CN113885228B - Distributed all-fiber laser phased array system and phase control method thereof - Google Patents

Distributed all-fiber laser phased array system and phase control method thereof Download PDF

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CN113885228B
CN113885228B CN202111163656.1A CN202111163656A CN113885228B CN 113885228 B CN113885228 B CN 113885228B CN 202111163656 A CN202111163656 A CN 202111163656A CN 113885228 B CN113885228 B CN 113885228B
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laser
phase
port
phase control
ith
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CN113885228A (en
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粟荣涛
常洪祥
龙金虎
蒋敏
张雨秋
周朴
马阎星
马鹏飞
吴坚
李�灿
姜曼
司磊
许晓军
陈金宝
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National University of Defense Technology
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    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/011—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  in optical waveguides, not otherwise provided for in this subclass
    • G02F1/0115—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  in optical waveguides, not otherwise provided for in this subclass in optical fibres
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/0136—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  for the control of polarisation, e.g. state of polarisation [SOP] control, polarisation scrambling, TE-TM mode conversion or separation
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F2203/00—Function characteristic
    • G02F2203/50—Phase-only modulation

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  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)

Abstract

The distributed all-fiber laser phased array system comprises a seed laser source, a1 multiplied by 2 laser beam splitter/combiner, a1 multiplied by N laser beam splitter/combiner, a phase modulator, a laser amplifier, a2 multiplied by 2 fiber coupler, a fiber end cap, a laser collimating mirror, a circulator, a photoelectric detector and a phase control module, and the phase detection and control of each path of laser are realized through an all-fiber optical path structure. According to the invention, the array laser does not need to be sampled by using the spectroscope, so that the expansibility and compactness of the laser phased array system are improved.

Description

Distributed all-fiber laser phased array system and phase control method thereof
Technical Field
The invention relates to the technical field of optical phased arrays, in particular to a distributed all-fiber laser phased array system and a phase control method thereof.
Background
The laser phased array technology controls the phase of each path of laser to ensure that the array laser meets certain phase distribution, thereby realizing the regulation and control of the array laser, and being widely applied to the fields of laser communication, laser radar, directional energy technology and the like. At present, a laser phased array system mainly adopts power amplification (English name is Master OscillatorPowerAmplifier, MOPA for short) of a master oscillator, and the aim of improving far-field facula energy concentration is achieved by locking array lasers into in-phase output. Fig. 1 is a schematic block diagram of a laser phased array in the prior art. The system mainly comprises seed laser 101, a 1 XN laser beam splitter/combiner 102, a plurality of phase modulators 103, a plurality of laser amplifiers 104, a plurality of optical fiber end caps 105, a plurality of laser collimating lenses 106, a laser beam combiner 107, a spectroscope 108, a focusing lens 109, an aperture diaphragm 110, a photodetector 111 and an optimization algorithm phase control module 112. After the seed laser 101 is split by the 1×n laser beam splitter/combiner 102, each path of laser enters the phase modulator 103. Each phase modulator 103 is optically connected to each corresponding laser amplifier 104. Each laser amplifier 104 is optically connected to a fiber end cap 105. Each optical fiber end cap 105 is respectively connected with the optical path of the laser collimator 106. The laser emitted by each laser collimator 106 is compressed by a laser beam combiner 107 to form an array laser and transmitted to a beam splitter 108. 99% of the power laser is split by the spectroscope 108 and then emitted to the action target; the <1% of the power laser beam is split by the beam splitter 108 and then carries optical information to be incident on the phase detection module, which is usually composed of a focusing lens 109, an aperture diaphragm 110 and a photodetector 111, and is used for extracting the central main lobe energy of the far-field spot of the composite beam. The electrical signal generated by the photodetector 111 is output to an optimization algorithm phase control module 112. The optimization algorithm phase control module 112 generates a control signal by an optimization algorithm and outputs it to each phase modulator 103. The phase control signal adjusts the piston phase of each laser to keep the output signal of the photodetector 111 at a maximum value, and the array laser remains at the same phase.
The laser phased array system can realize the same-phase output of high-power fiber laser, and achieves the aim of improving the quality of array beams. But this method requires the array laser to be sampled using a beam splitter. As the beam diameter of the laser array increases, so does the diameters of the beam splitter 108 and focusing lens 109, limiting the scalability of the laser phased array system. In addition, because the space light path is adopted for extracting the phase error, the space light path adjustment requirement of the system is higher, and the compactness of the system is also influenced.
Disclosure of Invention
Aiming at the defects existing in the prior art, the invention provides a distributed all-fiber laser phased array system and a phase control method thereof, and the phase detection and control of each path of laser are realized through an all-fiber structure.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
The distributed all-fiber laser phased array system comprises a seed laser source, a 1 multiplied by 2 laser beam splitter/combiner, a 1 multiplied by N laser beam splitter/combiner, a phase modulator, a laser amplifier, a 2 multiplied by 2 fiber coupler, a fiber end cap, a laser collimating mirror, a circulator, a photoelectric detector and a phase control module;
The seed light with the outgoing wavelength of lambda 1 of the seed laser source is divided into 2 paths by a 1X 2 laser beam splitter/combiner, wherein the first path of laser is divided into N sub lasers by a first 1X N laser beam splitter/combiner, the i sub lasers are subjected to phase modulation by an i phase modulator, and the i laser amplifier is subjected to power amplification and then input to an i 2X 2 optical fiber coupler;
Each 2 x2 fiber coupler has four ports, wherein a first port of an i 2 x2 fiber coupler is connected to an i laser amplifier, a second port of the 2 x2 fiber coupler is connected to an i fiber end cap, the i fiber end cap is connected to an i laser collimator, wherein i = 1,2, …, N; for the laser incident to the ith optical fiber end cap, most of the laser is output to the ith laser collimating mirror, and the other small part is reflected back to the original light path;
The second path of laser output by the 1X 2 laser beam splitter/combiner is input from the first port of the circulator, the second port of the circulator is connected with the first port of the second 1X N laser beam splitter/combiner, the ith second port of the second 1X N laser beam splitter/combiner is connected with the ith second phase modulator, and the ith second phase modulator is connected with the third port of the ith 2X 2 optical fiber coupler; the third port of the circulator is connected with a first photoelectric detector, and the first photoelectric detector is connected with a first phase control module; wherein the laser light input from the first port of the circulator is output only from the second port of the circulator, and the laser light input from the second port of the circulator is output only from the third port of the circulator;
the fourth port of the ith 2x 2 optical fiber coupler is connected with the ith second photoelectric detector; the ith photoelectric detector is connected with the ith second phase control module;
the first phase control module is connected with N first phase modulators, and the ith second phase control module is connected with the ith second phase modulator; or the first phase control module is connected with N second phase modulators, and the ith second phase control module is connected with the ith first phase modulator.
In a preferred embodiment of the present invention, the first phase control module is preloaded with an optimization algorithm, and generates a phase control signal through the optimization algorithm and outputs the phase control signal to the corresponding phase modulator; the N second phase control modules all operate heterodyne method, an acousto-optic modulator is arranged on the optical path of the second path of laser output by the 1X 2 laser beam splitter/combiner, and the acousto-optic modulator is used for generating a frequency shift, so that the second path of laser output by the 1X 2 laser beam splitter/combiner outputs laser with the wavelength of lambda 1 +delta lambda after passing through the acousto-optic modulator, and the laser output by the acousto-optic modulator is input from the first port of the circulator. The optimization algorithm in the invention is not limited, and various phase control optimization algorithms in the prior art, such as a single dithering method, an SPGD method and the like, can be adopted.
In another preferred embodiment of the present invention, the first phase control module and the N second phase control modules are preloaded with an optimization algorithm, and phase control signals are generated by the optimization algorithm and output to the corresponding phase modulators. The optimization algorithm in the invention is not limited, and various phase control optimization algorithms in the prior art, such as a single dithering method, an SPGD method and the like, can be adopted. Further, the system may further comprise N spatial optical phase modulators, and the ith laser collimator is correspondingly connected to the ith spatial optical phase modulator, where the ith spatial optical phase modulator is used for applying a fixed phase Φ i to the laser output by the ith laser collimator.
Preferably, the first phase control module is connected with N first phase modulators, the ith second phase control module is connected with the ith second phase modulator, phase control signals of the second phase modulators are generated through the second phase control modules and output to the corresponding second phase modulators, signals detected by the second photoelectric detectors are stabilized to a set state, phase control signals of the first phase modulators are generated through the first phase control module and output to the corresponding first phase modulators, signals detected by the first photoelectric detectors are stabilized to a maximum value, and further phase locking of output laser is achieved.
Preferably, the first phase control module is connected with N second phase modulators, the ith second phase control module is connected with the ith first phase modulator, phase control signals of the first phase modulators are generated through the second phase control modules and output to the corresponding first phase modulators, signals detected by the second photoelectric detectors are stabilized to a set state, phase control signals of the second phase modulators are generated through the first phase control modules and output to the corresponding second phase modulators, signals detected by the first photoelectric detectors are stabilized to a maximum value, and further phase locking of output laser is achieved.
In a preferred embodiment of the present invention, the 2×2 fiber coupler is used for splitting laser light. When laser light is input from the first port of the 2×2 fiber coupler, most of the laser light of power is output from the second port of the 2×2 fiber coupler, and other laser light of small power is output from the fourth port of the 2×2 fiber coupler. When the laser light is input from the third port of the 2×2 fiber coupler, preferably, all of the laser light is output from the fourth port of the 2×2 fiber coupler. Because of the 2×2 fiber couplers currently available, it is common to do less than all of the outputs from the fourth port of the 2×2 fiber coupler. Therefore, when laser light is input from the third port of the 2×2 fiber coupler, most of the laser light with power is generally output from the fourth port of the 2×2 fiber coupler, and other small portions of the laser light with power may be output from the second port. When the laser light is input from the second port of the 2×2 fiber coupler, preferably all of the laser light is output from the third port of the 2×2 fiber coupler. Also, because of the 2×2 fiber couplers currently available, it is common to do less than all of the output from the third port of the 2×2 fiber coupler. Thus, when laser light is input from the second port of the 2×2 fiber coupler, typically most of the laser light is output from the third port of the 2×2 fiber coupler, and other small portions of the laser light may be output from the first port.
In a preferred embodiment of the invention, laser light incident on the ith fiber cap via the optical fiber, wherein >99% of the power laser light is output to the ith laser collimator via the ith fiber cap and the remaining <1% of the power laser light is reflected back into the optical fiber via the ith fiber cap.
The invention also provides a phase control method of the distributed all-fiber laser phased array system, which comprises the following steps:
(1) Starting N second phase control modules, wherein each second phase control module generates a phase control signal and outputs the phase control signal to a corresponding phase modulator, so that the signal detected by each second photoelectric detector is stabilized to a set state;
(2) The first phase control module is started, the first phase control module generates a phase control signal and outputs the phase control signal to the corresponding phase modulator, so that the signal detected by the first photoelectric detector is stabilized to the maximum value, at the moment, laser emitted by the seed laser source is reflected by each optical fiber end cap, the phases of all the laser beams combined by the second 1 XN laser beam splitting/combining device are kept consistent, and meanwhile, the phases of all the laser beams emitted by the seed laser source are identical through power amplification, and the phase locking of the output laser is realized.
In a preferred embodiment of the present invention, the first phase control module and the N second phase control modules are preloaded with an optimization algorithm, and phase control signals are generated by the optimization algorithm and output to the corresponding phase modulators, and the phase control method is as follows:
(1) Starting N second phase control modules, generating phase control signals by each second phase control module and outputting the phase control signals to a corresponding phase modulator to enable signals detected by each second photoelectric detector to be stabilized to the maximum value, and at the moment, satisfying a first relation:
ψX+ψia＝ψY+ψic
Wherein the second port of the 1×2 laser beam splitter/combiner is connected to the first port of the first 1×n laser beam splitter/combiner, and ψ X represents the phase between the second port of the 1×2 laser beam splitter/combiner and the first port of the first 1×n laser beam splitter/combiner; the ith second port of the first 1×n laser beam splitter/combiner is connected to the first port of the ith 2×2 optical fiber coupler, and ψ ia represents the phase between the ith second port of the first 1×n laser beam splitter/combiner and the first port of the ith 2×2 optical fiber coupler; phi Y denotes a phase between the third port of the 1×2 laser beam splitter/combiner to the first port of the second 1×n laser beam splitter/combiner; and ψ ic denotes a phase between the i second port of the second 1×n laser beam splitter/combiner and the third port of the i 2×2 optical fiber coupler;
(2) Starting a first phase control module, generating a phase control signal by the first phase control module and outputting the phase control signal to a corresponding phase modulator to enable the signal detected by a first photoelectric detector to be stable to the maximum value, at the moment, reflecting laser emitted by a seed laser source through each optical fiber end cap, and keeping the phase of each path of laser combined by a second 1 XN laser beam splitting/combining device consistent, namely meeting a second relation:
ψ1a+2ψ1b+ψ1c＝ψ2a+2ψ2b+ψ2c＝…＝ψNa+2ψNb+ψNc
wherein ψ ib denotes the phase between the second port of the i 2×2 optical fiber coupler to the output end of the i optical fiber end cap;
substituting the first relation into the second relation to obtain a third relation:
ψ1a+ψ1b＝ψ2a+ψ2b＝…＝ψNa+ψNb
The third relation expression shows that the laser emitted by the seed laser source is amplified in power, and the phases of the lasers output by the fiber end caps are identical, so that the phase locking of the output laser is realized.
Furthermore, the invention also comprises a step (3) of applying a fixed phase phi i to the laser output by the ith laser collimator by utilizing the ith spatial light phase modulator, so that the phases of all the laser output by all the spatial light phase modulators are the same, namely phi 1,Φ2,…,ΦN, thereby realizing the phase regulation and control of the array light beams.
In a preferred embodiment of the present invention, the first phase control module is preloaded with an optimization algorithm, and generates a phase control signal through the optimization algorithm and outputs the phase control signal to the corresponding phase modulator; the N second phase control modules all operate heterodyne method, an acousto-optic modulator is arranged on the optical path of the second path of laser output by the 1X 2 laser beam splitter/combiner, the acousto-optic modulator is used for generating a frequency shift, so that the second path of laser output by the 1X 2 laser beam splitter/combiner outputs laser with the wavelength of lambda 1 +delta lambda after passing through the acousto-optic modulator, and the laser output by the acousto-optic modulator is input from the first port of the circulator, and the phase control method is as follows:
(1) Starting N second phase control modules, wherein the second phase control modules operate a heterodyne method, each second phase control module generates a phase control signal and outputs the phase control signal to a corresponding phase modulator, so that the signals detected by each second photoelectric detector are stabilized to a set state, and the fourth relation is satisfied under the set state:
(ψX+ψia)-(ψY+ψic)＝Φi
wherein the second port of the 1×2 laser beam splitter/combiner is connected to the first port of the first 1×n laser beam splitter/combiner, and ψ X represents the phase between the second port of the 1×2 laser beam splitter/combiner and the first port of the first 1×n laser beam splitter/combiner; the ith second port of the first 1×n laser beam splitter/combiner is connected to the first port of the ith 2×2 optical fiber coupler, and ψ ia represents the phase between the ith second port of the first 1×n laser beam splitter/combiner and the first port of the ith 2×2 optical fiber coupler; phi Y denotes a phase between the third port of the 1×2 laser beam splitter/combiner to the first port of the second 1×n laser beam splitter/combiner; and ψ ic denotes a phase between the i second port of the second 1×n laser beam splitter/combiner and the third port of the i 2×2 optical fiber coupler; Φ i is a fixed phase of the setting, i=1, 2, …, N.
(2) Starting a first phase control module, generating a phase control signal by the first phase control module and outputting the phase control signal to a corresponding phase modulator to enable the signal detected by a first photoelectric detector to be stable to the maximum value, at the moment, reflecting laser emitted by a seed laser source through each optical fiber end cap, and keeping the phase of each path of laser combined by a second 1 XN laser beam splitting/combining device consistent, namely meeting a fifth relation:
ψ1a+2ψ1b+ψ1c＝ψ2a+2ψ2b+ψ2c＝…＝ψNa+2ψNb+ψNc
wherein ψ ib denotes the phase between the second port of the i 2×2 optical fiber coupler to the output end of the i optical fiber end cap;
Substituting the fourth relation into the fifth relation to obtain a sixth relation:
ψ1a+ψ1b-Φ1＝ψ2a+ψ2b-Φ2＝…＝ψNa+ψNb-ΦN
The sixth relation indicates that the phase of each path of laser output by each fiber end cap is phi i, namely phi 1,Φ2,…,ΦN, after power amplification of the laser emitted by the seed laser source, so that the phase regulation and control of the array beam are realized.
Compared with the prior art, the invention has the beneficial technical effects that:
The optical path design of the invention adopts an all-fiber structure, and the phase detection and control of each path of laser are realized through the all-fiber structure.
According to the invention, the array laser does not need to be sampled by using the spectroscope, so that the expansibility and compactness of the laser phased array system are improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to the structures shown in these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic block diagram of a fiber laser phased array in the prior art;
FIG. 2 is a distributed all-fiber laser phased array system provided in a first embodiment of the invention;
FIG. 3 is a distributed all-fiber laser phased array system provided in a second embodiment of the invention;
FIG. 4 is a distributed all-fiber laser phased array system provided in a third embodiment of the invention;
FIG. 5 is a distributed all-fiber laser phased array system provided in a fourth embodiment of the invention;
The reference numerals in the drawings illustrate:
201. A seed laser source; 202-0, 1x 2 laser beam splitter/combiner; 202-1, a first 1 XN laser beam splitter/combiner; 202-2, a second 1 XN laser beam splitter/combiner; 203-1, a first phase modulator; 203-2, a second phase modulator; 204. a laser amplifier; 205. a 2 x2 fiber coupler; 206. an optical fiber end cap; 207. a laser collimator; 208. a spatial optical phase modulator; 209-1, a first photodetector; 209-2, a second photodetector; 210-1, a first phase control module; 210-2, a second phase control module; 211. a circulator; 212. an acousto-optic modulator.
The achievement of the objects, functional features and advantages of the present invention will be further described with reference to the accompanying drawings, in conjunction with the embodiments.
Detailed Description
In order to make the objects, technical solutions and advantages of the present disclosure more apparent, the present invention will be further described in detail below with reference to specific embodiments thereof, and in accordance with the accompanying drawings. In the drawings or the description, the non-description and a part of english abbreviations are known to those skilled in the art. Some specific parameters given in the present embodiment are given by way of example only, and the values may be changed to appropriate values accordingly in different real-time manners.
Referring to fig. 2, an embodiment of the present invention provides a distributed all-fiber laser phased array system, which includes a seed laser source 201, a1×2 laser beam splitter/combiner 202-0, a first 1×n laser beam splitter/combiner 202-1, a second 1×n laser beam splitter/combiner 202-2, N first phase modulators 203-1, N laser amplifiers 204, N2×2 fiber couplers 205, N fiber end caps 206, N laser collimating mirrors 207, N spatial optical phase modulators 208, a first photodetector 209-1, N second photodetectors 209-2, a first phase control module 210-1, N second phase control modules 210-2, and a circulator 211. The first phase control module 210-1 and the N second phase control modules 210-2 are preloaded with an optimization algorithm, and phase control signals are generated by the optimization algorithm and output to the corresponding phase modulators. The optimization algorithm in the invention is not limited, and various phase control optimization algorithms in the prior art, such as a single dithering method, an SPGD method and the like, can be adopted.
The seed laser source 201 is used for emitting seed light with wavelength lambda 1, the seed laser source 201 is connected with a first port of the 1×2 laser beam splitter/combiner 202-0, the seed light is split into 2 paths and then is output from a second port and a third port of the 1×2 laser beam splitter/combiner 202-0, the second port of the 1×2 laser beam splitter/combiner 202-0 is connected with a first port of the first 1×n laser beam splitter/combiner 202-1 and is split into N sub-laser light, an i first phase modulator 203-1, an i laser amplifier 204 and an i 2×2 optical fiber coupler 205 are sequentially connected on an optical path after the i second port of the first 1×n laser beam splitter/combiner 202-1, wherein the i laser amplifier 204 is connected with the first port of the i 2×2 optical fiber coupler 205, the second port of the i 2×2 optical fiber coupler 205 is connected with the i optical fiber 206, the i second port of the i 2×2 optical fiber coupler 205 is connected with the i optical fiber 206, and the i optical fiber coupler 202 is connected with the i optical fiber end cap 39, wherein i is 2=1, and the N optical fiber end cap ….
The seed light with the outgoing wavelength of lambda 1 from the seed laser source 201 is divided into 2 paths by a1×2 laser beam splitter/combiner 202-0, wherein the first path of laser is divided into N sub-lasers by a first 1×N laser beam splitter/combiner 202-1, the i sub-lasers are subjected to phase modulation by an i-th phase modulator 203-1, and the i-th laser amplifier 204 is subjected to power amplification and then input to an i-2×2 optical fiber coupler 205; each 2×2 fiber coupler 205 has four ports, wherein a first port of the ith 2×2 fiber coupler 205 is connected to the ith laser amplifier 204, a second port of the 2×2 fiber coupler 205 is connected to the ith fiber end cap 206, the ith fiber end cap 206 is connected to the ith laser collimator 207, the ith laser collimator 207 is correspondingly connected to the ith spatial optical phase modulator 208, and the ith spatial optical phase modulator 208 is used for applying a fixed phase Φ i to the laser output by the ith laser collimator 207, where i=1, 2, …, N; for the laser light incident on the ith fiber end cap 206, wherein >99% of the laser light of power is output to the ith laser collimator 207 through the ith fiber end cap 206, the remaining <1% of the laser light of power is reflected back into the original optical path through the ith fiber end cap 206.
The third port of the 1×2 laser beam splitter/combiner 202-0 is connected to the first port of the circulator, and the second laser beam output through the third port of the 1×2 laser beam splitter/combiner 202-0 is input from the first port of the circulator 211. The second port of the circulator 211 is connected to the first port of the second 1×n laser beam splitter/combiner 202-2, the ith second port of the second 1×n laser beam splitter/combiner 202-2 is connected to the ith second phase modulator 203-2, and the ith second phase modulator 203-2 is connected to the third port of the ith 2×2 optical fiber coupler 205; the third port of the circulator 211 is connected to the first photodetector 209-1, the first photodetector 209-1 is connected to the first phase control module 210-1, and the first phase control module 210-1 is connected to the N first phase modulators 203-1, wherein the laser light input from the first port of the circulator 211 can only be output from the second port of the circulator 211, and the laser light input from the second port of the circulator 211 can only be output from the third port of the circulator 211.
The fourth port of the i 2×2 fiber coupler 205 is connected to the i second photodetector 209-2, the i second photodetector 209-2 is connected to the i second phase control module 210-2, and the i second phase control module 210-2 is connected to the i second phase modulator 203-2.
The 2×2 fiber coupler 205 is configured to split laser light, and has four ports, i.e., a first port, a second port, a third port, and a fourth port. When laser light is input from the first port of the 2×2 fiber coupler 205, most of the laser light of power is output from the second port of the 2×2 fiber coupler 205, and other laser light of small power is output from the fourth port of the 2×2 fiber coupler 205; when the laser light is input from the third port of the 2×2 fiber coupler 205, it is preferable that all the laser light input from the third port of the 2×2 fiber coupler 205 is output from the fourth port of the 2×2 fiber coupler 205. When the laser light is input from the second port of the 2×2 fiber coupler 205, it is preferable that all the laser light input from the second port of the 2×2 fiber coupler 205 is output from the third port of the 2×2 fiber coupler 205.
The phase control signals of the second phase modulators 203-2 are generated by the second phase control modules 210-2 and output to the corresponding second phase modulators 203-2, so that the signals detected by the second photodetectors 209-2 are stabilized to the maximum value, the phase control signals of the first phase modulators 203-1 are generated by the first phase control modules 210-1 and output to the corresponding first phase modulators 203-1, so that the signals detected by the first photodetectors 209-1 are stabilized to the maximum value, and further, the phase locking of the output laser is realized.
The phase control method of the distributed all-fiber laser phased array system provided in the embodiment shown in fig. 2 comprises the following steps:
(1) The N second phase control modules 210-2 are turned on, and each second phase control module 210-2 generates a phase control signal and outputs the phase control signal to the corresponding second phase modulator 203-2, so that the signal detected by each second photodetector 209-2 is stabilized to a maximum value, and at this time, the following relational expression is satisfied:
ψX+ψia＝ψY+ψic (1)
Wherein ψ X represents the phase between the second port of the 1×2 laser beam splitter/combiner 202-0 to the first port of the first 1×n laser beam splitter/combiner 202-1; phi ia denotes the phase between the i second port of the first 1×n laser beam splitter/combiner 202-1 and the first port of the i 2×2 optical fiber coupler 205; phi Y denotes the phase between the third port of the 1 x2 laser beam splitter/combiner 202-0 to the first port of the second 1 x N laser beam splitter/combiner 202-2; phi ic denotes the phase between the i second port of the second 1×n laser beam splitter/combiner 202-2 and the third port of the i 2×2 optical fiber coupler 205;
(2) The first phase control module 210-1 is turned on, the first phase control module 210-1 generates a phase control signal and outputs the phase control signal to each first phase modulator 203-1, so that the signal detected by the first photodetector 209-1 is stabilized to the maximum value, at this time, the laser emitted by the seed laser source 201 is reflected by each optical fiber end cap 206, and then the phases of the laser paths combined by the second 1×n laser beam splitter/combiner 202-2 are kept consistent, that is, the following relational expression is satisfied:
ψ1a+2ψ1b+ψ1c＝ψ2a+2ψ2b+ψ2c＝…＝ψNa+2ψNb+ψNc (2)
Wherein ψ ib represents the phase between the second port of the i2×2 optical fiber coupler 205 to the output of the i optical fiber end cap 206;
Substituting equation (1) into equation (2) yields the following result:
ψ1a+ψ1b＝ψ2a+ψ2b＝…＝ψNa+ψNb (3)
Equation (3) shows that the laser beams emitted from the seed laser source 201 are amplified in power, and the phases of the laser beams output from the fiber end caps 206 are identical to each other, so that the phase lock of the output laser beams is achieved.
The method further comprises a step (3) of applying a fixed phase phi i to the laser output by the ith laser collimator 207 by using the ith spatial light phase modulator 208, so that the phases of the laser paths output by the spatial light phase modulators are identical, namely phi 1,Φ2,…,ΦN, respectively, and the phase regulation and control of the array beam are realized.
Referring to fig. 3, an embodiment of the present invention provides a distributed all-fiber laser phased array system, which includes a seed laser source 201, a1×2 laser beam splitter/combiner 202-0, a first 1×n laser beam splitter/combiner 202-1, a second 1×n laser beam splitter/combiner 202-2, N first phase modulators 203-1, N laser amplifiers 204, N2×2 fiber couplers 205, N fiber end caps 206, N laser collimating mirrors 207, N spatial optical phase modulators 208, a first photodetector 209-1, N second photodetectors 209-2, a first phase control module 210-1, N second phase control modules 210-2, and a circulator 211. The first phase control module 210-1 and the N second phase control modules 210-2 are preloaded with an optimization algorithm, and phase control signals are generated by the optimization algorithm and output to the corresponding phase modulators. The optimization algorithm in the invention is not limited, and various phase control optimization algorithms in the prior art, such as a single dithering method, an SPGD method and the like, can be adopted.
The seed laser source 201 is used for emitting seed light with wavelength lambda 1, the seed laser source 201 is connected with a first port of the 1×2 laser beam splitter/combiner 202-0, the seed light is split into 2 paths and then is output from a second port and a third port of the 1×2 laser beam splitter/combiner 202-0, the second port of the 1×2 laser beam splitter/combiner 202-0 is connected with a first port of the first 1×n laser beam splitter/combiner 202-1 and is split into N sub-laser light, an i first phase modulator 203-1, an i laser amplifier 204 and an i 2×2 optical fiber coupler 205 are sequentially connected on an optical path after the i second port of the first 1×n laser beam splitter/combiner 202-1, wherein the i laser amplifier 204 is connected with the first port of the i 2×2 optical fiber coupler 205, the second port of the i 2×2 optical fiber coupler 205 is connected with the i optical fiber 206, the i second port of the i 2×2 optical fiber coupler 205 is connected with the i optical fiber 206, and the i optical fiber coupler 202 is connected with the i optical fiber end cap 39, wherein i is 2=1, and the N optical fiber end cap ….
The seed light with the outgoing wavelength of lambda 1 from the seed laser source 201 is divided into 2 paths by a1×2 laser beam splitter/combiner 202-0, wherein the first path of laser is divided into N sub-lasers by a first 1×N laser beam splitter/combiner 202-1, wherein the ith sub-laser is subjected to phase modulation by an ith phase modulator 203-1, and the ith laser amplifier 204 is subjected to power amplification and then is input into an ith 2×2 optical fiber coupler 205; each 2×2 fiber coupler 205 has four ports, where a first port of the ith 2×2 fiber coupler 205 is connected to the ith laser amplifier 204, a second port of the 2×2 fiber coupler 205 is connected to the ith fiber end cap 206, the ith fiber end cap 206 is connected to the ith laser collimator 207, the ith laser collimator 207 is correspondingly connected to the ith spatial optical phase modulator 208, and the ith spatial optical phase modulator 208 is used to apply a fixed phase Φ i to the laser output by the ith laser collimator 207. Wherein i=1, 2, …, N; for the laser light incident on the ith fiber end cap 206, wherein >99% of the laser light of power is output to the ith laser collimator 207 through the ith fiber end cap 206, the remaining <1% of the laser light of power is reflected back into the original optical path through the ith fiber end cap 206.
The third port of the 1×2 laser beam splitter/combiner 202-0 is connected to the first port of the circulator, and the second laser beam output through the third port of the 1×2 laser beam splitter/combiner 202-0 is input from the first port of the circulator 211. The second port of the circulator 211 is connected to the first port of the second 1×n laser beam splitter/combiner 202-2, the ith second port of the second 1×n laser beam splitter/combiner 202-2 is connected to the ith second phase modulator 203-2, and the ith second phase modulator 203-2 is connected to the third port of the ith 2×2 optical fiber coupler 205; the third port of the circulator 211 is connected to the first photodetector 209-1, the first photodetector 209-1 is connected to the first phase control module 210-1, and the first phase control module 210-1 is connected to the N second phase modulators 203-2, wherein the laser light input from the first port of the circulator 211 can only be output from the second port of the circulator 211, and the laser light input from the second port of the circulator 211 can only be output from the third port of the circulator 211.
The fourth port of the i 2×2 fiber coupler 205 is connected to the i second photodetector 209-2, the i second photodetector 209-2 is connected to the i second phase control module 210-2, and the i second phase control module 210-2 is connected to the i first phase modulator 203-1.
The 2×2 fiber coupler 205 is configured to split laser light, and has four ports, i.e., a first port, a second port, a third port, and a fourth port. When laser light is input from the first port of the 2×2 fiber coupler 205, most of the laser light of power is output from the second port of the 2×2 fiber coupler 205, and other laser light of small power is output from the fourth port of the 2×2 fiber coupler 205; when the laser light is input from the third port of the 2×2 fiber coupler 205, it is preferable that all the laser light input from the third port of the 2×2 fiber coupler 205 is output from the fourth port of the 2×2 fiber coupler 205. When the laser light is input from the second port of the 2×2 fiber coupler 205, it is preferable that all the laser light input from the second port of the 2×2 fiber coupler 205 is output from the third port of the 2×2 fiber coupler 205.
The phase control signals of the first phase modulators 203-1 are generated by the second phase control modules 210-2 and output to the corresponding first phase modulators 203-1, so that the signals detected by the second photodetectors 209-2 are stabilized to the maximum value, the phase control signals of the second phase modulators 203-2 are generated by the first phase control modules 210-1 and output to the corresponding second phase modulators 203-2, so that the signals detected by the first photodetectors 209-1 are stabilized to the maximum value, and further, the phase locking of the output laser is realized.
The phase control method of the distributed all-fiber laser phased array system provided in the embodiment shown in fig. 3 comprises the following steps:
(1) The N second phase control modules 210-2 are turned on, and each second phase control module 210-2 generates a phase control signal and outputs the phase control signal to the corresponding first phase modulator 203-1, so that the signal detected by each second photodetector 209-2 is stabilized to a maximum value, and at this time, the following relational expression is satisfied:
ψX+ψia＝ψY+ψic (1)
Wherein ψ X represents the phase between the second port of the 1×2 laser beam splitter/combiner 202-0 to the first port of the first 1×n laser beam splitter/combiner 202-1; phi ia denotes the phase between the i second port of the first 1×n laser beam splitter/combiner 202-1 and the first port of the i 2×2 optical fiber coupler 205; phi Y denotes the phase between the third port of the 1 x2 laser beam splitter/combiner 202-0 to the first port of the second 1 x N laser beam splitter/combiner 202-2; phi ic denotes the phase between the i second port of the second 1×n laser beam splitter/combiner 202-2 and the third port of the i 2×2 optical fiber coupler 205;
(2) The first phase control module 210-1 is turned on, the first phase control module 210-1 generates a phase control signal and outputs the phase control signal to each second phase modulator 203-2, so that the signal detected by the first photodetector 209-1 is stabilized to the maximum value, at this time, the laser emitted by the seed laser source 201 is reflected by each optical fiber end cap 206, and then the phases of the laser paths combined by the second 1×n laser beam splitter/combiner 202-2 are kept consistent, that is, the following relation is satisfied:
ψ1a+2ψ1b+ψ1c＝ψ2a+2ψ2b+ψ2c＝…＝ψNa+2ψNb+ψNc (2)
Wherein ψ ib represents the phase between the second port of the i2×2 optical fiber coupler 205 to the output of the i optical fiber end cap 206;
Substituting equation (1) into equation (2) yields the following result:
ψ1a+ψ1b＝ψ2a+ψ2b＝…＝ψNa+ψNb (3)
Equation (3) shows that the laser beams emitted from the seed laser source 201 are amplified in power, and the phases of the laser beams output from the fiber end caps 206 are identical to each other, so that the phase lock of the output laser beams is achieved.
Further, the method also comprises a step (3) of applying a fixed phase phi i to the laser output by the ith laser collimator 207 by using the ith spatial light phase modulator 208, so that the phase of each path of laser output by each spatial light phase modulator 208 is phi i, thereby realizing the phase regulation of the array beam.
Referring to fig. 4, an embodiment of the present invention provides a distributed all-fiber laser phased array system, which includes a seed laser source 201, a 1×2 laser beam splitter/combiner 202-0, a first 1×n laser beam splitter/combiner 202-1, a second 1×n laser beam splitter/combiner 202-2, N first phase modulators 203-1, N laser amplifiers 204, N2×2 fiber couplers 205, N fiber end caps 206, N laser collimators 207, a first photodetector 209-1, N second photodetectors 209-2, a first phase control module 210-1, N second phase control modules 210-2, a circulator 211, and an acousto-optic modulator 212.
The first phase control module 210-1 is preloaded with an optimization algorithm, and generates a phase control signal through the optimization algorithm and outputs the phase control signal to the corresponding phase modulator. The optimization algorithm in the invention is not limited, and various phase control optimization algorithms in the prior art, such as a single dithering method, an SPGD method and the like, can be adopted. And the N second phase control modules all operate heterodyne methods.
The seed laser source 201 is used for emitting seed light with wavelength lambda 1, the seed laser source 201 is connected with a first port of the 1×2 laser beam splitter/combiner 202-0, the seed light is split into 2 paths and then is output from a second port and a third port of the 1×2 laser beam splitter/combiner 202-0, the second port of the 1×2 laser beam splitter/combiner 202-0 is connected with a first port of the first 1×n laser beam splitter/combiner 202-1 and is split into N sub-laser light, an i first phase modulator 203-1, an i laser amplifier 204 and an i 2×2 optical fiber coupler 205 are sequentially connected on an optical path after the i second port of the first 1×n laser beam splitter/combiner 202-1, wherein the i laser amplifier 204 is connected with the first port of the i 2×2 optical fiber coupler 205, the second port of the i 2×2 optical fiber coupler 205 is connected with the i optical fiber 206, the i second port of the i 2×2 optical fiber coupler 205 is connected with the i optical fiber 206, and the i optical fiber coupler 202 is connected with the i optical fiber end cap 39, wherein i is 2=1, and the N optical fiber end cap ….
The seed light with the outgoing wavelength of lambda 1 from the seed laser source 201 is divided into 2 paths by a 1×2 laser beam splitter/combiner 202-0, wherein the first path of laser is divided into N sub-lasers by a first 1×N laser beam splitter/combiner 202-1, the i sub-lasers are subjected to phase modulation by an i-th phase modulator 203-1, and the i-th laser amplifier 204 is subjected to power amplification and then input to an i-2×2 optical fiber coupler 205; each 2 x 2 fiber coupler 205 has four ports, with a first port of the i 2 x 2 fiber coupler 205 connected to the i laser amplifier 204, a second port of the 2 x 2 fiber coupler 205 connected to the i optical fiber end cap 206, and the i optical fiber end cap 206 connected to the i laser collimator 207, where i = 1,2, …, N; for the laser light incident on the ith fiber end cap 206, wherein >99% of the laser light of power is output to the ith laser collimator 207 through the ith fiber end cap 206, the remaining <1% of the laser light of power is reflected back into the original optical path through the ith fiber end cap 206.
The third port of the 1×2 laser beam splitter/combiner 202-0 is connected to the acousto-optic modulator 212, and the acousto-optic modulator 212 is configured to generate a frequency shift, so that the second path of laser light output by the 1×2 laser beam splitter/combiner 202-0 outputs laser light with a wavelength of λ 1 +Δλ after passing through the acousto-optic modulator 212. The acousto-optic modulator 212 is connected to the first port of the circulator 211, and the second laser beam output from the third port of the 1×2 laser beam splitter/combiner 202-0 is input from the first port of the circulator 211 by the laser beam with the wavelength λ 1 +Δλ output from the acousto-optic modulator 212. The second port of the circulator 211 is connected to the first port of the second 1×n laser beam splitter/combiner 202-2, the ith second port of the second 1×n laser beam splitter/combiner 202-2 is connected to the ith second phase modulator 203-2, and the ith second phase modulator 203-2 is connected to the third port of the ith 2×2 optical fiber coupler 205; the third port of the circulator 211 is connected to the first photodetector 209-1, the first photodetector 209-1 is connected to the first phase control module 210-1, and the first phase control module 210-1 is connected to the N first phase modulators 203-1, wherein the laser light input from the first port of the circulator 211 can only be output from the second port of the circulator 211, and the laser light input from the second port of the circulator 211 can only be output from the third port of the circulator 211.
The fourth port of the i 2×2 fiber coupler 205 is connected to the i second photodetector 209-2, the i second photodetector 209-2 is connected to the i second phase control module 210-2, and the i second phase control module 210-2 is connected to the i second phase modulator 203-2.
The 2×2 fiber coupler 205 is configured to split laser light, and has four ports, i.e., a first port, a second port, a third port, and a fourth port. When laser light is input from the first port of the 2×2 fiber coupler 205, most of the laser light of power is output from the second port of the 2×2 fiber coupler 205, and other laser light of small power is output from the fourth port of the 2×2 fiber coupler 205; when the laser light is input from the third port of the 2×2 fiber coupler 205, it is preferable that all the laser light input from the third port of the 2×2 fiber coupler 205 is output from the fourth port of the 2×2 fiber coupler 205. When the laser light is input from the second port of the 2×2 fiber coupler 205, it is preferable that all the laser light input from the second port of the 2×2 fiber coupler 205 is output from the third port of the 2×2 fiber coupler 205.
The phase control signals of the second phase modulators 203-2 are generated by the second phase control modules 210-2 and output to the corresponding second phase modulators 203-2, so that the signals detected by the second photodetectors 209-2 are stabilized to a set state, the phase control signals of the first phase modulators 203-1 are generated by the first phase control modules 210-1 and output to the corresponding first phase modulators 203-1, so that the signals detected by the first photodetectors 209-1 are stabilized to a maximum value, and further, the phase locking of the output laser is realized.
The phase control method of the distributed all-fiber laser phased array system provided in the embodiment shown in fig. 4 includes the following steps:
(1) Starting N second phase control modules, operating a heterodyne method by the second phase control modules, generating phase control signals by each second phase control module, outputting the phase control signals to a corresponding phase modulator, and stabilizing the signals detected by each second photoelectric detector to a set state, wherein the set state satisfies the following relation:
(ψX+ψia)-(ψY+ψic)＝Φi (4)
Wherein the second port of the 1×2 laser beam splitter/combiner is connected to the first port of the first 1×n laser beam splitter/combiner, and ψx represents the phase between the second port of the 1×2 laser beam splitter/combiner and the first port of the first 1×n laser beam splitter/combiner; the ith second port of the first 1×n laser beam splitter/combiner is connected to the first port of the ith 2×2 optical fiber coupler, and ψ ia represents the phase between the ith second port of the first 1×n laser beam splitter/combiner and the first port of the ith 2×2 optical fiber coupler; phi Y denotes a phase between the third port of the 1×2 laser beam splitter/combiner to the first port of the second 1×n laser beam splitter/combiner; and ψ ic denotes a phase between the i second port of the second 1×n laser beam splitter/combiner and the third port of the i 2×2 optical fiber coupler; Φ i is a fixed phase of the setting, i=1, 2, …, N.
(2) Starting a first phase control module, generating a phase control signal by the first phase control module and outputting the phase control signal to a corresponding phase modulator to enable the signal detected by a first photoelectric detector to be stable to the maximum value, reflecting laser emitted by a seed laser source through each optical fiber end cap, and keeping the phase of each path of laser combined by a second 1 XN laser beam splitter/combiner consistent, wherein the following relation is satisfied:
ψ1a+2ψ1b+ψ1c＝ψ2a+2ψ2b+ψ2c＝…＝ψNa+2ψNb+ψNc (5)
wherein ψ ib denotes the phase between the second port of the i 2×2 optical fiber coupler to the output end of the i optical fiber end cap;
substituting equation (4) into equation (5) yields the following result:
ψ1a+ψ1b-Φ1＝ψ2a+ψ2b-Φ2＝…＝ψNa+ψNb-ΦN (6)
The formula (6) shows that the phase of each path of laser output by each optical fiber end cap is phi i respectively, namely phi 1,Φ2,…,ΦN respectively, after power amplification of the laser emitted by the seed laser source, so that the phase regulation and control of the array light beam are realized.
Referring to fig. 5, an embodiment of the present invention provides a distributed all-fiber laser phased array system, which includes a seed laser source 201, a 1×2 laser beam splitter/combiner 202-0, a first 1×n laser beam splitter/combiner 202-1, a second 1×n laser beam splitter/combiner 202-2, N first phase modulators 203-1, N laser amplifiers 204, N2×2 fiber couplers 205, N fiber end caps 206, N laser collimators 207, a first photodetector 209-1, N second photodetectors 209-2, a first phase control module 210-1, N second phase control modules 210-2, a circulator 211, and an acousto-optic modulator 212.
The first phase control module 210-1 is preloaded with an optimization algorithm, and generates a phase control signal through the optimization algorithm and outputs the phase control signal to the corresponding phase modulator. The optimization algorithm in the invention is not limited, and various phase control optimization algorithms in the prior art, such as a single dithering method, an SPGD method and the like, can be adopted. And the N second phase control modules all operate heterodyne methods.
The seed laser source 201 is used for emitting seed light with wavelength lambda 1, the seed laser source 201 is connected with a first port of the 1×2 laser beam splitter/combiner 202-0, the seed light is split into 2 paths and then is output from a second port and a third port of the 1×2 laser beam splitter/combiner 202-0, the second port of the 1×2 laser beam splitter/combiner 202-0 is connected with a first port of the first 1×n laser beam splitter/combiner 202-1 and is split into N sub-laser light, an i first phase modulator 203-1, an i laser amplifier 204 and an i 2×2 optical fiber coupler 205 are sequentially connected on an optical path after the i second port of the first 1×n laser beam splitter/combiner 202-1, wherein the i laser amplifier 204 is connected with the first port of the i 2×2 optical fiber coupler 205, the second port of the i 2×2 optical fiber coupler 205 is connected with the i optical fiber 206, the i second port of the i 2×2 optical fiber coupler 205 is connected with the i optical fiber 206, and the i optical fiber coupler 202 is connected with the i optical fiber end cap 39, wherein i is 2=1, and the N optical fiber end cap ….
The seed light with the outgoing wavelength of lambda 1 from the seed laser source 201 is divided into 2 paths by a1×2 laser beam splitter/combiner 202-0, wherein the first path of laser is divided into N sub-lasers by a first 1×N laser beam splitter/combiner 202-1, wherein the ith sub-laser is subjected to phase modulation by an ith phase modulator 203-1, and the ith laser amplifier 204 is subjected to power amplification and then is input into an ith 2×2 optical fiber coupler 205; each 2 x2 fiber coupler 205 has four ports, with a first port of the i 2 x2 fiber coupler 205 connected to the i laser amplifier 204, a second port of the 2 x2 fiber coupler 205 connected to the i optical fiber end cap 206, and the i optical fiber end cap 206 connected to the i laser collimator 207, where i = 1,2, …, N; for the laser light incident on the ith fiber end cap 206, wherein >99% of the laser light of power is output to the ith laser collimator 207 through the ith fiber end cap 206, the remaining <1% of the laser light of power is reflected back into the original optical path through the ith fiber end cap 206.
The third port of the 1×2 laser beam splitter/combiner 202-0 is connected to the acousto-optic modulator 212, and the acousto-optic modulator 212 is configured to generate a frequency shift, so that the second path of laser light output by the 1×2 laser beam splitter/combiner 202-0 outputs laser light with a wavelength of λ 1 +Δλ after passing through the acousto-optic modulator 212. The acousto-optic modulator 212 is connected to the first port of the circulator 211, and the second laser beam output from the third port of the 1×2 laser beam splitter/combiner 202-0 is input from the first port of the circulator 211 by the laser beam with the wavelength λ 1 +Δλ output from the acousto-optic modulator 212. The second port of the circulator 211 is connected to the first port of the second 1×n laser beam splitter/combiner 202-2, the ith second port of the second 1×n laser beam splitter/combiner 202-2 is connected to the ith second phase modulator 203-2, and the ith second phase modulator 203-2 is connected to the third port of the ith 2×2 optical fiber coupler 205; the third port of the circulator 211 is connected to the first photodetector 209-1, the first photodetector 209-1 is connected to the first phase control module 210-1, and the first phase control module 210-1 is connected to the N second phase modulators 203-2, wherein the laser light input from the first port of the circulator 211 can only be output from the second port of the circulator 211, and the laser light input from the second port of the circulator 211 can only be output from the third port of the circulator 211.
The fourth port of the i 2×2 fiber coupler 205 is connected to the i second photodetector 209-2, the i second photodetector 209-2 is connected to the i second phase control module 210-2, and the i second phase control module 210-2 is connected to the i first phase modulator 203-1.
The 2×2 fiber coupler 205 is configured to split laser light, and has four ports, i.e., a first port, a second port, a third port, and a fourth port. When laser light is input from the first port of the 2×2 fiber coupler 205, most of the laser light of power is output from the second port of the 2×2 fiber coupler 205, and other laser light of small power is output from the fourth port of the 2×2 fiber coupler 205; when the laser light is input from the third port of the 2×2 fiber coupler 205, it is preferable that all the laser light input from the third port of the 2×2 fiber coupler 205 is output from the fourth port of the 2×2 fiber coupler 205. When the laser light is input from the second port of the 2×2 fiber coupler 205, it is preferable that all the laser light input from the second port of the 2×2 fiber coupler 205 is output from the third port of the 2×2 fiber coupler 205.
The phase control signals of the first phase modulators 203-1 are generated by the second phase control modules 210-2 and output to the corresponding first phase modulators 203-1, so that the signals detected by the second photodetectors 209-2 are stabilized to a set state, the phase control signals of the second phase modulators 203-2 are generated by the first phase control modules 210-1 and output to the corresponding second phase modulators 203-2, so that the signals detected by the first photodetectors 209-1 are stabilized to a maximum value, and further, the phase locking of the output laser is realized.
The phase control method of the distributed all-fiber laser phased array system provided in the embodiment shown in fig. 5 comprises the following steps:
(1) Starting N second phase control modules 210-2, operating heterodyne method by the second phase control modules 210-2, generating phase control signals by each second phase control module 210-2 and outputting the phase control signals to corresponding phase modulators, and stabilizing the signals detected by each second photodetector 209-2 to a set state, wherein the set state satisfies the following relation:
(ψX+ψia)-(ψY+ψic)＝Φi (4)
wherein the second port of the 1×2 laser beam splitter/combiner 202-0 is connected to the first port of the first 1×n laser beam splitter/combiner 202-1, and ψ X represents the phase between the second port of the 1×2 laser beam splitter/combiner 202-0 and the first port of the first 1×n laser beam splitter/combiner 202-1; the ith second port of the first 1×n laser beam splitter/combiner 202-1 is connected to the first port of the ith 2×2 optical fiber coupler 205, and ψ ia represents the phase between the ith second port of the first 1×n laser beam splitter/combiner 202-1 and the first port of the ith 2×2 optical fiber coupler 205; phi Y denotes a phase between the third port of the 1×2 laser beam splitter/combiner to the first port of the second 1×n laser beam splitter/combiner; and ψ ic denotes a phase between the i second port of the second 1×n laser beam splitter/combiner and the third port of the i 2×2 optical fiber coupler; Φ i is a fixed phase of the setting, i=1, 2, …, N.
(2) The first phase control module 210-1 is turned on, the first phase control module 210-1 generates a phase control signal and outputs the phase control signal to the corresponding phase modulator, so that the signal detected by the first photodetector 209-1 is stabilized to the maximum value, at this time, the laser emitted by the seed laser source 201 is reflected by each optical fiber end cap 206, and then the phases of the laser paths combined by the second 1×n laser beam splitter/combiner 202-2 are kept consistent, that is, the following relation is satisfied:
ψ1a+2ψ1b+ψ1c＝ψ2a+2ψ2b+ψ2c＝…＝ψNa+2ψNb+ψNc (5)
Wherein ψ ib represents the phase between the second port of the i2×2 optical fiber coupler 205 to the output of the i optical fiber end cap 206;
substituting equation (4) into equation (5) yields the following result:
ψ1a+ψ1b-Φ1＝ψ2a+ψ2b-Φ2＝…＝ψNa+ψNb-ΦN (6)
Equation (6) shows that the phase of each path of laser output from each fiber end cap 206 is Φ i, that is, Φ 1,Φ2,…,ΦN, after power amplification, of the laser emitted from the seed laser source 201, so as to realize phase regulation of the array beam.
The above description of the preferred embodiments of the present invention has been included to describe in detail the technical features of the present invention, and is not intended to limit the invention to the specific forms described in the embodiments, and other modifications and variations according to the gist of the present invention are also protected by this patent. The gist of the present disclosure is defined by the claims, not by the specific description of the embodiments.

Claims (11)

1. The distributed all-fiber laser phased array system is characterized by comprising a seed laser source, a1 multiplied by 2 laser beam splitter/combiner, a1 multiplied by N laser beam splitter/combiner, a phase modulator, a laser amplifier, a2 multiplied by 2 fiber coupler, a fiber end cap, a laser collimating lens, a circulator, a photoelectric detector and a phase control module;
The seed light with the outgoing wavelength of lambda 1 of the seed laser source is divided into 2 paths by a 1X 2 laser beam splitter/combiner, wherein the first path of laser is divided into N sub lasers by a first 1X N laser beam splitter/combiner, the i sub lasers are subjected to phase modulation by an i phase modulator, and the i laser amplifier is subjected to power amplification and then input to an i 2X 2 optical fiber coupler;
Each 2 x2 fiber coupler has four ports, wherein a first port of an i 2 x2 fiber coupler is connected to an i laser amplifier, a second port of the 2 x2 fiber coupler is connected to an i fiber end cap, the i fiber end cap is connected to an i laser collimator, wherein i = 1,2, …, N; for the laser incident to the ith optical fiber end cap, most of the laser is output to the ith laser collimating mirror, and the other small part is reflected back to the original light path;
The second path of laser output by the 1X 2 laser beam splitter/combiner is input from the first port of the circulator, the second port of the circulator is connected with the first port of the second 1X N laser beam splitter/combiner, the ith second port of the second 1X N laser beam splitter/combiner is connected with the ith second phase modulator, and the ith second phase modulator is connected with the third port of the ith 2X 2 optical fiber coupler; the third port of the circulator is connected with a first photoelectric detector, and the first photoelectric detector is connected with a first phase control module; wherein the laser light input from the first port of the circulator is output only from the second port of the circulator, and the laser light input from the second port of the circulator is output only from the third port of the circulator;
the fourth port of the ith 2x 2 optical fiber coupler is connected with the ith second photoelectric detector; the ith photoelectric detector is connected with the ith second phase control module;
the first phase control module is connected with N first phase modulators, and the ith second phase control module is connected with the ith second phase modulator; or the first phase control module is connected with N second phase modulators, and the ith second phase control module is connected with the ith first phase modulator.
2. The distributed all-fiber laser phased array system of claim 1, wherein the 2 x2 fiber coupler outputs a majority of the power laser light from a second port of the 2 x2 fiber coupler and other minority of the power laser light from a fourth port of the 2 x2 fiber coupler when the laser light is input from a first port of the 2 x2 fiber coupler;
When the laser is input from the third port of the 2×2 fiber coupler, most of the laser with power is output from the fourth port of the 2×2 fiber coupler;
when laser light is input from the second port of the 2×2 fiber coupler, most of the power laser light is output from the third port of the 2×2 fiber coupler.
3. The distributed all-fiber laser phased array system of claim 1, wherein laser light incident on the ith fiber cap via the fiber, wherein >99% of the power laser light is output to the ith laser collimator via the ith fiber cap, and the remaining <1% of the power laser light is reflected back into the fiber via the ith fiber cap.
4. The distributed all-fiber laser phased array system of claim 1, wherein the first phase control module is preloaded with an optimization algorithm by which a phase control signal is generated and output to a corresponding phase modulator; the N second phase control modules all operate heterodyne method, an acousto-optic modulator is arranged on the optical path of the second path of laser output by the 1X 2 laser beam splitter/combiner, and the acousto-optic modulator is used for generating a frequency shift, so that the second path of laser output by the 1X 2 laser beam splitter/combiner outputs laser with the wavelength of lambda 1 +delta lambda after passing through the acousto-optic modulator, and the laser output by the acousto-optic modulator is input from the first port of the circulator.
5. The distributed all-fiber laser phased array system of claim 1, wherein the first phase control module and the N second phase control modules are preloaded with an optimization algorithm by which phase control signals are generated and output to corresponding phase modulators.
6. The distributed all-fiber laser phased array system of claim 5, further comprising N spatial light phase modulators, an ith laser collimator being correspondingly connected to the ith spatial light phase modulator, the ith spatial light phase modulator being configured to apply a fixed phase Φ i to laser light output by the ith laser collimator.
7. The distributed all-fiber laser phased array system according to any one of claims 1 to 6, wherein when the first phase control module is connected to N first phase modulators and the ith second phase control module is connected to the ith second phase modulator, the phase control signals of the second phase modulators are generated by the second phase control modules and output to the corresponding second phase modulators, so that the signals detected by the second photodetectors are stabilized to a set state, the phase control signals of the first phase modulators are generated by the first phase control module and output to the corresponding first phase modulators, so that the signals detected by the first photodetectors are stabilized to a maximum value, and further, the phase locking of the output laser is realized.
8. The distributed all-fiber laser phased array system according to any one of claims 1 to 6, wherein when the first phase control module is connected to N second phase modulators and the ith second phase control module is connected to the ith first phase modulator, the phase control signals of the first phase modulators are generated by the second phase control modules and output to the corresponding first phase modulators, so that the signals detected by the second photodetectors are stabilized to a set state, the phase control signals of the second phase modulators are generated by the first phase control modules and output to the corresponding second phase modulators, so that the signals detected by the first photodetectors are stabilized to a maximum value, and further, the phase locking of the output laser is realized.
9. The phase control method of a distributed all-fiber laser phased array system according to claim 1, wherein the first phase control module and the N second phase control modules in the distributed all-fiber laser phased array system are preloaded with an optimization algorithm, and phase control signals are generated by the optimization algorithm and output to corresponding phase modulators, and the phase control method comprises the steps of:
(1) Starting N second phase control modules, generating phase control signals by each second phase control module and outputting the phase control signals to a corresponding phase modulator to enable signals detected by each second photoelectric detector to be stabilized to the maximum value, and at the moment, satisfying a first relation:
ψX+ψia＝ψY+ψic
Wherein the second port of the 1×2 laser beam splitter/combiner is connected to the first port of the first 1×n laser beam splitter/combiner, and ψ X represents the phase between the second port of the 1×2 laser beam splitter/combiner and the first port of the first 1×n laser beam splitter/combiner; the ith second port of the first 1×n laser beam splitter/combiner is connected to the first port of the ith 2×2 optical fiber coupler, and ψ ia represents the phase between the ith second port of the first 1×n laser beam splitter/combiner and the first port of the ith 2×2 optical fiber coupler; phi Y denotes a phase between the third port of the 1×2 laser beam splitter/combiner to the first port of the second 1×n laser beam splitter/combiner; and ψ ic denotes a phase between the i second port of the second 1×n laser beam splitter/combiner and the third port of the i 2×2 optical fiber coupler;
(2) Starting a first phase control module, generating a phase control signal by the first phase control module and outputting the phase control signal to a corresponding phase modulator to enable the signal detected by a first photoelectric detector to be stable to the maximum value, at the moment, reflecting laser emitted by a seed laser source through each optical fiber end cap, and keeping the phase of each path of laser combined by a second 1 XN laser beam splitting/combining device consistent, namely meeting a second relation:
ψ1a+2ψ1b+ψ1c＝ψ2a+2ψ2b+ψ2c＝…＝ψNa+2ψNb+ψNc
wherein ψ ib denotes the phase between the second port of the i 2×2 optical fiber coupler to the output end of the i optical fiber end cap;
substituting the first relation into the second relation to obtain a third relation:
ψ1a+ψ1b＝ψ2a+ψ2b＝…＝ψNa+ψNb
The third relation expression shows that the laser emitted by the seed laser source is amplified in power, and the phases of the lasers output by the fiber end caps are identical, so that the phase locking of the output laser is realized.
10. The phase control method according to claim 9, further comprising the step (3) of applying a fixed phase Φ i to the laser light output from the ith laser collimator by using the ith spatial light phase modulator, so that the phases of the laser light output from the spatial light phase modulators are identical, that is, Φ 1,Φ2,…,ΦN, respectively, thereby realizing the phase control of the array beam.
11. The phase control method of the distributed all-fiber laser phased array system according to claim 1, wherein an optimization algorithm is preloaded on the first phase control module in the distributed all-fiber laser phased array system, and a phase control signal is generated through the optimization algorithm and is output to a corresponding phase modulator; the N second phase control modules all operate heterodyne method, an acousto-optic modulator is arranged on the optical path of the second path of laser output by the 1X 2 laser beam splitter/combiner, the acousto-optic modulator is used for generating a frequency shift, so that the second path of laser output by the 1X 2 laser beam splitter/combiner outputs laser with the wavelength of lambda 1 +delta lambda after passing through the acousto-optic modulator, and the laser output by the acousto-optic modulator is input from the first port of the circulator, and the phase control method is as follows:
(1) Starting N second phase control modules, wherein the second phase control modules operate a heterodyne method, each second phase control module generates a phase control signal and outputs the phase control signal to a corresponding phase modulator, so that the signals detected by each second photoelectric detector are stabilized to a set state, and the fourth relation is satisfied under the set state:
(ψX+ψia)-(ψY+ψic)＝Φi
Wherein the second port of the 1×2 laser beam splitter/combiner is connected to the first port of the first 1×n laser beam splitter/combiner, and ψx represents the phase between the second port of the 1×2 laser beam splitter/combiner and the first port of the first 1×n laser beam splitter/combiner; the ith second port of the first 1×n laser beam splitter/combiner is connected to the first port of the ith 2×2 optical fiber coupler, and ψ ia represents the phase between the ith second port of the first 1×n laser beam splitter/combiner and the first port of the ith 2×2 optical fiber coupler; phi Y denotes a phase between the third port of the 1×2 laser beam splitter/combiner to the first port of the second 1×n laser beam splitter/combiner; and ψ ic denotes a phase between the i second port of the second 1×n laser beam splitter/combiner and the third port of the i 2×2 optical fiber coupler; phi i is a set fixed phase;
(2) Starting a first phase control module, generating a phase control signal by the first phase control module and outputting the phase control signal to a corresponding phase modulator to enable the signal detected by a first photoelectric detector to be stable to the maximum value, at the moment, reflecting laser emitted by a seed laser source through each optical fiber end cap, and keeping the phase of each path of laser combined by a second 1 XN laser beam splitting/combining device consistent, namely meeting a fifth relation:
ψ1a+2ψ1b+ψ1c＝ψ2a+2ψ2b+ψ2c＝…＝ψNa+2ψNb+ψNc
wherein ψ ib denotes the phase between the second port of the i 2×2 optical fiber coupler to the output end of the i optical fiber end cap;
Substituting the fourth relation into the fifth relation to obtain a sixth relation:
ψ1a+ψ1b-Φ1＝ψ2a+ψ2b-Φ2＝…＝ψNa+ψNb-ΦN
the sixth relation indicates that the laser emitted by the seed laser source is amplified, and the phases of the laser outputs of all paths of laser output by all fiber end caps are the same, namely phi 1,Φ2,…,ΦN, so that the phase regulation and control of the array light beams are realized.
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