CN113410741A - High-repetition-frequency sub-nanosecond all-fiber green light and ultraviolet laser - Google Patents

High-repetition-frequency sub-nanosecond all-fiber green light and ultraviolet laser Download PDF

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CN113410741A
CN113410741A CN202110735069.9A CN202110735069A CN113410741A CN 113410741 A CN113410741 A CN 113410741A CN 202110735069 A CN202110735069 A CN 202110735069A CN 113410741 A CN113410741 A CN 113410741A
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fiber
frequency
amplification
laser
seed source
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黄国溪
张帆
尹君
冯云
林强
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Shenzhen Gongda Laser Co ltd
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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
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/06791—Fibre ring lasers
    • 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
    • H01S3/106—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity
    • H01S3/108—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity using non-linear optical devices, e.g. exhibiting Brillouin or Raman scattering
    • H01S3/109—Frequency multiplication, e.g. harmonic generation
    • 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
    • H01S3/23—Arrangements of two or more lasers not provided for in groups H01S3/02 - H01S3/22, e.g. tandem arrangements of separate active media
    • H01S3/2308—Amplifier arrangements, e.g. MOPA
    • H01S3/2316—Cascaded amplifiers

Abstract

The invention discloses a high-repetition-frequency subnanosecond all-fiber green light and ultraviolet laser, which relates to the technical field of lasers and comprises a single-frequency continuous narrow-line-width DFB-LD semiconductor seed source laser, wherein a circulator, a grating MSG and a Mach-Zehnder intensity modulator are sequentially arranged on the axis of the output end of the DFB-LD semiconductor seed source laser; the adjustable subnanosecond seed source optical pulse signal is obtained after modulation of two cascaded Mach-Zehnder intensity modulators, high-efficiency frequency multiplication is realized by primary amplification, secondary amplification, tertiary amplification and cascaded frequency conversion of the subnanosecond seed source optical pulse signal, high-power pulse output realized by multistage amplification of a semiconductor seed source with the pulse width and the repetition frequency capable of being adjusted at will is realized, both the pulse width and the repetition frequency have a large adjusting range, tuning from high repetition frequency and ultra-narrow pulse width can also be realized, the average power can reach thousands of watts to ten thousand of watts, and the increasing power requirement in industrial processing can be met.

Description

High-repetition-frequency sub-nanosecond all-fiber green light and ultraviolet laser
Technical Field
The invention relates to the technical field of lasers, in particular to a high-repetition-frequency sub-nanosecond all-fiber green light and ultraviolet laser.
Background
In recent years, solid-state lasers have been rapidly developed, and green lasers have been receiving more and more attention. The green laser has short output wavelength and high processing precision, so the green laser has very wide application in the aspects of cutting, drilling and the like of materials such as ceramic wafers, glass, PCB boards, solar cells and the like, and particularly has obvious application value in the aspects of laser micromachining, laser detection and display lamps of subnanosecond green lasers.
In the prior art, a high repetition frequency narrow pulse width green light single mode laser disclosed in the patent document with the application number CN201410295146.3 and a sub-nanosecond green light laser disclosed in the patent document with the application number CN201810974644.9 are both solid green light lasers using a full space structure; 1. the solid green laser has a full-space structure, so the requirements on stability and environment cleanliness are high, and the solid green laser cannot work stably and reliably for a long time and is free from maintenance in actual industrial application; 2. the laser pulse repetition frequency of the solid laser can only reach hundreds of kHz at most, so that the application (the repetition frequency is several MHz to dozens of hundreds of MHz) with higher processing efficiency requirement can not meet the requirement; 3. the pulse width of the solid laser can only reach 10ns magnitude at present, and cannot meet the requirement of more precise processing (generally 100 ps-1 ns is needed); 4. due to the influence and limitation of the thermal lens effect, the solid-state laser is limited in maximum average power, generally can only output signal light of not more than hundred watt level at maximum, and cannot meet the increasing power increasing requirement in the industry.
Disclosure of Invention
The invention aims to provide a high-repetition-frequency sub-nanosecond all-fiber green light and ultraviolet laser to solve the problems in the background technology.
In order to achieve the purpose, the invention provides the following technical scheme:
a high-repetition-frequency subnanosecond all-fiber green light and ultraviolet laser comprises a single-frequency continuous narrow-line-width DFB-LD semiconductor seed source laser, wherein a circulator, a grating MSG and a Mach-Zehnder intensity modulator are sequentially arranged on the axis of the output end of the DFB-LD semiconductor seed source laser;
and modulating the modulated optical pulse signals by two cascaded Mach-Zehnder intensity modulators to obtain adjustable subnanosecond seed source optical pulse signals, wherein the subnanosecond seed source optical pulse signals sequentially undergo primary amplification, secondary amplification, tertiary amplification and cascaded frequency conversion to realize efficient frequency multiplication.
Preferably, the power of the single-frequency continuous narrow-linewidth DFB-LD semiconductor seed source laser is 30mW-100mW, and the sub-nanosecond seed source light pulse signal is an adjustable pulse signal with a high extinction ratio of 50-60 dB and a pulse width of 150 ps-2 ns.
Preferably, the primary amplification comprises a polarization maintaining isolator filter, an ytterbium-doped optical fiber, a pump source LD with a lock wavelength of 976nm and an amplification structure of a double-end single-mode WDM which are sequentially distributed, wherein the fiber core of the ytterbium-doped optical fiber is 5 μm, and the cladding of the ytterbium-doped optical fiber is 130 μm;
the second-stage amplification comprises an all-fiber simulation adapter MFA, a polarization-maintaining isolator filter, an ytterbium-doped fiber, a Combiner (2+1) and a pumping source LD with a lock wavelength of 976nm, wherein the fiber core of the ytterbium-doped fiber is 12 microns, and the cladding of the ytterbium-doped fiber is 130 microns;
the three-stage amplification comprises an all-fiber simulation adapter MFA, a polarization-maintaining isolator filter, a large-mode-field ytterbium-doped chiral fiber, (6+1) Combiner, an FBG fiber grating, a pump source LD with a lock wavelength of 976nm and a polarization analyzer which are sequentially arranged, wherein a fiber core of the large-mode-field ytterbium-doped chiral fiber is 33um, and a cladding is 125 um.
Preferably, the cascade frequency conversion comprises a double-stage space optical isolator, a collimating lens, a focusing lens and a lithium triborate crystal which are sequentially arranged.
Preferably, the single-frequency continuous narrow-linewidth DFB-LD semiconductor seed source laser 113 is modulated twice in succession by two cascaded mach-zehnder intensity modulators, the modulation bandwidth of the two lithium niobate mach-zehnder intensity modulators is 10GHz, the same rising edge time is 70ps, the radio frequency input signal, the input voltage amplitude and the modulation pulse width of the two cascaded intensity modulators are all the same, the generated pulse has a rectangular waveform with a sharp rising edge and a falling edge, the pulse width and the repetition frequency are τ and 1/T, and the Static Extinction Ratio (SER) is measured as the extinction ratio after the signal light passes through the modulators when no electric signal is input to the radio frequency port of the mach-zehnder intensity modulator:
Figure BDA0003140000250000021
wherein, PminIs the minimum output, P, obtained for adjusting the DC bias voltage of the DC portmaxIs the maximum output, the DER is measured using the radio frequency signal sent to the MZIM radio frequency port, the DC bias voltage is set to the minimum drive point of the MZIM's transfer function, the optical average power paveExpressed as follows:
Figure BDA0003140000250000031
wherein P ismaxIs 6.22 milliwatts, hminIs obtained as hmin57.9nW, which corresponds to when Pmax＝hmaxWhen the DER is 50.3dB, 44dB of DER is ensured in cascade modulation, the optical pulse contains 90% of the total energy, and the out-of-tolerance of 10dB is the standard for pulse quality.
Preferably, the feedback bias method of the mach-zehnder intensity modulator is as follows: the function generator generates a signal and a direct current bias voltage, the signal and the direct current bias voltage are input and output from a direct current input end of the Mach-Zehnder modulator together, a rectangular wave voltage signal is added at a radio frequency signal end, a modulated optical pulse signal passes through a coupler, one end of the modulated optical pulse signal is split into light to the PD detector, the other end of the modulated optical pulse signal is output to a phase-locked amplification circuit (LIA), a Y component of the signal Vs is used as an input quantity of a Bias Controller (BC) and is used as a feedback signal of bias control, based on the configuration, the static extinction ratio SER obtained by calculation is 32.7dB and the dynamic extinction ratio DER is 32.3dB for single-stage Mach-Zehnder intensity modulation, the static extinction ratio SER obtained by using bipolar cascade Mach-Zehnder intensity modulation is 55.4dB and the dynamic extinction ratio DER is 50.3dB, and the extinction ratio of the seed source is improved by more than 20dB through a cascade modulation scheme.
Preferably, the cascade frequency conversion further comprises an external cavity frequency doubling module, wherein the external cavity frequency doubling module is used for connecting multiple groups of lithium triborate crystals 111 in series and controlling the temperature respectively, the temperature of the first group of crystals in the two groups of crystals in series is 149.5 ℃, and the length of the crystals is 14 mm; the temperature of the second group of crystals is 148.5 ℃, the length of the crystals is 9mm, the temperature of the first group of crystals in the series connection of the three groups of crystals is 150 ℃, and the length of the crystals is 14 mm; the temperature of the second group of crystals is 149 ℃, and the length of the crystals is 9 mm; the temperature of the third group of crystals was 148 ℃ and the length of the crystals was 7 mm.
Preferably, after beam splitting of the seed source laser, three-stage amplification and multi-stage cascade frequency multiplication are performed, and then laser beam combination is performed to realize a fiber green light and ultraviolet laser with higher power.
The working steps of the all-fiber green light and ultraviolet laser with high repetition frequency and subnanosecond are as follows:
1) firstly, a single-frequency continuous narrow-line-width DFB-LD semiconductor seed source laser 113 is adopted, a seed source signal emitted by the laser 113 enters a port 1 of a circulator 101 after being coupled and output through a polarization maintaining fiber, then is output from a port 2, is output from a port 3 after passing through a mode selection high-reflection grating MSG and a polarization controller, and is modulated by two cascaded Mach-Zehnder intensity modulators 114 to obtain an adjustable subnanosecond seed source optical pulse signal;
2) the subnanosecond seed source light pulse signal is firstly subjected to primary amplification, the primary amplification adopts an amplification structure of a double-end single-mode WDM103, and then enters secondary amplification after passing through an all-fiber analog adapter MFA;
3) the secondary amplification adopts a reverse pumping mode to realize secondary amplification, the power of seed light is increased to the level of 0.5-1W, and then the seed light enters the tertiary amplification through an all-fiber simulation adapter MFA;
4) the three-stage amplification adopts a large-mode-field ytterbium-doped chiral fiber 106, an inclined FBG fiber grating is integrated at the tail end of the large-mode-field ytterbium-doped chiral fiber 106 for mode control and adjustment, the three-stage amplification adopts 6+1) Combiner 117 for reverse pumping, five groups of 130W pumping sources with the locked wavelength of 976nm are used for pumping, a tail fiber is reserved for polarization state monitoring and analysis of signal light, and the tail fiber is actively fed back to a polarization controller of a seed source end;
5) according to the monitoring and analysis of the polarization state of the three-stage amplified fundamental frequency light, the polarization state of the seed source end is fed back and regulated in a real-time self-adaptive manner, the fundamental frequency light amplification with the optimal extinction ratio is realized, and the fundamental frequency light of hundreds of watts after being amplified by the three-stage all-fiber passes through the double-stage spatial optical isolator 108, the collimating lens 109 and the focusing lens 110 and then enters the external cavity frequency doubling module. The external cavity frequency doubling module adopts a mode that a plurality of groups of lithium triborate crystals 111 are connected in series to cascade frequency doubling to further improve the frequency doubling efficiency of the fundamental frequency light, and the final high-efficiency frequency doubling which is more than 65% is realized by optimizing the external cavity frequency doubling structure and parameters and a plurality of groups of lithium triborate crystals 111 which are optimally designed, so that the green laser with high power, high beam quality and high peak power is obtained;
6) and finally, arranging a dichroic mirror at the output end, and filtering out the participating infrared fundamental frequency light to obtain the finally output green light.
Compared with the prior art, the invention has the beneficial effects that:
1) the invention provides a scheme of a green laser with all optical fibers, high repetition frequency and high average power, the scheme of the all optical fibers ensures the stability and the reliability, and the scheme is verified in the application of a high-power continuous optical fiber laser;
2) because the technical scheme adopts an MOPA main oscillation power amplification structure, which is high-power pulse output realized by carrying out multistage amplification on a semiconductor seed source with the pulse width and the repetition frequency capable of being adjusted at will, the pulse width and the repetition frequency have a large adjustment range, and simultaneously, the high repetition frequency from Hz to 100MHz and the ultra-narrow pulse width tuning from 50ps to 2ns can be realized;
3) finally, compared with a solid gain medium bulk crystal, the gain medium doped gain fiber of the fiber laser has a very large surface area to volume ratio and the heat dissipation capability far exceeds that of a solid laser, so that the average power of the fiber laser can reach thousands of watts or even tens of thousands of watts, and the increasingly growing power requirement in industrial processing can be completely met.
Drawings
Fig. 1 is a schematic structural diagram of a high repetition frequency, sub-nanosecond all-fiber green and ultraviolet laser.
FIG. 2 is a schematic structural diagram of a cascaded Mach-Zehnder intensity modulation method in a high-repetition-frequency subnanosecond all-fiber green light and ultraviolet laser.
FIG. 3 is a schematic structural diagram of a 150 ps-2 ns adjustable pulse width waveform in a high repetition frequency, sub-nanosecond all-fiber green light and ultraviolet laser.
Fig. 4 is a schematic structural diagram of a feedback bias control scheme of a mach-zehnder intensity modulator MZIM in a high-repetition-frequency sub-nanosecond all-fiber green light and ultraviolet laser.
Fig. 5 is a schematic structural diagram of a multi-crystal cascade scheme in a high repetition frequency, sub-nanosecond all-fiber green and ultraviolet laser.
Fig. 6 is a schematic structural diagram of a power boosting scheme for combining multiple lasers in a high repetition frequency sub-nanosecond all-fiber green light and ultraviolet laser.
Detailed Description
The technical solution of the present invention will be described in further detail with reference to specific embodiments.
Referring to fig. 1, a high repetition frequency and subnanosecond all-fiber green light and ultraviolet laser comprises a single-frequency continuous narrow-line-width DFB-LD semiconductor seed source laser 113, wherein a circulator 101, a grating MSG and a mach-zehnder intensity modulator 114 are sequentially arranged on an axis of an output end of the DFB-LD semiconductor seed source laser 113, and are modulated by two cascaded mach-zehnder intensity modulators 11 to obtain an adjustable subnanosecond seed source light pulse signal, and the subnanosecond seed source light pulse signal is sequentially subjected to first-stage amplification, second-stage amplification, third-stage amplification and cascaded frequency conversion to realize efficient frequency multiplication;
the power of the single-frequency continuous narrow-line-width DFB-LD semiconductor seed source laser 113 is 30mW-100mW, and the sub-nanosecond seed source light pulse signal is an adjustable pulse signal with a high extinction ratio of 50-60 dB and a pulse width of 150 ps-2 ns.
Specifically, the primary amplification comprises a polarization maintaining isolator filter 102, an ytterbium-doped optical fiber 104, a pump source LD115 with a lock wavelength of 976nm and an amplification structure of a double-end single-mode WDM103 which are sequentially distributed, wherein a fiber core of the ytterbium-doped optical fiber 104 is 5 μm, and a cladding is 130 μm; the secondary amplification comprises an all-fiber simulation adapter MFA, a polarization-maintaining isolator filter 102, an ytterbium-doped fiber 104, a Combiner 103 (2+1) and a pump source LD115 with a lock wavelength of 976nm, wherein the fiber core of the ytterbium-doped fiber 104 is 12 microns, and the cladding is 130 microns; the three-stage amplification comprises an all-fiber simulation adapter MFA, a polarization-maintaining isolator filter 102, a large-mode-field ytterbium-doped chiral fiber 106, a (6+1) Combiner 117, an FBG fiber grating, a pump source LD115 with a lock wavelength of 976nm and a polarization analyzer 107 which are sequentially arranged, wherein the fiber core of the large-mode-field ytterbium-doped chiral fiber 106 is 33um, and the cladding is 125 um; the cascade frequency conversion comprises a double-stage space optical isolator 108, a collimating lens 109, a focusing lens 110 and a lithium triborate crystal 111 which are sequentially arranged.
As a further scheme of the embodiment of the present invention, please refer to fig. 2, where the single-frequency continuous narrow-linewidth DFB-LD semiconductor seed source laser 113 is modulated twice in succession by two cascaded mach-zehnder intensity modulators, the modulation bandwidths of the two lithium niobate mach-zehnder intensity modulators are 10GHz, the same rising edge time is 70ps, the radio frequency input signals, the input voltage amplitudes and the modulation pulse widths of the two cascaded intensity modulators are all the same, please refer to fig. 3, the generated pulses have sharp rectangular waveforms of rising edges and falling edges, the pulse widths and the repetition frequencies are τ and 1/T, and the Static Extinction Ratio (SER) measures the extinction ratio of the signal light after passing through the modulators when no electrical signal is input to the radio frequency port of the mach-zehnder intensity modulator:
Figure BDA0003140000250000061
wherein, PminIs the minimum output, P, obtained for adjusting the DC bias voltage of the DC portmaxIs the maximum output, the DER is measured using the radio frequency signal sent to the MZIM radio frequency port, the DC bias voltage is set to the minimum drive point of the MZIM's transfer function, the optical average power paveExpressed as follows:
Figure BDA0003140000250000062
wherein P ismaxIs 6.22 milliwatts, hminIs obtained as hmin57.9nW, which corresponds to when Pmax＝hmaxWhen the DER is 50.3dB, 44dB of DER is ensured in cascade modulation, the optical pulse contains 90% of the total energy, and the out-of-tolerance of 10dB is the standard for pulse quality.
Referring to fig. 4 as a further solution of the embodiment of the present invention, a feedback bias method of the mach-zehnder intensity modulator 114 is as follows: the function generator generates a signal and adds a direct current bias voltage to be input and output from a direct current input end of the Mach-Zehnder modulator, a rectangular wave voltage signal is added at a radio frequency signal end, the modulated optical pulse signal passes through a coupler, one end of the modulated optical pulse signal is split to the PD detector, and the other end of the modulated optical pulse signal is output to a phase-locked amplifier circuit (LIA). Based on the configuration that the Y component of the signal Vs is used as the input quantity of a Bias Controller (BC) and is used as a feedback signal of bias control, the static extinction ratio SER obtained by calculation is 32.7dB and the dynamic extinction ratio DER is 32.3dB for single-stage Mach-Zehnder intensity modulation, the static extinction ratio SER obtained by bipolar cascade Mach-Zehnder intensity modulation is 55.4dB and the dynamic extinction ratio DER is 50.3dB, and the seed source extinction ratio is improved by more than 20dB through a cascade modulation scheme.
As a further scheme of the embodiment of the present invention, please refer to fig. 5, wherein the cascade frequency conversion further includes an external cavity frequency doubling module, the external cavity frequency doubling module connects multiple groups of lithium triborate crystals 111 in series and controls the temperature respectively, the temperature of the first group of crystals in the series connection of the two groups of crystals is 149.5 ℃, and the length of the crystals is 14 mm; the temperature of the second group of crystals is 148.5 ℃, the length of the crystals is 9mm, the temperature of the first group of crystals in the series connection of the three groups of crystals is 150 ℃, and the length of the crystals is 14 mm; the temperature of the second group of crystals is 149 ℃, and the length of the crystals is 9 mm; the temperature of the third group of crystals was 148 ℃ and the length of the crystals was 7 mm.
As a further scheme of the embodiment of the present invention, please refer to fig. 6, after beam splitting of the seed source laser, three-stage amplification and multi-stage cascade frequency doubling, beam combining of the laser is performed to realize a fiber green light and ultraviolet laser with higher power.
Specifically, the working steps of the all-fiber green light and ultraviolet laser with high repetition frequency and subnanosecond are as follows:
1) firstly, a single-frequency continuous narrow-line-width DFB-LD semiconductor seed source laser 113 is adopted, a seed source signal emitted by the laser 113 enters a port 1 of a circulator 101 after being coupled and output through a polarization maintaining fiber, then is output from a port 2, is output from a port 3 after passing through a mode selection high-reflection grating MSG and a polarization controller, and is modulated by two cascaded Mach-Zehnder intensity modulators 114 to obtain an adjustable subnanosecond seed source optical pulse signal;
2) the subnanosecond seed source light pulse signal is firstly subjected to primary amplification, the primary amplification adopts an amplification structure of a double-end single-mode WDM103, and then enters secondary amplification after passing through an all-fiber analog adapter MFA;
3) the secondary amplification adopts a reverse pumping mode to realize secondary amplification, the power of seed light is increased to the level of 0.5-1W, and then the seed light enters the tertiary amplification through an all-fiber simulation adapter MFA;
4) the three-stage amplification adopts a large-mode-field ytterbium-doped chiral fiber 106, an inclined FBG fiber grating is integrated at the tail end of the large-mode-field ytterbium-doped chiral fiber 106 for mode control and adjustment, the three-stage amplification adopts 6+1) Combiner 117 for reverse pumping, five groups of 130W pumping sources with the locked wavelength of 976nm are used for pumping, a tail fiber is reserved for polarization state monitoring and analysis of signal light, and the tail fiber is actively fed back to a polarization controller of a seed source end;
5) according to the monitoring and analysis of the polarization state of the three-stage amplified fundamental frequency light, the polarization state of the seed source end is fed back and regulated in a real-time self-adaptive manner, the fundamental frequency light amplification with the optimal extinction ratio is realized, and the fundamental frequency light of hundreds of watts after being amplified by the three-stage all-fiber passes through the double-stage spatial optical isolator 108, the collimating lens 109 and the focusing lens 110 and then enters the external cavity frequency doubling module. The external cavity frequency doubling module adopts a mode that a plurality of groups of lithium triborate crystals 111 are connected in series to cascade frequency doubling to further improve the frequency doubling efficiency of the fundamental frequency light, and the final high-efficiency frequency doubling which is more than 65% is realized by optimizing the external cavity frequency doubling structure and parameters and a plurality of groups of lithium triborate crystals 111 which are optimally designed, so that the green laser with high power, high beam quality and high peak power is obtained;
6) finally, at the output end, a dichroic mirror 112 is adopted to filter out the participating infrared fundamental frequency light, and then the final output green light is obtained.
While the preferred embodiments of the present invention have been described in detail, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the knowledge of those skilled in the art.

Claims (9)

1. A high repetition frequency, sub-nanosecond all-fiber green light and ultraviolet laser is characterized by comprising a single-frequency continuous narrow-line-width DFB-LD semiconductor seed source laser, wherein a circulator, a grating MSG and a Mach-Zehnder intensity modulator are sequentially arranged on the axis of the output end of the DFB-LD semiconductor seed source laser;
and modulating the modulated optical pulse signals by two cascaded Mach-Zehnder intensity modulators to obtain adjustable subnanosecond seed source optical pulse signals, wherein the subnanosecond seed source optical pulse signals sequentially undergo primary amplification, secondary amplification, tertiary amplification and cascaded frequency conversion to realize efficient frequency multiplication.
2. The high repetition frequency, sub-nanosecond all-fiber green and ultraviolet laser as claimed in claim 1, wherein the power of the single-frequency continuous narrow linewidth DFB-LD semiconductor seed source laser is 30mW-100mW, the sub-nanosecond seed source light pulse signal is an adjustable pulse signal with a high extinction ratio of 50-60 dB and a pulse width of 150 ps-2 ns.
3. The high repetition frequency, sub-nanosecond, all-fiber green and uv laser according to claim 1 or 2, wherein the primary amplification comprises a polarization maintaining isolator filter, a ytterbium doped fiber, a pump source LD with a lock wavelength of 976nm, and an amplification structure of a two-end single-mode WDM, which are arranged in sequence, the core of the ytterbium doped fiber is 5 μm, and the cladding is 130 μm;
the second-stage amplification comprises an all-fiber simulation adapter MFA, a polarization-maintaining isolator filter, an ytterbium-doped fiber, a Combiner (2+1) and a pumping source LD with a lock wavelength of 976nm, wherein the fiber core of the ytterbium-doped fiber is 12 microns, and the cladding of the ytterbium-doped fiber is 130 microns;
the three-stage amplification comprises an all-fiber simulation adapter MFA, a polarization-maintaining isolator filter, a large-mode-field ytterbium-doped chiral fiber, (6+1) Combiner, an FBG fiber grating, a pump source LD with a lock wavelength of 976nm and a polarization analyzer which are sequentially arranged, wherein a fiber core of the large-mode-field ytterbium-doped chiral fiber is 33um, and a cladding is 125 um.
4. The high repetition frequency, sub-nanosecond all-fiber green and ultraviolet laser of claim 3, wherein the cascaded frequency conversion comprises a two-stage spatial optical isolator, a collimating lens, a focusing lens, and a lithium triborate crystal arranged in that order.
5. The high repetition frequency, sub-nanosecond, all-fiber green and ultraviolet laser of claim 4, it is characterized in that the single-frequency continuous narrow-linewidth DFB-LD semiconductor seed source laser 113 is modulated twice continuously by two cascaded Mach-Zehnder intensity modulators, the modulation bandwidth of the two Mach-Zehnder intensity modulators of lithium niobate is 10GHz, the same rising edge time is 70ps, the radio frequency input signals, the input voltage amplitude and the modulation pulse width of the two cascade intensity modulators are all the same, the generated pulse has a sharp rectangular waveform with a rising edge and a falling edge, the pulse width and the repetition frequency are respectively tau and 1/T, and the Static Extinction Ratio (SER) is measured as follows when no electric signal is input into the radio frequency port of the Mach-Zehnder intensity modulator, the extinction ratio of the signal light after passing through the modulator is:
Figure FDA0003140000240000021
wherein, PminIs the minimum output, P, obtained for adjusting the DC bias voltage of the DC portmaxIs the maximum output, the DER is measured using the radio frequency signal sent to the MZIM radio frequency port, the DC bias voltage is set to the minimum drive point of the MZIM's transfer function, the optical average power paveExpressed as follows:
Figure FDA0003140000240000022
wherein P ismaxIs 6.22 milliwatts, hminIs obtained as hmin57.9nW, which corresponds to when Pmax＝hmaxWhen the DER is 50.3dB, 44dB of DER is ensured in cascade modulation, the optical pulse contains 90% of the total energy, and the out-of-tolerance of 10dB is the standard for pulse quality.
6. The high repetition frequency, sub-nanosecond, all-fiber green and ultraviolet laser according to claim 5, wherein the feedback bias method of the mach-zehnder intensity modulator is as follows: the function generator generates a signal and a direct current bias voltage, the signal and the direct current bias voltage are input and output from a direct current input end of the Mach-Zehnder modulator together, a rectangular wave voltage signal is added at a radio frequency signal end, a modulated optical pulse signal passes through a coupler, one end of the modulated optical pulse signal is split into light to the PD detector, the other end of the modulated optical pulse signal is output to a phase-locked amplification circuit (LIA), a Y component of the signal Vs is used as an input quantity of a Bias Controller (BC) and is used as a feedback signal of bias control, based on the configuration, the static extinction ratio SER obtained by calculation is 32.7dB and the dynamic extinction ratio DER is 32.3dB for single-stage Mach-Zehnder intensity modulation, the static extinction ratio SER obtained by using bipolar cascade Mach-Zehnder intensity modulation is 55.4dB and the dynamic extinction ratio DER is 50.3dB, and the extinction ratio of the seed source is improved by more than 20dB through a cascade modulation scheme.
7. The high repetition frequency, sub-nanosecond, all-fiber green and ultraviolet laser according to claim 6, wherein said cascaded frequency conversion further comprises an external cavity frequency doubling module, said external cavity frequency doubling module serially connecting multiple sets of lithium triborate crystals 111 and controlling temperature respectively, the first set of the two sets of crystals in series having a crystal temperature of 149.5 ℃ and a crystal length of 14 mm; the temperature of the second group of crystals is 148.5 ℃, the length of the crystals is 9mm, the temperature of the first group of crystals in the series connection of the three groups of crystals is 150 ℃, and the length of the crystals is 14 mm; the temperature of the second group of crystals is 149 ℃, and the length of the crystals is 9 mm; the temperature of the third group of crystals was 148 ℃ and the length of the crystals was 7 mm.
8. The high repetition frequency, sub-nanosecond all-fiber green and ultraviolet laser as recited in claim 7, wherein the seed source laser is split, and is subjected to three-stage amplification and multi-stage cascade frequency multiplication, and then is subjected to laser beam combination to realize a higher-power fiber green and ultraviolet laser.
9. The high repetition frequency, sub-nanosecond, all-fiber green and uv laser of claim 8, wherein said high repetition frequency, sub-nanosecond, all-fiber green and uv laser operates by:
1) firstly, a single-frequency continuous narrow-line-width DFB-LD semiconductor seed source laser 113 is adopted, a seed source signal emitted by the laser 113 enters a port 1 of a circulator 101 after being coupled and output through a polarization maintaining fiber, then is output from a port 2, is output from a port 3 after passing through a mode selection high-reflection grating MSG and a polarization controller, and is modulated by two cascaded Mach-Zehnder intensity modulators 114 to obtain an adjustable subnanosecond seed source optical pulse signal;
2) the subnanosecond seed source light pulse signal is firstly subjected to primary amplification, the primary amplification adopts an amplification structure of a double-end single-mode WDM103, and then enters secondary amplification after passing through an all-fiber analog adapter MFA;
3) the secondary amplification adopts a reverse pumping mode to realize secondary amplification, the power of seed light is increased to the level of 0.5-1W, and then the seed light enters the tertiary amplification through an all-fiber simulation adapter MFA;
4) the three-stage amplification adopts a large-mode-field ytterbium-doped chiral fiber 106, an inclined FBG fiber grating is integrated at the tail end of the large-mode-field ytterbium-doped chiral fiber 106 for mode control and adjustment, the three-stage amplification adopts 6+1) Combiner 117 for reverse pumping, five groups of 130W pumping sources with the locked wavelength of 976nm are used for pumping, a tail fiber is reserved for polarization state monitoring and analysis of signal light, and the tail fiber is actively fed back to a polarization controller of a seed source end;
5) according to the monitoring and analysis of the polarization state of the three-stage amplified fundamental frequency light, the polarization state of the seed source end is fed back and regulated in a real-time self-adaptive manner, the fundamental frequency light amplification with the optimal extinction ratio is realized, and the fundamental frequency light of hundreds of watts after being amplified by the three-stage all-fiber passes through the double-stage spatial optical isolator 108, the collimating lens 109 and the focusing lens 110 and then enters the external cavity frequency doubling module. The external cavity frequency doubling module adopts a mode that a plurality of groups of lithium triborate crystals 111 are connected in series to cascade frequency doubling to further improve the frequency doubling efficiency of the fundamental frequency light, and the final high-efficiency frequency doubling which is more than 65% is realized by optimizing the external cavity frequency doubling structure and parameters and a plurality of groups of lithium triborate crystals 111 which are optimally designed, so that the green laser with high power, high beam quality and high peak power is obtained;
6) and finally, arranging a dichroic mirror at the output end, and filtering out the participating infrared fundamental frequency light to obtain the finally output green light.
CN202110735069.9A 2021-06-30 2021-06-30 High-repetition-frequency sub-nanosecond all-fiber green light and ultraviolet laser Pending CN113410741A (en)

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