CN113809620A - Large-energy long-pulse 1-micrometer single-frequency nanosecond laser for laser coherent wind-finding radar - Google Patents

Large-energy long-pulse 1-micrometer single-frequency nanosecond laser for laser coherent wind-finding radar Download PDF

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CN113809620A
CN113809620A CN202111037594.XA CN202111037594A CN113809620A CN 113809620 A CN113809620 A CN 113809620A CN 202111037594 A CN202111037594 A CN 202111037594A CN 113809620 A CN113809620 A CN 113809620A
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laser
pulse
plano
convex lens
pumped
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CN113809620B (en
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张百涛
施炳楠
李佳桐
聂鸿坤
叶帅
杨克建
李涛
何京良
王冲
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Shandong Birui Laser Technology Co ltd
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Shandong University
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
    • H01S3/0057—Temporal shaping, e.g. pulse compression, frequency chirping
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/88—Lidar systems specially adapted for specific applications
    • G01S17/95—Lidar systems specially adapted for specific applications for meteorological use
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/483—Details of pulse systems
    • G01S7/484—Transmitters
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
    • H01S3/0071—Beam steering, e.g. whereby a mirror outside the cavity is present to change the beam direction
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H01S3/0941—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light of a laser diode
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • 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
    • H01S3/117—Q-switching using intracavity acousto-optic devices
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/005—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping
    • H01S5/0057—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping for temporal shaping, e.g. pulse compression, frequency chirping
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/005—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping
    • H01S5/0071—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping for beam steering, e.g. using a mirror outside the cavity to change the beam direction
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/02—Structural details or components not essential to laser action
    • H01S5/022—Mountings; Housings
    • H01S5/0225—Out-coupling of light
    • H01S5/02253—Out-coupling of light using lenses
    • H—ELECTRICITY
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    • H01S5/00—Semiconductor lasers
    • H01S5/04—Processes or apparatus for excitation, e.g. pumping, e.g. by electron beams
    • H01S5/041—Optical pumping
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
    • H01S5/0615—Q-switching, i.e. in which the quality factor of the optical resonator is rapidly changed
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
    • Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

Abstract

The invention relates to a large-energy long-pulse 1-micron single-frequency nanosecond laser for a laser coherent wind-finding radar, which adopts a 1-micron single-frequency continuous laser as a seed source and ensures the frequency and line width stability of the whole system. A pulse semiconductor Laser (LD) is used as a pumping source, so that the pulse amplification efficiency is effectively improved, and the spontaneous emission Amplification (ASE) in the amplification process is inhibited. And then, the continuous seed light is chopped into high-contrast pulse laser with the rising edge of a half-Gaussian waveform and the falling edge of a steep pulse through two acousto-optic modulators. The pulse energy is then continuously increased by the following end-pump-side pump/slab mixing amplifier stage, while the pulse width is also gradually broadened by the pulse shaping effect caused by gain saturation. And a method of adding a small-hole diaphragm and optimizing the pulse width of each level of pumping light is adopted, so that ASE in the amplification process of each amplification level is effectively inhibited.

Description

Large-energy long-pulse 1-micrometer single-frequency nanosecond laser for laser coherent wind-finding radar
Technical Field
The invention belongs to the technical field of all-solid-state laser, and particularly relates to a long-pulse 1-micron single-frequency nanosecond laser with large energy and hundreds of ns pulse width for a laser coherent wind-finding radar.
Background
The laser coherent wind-measuring radar has great application requirements in the military and civil fields of near-earth space military environment forecast, extreme weather early warning, wind energy utilization, atmospheric pollution monitoring and the like. The laser light source is a key core component of the coherent wind-measuring radar, and the performance index of the laser light source directly determines the detection distance, sensitivity and precision of the coherent wind-measuring radar. It is known from the interference theory that to obtain a significant interference effect, the maximum optical path difference required for the interference effect is smaller than the coherence length, and therefore, a long-distance coherent wind radar needs a narrow line width light source to provide a long coherence length. Meanwhile, the narrow line width is also beneficial to improving the measurement precision. In addition, the pulse width of the laser emitted by the light source is inversely proportional to the spectrum width of the echo signal in the wind measuring radar, and the longer pulse width leads to the narrowing of the power spectrum, thereby improving the wind speed measurement accuracy.
At present, a common method for obtaining a large-energy 1 μm single-frequency nanosecond pulse laser is a single-frequency pulse laser and a main oscillation amplifier for seed injection. The method comprises the steps of injecting narrow-linewidth single-frequency continuous seed light into a Q-switched resonant cavity, continuously tuning the cavity length through piezoelectric ceramics, and opening a Q switch to output single-frequency pulse laser when detecting that the seed light resonates in the cavity. Although the method can obtain large-energy single-frequency pulse output, the method is limited by a resonance detection technology and piezoelectric ceramic performance, the frequency stability and the line width stability of the method are poor, and the accuracy of wind speed measurement and wind field distance measurement of a wind measuring radar is reduced. Meanwhile, the pulse width of the single-frequency pulse laser generated by the method is narrow (generally less than one hundred nanoseconds (100ns)), and the pulse waveform is uncontrollable, so that the pulse width of the single-frequency pulse laser in the subsequent amplification process becomes narrower, and the wind speed measurement accuracy is not improved.
Chinese patent document CN111129922A discloses a single-frequency laser amplification system with a large energy hundred ns pulse width of 1.0 μm, which uses a 1.0 μm DFB semiconductor laser as a seed source, uses an optical fiber amplification module to chop, chops a continuous seed source into pulse laser with a lorentz rising edge through an acousto-optic modulator, then amplifies the pulse laser by using a solid amplification stage, widens the pulse by using the amplification effect of the solid amplification stage, and obtains 1.0 μm pulse laser with a pulse width greater than hundred ns. However, the continuous LD is adopted as a pumping source in the patent, so that the amplification efficiency is low, and the pulse laser amplification is not facilitated; and only by processing the end face of the laser crystal into a certain angle, spontaneous emission stimulated Amplification (ASE) in the amplification process is difficult to completely inhibit, so that the component of the ASE can be doped in the output pulse laser, and the amplification efficiency of the amplifier and the signal-to-noise ratio, single frequency, stability and beam quality of the output laser are further influenced.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a large-energy long-pulse 1-micron single-frequency nanosecond laser. And a single-frequency continuous laser is used as a seed source, so that the frequency and line width stability of the whole system are ensured. By adopting a double-acousto-optic chopping technology, the pulse contrast is improved, and simultaneously, the pulse waveform is pre-shaped to form high-contrast pulse laser with a half-Gaussian waveform as a rising edge and a steep falling edge, so that the pulse width is gradually widened by utilizing the gain saturation effect of a subsequent amplifier stage. The amplification stage adopts a mode of end pump-side pump/plate strip mixed amplification to improve laser energy, adverse effects caused by spontaneous emission stimulated Amplification (ASE) effect in the amplification process are fully inhibited through optimizing the pumping pulse width of the amplification stage and an electro-optical switch chopping technology, and the pulse signal-to-noise ratio is further improved. The invention can finally obtain the large-energy and long-pulse 1-micron single-frequency laser output with the energy of hundreds of mJ magnitude and the pulse width of 100-500ns, and provides a new technical scheme for the laser light source for the long-distance coherent laser coherent wind-finding radar.
Interpretation of terms:
1. the half-gaussian waveform is a functional image generated by a gaussian function in a domain (— infinity, 0).
2. ASE, refers to the continuous gain of stimulated amplification of spontaneous emission during its propagation in the gain medium.
In order to achieve the purpose, the invention adopts the following technical scheme:
a large-energy long-pulse 1-micron single-frequency nanosecond laser for a laser wind-measuring radar comprises a single-frequency continuous laser seed source, a double-acoustic-light modulator, a beam shaper, a first small-hole diaphragm, a three-stage end-pumped single-pass preamplifier, an electro-optic chopper and a primary main amplifier which are sequentially arranged along a light path;
the three-stage end-pumped single-pass preamplifier comprises a first-stage end-pumped single-pass preamplifier, a second-stage end-pumped single-pass preamplifier and a third-stage end-pumped single-pass preamplifier;
after double-acoustic-light modulation chopping of the double-acoustic-light modulator, single-frequency continuous seed light emitted by the single-frequency continuous laser seed source is converted into long-pulse single-frequency nanosecond pulse laser, time domain shaping is carried out on the pulse waveform, the long-pulse single-frequency nanosecond pulse laser is shaped into high-contrast pulse laser with a half-Gaussian waveform and a steep falling edge, the high-contrast pulse laser respectively passes through the beam shaper and the first small-hole diaphragm and then enters the first-stage end-face pumping single-pass preamplifier, the second-stage end-face pumping single-pass preamplifier and the third-stage end-face pumping single-pass preamplifier for amplification, the duty ratio and the position of the small-hole diaphragm of each amplification-stage semiconductor laser pumping source of the first-stage end-face pumping single-pass preamplifier, the second-face pumping single-pass preamplifier and the third-stage end-face pumping single-pass preamplifier are optimized, ASE of each amplification stage is inhibited, and ASE in the amplified pulse laser is further filtered through the electro-light chopper, and finally, the laser enters a primary main amplifier for amplification, and finally the large-energy long-pulse 1-micron single-frequency nanosecond laser is obtained.
According to the optimization of the invention, a first half-wave plate, a first isolator, a second half-wave plate and a first 45-degree 1-micron high-reflection mirror are sequentially arranged behind the first aperture diaphragm, and the dual-acousto-optic modulator comprises a first dual-acousto-optic modulator and a second dual-acousto-optic modulator;
the first double acousto-optic modulator, the second double acousto-optic modulator, the beam shaper, the first half-wave plate of the aperture diaphragm, the first isolator, the second half-wave plate and the first 45-degree 1 mu m high-reflection mirror form an optical isolation system.
According to the invention, the first-stage end-pumped single-pass preamplifier comprises a second 45-degree 1-micron high-reflection mirror, a first plano-convex lens, a first laser crystal, a first 45-degree dichroic mirror, a second plano-convex lens, a third plano-convex lens, a first pulse LD and a second aperture diaphragm;
the second-stage end-pumped single-pass preamplifier comprises a third 45-degree 1-micrometer high-reflection mirror, a fourth plano-convex lens, a second laser crystal, a second 45-degree dichroic mirror, a fifth plano-convex lens, a sixth plano-convex lens, a second pulse LD and a third aperture diaphragm;
the third-stage end-pumped single-pass preamplifier comprises a fourth 45-degree 1-micrometer high-reflection mirror, a seventh plano-convex lens, a first film polaroid, a third laser crystal, a third 45-degree dichroic mirror, an eighth plano-convex lens, a ninth plano-convex lens and a third pulse LD;
the laser enters the first laser crystal through the focusing of the first plano-convex lens for single-pass amplification, and the pumping light emitted by the first pulse LD is also focused into the first laser crystal through a coupling system consisting of the second plano-convex lens and the third plano-convex lens;
the pulse laser amplified by the first-stage end-pumped single-pass preamplifier is output through the first 45-degree dichroic mirror, and enters the second-stage end-pumped single-pass preamplifier through the third 45-degree 1-micrometer high-reflection mirror after passing through the second aperture diaphragm, the laser is focused by the fourth plano-convex lens and enters the second laser crystal for single-pass amplification, and the pump light emitted by the second pulse LD is also focused into the second laser crystal through a coupling system consisting of the fifth plano-convex lens and the sixth plano-convex lens;
the pulse laser amplified by the second-stage end-face pumping single-pass preamplifier is output through the second 45-degree dichroic mirror, and enters the third-stage end-face pumping single-pass preamplifier through the fourth 45-degree 1-micrometer high-reflection mirror after passing through the third aperture diaphragm, the laser enters the third laser crystal for single-pass amplification through the seventh plano-convex lens and the first film polaroid, the pump light emitted by the third pulse LD is also focused into the third laser crystal through a coupling system consisting of the eighth plano-convex lens and the ninth plano-convex lens, and the amplified pulse laser is output through the third 45-degree dichroic mirror.
According to the invention, the laser further comprises a fifth 45-degree 1 μm high-reflection mirror, a tenth plano-convex lens, a second isolator, a third half-wave plate, the electro-optic chopper, a second thin film polarizer and a sixth 45-degree 1 μm high-reflection mirror which are arranged along the optical path in sequence;
the laser amplified by the third-stage end-pumped single-pass preamplifier sequentially passes through a fifth 45-degree 1-micrometer high-reflection mirror, a tenth plano-convex lens, a second isolator, a third half-wave plate, the electro-optic chopper and a second thin film polaroid, and then enters the first-stage main amplifier through the sixth 45-degree 1-micrometer high-reflection mirror to carry out final pulse energy amplification.
According to the invention, preferably, the primary main amplifier is a side pumping amplification module, and an eleventh plano-convex lens and a twelfth plano-convex lens are arranged on the rear edge of the primary main amplifier;
and after the final pulse energy amplification is carried out by the side pumping amplification module, namely the primary main amplifier, the beam is expanded and output by a telescope system consisting of the eleventh plano-convex lens and the twelfth plano-convex lens.
According to the invention, the side-pumped amplification module is preferably a pulsed LD side-pumped Nd3+Ion laser crystal or single crystal fiber module, or pulse LD side-pumped Yb3+Ion laser crystal or single crystal fiber module.
According to the optimization of the invention, the single-frequency continuous laser seed source is a single-frequency fiber laser, a nonlinear ring cavity structure solid single-frequency laser, a DFB laser or an external cavity semiconductor laser, and the linewidth of the laser output by the single-frequency continuous laser seed source is less than 10 kHz.
According to the present invention, preferably, the first pulse LD, the second pulse LD, and the third pulse LD are all fiber-coupled outputs, the core diameter thereof is 200 μm or 400 μm, and the center wavelengths of the first pulse LD, the second pulse LD, and the third pulse LD are all 808nm or 880nm, or 940nm or 976 nm.
The diameters of the focusing light spots of the pump lights emitted by the first pulse LD and the second pulse LD are 250 μm, and the diameter of the focusing light spot of the pump light emitted by the third pulse LD is 400 μm;
the pumping pulse widths of the first pulse LD, the second pulse LD and the third pulse LD are in a ratio of 1: 0.7: the ratio of 0.4 is gradually decreased.
According to the invention, the two ends of the first laser crystal, the second laser crystal and the third laser crystal are processed into 2-5 DEG wedge angles, and the first laser crystal, the second laser crystal and the third laser crystal are Nd3+Ion-doped laser crystal or Yb3+And ion doping the laser crystal.
According to the invention, the electro-optical crystal in the electro-optical chopper is a BBO electro-optical crystal, an RTP electro-optical crystal or a KDP electro-optical crystal.
According to the optimization of the invention, the primary main amplifier is a partial end-pumped mixed-cavity slab amplifier, the laser further comprises a plano-convex cylindrical mirror used in the first vertical direction, a plano-convex cylindrical mirror used in the first horizontal direction, a 0-degree 1-micrometer high-reflection wedge mirror, a slab laser crystal, a 0-degree dichroic mirror, a spherical lens group, a plano-convex cylindrical lens group used in the first horizontal direction, a planar waveguide used in the horizontal direction, a plano-convex cylindrical lens group used in the second horizontal direction, a pulse LD array, a 45-degree 1-micrometer high-reflection wedge mirror, a sixth 45-degree 1-micrometer high-reflection mirror, a plano-convex cylindrical mirror used in the second vertical direction, a plano-convex cylindrical mirror used in the third horizontal direction, and a plano-convex cylindrical mirror used in the fourth horizontal direction;
the pulse laser amplified by the third-stage end-pumped single-pass preamplifier uses a plano-convex cylindrical mirror in the first vertical direction and a plano-convex cylindrical mirror in the first horizontal direction to focus a light beam into an elliptical light beam which is matched with a cavity mode of a part of end-pumped mixed cavity slab amplifier in the vertical direction and has a proper divergence angle in the horizontal direction, and then the elliptical light beam enters the part of end-pumped mixed cavity slab amplifier, namely the first-stage main amplifier;
laser passes through a mixing cavity structure of a part of end-pumped mixing cavity slab amplifier formed by a 0-degree 1-micrometer high-reflection wedge-shaped mirror and a 0-degree dichroic mirror, repeatedly passes through the slab laser crystal in the horizontal direction for multiple times, extracts energy stored in the slab laser crystal, and then is output through a sixth 45-degree 1-micrometer high-reflection mirror;
finally, the amplified pulse laser enters a beam-reducing telescope system consisting of a plano-convex cylindrical mirror in the second vertical direction, a plano-convex cylindrical mirror in the third horizontal direction and a plano-convex cylindrical mirror in the fourth horizontal direction after being reflected by a sixth 45-degree 1-micron high-reflection mirror, and the elliptic light beam is converted into a circular light beam to be output.
According to the invention, the partial end-pumped mixed cavity slab amplifier is preferably a pulsed LD array partial end-pumped Nd3+Ion slab laser crystal or pulsed LD array partial end-pumped Yb3+An ion slab laser crystal.
According to a preferred embodiment of the invention, the slab laser crystal is Nd: YAG or Nd3+Ion-doped other crystals; the slab laser crystal is Yb: YAG or Yb3+Ion doped other crystals.
Preferably according to the invention, the pulsed LD array is 4bar or 6bar or 8bar with a center wavelength of 808nm or 880nm, or 940nm or 976 nm.
Compared with the prior art, the large-energy long-pulse 1-micron single-frequency nanosecond laser for the laser wind-finding radar has the following beneficial effects:
1. the linewidth of an optical fiber single-frequency laser or an NPRO solid laser or a DFB/external cavity type semiconductor laser is less than 10kHz, so that the linewidth of the whole high-energy single-frequency laser is ensured;
2. the double-acousto-optic modulator is adopted to carry out chopping and pulse waveform modulation on the continuous single-frequency seed light, so that the signal-to-noise ratio of the single-frequency pulse laser is improved, the gain extraction of a rear-end amplification stage is fully facilitated, the amplification efficiency is improved, and the output of large-energy and long-pulse laser with hundreds of Hz and hundreds of ns is realized;
3. the pulse LD is used as a pumping source, so that the amplification efficiency is greatly improved, and the signal-to-noise ratio and the amplification efficiency of the pulse are improved by optimizing the duty ratio of each pre-amplification-level pulse semiconductor laser, arranging a small-hole diaphragm in a light path and effectively inhibiting ASE (amplified spontaneous emission) in the amplification process by adopting an electro-optical chopper;
4. the invention can simultaneously realize large-energy and long-pulse single-frequency nanosecond laser output of hundreds of Hz, ns and mJ
Drawings
FIG. 1 is a schematic diagram of a single frequency nanosecond laser seed source pulse waveform after passing through a dual acousto-optic modulator;
FIG. 2 is a schematic structural diagram of a large-energy, long-pulse 1 μm single-frequency nanosecond laser for a laser coherent wind-finding radar in embodiment 1 of the present invention;
FIG. 3 is a schematic structural diagram of a large-energy, long-pulse 1 μm single-frequency nanosecond laser for a laser coherent wind-finding radar in embodiment 2 of the invention;
FIG. 4 is a schematic diagram of the output parameter index of a large-energy, long-pulse 1 μm single-frequency laser;
1. a single-frequency continuous laser seed source, 2, a first acousto-optic modulator, 3, a second acousto-optic modulator, 4, a beam shaper, 5, a first aperture diaphragm, 6, a first half-wave plate, 7, a first isolator, 8, a second half-wave plate, 9, a first 45 DEG 1 mu m high-reflection mirror, 10, a second 45 DEG 1 mu m high-reflection mirror, 11, a first plano-convex lens, 12, a first laser crystal, 13, a first 45 DEG dichroic mirror, 14, a second plano-convex lens, 15, a third plano-convex lens, 16, a first pulse LD, 17, a second aperture diaphragm, 18, a third 45 DEG 1 mu m high-reflection mirror, 19, a fourth plano-convex lens, 20, a second laser crystal, 21, a second 45 DEG dichroic mirror, 22, a fifth plano-convex lens, 23, a sixth plano-convex lens, 24, a second pulse LD, 25, a third aperture diaphragm, 26, a fourth 45 DEG 1 mu m high-reflection mirror, 27, a seventh plano-convex lens, 28. a first thin film polarizer, 29, a third laser crystal, 30, a third 45 ° dichroic mirror, 31, an eighth plano-convex lens, 32, a ninth plano-convex lens, 33, a third pulse LD, 34, a fifth 45 ° 1 μm high-reflection mirror, 35, a tenth plano-convex lens, 36, a second isolator, 37, a third half-wave plate, 38, an electro-optical chopper, 39, a second thin film polarizer, 40, a sixth 45 ° 1 μm high-reflection mirror, 41, a side pumping amplification module, 42, an eleventh plano-convex lens, 43, a twelfth plano-convex lens; 44. the laser comprises a first vertical direction, a first horizontal direction, a second vertical direction, a third horizontal direction, a fourth vertical direction and a sixth horizontal direction, wherein the first vertical direction uses a planoconvex cylindrical mirror, 45, the first horizontal direction uses a planoconvex cylindrical mirror, 46, 0 degrees 1 mu m high-reflection wedge mirror, 47, lath laser crystals, 48, 0 degrees dichroic mirror, 49, a spherical lens group, 50, the first horizontal direction uses a planoconvex cylindrical mirror group, 51, the horizontal direction uses a planar waveguide, 52, the second horizontal direction uses a planoconvex cylindrical mirror group, 53, a pulse LD array, 54, 45 degrees 1 mu m high-reflection wedge mirror, 55, the sixth 45 degrees 1 mu m high-reflection mirror, 56, the second vertical direction uses a planoconvex cylindrical mirror, 57, the third horizontal direction uses a planoconvex cylindrical mirror, 58, and the fourth horizontal direction uses a planoconvex cylindrical mirror.
Detailed Description
The invention is further described below, but not limited thereto, with reference to the drawings and examples of the specification.
Example 1
A large-energy long-pulse 1-micron single-frequency nanosecond laser for a laser wind-finding radar is shown in a figure 2 and comprises a single-frequency continuous laser seed source 1, a double-acoustic-optical modulator, a beam shaper 4, a first small-hole diaphragm 5, a three-level end-face pumping single-pass preamplifier, an electro-optic chopper 38 and a primary main amplifier which are sequentially arranged along a light path;
the three-stage end-pumped single-pass preamplifier comprises a first-stage end-pumped single-pass preamplifier, a second-stage end-pumped single-pass preamplifier and a third-stage end-pumped single-pass preamplifier;
after double-acoustic-light modulation chopping, single-frequency continuous seed light emitted by a single-frequency continuous laser seed source 1 is changed into long-pulse single-frequency nanosecond pulse laser, and simultaneously time domain shaping is carried out on the pulse waveform, the long-pulse single-frequency nanosecond pulse laser is shaped into high-contrast pulse laser (the pulse waveform is shown in figure 1) with a half-Gaussian waveform and a steep falling edge, the high-contrast pulse laser respectively enters a first-stage end-pumped single-pass preamplifier, a second-stage end-pumped single-pass preamplifier and a third-stage end-pumped single-pass preamplifier for amplification after respectively passing through a beam shaper 4 and a first small-hole diaphragm 5, the duty ratios of semiconductor laser pumping sources of each amplification stage of the first-stage end-pumped single-pass preamplifier, the second-stage end-pumped single-pass preamplifier and the third-stage end-pumped single-pass preamplifier are optimized, ASE of each amplification stage is inhibited, and ASE in the amplified pulse laser is further filtered through an electro-light chopper 38, and finally, the laser enters a primary main amplifier for amplification, and finally the large-energy long-pulse 1-micron single-frequency nanosecond laser is obtained. The duty ratio of each amplification stage pulse LD and the position of the first aperture diaphragm 5 are continuously changed in the experiment to find the maximum target of the ratio of the amplification pulse energy to the ASE energy. This optimum duty cycle and the first aperture stop 5 position need to be determined by specific experiments.
A first half-wave plate 6, a first isolator 7, a second half-wave plate 8 and a first 45-degree 1-micron high-reflection mirror 9 are sequentially arranged behind the first aperture diaphragm 5, and the dual-acousto-optic modulator comprises a first dual-acousto-optic modulator 2 and a second dual-acousto-optic modulator 3;
the light isolation system comprises a first double acousto-optic modulator 2, a second double acousto-optic modulator 3, a beam shaper 4, a first aperture diaphragm 5, a first half-wave plate 6, a first isolator 7, a second half-wave plate 8 and a first 45-degree 1-micrometer high-reflection mirror 9.
The first-stage end-pumped single-pass preamplifier comprises a second 45-degree 1-micrometer high-reflection mirror 10, a first plano-convex lens 11, a first laser crystal 12, a first 45-degree dichroic mirror 13, a second plano-convex lens 14, a third plano-convex lens 15, a first pulse LD16 and a second aperture diaphragm 17;
the second-stage end-pumped single-pass preamplifier comprises a third 45-degree 1-micrometer high reflecting mirror 18, a fourth plano-convex lens 19, a second laser crystal 20, a second 45-degree dichroic mirror 21, a fifth plano-convex lens 22, a sixth plano-convex lens 23, a second pulse LD24 and a third aperture diaphragm 25;
the third-stage end-pumped single-pass preamplifier comprises a fourth 45-degree 1-micron high-reflection mirror 26, a seventh plano-convex lens 27, a first thin-film polarizing plate 28, a third laser crystal 29, a third 45-degree dichroic mirror 30, an eighth plano-convex lens 31, a ninth plano-convex lens 32 and a third pulse LD 33;
laser is focused by a first plano-convex lens 11 and enters a first laser crystal 12(Nd: YAG) for single-pass amplification, and pumping light emitted by a first pulse LD16 is also focused into the first laser crystal 12 through a coupling system consisting of a second plano-convex lens 14 and a third plano-convex lens 15;
the pulse laser amplified by the first-stage end-pumped single-pass preamplifier is output through a first 45-degree dichroic mirror 13, enters the second-stage end-pumped single-pass preamplifier through a third 45-degree 1-micron high-reflection mirror 18 after passing through a second small-aperture diaphragm 17, is focused through a fourth plano-convex lens 19 and enters a second laser crystal 20(Nd: YAG) for single-pass amplification, and the pump light emitted by a second pulse LD24 is also focused into the second laser crystal 20 through a coupling system consisting of a fifth plano-convex lens 22 and a sixth plano-convex lens 23;
the pulse laser amplified by the second-stage end-pumped single-pass preamplifier is output by a second 45-degree dichroic mirror 21, enters the third-stage end-pumped single-pass preamplifier through a fourth 45-degree 1-micron high-reflection mirror 26 after passing through a third aperture diaphragm 25, is focused by a seventh plano-convex lens 27 and a first thin film polarizing plate 28 and enters a third laser crystal 29(Nd: YAG) for single-pass amplification, the pump light emitted by a third pulse LD33 is also focused into the third laser crystal 29 through a coupling system consisting of an eighth plano-convex lens 31 and a ninth plano-convex lens 32, and the amplified pulse laser is output by a third 45-degree dichroic mirror 30.
The laser also comprises a fifth 45-degree 1-micron high-reflection mirror 34, a tenth plano-convex lens 35, a second isolator 36, a third half-wave plate 37, an electro-optical chopper 38, a second thin film polaroid 39 and a sixth 45-degree 1-micron high-reflection mirror 40 which are sequentially arranged along the light path;
the laser amplified by the third-stage end-pumped single-pass preamplifier sequentially passes through a fifth 45-degree 1-micrometer high-reflection mirror 34, a tenth plano-convex lens 35, a second isolator 36, a third half-wave plate 37, an electro-optic chopper 38 and a second thin film polarizing plate 39, and then enters a first-stage main amplifier through a sixth 45-degree 1-micrometer high-reflection mirror 40 to be subjected to final pulse energy amplification.
The primary main amplifier is a side pumping amplification module 41, and an eleventh plano-convex lens 42 and a twelfth plano-convex lens 43 are arranged behind the primary main amplifier along a light path;
after the final pulse energy amplification is performed by a side pumping (Nd: YAG) amplification module 41, i.e. a primary main amplifier, the beam is expanded and outputted by a telescope system consisting of an eleventh plano-convex lens 42 and a twelfth plano-convex lens 43.
The side pumping amplification module 41 is a pulse LD side pumping Nd3+Ion laser crystal or single crystal fiber module, or pulse LD side-pumped Yb3+Ion laser crystal or single crystal fiber module. Wherein the crystal is cut at one end with>The wedge angle of 2 degrees prevents self-oscillation.
The single-frequency continuous laser seed source 1 is a single-frequency fiber laser, a solid single-frequency laser with a nonlinear ring cavity (NPRO) structure, a DFB (distributed Feedback laser) laser or an external cavity type semiconductor laser, and the linewidth of laser output by the single-frequency continuous laser seed source is less than 10 kHz.
The first pulse LD16, the second pulse LD24 and the third pulse LD33 are all fiber coupling outputs, the core diameter is 200 μm or 400 μm, and the center wavelength of the first pulse LD16, the second pulse LD24 and the third pulse LD33 is 808nm or 880nm, or 940nm or 976 nm. The first pulse LD, the second pulse LD and the third pulse LD are in a pulse working mode, and the duty ratio is adjustable.
The diameters of the focusing spots of the pump lights emitted by the first pulse LD16 and the second pulse LD24 are 250 μm, and the diameter of the focusing spot of the pump light emitted by the third pulse LD33 is 400 μm; the size of the pump light focusing spot is matched with that of the seed light so as to achieve the optimal amplification effect.
The pumping pulse widths of the first pulse LD16, the second pulse LD24, and the third pulse LD33 are set to be 1: 0.7: the ratio of 0.4 is gradually decreased. The pulse laser energy is amplified while suppressing ASE as much as possible by optimizing the pumping pulse width of each stage.
The two ends of the first laser crystal 12, the second laser crystal 20 and the third laser crystal 29 are processed into 2-5 DEG wedge angles, and the first laser crystal 12, the second laser crystal 20 and the third laser crystal 29 are Nd3+Ion-doped laser crystal or Yb3+And ion doping the laser crystal.
The electro-optical crystal in the electro-optical chopper 38 is a BBO electro-optical crystal, an RTP electro-optical crystal or a KDP electro-optical crystal.
The working process of the large-energy long-pulse 1-micron single-frequency nanosecond laser for the laser wind radar is as follows:
continuous laser output from the single-frequency continuous laser seed source 1 is subjected to chopping and pulse shaping through the first acousto-optic modulator 2 and the second acousto-optic modulator 3 to obtain required pulse laser; then after being collimated by a beam shaper 4, the collimated light enters a first-stage end-pumped single-pass preamplifier through an optical isolation system consisting of a first half-wave plate, a first isolator 7, and the energy is amplified to about hundred muJ; the pulse laser amplified by the first-stage end-face pumping single-pass preamplifier is amplified to about 1mJ by the second-stage end-face pumping single-pass preamplifier; then amplifying the amplified signal to about 10mJ by a third-stage end-pumped single-pass preamplifier, passing the amplified signal through an optical isolation system, entering an electro-optical chopper 38 consisting of an electro-optical switch and a thin film polaroid, and further filtering an ASE component; finally, the energy is amplified to the order of hundreds mJ by the side pumping amplification module 41.
FIG. 4 is a schematic diagram of the output parameter index of a large-energy, long-pulse 1 μm single-frequency laser; (a) the laser output energy (logarithmic scale) of each amplification stage is given, (b) the energy (logarithmic scale) of ASE after passing through each amplification stage is given, (c) the output pulse sequence is given, (d) the output beam quality is given, and (e) the line width of the amplification pulse is given. It can be seen from fig. 4 that the repetition frequency of the single-frequency nanosecond laser can reach 100Hz, the single pulse energy can reach 100mJ, meanwhile, the ASE can be controlled below 10 muj, the line width is only 50kHz, and the single-frequency nanosecond laser has excellent beam quality and can well meet the requirements of long-distance laser coherent wind-finding radars.
Example 2
A large-energy, long-pulse 1 μm single-frequency nanosecond laser for a lidar according to embodiment 1, differing in that: as shown in fig. 3, the primary main amplifier is a partial end-pumped hybrid cavity slab amplifier, the laser further includes a plano-convex cylindrical mirror 44 used in the first vertical direction, a plano-convex cylindrical mirror 45 used in the first horizontal direction, a 0 ° 1 μm high-reflectivity wedge mirror 46, a slab laser crystal 47, a 0 ° dichroic mirror 48, a spherical lens group 49, a plano-convex cylindrical mirror group 50 used in the first horizontal direction, a planar waveguide 51 used in the horizontal direction, a plano-convex cylindrical mirror group 52 used in the second horizontal direction, a pulse LD array 53, a 45 ° 1 μm high-reflectivity wedge mirror 54, a sixth 45 ° 1 μm high-reflectivity mirror 55, a plano-convex cylindrical mirror 56 used in the second vertical direction, a plano-convex cylindrical mirror 57 used in the third horizontal direction, and a plano-convex cylindrical mirror 58 used in the fourth horizontal direction;
the pulse laser amplified by the third-stage end-pumped single-pass preamplifier focuses the light beam into an elliptical light beam with a proper divergence angle in the horizontal direction through a plano-convex cylindrical mirror 44 in the first vertical direction and a plano-convex cylindrical mirror 45 in the first horizontal direction, and then enters a part of end-pumped mixed cavity slab amplifiers, namely a first-stage main amplifier;
laser passes through a mixing cavity structure of a part of end-pumped mixing cavity slab amplifier formed by a 0-degree 1-micron high-reflection wedge-shaped mirror 46 and a 0-degree dichroic mirror 48, passes through a slab laser crystal 47 repeatedly in the horizontal direction, extracts energy stored in the slab laser crystal, and is output through a sixth 45-degree 1-micron high-reflection mirror 55;
finally, the amplified pulse laser is reflected by a sixth 45-degree 1-micron high-reflection mirror 55, enters a beam-reducing telescope system consisting of a plano-convex cylindrical mirror 56 used in the second vertical direction, a plano-convex cylindrical mirror 57 used in the third horizontal direction and a plano-convex cylindrical mirror 58 used in the fourth horizontal direction, and is converted from an elliptical beam into a circular beam to be output.
The pump light coupling system comprises a first horizontal plane convex cylindrical lens group 50, a second horizontal plane convex cylindrical lens group 52, a horizontal plane waveguide and a spherical lens group; in the horizontal direction, the pump light emitted by the pulsed LD array 53 is focused in the first horizontal direction by the plano-convex cylindrical lens group 50, enters the horizontal direction for homogenization by the planar waveguide, and is finally integrated into a uniform pump line having the same width as the slab laser crystal 47 by an imaging system composed of the planar waveguide and the spherical lens group in the horizontal direction; in the vertical direction, only the spherical lens group performs the focusing function, and the pump light is focused into the slab laser crystal 47.
The partial end-pumped mixed cavity slab amplifier is a pulse LD array 53 partial end-pumped Nd3+Ion slab laser crystal or pulsed LD array 53 partial end-pumped Yb3+An ion slab laser crystal.
The slab laser crystal 47 is Nd: YAG or Nd3+Ion-doped other crystals; such as Nd: YVO4Nd is YAP, etc.; the slab laser crystal 47 is Yb: YAG or Yb3+Ion doped other crystals. Such as Yb: CaF2、Yb:YVO4And the like.
The pulsed LD array 53 is 4bar or 6bar or 8bar with a center wavelength of 808nm or 880nm, or 940nm or 976 nm.
The working process of the large-energy long-pulse 1-micron single-frequency nanosecond laser for the laser wind radar is as follows:
continuous laser output from the single-frequency continuous laser seed source 1 is subjected to chopping and pulse shaping through the first acousto-optic modulator 2 and the second acousto-optic modulator 3 to obtain required pulse laser; then after being collimated by a beam shaper 4, the collimated light enters a first-stage end-pumped single-pass preamplifier through an optical isolation system consisting of a first half-wave plate, a first isolator 7, and the energy is amplified to about hundred muJ; the pulse laser amplified by the first-stage end-face pumping single-pass preamplifier is amplified to about 1mJ by the second-stage end-face pumping single-pass preamplifier; then the amplified signal is amplified to about 10mJ by a third-stage end-pumped single-pass preamplifier, passes through an optical isolation system, enters an electro-optical chopper 38 consisting of an electro-optical switch and a thin film polaroid, and further filters an ASE component; pulse laser is shaped into an elliptical beam through two cylindrical mirrors in the horizontal direction and the vertical direction, then the elliptical beam enters a main amplification stage formed by a part of end face pumping mixing cavity slab amplifiers to amplify energy to a hundred mJ magnitude, and finally the elliptical beam is shaped into a circular beam through a beam shaping system formed by a horizontal direction beam-shrinking telescope and a vertical direction cylindrical mirror and is output.

Claims (10)

1. A large-energy long-pulse 1-micron single-frequency nanosecond laser for a laser wind-measuring radar is characterized by comprising a single-frequency continuous laser seed source, a double-acousto-optic modulator, a beam shaper, a first small-hole diaphragm, a three-level end-pumped single-pass preamplifier, an electro-optic chopper and a primary main amplifier which are sequentially arranged along a light path;
the three-stage end-pumped single-pass preamplifier comprises a first-stage end-pumped single-pass preamplifier, a second-stage end-pumped single-pass preamplifier and a third-stage end-pumped single-pass preamplifier;
after double-acoustic-light modulation chopping of the double-acoustic-light modulator, single-frequency continuous seed light emitted by the single-frequency continuous laser seed source is converted into long-pulse single-frequency nanosecond pulse laser, time domain shaping is carried out on the pulse waveform, the long-pulse single-frequency nanosecond pulse laser is shaped into high-contrast pulse laser with a half-Gaussian waveform and a steep falling edge, the high-contrast pulse laser respectively passes through the beam shaper and the first small-hole diaphragm and then enters the first-stage end-face pumping single-pass preamplifier, the second-stage end-face pumping single-pass preamplifier and the third-stage end-face pumping single-pass preamplifier for amplification, the duty ratio and the position of the small-hole diaphragm of each amplification-stage semiconductor laser pumping source of the first-stage end-face pumping single-pass preamplifier, the second-face pumping single-pass preamplifier and the third-stage end-face pumping single-pass preamplifier are optimized, ASE of each amplification stage is inhibited, and ASE in the amplified pulse laser is further filtered through the electro-light chopper, and finally, the laser enters a primary main amplifier for amplification, and finally the large-energy long-pulse 1-micron single-frequency nanosecond laser is obtained.
2. The large-energy long-pulse 1-micron single-frequency nanosecond laser for the laser wind-measuring radar according to claim 1, wherein a first half-wave plate, a first isolator, a second half-wave plate and a first 45-degree 1-micron high-reflection mirror are sequentially arranged behind the first aperture diaphragm, and the dual-acoustic-light modulator comprises a first dual-acoustic-light modulator and a second dual-acoustic-light modulator;
the first double acousto-optic modulator, the second double acousto-optic modulator, the beam shaper, the first half-wave plate of the aperture diaphragm, the first isolator, the second half-wave plate and the first 45-degree 1 mu m high-reflection mirror form an optical isolation system.
3. The large-energy, long-pulse 1-micron single-frequency nanosecond laser for the laser wind-finding radar according to claim 1, wherein the first-stage end-pumped single-pass preamplifier comprises a second 45 ° 1-micron high-reflection mirror, a first plano-convex lens, a first laser crystal, a first 45 ° dichroic mirror, a second plano-convex lens, a third plano-convex lens, a first pulse LD, and a second small-hole diaphragm;
the second-stage end-pumped single-pass preamplifier comprises a third 45-degree 1-micrometer high-reflection mirror, a fourth plano-convex lens, a second laser crystal, a second 45-degree dichroic mirror, a fifth plano-convex lens, a sixth plano-convex lens, a second pulse LD and a third aperture diaphragm;
the third-stage end-pumped single-pass preamplifier comprises a fourth 45-degree 1-micrometer high-reflection mirror, a seventh plano-convex lens, a first film polaroid, a third laser crystal, a third 45-degree dichroic mirror, an eighth plano-convex lens, a ninth plano-convex lens and a third pulse LD;
the laser enters the first laser crystal through the focusing of the first plano-convex lens for single-pass amplification, and the pumping light emitted by the first pulse LD is also focused into the first laser crystal through a coupling system consisting of the second plano-convex lens and the third plano-convex lens;
the pulse laser amplified by the first-stage end-pumped single-pass preamplifier is output through the first 45-degree dichroic mirror, and enters the second-stage end-pumped single-pass preamplifier through the third 45-degree 1-micrometer high-reflection mirror after passing through the second aperture diaphragm, the laser is focused by the fourth plano-convex lens and enters the second laser crystal for single-pass amplification, and the pump light emitted by the second pulse LD is also focused into the second laser crystal through a coupling system consisting of the fifth plano-convex lens and the sixth plano-convex lens;
the pulse laser amplified by the second-stage end-face pumping single-pass preamplifier is output through the second 45-degree dichroic mirror, and enters the third-stage end-face pumping single-pass preamplifier through the fourth 45-degree 1-micrometer high-reflection mirror after passing through the third aperture diaphragm, the laser enters the third laser crystal for single-pass amplification through the seventh plano-convex lens and the first film polaroid, the pump light emitted by the third pulse LD is also focused into the third laser crystal through a coupling system consisting of the eighth plano-convex lens and the ninth plano-convex lens, and the amplified pulse laser is output through the third 45-degree dichroic mirror.
4. The large-energy long-pulse 1-micron single-frequency nanosecond laser for the laser wind-finding radar according to claim 1, characterized in that the laser further comprises a fifth 45-degree 1-micron high-reflection mirror, a tenth plano-convex lens, a second isolator, a third half-wave plate, the electro-optical chopper, a second thin-film polarizer and a sixth 45-degree 1-micron high-reflection mirror which are sequentially arranged along the optical path;
the laser amplified by the third-stage end-pumped single-pass preamplifier sequentially passes through a fifth 45-degree 1-micrometer high-reflection mirror, a tenth plano-convex lens, a second isolator, a third half-wave plate, the electro-optic chopper and a second thin film polaroid, and then enters the first-stage main amplifier through the sixth 45-degree 1-micrometer high-reflection mirror to carry out final pulse energy amplification.
5. The large-energy long-pulse 1-micron single-frequency nanosecond laser for the laser wind-finding radar according to claim 1, wherein the primary main amplifier is a side-pumped amplification module, and an eleventh plano-convex lens and a twelfth plano-convex lens are arranged on a rear edge light path of the primary main amplifier;
and after the final pulse energy amplification is carried out by the side pumping amplification module, namely the primary main amplifier, the beam is expanded and output by a telescope system consisting of the eleventh plano-convex lens and the twelfth plano-convex lens.
6. The large-energy long-pulse 1-micron single-frequency nanosecond laser for the lidar of claim 5, wherein the side-pumped amplification module is a pulsed LD side-pumped Nd3+Ion laser crystal or single crystal fiber module, or pulse LD side-pumped Yb3+Ion laser crystal or single crystal fiber module.
7. The large-energy long-pulse 1-micrometer single-frequency nanosecond laser for the laser wind-finding radar according to claim 1, wherein the single-frequency continuous laser seed source is a single-frequency fiber laser, a non-linear ring cavity structure solid single-frequency laser, a DFB laser or an external cavity semiconductor laser, and the linewidth of the output laser of the single-frequency continuous laser seed source is less than 10 kHz;
the first pulse LD, the second pulse LD and the third pulse LD are all fiber coupling output, the core diameter is 200 μm or 400 μm, and the central wavelength of the first pulse LD, the second pulse LD and the third pulse LD is 808nm or 880nm, or 940nm or 976 nm;
the diameters of the focusing light spots of the pump lights emitted by the first pulse LD and the second pulse LD are 250 μm, and the diameter of the focusing light spot of the pump light emitted by the third pulse LD is 400 μm;
the pumping pulse widths of the first pulse LD, the second pulse LD and the third pulse LD are in a ratio of 1: 0.7: the proportion of 0.4 is gradually decreased;
the two ends of the first laser crystal, the second laser crystal and the third laser crystal are processed into 2-5 DEG wedge angles, and the first laser crystal, the second laser crystal and the third laser crystal are Nd3+Ion-doped laser crystal or Yb3+Ion-doped laser crystals;
the electro-optical crystal in the electro-optical chopper is a BBO electro-optical crystal, an RTP electro-optical crystal or a KDP electro-optical crystal.
8. The large-energy long-pulse 1- μm single-frequency nanosecond laser device according to claim 1, wherein the primary main amplifier is a partially end-pumped hybrid cavity slab amplifier, and the laser device further comprises a plano-convex cylindrical mirror for the first vertical direction, a plano-convex cylindrical mirror for the first horizontal direction, a 0 ° 1 μm high-reflection wedge mirror, a slab laser crystal, a 0 ° dichroic mirror, a spherical lens group, a plano-convex cylindrical mirror group for the first horizontal direction, a planar waveguide for the horizontal direction, a plano-convex cylindrical mirror group for the second horizontal direction, a pulse LD array, a 45 ° 1 μm high-reflection wedge mirror, a sixth 45 ° 1 μm high-reflection mirror, a plano-convex cylindrical mirror for the second vertical direction, a plano-convex cylindrical mirror for the third horizontal direction, and a plano-convex cylindrical mirror for the fourth horizontal direction;
the pulse laser amplified by the third-stage end-pumped single-pass preamplifier uses a plano-convex cylindrical mirror in the first vertical direction and a plano-convex cylindrical mirror in the first horizontal direction to focus a light beam into an elliptical light beam which is matched with a cavity mode of a part of end-pumped mixed cavity slab amplifier in the vertical direction and has a proper divergence angle in the horizontal direction, and then the elliptical light beam enters the part of end-pumped mixed cavity slab amplifier, namely the first-stage main amplifier;
laser passes through a mixing cavity structure of a part of end-pumped mixing cavity slab amplifier formed by a 0-degree 1-micrometer high-reflection wedge-shaped mirror and a 0-degree dichroic mirror, repeatedly passes through the slab laser crystal in the horizontal direction for multiple times, extracts energy stored in the slab laser crystal, and then is output through a sixth 45-degree 1-micrometer high-reflection mirror;
finally, the amplified pulse laser enters a beam-reducing telescope system consisting of a plano-convex cylindrical mirror in the second vertical direction, a plano-convex cylindrical mirror in the third horizontal direction and a plano-convex cylindrical mirror in the fourth horizontal direction after being reflected by a sixth 45-degree 1-micron high-reflection mirror, and the elliptic light beam is converted into a circular light beam to be output.
9. The large-energy, long-pulse 1-micron single-frequency nanosecond laser for lidar according to claim 8, wherein the mixing cavity plate is partially end-pumpedThe strip amplifier is a pulse LD array partial end-face pump Nd3+Ion slab laser crystal or pulsed LD array partial end-pumped Yb3+An ion slab laser crystal.
10. The large-energy, long-pulse 1- μm single-frequency nanosecond laser for lidar according to claim 8 or 9, wherein the slab laser crystal is Nd: YAG or Nd3+Ion-doped other crystals; the slab laser crystal is Yb: YAG or Yb3+Ion-doped other crystals;
the pulsed LD array is 4bar or 6bar or 8bar with center wavelength of 808nm or 880nm, or 940nm or 976 nm.
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