with a first thin film polaroid and a second thin film polaroid, the first thin film polaroid is arranged on the left side of the crystal, and the second thin film polaroid is arranged on the right side of the crystal;
a first half-wave plate is arranged between the first reflecting mirror and the first thin film polaroid;
a second half-wave plate is arranged between the crystal and the second film polaroid, and the first half-wave plate and the second half-wave plate are 1.06 mu m half-wave plates.
7. A 1ns pulse width single frequency pulse laser as defined in claim 1, wherein said thin film polarizer is a 45 degree thin film polarizer.
8. A control method of a 1 ns-level pulse width single frequency pulse laser according to any one of claims 1 to 7, characterized in that the control method of the 1 ns-level pulse width single frequency pulse laser comprises: the seed light continuous single-frequency seed light source is a single-frequency continuous light source, sequentially passes through the pump laser, the first half wave plate and the first film vibration plate, is input into the crystal by adjusting the rotation angle of the first half wave plate, and then the rest seed light sequentially passes through the second film vibration plate, the second reflecting mirror, the third reflecting mirror 10 and the first film vibration plate to be injected into the crystal again by adjusting the angle of the second half wave plate; the length of the resonant cavity is finely adjusted through piezoelectric ceramics, so that the maximum resonance point is realized in the resonant cavity by injecting seed light into the resonant cavity, a resonance signal is monitored by a photoelectric detector, after the resonance point is reached, a CPLD controller releases a control signal of an acousto-optic switch, the control signal is conducted, seed injection is realized, and a fluorescence crossing mode of laser crystal oscillation is made to compete so as to realize the longitudinal mode same as the seed light;
after seed injection, the p polarization state of laser generated by the crystal passes through the second half wave plate to form an s polarization state, and then sequentially passes through the second reflecting mirror, the third reflecting mirror and the first film vibration plate to pass through the laser crystal again, so that a double-pass gain is formed; the laser amplified by the double-pass gain passes through a second half wave plate, the polarization state of the laser is changed into p-polarization state, and single-frequency pulse laser is formed by a second film vibration plate, an acousto-optic switch, a saturated body output lens and an output coupling lens.
9. The method for controlling a 1 ns-level pulse width single frequency pulse laser according to claim 8, wherein the process of injecting seed light twice into the crystal of the method for controlling a 1 ns-level pulse width single frequency pulse laser is represented as a first mirror in the figure:
the injected seed light is adjusted to a P polarization state through a half-wave plate, then is injected into a driven laser resonant cavity from a first film vibration plate, and is changed into an S polarization state after passing through a second half-wave plate, so that the seed light is reflected by the second film vibration plate, then passes through a second half-wave plate, a third mirror and the first film vibration plate, and then passes through a half-wave plate second half-wave plate again, and after passing through the half-wave plate second half-wave plate for the second time, the S polarization state is changed into the P polarization state. The seed light is injected into the slave laser cavity in two different polarization states.
10. The method for controlling a 1 ns-level pulse width single-frequency pulse laser according to claim 8, wherein the crystal oscillation light of the method for controlling a 1 ns-level pulse width single-frequency pulse laser has a double-pass gain, the laser crystal Nd is injected with seed light, the generated P-polarization oscillation light is changed into S-polarization after passing through a second half-wave plate, then the S-polarization is changed into S-polarization after passing through a second reflecting mirror, a third reflecting mirror and a first film vibration plate in sequence, the S-polarization is changed into P-polarization after passing through the second half-wave plate again, and the oscillation light is emitted from the second film vibration plate.
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