CN110176712B - Random fiber laser generation method and system - Google Patents
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- 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
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
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Abstract
The invention provides a random fiber laser generation method and a system, comprising an excitation light generation subsystem and a random fiber laser resonant cavity; the excitation light generation subsystem generates two paths of time-domain stable excitation light; two paths of time-domain stable excitation light are respectively injected into a random fiber laser resonant cavity from front to back, and the random fiber laser resonant cavity realizes random fiber laser generation under pumping of the excitation light by relying on distributed Raman gain and random Rayleigh scattering feedback. The invention adopts the time domain stable excitation source to pump the random Raman fiber laser, suppresses the high-order Raman Stokes random fiber laser and outputs laser noise, realizes the output of high-power and low-noise random fiber laser, and provides a new thought for the design of fiber light sources in the fields of multi-point detection, fiber sensing, optical imaging and the like.
Description
Technical Field
The invention belongs to the technical field of strong laser and nonlinear fiber optics, and particularly relates to a high-power low-noise random fiber laser generation method and system.
Background
The laser is derived from an atomic system stimulated radiation process to generate a large number of homomorphic and ultra-high degeneracy photon states, so that a system with good directivity, high monochromaticity, high coherence and high brightness laser output is realized. In general, an excitation source, a laser working substance, and a resonator are three major elements constituting a laser. Wherein: the excitation source is used as pumping light to pump laser working substances to realize particle number inversion, and the resonant cavity realizes self-excited oscillation and gain is larger than loss conditions to realize laser oscillation. For the fiber laser, semiconductor lasers, solid state lasers, fiber lasers and other different types of lasers can be used as excitation sources of the fiber laser. The resonant cavity can be generally formed by feedback devices such as fiber gratings, sagnac rings and the like, and can also be provided with feedback by random processes such as dynamic random gratings, random Rayleigh scattering and the like. The laser working substance is a two-dimensional waveguide fiber for providing amplification gain, and can be different rare earth ion doped gain fibers such as ytterbium doped fiber, erbium doped fiber, thulium doped fiber, holmium doped fiber and the like containing real energy level, or can be nonlinear gain fiber containing virtual energy level. By utilizing the generation mechanism, different types of optical fiber light sources such as ytterbium-doped optical fiber lasers, erbium-ytterbium co-doped optical fiber lasers, thulium-doped optical fiber lasers, holmium-doped optical fiber lasers, raman optical fiber lasers, brillouin optical fiber lasers, super-fluorescent light sources, random optical fiber lasers and the like can be realized.
Compared with other types of fiber lasers, the random Raman fiber laser realizes optical amplification by utilizing virtual energy distribution type Raman gain and random feedback, and has special advantages in improving the performance of output laser. Specifically, the amplification gain in the random Raman fiber laser is provided by a distributed Raman amplification process, the lasing wavelength is not limited by the emission wavelength of doped ions, the space hole burning effect caused by the inversion of the particle number of the rare earth ion doped fiber in the amplification process does not exist, and the random Raman fiber laser has great potential for developing to a high-power ultra-wide wavelength range. In addition, in the random Raman fiber laser, the output end does not need a fixed feedback device, the realization structure is simple, the time domain fluctuation of the laser caused by the filter characteristic of the feedback device at the output end can be effectively avoided, and the random Raman fiber laser is an effective way for realizing low-noise fiber laser output.
In random raman fiber lasers, in order to suppress the effect of inter-mode four-wave mixing on spectral purity, and to provide sufficient distributed feedback and amplification gain, it is generally necessary to use optical fibers with smaller cores and fiber lengths typically on the order of hundreds of meters or more. Therefore, the high-order raman stokes random fiber laser can seriously affect the system development to high power. In order to overcome the above problems, researchers have proposed to suppress the generation of high-order raman stokes random fiber lasers in random raman fiber lasers using novel fiber designs such as twin-core fiber, tapered fiber, and the like. However, the high-order raman stokes random fiber laser suppression method relying on the novel fiber design has high technical complexity, large implementation difficulty and high cost. In addition, high-power random Raman fiber lasers which simultaneously give consideration to high-order Raman Stokes random fiber lasers and output laser noise suppression are not reported yet. Therefore, the noise suppression of the high-order Raman Stokes random fiber laser and the output laser is comprehensively considered, and a new effective technical means for realizing high-power and low-noise random fiber laser is provided, so that the method has important scientific significance and practical needs.
Disclosure of Invention
Aiming at the defects existing in the technical field of strong laser and nonlinear fiber optics, the invention provides a random fiber laser generation method and a system based on the noise transfer characteristic of an excitation source in a random Raman fiber laser.
In order to achieve the technical purpose, the technical scheme of the invention is as follows:
two paths of time-domain stable excitation light are respectively injected into a random fiber laser resonant cavity from front to back, and the random fiber laser resonant cavity realizes random fiber laser generation under pumping of the excitation light by relying on distributed Raman gain and random Rayleigh scattering feedback. Wherein, time domain stabilization refers to the absence of self-mode locking pulses, relaxation oscillation pulses, and turbulence-like pulses in the excitation light.
In the invention, the following components are added: the method for generating the time-domain stable excitation light comprises the following steps: the single-frequency laser or the multi-single-frequency laser with stable time domain generates exciting light with stable time domain and high power after beam splitting, power amplification and beam combination.
In the invention, the random fiber laser resonant cavity has two implementation modes, one is a full-open cavity random fiber laser resonant cavity, and the other is a half-open cavity random fiber laser resonant cavity.
In the first scheme, the random fiber laser resonant cavity is a full-open cavity random fiber laser resonant cavity, the full-open cavity random fiber laser resonant cavity is formed by a gain-feedback fiber, and the gain-feedback fiber simultaneously provides distributed Raman amplification gain and random Rayleigh scattering feedback under pumping of excitation light, so that random fiber laser vibrates in the cavity and emits light.
Aiming at the resonant cavity of the full-open-cavity random fiber laser, the gain-feedback fiber simultaneously provides distributed Raman gain and random Rayleigh scattering feedback to realize the generation of random fiber laser; in this structure, the excitation light has a center wavelength lambda 0 The frequency shift of the Raman Stokes random fiber laser corresponding to the matrix material of the gain-feedback fiber in the wavelength domain is delta lambda, and the center wavelength is lambda in the random fiber laser generation process 0 Serves as excitation light having a center wavelength lambda 1 The pumping light of 1-order Raman Stokes random fiber laser can realize the central wavelength lambda through distributed Raman gain and random Rayleigh scattering feedback 1 (λ 1 ＝λ 0 +Δλ) 1 st order raman stokes random fiber laser generation and amplification. The main limiting factors of the system to high power development are: when the injection power of the excitation light is continuously increased, the center wavelength is lambda 0 The excitation light power of (2) is firstly converted into the central wavelength lambda through distributed Raman gain and random Rayleigh scattering feedback 1 (λ 1 ＝λ 0 +Δλ) 1 st order raman stokes random fiber laser. However, when further mentionedWhen the excitation light power is raised, the center wavelength is lambda 1 (λ 1 ＝λ 0 +Δλ) 1-order raman stokes random fiber laser will be directed to a higher order center wavelength λ by distributed raman gain 2 (λ 2 ＝λ 1 +Δλ) 2-order raman stokes random fiber laser conversion resulting in a center wavelength λ 1 Is limited in the random fiber laser output power boost. In the random fiber laser generation process, the center wavelength is lambda 0 The excitation optical time domain noise of (2) can be transmitted to the center wavelength lambda under the action of distributed Raman amplification and random Rayleigh scattering feedback 1 The 1 st order raman stokes random fiber laser of (2) results in an enhancement of the 1 st order raman stokes random fiber laser time domain noise. Due to the central wavelength lambda 1 The 1 st order raman stokes random fiber laser of (2) acts as a higher order central wavelength lambda 2 (λ 2 ＝λ 1 +Deltaλ), so the time domain noise enhancement of the pumping light of the 2-order Raman Stokes random fiber laser can obviously reduce the generation threshold of the 2-order Raman Stokes random fiber laser, and finally the system output power is limited to increase, and the output laser noise intensity is limited. The invention adopts the exciting light with stable time domain (namely ultra-low time domain noise), can effectively inhibit the noise transmission in the random fiber laser generation process, further improves the generation threshold of the high-order Raman Stokes random fiber laser, effectively inhibits the noise level of the output laser and realizes the output of high-power low-noise random fiber laser.
In a second scheme, the random fiber laser resonant cavity is a half-open cavity random fiber laser resonant cavity, the half-open cavity random fiber laser resonant cavity comprises an auxiliary feedback module and a gain-feedback fiber, the auxiliary feedback module provides auxiliary feedback of a forward end face under pumping of exciting light, and the gain-feedback fiber provides distributed Raman amplification gain and random Rayleigh scattering feedback, and the two functions simultaneously realize random fiber laser output. Wherein, the auxiliary feedback module is composed of k feedback devices, the feedback devices are fiber bragg gratings, sagnac rings or random dynamic fiber bragg gratings, and k is more than or equal to 1.. .
Gain due to random fiber laserProvided by distributed raman gain in the gain-feedback fiber, the reflection peak of the auxiliary feedback module should correspond to the raman stokes peak of each order of the excitation light center wavelength. Specifically, the excitation light center wavelength is represented by λ 0 If the amplification of the 1 st order raman stokes random fiber laser is realized through the auxiliary feedback, the distributed raman gain and the random rayleigh scattering feedback, the auxiliary feedback module can only adopt one fiber with the center wavelength lambda 1 A feedback device for realizing high reflection of the laser light of (1), wherein lambda 1 ＝λ 0 And +Deltalambda, deltalambda is the frequency shift of the Raman Stokes random fiber laser corresponding to the gain-feedback fiber matrix material in the wavelength domain. If the amplification of the k-order Raman Stokes random fiber laser is realized through auxiliary feedback, distributed Raman gain and random Rayleigh scattering feedback, the auxiliary feedback module can obtain the amplification of the k-order Raman Stokes random fiber laser with the center wavelength of lambda 1 To lambda k The laser of (2) can be formed into feedback device or random feedback device for implementing high reflection, also can be formed from k feedback devices respectively for lambda 1 、λ 2 …λ k The laser realizes the feedback device or random feedback device cascade of high reflection. Wherein lambda is i ＝λ i-1 +Deltaλ (i is greater than or equal to 1 and less than or equal to k), wherein Deltaλ is the frequency shift of the Raman Stokes random fiber laser corresponding to the gain-feedback fiber matrix material in the wavelength domain.
For a half-open cavity random fiber laser generating system, the resonant cavity is composed of an auxiliary feedback module and a gain-feedback fiber. The auxiliary feedback module provides auxiliary feedback of the forward end face, and the gain-feedback optical fiber provides distributed Raman amplification gain and random Rayleigh scattering feedback to realize random fiber laser output. If the center wavelength is lambda through auxiliary feedback, distributed Raman gain and random Rayleigh scattering feedback k The amplification of the kth order raman stokes random fiber laser of (2) is such that the center wavelength is lambda when the injection power of the excitation light is continuously increased 0 The exciting light power of (2) is converted into the central wavelength lambda through the distributed Raman gain and random Rayleigh scattering feedback provided by the 1 st feedback device and the gain-feedback optical fiber 1 (λ 1 ＝λ 0 +Δλ) 1 st order raman stokes random fiber lasers; enlarged centerWavelength lambda 1 (λ 1 ＝λ 0 +Δλ) will be further converted to a center wavelength λ by the distributed raman gain and random rayleigh scattering feedback provided by the 2 nd feedback device and the gain-feedback fiber as the pumping light of the 2 nd order raman stokes random fiber laser 2 (λ 2 ＝λ 1 +Δλ) 2-order raman stokes random fiber lasers; sequentially recursively, the amplified center wavelength is lambda k-1 (λ k-1 ＝λ k-2 +Δλ) will be the center wavelength λ of the k-1 order raman stokes random fiber laser k The pumping light of the kth order raman stokes random fiber laser is converted into a distributed raman gain and random rayleigh scattering feedback provided by the kth feedback device and the gain-feedback fiber into a central wavelength lambda k (λ k ＝λ k-1 +Δλ) order k raman stokes random fiber lasers. However, when the excitation light power is further increased, the center wavelength is λ k The k-order Raman Stokes random fiber laser of (2) will be fed back to the higher order center wavelength as lambda through distributed Raman gain and random Rayleigh scattering k+1 (λ k+1 ＝λ k +Δλ) order k+1 raman stokes random fiber laser conversion resulting in a center wavelength λ k Is limited in the random fiber laser output power boost. In the random fiber laser generation process, the center wavelength is lambda 0 The excitation optical time domain noise of (2) can be transmitted to the center wavelength lambda under the action of distributed Raman amplification and random Rayleigh scattering feedback 1 The 1 st order raman stokes random fiber laser of (2) results in an enhancement of the 1 st order raman stokes random fiber laser time domain noise. The center wavelength is lambda 1 Is used as the 1 st order Raman Stokes random fiber laser with the central wavelength lambda 2 (λ 2 ＝λ 1 +Δλ) of the 2-order raman stokes random fiber laser, the time domain noise thereof is transmitted to the 2-order raman stokes random fiber laser. Sequentially recursively, the amplified center wavelength is lambda k-1 (λ k-1 ＝λ k-2 +Δλ) will be the center wavelength λ of the k-1 order raman stokes random fiber laser k The pumping light of the kth order raman stokes random fiber laser, and thus the time domain noise thereof is transmitted to the kth order raman stokes random fiber laser, resulting in the enhancement of the time domain noise of the kth order raman stokes random fiber laser. Further, the enhancement of time domain noise of the kth order raman stokes random fiber laser results in a higher order center wavelength λ k+1 (λ k+1 ＝λ k +Δλ), the k+1 order raman stokes random fiber laser generation threshold is significantly reduced, ultimately resulting in limited system output power boost and output laser noise intensity. In order to avoid the limitation of output power improvement and the noise intensity of output laser, the invention adopts exciting light with stable time domain (namely ultra-low time domain noise), can effectively inhibit the noise transmission in the random fiber laser generation process, further improve the generation threshold of the high-order Raman Stokes random fiber laser, effectively inhibit the noise level of the output laser and realize the output of high-power low-noise random fiber laser.
In the random fiber laser resonant cavity, the matrix material of the gain-feedback fiber is selected variously, and the gain-feedback fiber can be a silica hard glass matrix material or a soft glass mechanism material such as silicate, phosphate, sulfide and the like.
A random fiber laser generating system comprises an excitation light generating subsystem and a random fiber laser resonant cavity;
the excitation light generation subsystem generates two paths of time-domain stable excitation light; two paths of time-domain stable excitation light are respectively injected into a random fiber laser resonant cavity from the front direction and the back direction, and the random fiber laser resonant cavity generates random fiber laser and outputs the random fiber laser.
In the invention, the excitation light generation subsystem comprises an excitation source seed, an all-fiber beam splitter array, an excitation source seed amplifying array, an excitation beam combining array and an excitation-signal beam combining module;
the excitation source seeds generate single-frequency fiber laser or multi-single-frequency fiber laser with stable time domain;
the all-fiber beam splitter array divides the laser emitted by the excitation source seed into 2n sub-lasers;
the excitation source seed amplification array comprises two amplification submodules, wherein each amplification submodule comprises n paths of all-fiber amplifiers which are respectively used for amplifying the power of n-path excitation lasers;
The excitation light beam combining array comprises two all-fiber excitation light beam combining devices, and each all-fiber excitation light beam combining device combines n paths of amplified excitation light into one beam of high-power excitation light output;
the excitation-signal beam combiner module consists of two all-fiber excitation-signal beam combiners; the two paths of high-power excitation light synthesized and output by the two all-fiber excitation beam combiners are respectively injected into the resonant cavity of the random fiber laser from front to back through the excitation light incidence ends of the two all-fiber excitation-signal beam combiners.
The random fiber laser resonant cavity can adopt a full-open cavity random fiber laser resonant cavity, and the full-open cavity random fiber laser resonant cavity only comprises a gain-feedback fiber. The gain-feedback optical fiber simultaneously provides distributed Raman gain and random Rayleigh scattering feedback to realize random fiber laser generation; the center wavelength of the exciting light output by the all-fiber exciting light beam combiner is lambda 0 The frequency shift of the Raman Stokes random fiber laser corresponding to the matrix material of the gain-feedback fiber in the wavelength domain is delta lambda, and the center wavelength is lambda in the random fiber laser generation process 0 Serves as excitation light having a center wavelength lambda 1 Pumping light of 1-order Raman Stokes random fiber laser, realizing center wavelength lambda through distributed Raman gain and random Rayleigh scattering feedback 1 Is a 1-order Raman Stokes random fiber laser, wherein lambda 1 ＝λ 0 +Δλ。
The random fiber laser resonant cavity can also adopt a half-open cavity random fiber laser resonant cavity. The half-open cavity random fiber laser resonant cavity comprises an auxiliary feedback module and a gain-feedback fiber, wherein the auxiliary feedback module provides auxiliary feedback of a forward end face, the gain-feedback fiber provides distributed Raman amplification gain and random Rayleigh scattering feedback, and the distributed Raman amplification gain and the random Rayleigh scattering feedback work together to realize random fiber laser output; wherein the auxiliary feedback module consists of k feedback devices and a feedback deviceThe component is a fiber grating, a Sagnac ring or a random dynamic fiber grating; the reflection peak of the ith feedback device corresponds to a center wavelength lambda 0 I < th > order raman stokes random fiber laser peak of excitation light of (1) is equal to or more than i is equal to or less than k; let the center wavelength of the exciting light output by the all-fiber exciting beam combiner be lambda 0 The frequency shift of the Raman Stokes random fiber laser corresponding to the matrix material of the gain-feedback fiber in the wavelength domain is delta lambda, and the ith Raman Stokes random fiber laser peak is positioned at lambda i ＝λ i-1 +Δλ. The center wavelength is lambda 0 First converted to a center wavelength lambda by distributed raman gain and random rayleigh scattering feedback provided by a 1 st feedback device and a gain-feedback fiber 1 1-order raman stokes random fiber laser of (c), wherein lambda 1 ＝λ 0 +Δλ; the amplified center wavelength is lambda 1 The 1-order Raman Stokes random fiber laser of (2) order Raman Stokes random fiber laser is used as pumping light of the 2 nd order Raman Stokes random fiber laser, and distributed Raman gain and random Rayleigh scattering feedback provided by the 2 nd feedback device and the gain-feedback fiber are further converted into a central wavelength lambda 2 2-order raman stokes random fiber laser of (c), wherein lambda 2 ＝λ 1 +Δλ; sequentially recursively, the amplified center wavelength is lambda k-1 The k-1 order Raman Stokes random fiber laser of (2) will be taken as the center wavelength lambda k The pumping light of the kth order raman stokes random fiber laser is converted into a distributed raman gain and random rayleigh scattering feedback provided by the kth feedback device and the gain-feedback fiber into a central wavelength lambda k Is a Raman Stokes random fiber laser of the kth order, wherein lambda k-1 ＝λ k-2 +Δλ，λ k ＝λ k-1 +Δλ。
Since the gain generated by the random fiber laser is provided by the distributed raman gain in the gain-feedback fiber, the reflection peak of the auxiliary feedback module should correspond to the raman stokes peak of each order of the excitation light center wavelength. Specifically, the excitation light has a center wavelength λ 0 If the 1 st order raman stratoside is realized through auxiliary feedback, distributed raman gain and random rayleigh scattering feedbackThe auxiliary feedback module can only adopt one amplification of the Kerr random fiber laser with the center wavelength lambda 1 A feedback device for realizing high reflection of the laser light of (1), wherein lambda 1 ＝λ 0 And +Deltalambda, deltalambda is the frequency shift of the Raman Stokes random fiber laser corresponding to the gain-feedback fiber matrix material in the wavelength domain. If the amplification of the k-order Raman Stokes random fiber laser is realized through auxiliary feedback, distributed Raman gain and random Rayleigh scattering feedback, the auxiliary feedback module can obtain the amplification of the k-order Raman Stokes random fiber laser with the center wavelength of lambda 1 To lambda k The laser of (2) can be formed into feedback device or random feedback device for implementing high reflection, also can be formed from k feedback devices respectively for lambda 1 、λ 2 …λ k The laser realizes the feedback device or random feedback device cascade of high reflection. Wherein lambda is i ＝λ i-1 +Deltaλ (i is greater than or equal to 1 and less than or equal to k), wherein Deltaλ is the frequency shift of the Raman Stokes random fiber laser corresponding to the gain-feedback fiber matrix material in the wavelength domain.
In the resonant cavity of the random fiber laser, the matrix material of the gain-feedback fiber is selected variously, and can be a silica hard glass matrix material or a soft glass mechanism material such as silicate, phosphate, sulfide and the like.
In the invention, the signal output ends of the two all-fiber excitation-signal beam combiners of the excitation-signal beam combining module form an output port module of the random fiber laser generating system. The random fiber laser generated by the random fiber laser resonant cavity is led out to a free space after passing through the output port module.
In the invention, the excitation source seed is a single-frequency laser with stable time domain, and the single-frequency laser with stable time domain is a solid laser which is output through optical fiber coupling, or a semiconductor laser which is output through optical fiber coupling, or a distributed Bragg reflection type single-frequency optical fiber laser, or a distributed feedback type single-frequency optical fiber laser, or a ring cavity single-frequency optical fiber laser.
The excitation source seed can also be a time-domain stable multi-single-frequency laser generated by a time-domain stable single-frequency laser through external phase modulation, and the implementation mode is as follows: the output optical fiber of the single-frequency laser with stable time domain is connected to the optical fiber coupling type phase modulation device, and an external electric phase modulation signal is applied to the phase modulation device to broaden the single-frequency laser into multiple single-frequency laser outputs. The optical fiber coupling type phase modulation device is generally an electro-optic modulator, and the electro-optic modulator can be a lithium niobate material, a graphene material or other two-dimensional materials capable of realizing electro-optic modulation. The applied external electrical phase modulation signal may be a sinusoidal signal, a white noise signal, a rectangular pulse signal, a triangular pulse signal, a hyperbolic secant pulse signal, a binary pseudo-random phase encoded signal, or the like.
The excitation source seed can also be a time-domain stable multi-single-frequency laser generated by combining a plurality of time-domain stable single-frequency lasers with different wavelengths, and the implementation mode is as follows: and synthesizing a plurality of time-domain stable single-frequency lasers with different wavelengths into a beam of time-domain stable multi-single-frequency laser output by an all-fiber power beam combiner or an all-fiber wavelength division multiplexer.
In the invention, the all-fiber beam splitter array divides the laser output by the excitation source seed into 2n sub-lasers, the implementation mode of the all-fiber beam splitter array is not limited, and the all-fiber beam splitter array can be composed of one 1×2n all-fiber beam splitter, can be composed of one 1×2all-fiber beam splitter and 2 1×n all-fiber beam splitters in cascade connection, and can also be realized by a plurality of all-fiber beam splitters in cascade connection with other beam splitting ratios. The method for manufacturing the all-fiber beam splitter is not limited, and may be a fusion tapering method or a diaphragm method.
In the invention, the excitation source seed amplification array is used for realizing power amplification of n-sub excitation lasers and comprises two amplification sub-modules. Each amplification sub-module contains n-way all-fiber amplifiers. The amplification level of each all-fiber amplifier is not limited, and the all-fiber amplifier can be a single-stage all-fiber amplifier or a multi-stage cascade all-fiber amplifier. The wavelength range of the excitation source seed laser is within the amplifying wavelength range of the all-fiber amplifier.
In the invention, the excitation light beam combining array combines 2n paths of amplified excitation lights into two paths of high-power excitation lights, and the excitation light beam combining array comprises two all-fiber excitation light beam combiners, and each all-fiber excitation light beam combiners realizes the synthesis of n paths of amplified excitation lights.
In the invention, the excitation-signal beam combination module comprises two all-fiber excitation-signal beam combiners, which are used for coupling excitation light into the resonant cavity of the random fiber laser and guiding out laser generated by the resonant cavity of the random fiber laser. The method for manufacturing the all-fiber excitation-signal combiner is not limited, and can be a fusion tapering method or a diaphragm method.
In the invention, the output port module is composed of signal output ends of two all-fiber excitation-signal beam combiners of the excitation-signal beam combiners. In order to avoid the influence of end surface feedback on the resonant cavity of the random fiber laser, two output ends of the output port module need to be subjected to anti-feedback treatment such as bevel cutting, optical coating and the like.
The key of the invention for restraining the high-order Raman Stokes random fiber laser and outputting laser noise and realizing high-power and low-noise random fiber laser output is as follows: by adopting the exciting light with stable time domain, the noise transmission in the random fiber laser generation process can be effectively restrained, so that the generation threshold of the high-order Raman Stokes random fiber laser is further improved, the noise level of the output laser is effectively restrained, and the high-power and low-noise random fiber laser output is realized. The method is particularly characterized in that the excitation source seeds generate single-frequency fiber laser or multi-single-frequency fiber laser with stable time domain.
At present, an excitation source applied to a random fiber laser system is mainly realized by a wide-spectrum semiconductor laser, a wide-spectrum fiber laser oscillator or a wide-spectrum super-fluorescent fiber light source and the like which are coupled and output by optical fibers. Compared with the excitation source widely applied in the prior art, the single-frequency laser of the optical fiber coupling output adopted by the invention can realize the time domain stable output close to the limit of quantum noise, and the multi-single-frequency laser generated by the single-frequency laser of the optical fiber coupling output through external phase modulation or the multi-single-frequency optical fiber laser generated by the single-frequency laser beam combining of the optical fiber coupling output with a plurality of different wavelengths has low time domain noise, thus being an ideal excitation source seed serving as a high-power and low-noise random optical fiber laser system.
Compared with the prior art, the invention can produce the following technical effects:
1. the invention provides a novel technical scheme for realizing high-power and low-noise random fiber laser output by adopting time-domain stable single-frequency laser or multi-single-frequency laser as an excitation source of a random fiber laser system based on the influence of the time-domain noise transfer characteristic of an excitation source on the threshold value of the high-order Raman Stokes random fiber laser and the noise characteristic of output laser, thereby simultaneously inhibiting the time-domain noise of the high-order Raman Stokes random fiber laser and the output laser.
2. In the invention, the excitation source seeds are realized in various modes, wherein: the time domain stable single-frequency laser can be a solid laser which is output through optical fiber coupling, a semiconductor laser which is output through optical fiber coupling, or a single-frequency optical fiber laser such as a distributed Bragg reflection type single-frequency optical fiber laser, a distributed feedback type single-frequency optical fiber laser, a ring cavity single-frequency optical fiber laser and the like. If the excitation source seed is multi-single-frequency laser generated by the time domain stable single-frequency laser through external phase modulation, the implementation mode is as follows: the output optical fiber end of the time domain stable single-frequency laser is connected with an optical fiber coupling type phase modulation device, an external electric phase modulation signal is applied to the phase modulation device, and the time domain stable single-frequency laser is widened to be a multi-single-frequency laser output. The optical fiber coupling type phase modulation device is generally an electro-optic modulator, and the material of the electro-optic modulator can be lithium niobate, graphene and the like. The applied external electrical phase modulation signal may be a sinusoidal signal, a white noise signal, a rectangular pulse signal, a triangular pulse signal, a hyperbolic secant pulse signal, a binary pseudo-random phase encoded signal, or the like. If the excitation source seed is a time domain stable multi-single-frequency laser generated by combining a plurality of time domain stable single-frequency lasers with different wavelengths, the all-fiber power combiner can be used for combining the plurality of time domain stable single-frequency lasers with different wavelengths into one beam of laser output, and the all-fiber wavelength division multiplexer can also be used for combining the plurality of time domain stable single-frequency lasers with different wavelengths into one beam of laser output.
3. In the invention, the implementation mode of the all-fiber beam splitter array is not limited, and the all-fiber beam splitter array can be formed by one 1X 2n all-fiber beam splitter, can be formed by cascading one 1X 2 all-fiber beam splitter and 2 1X n all-fiber beam splitters, and can also be realized by cascading a plurality of all-fiber beam splitters with other beam splitting ratios.
4. In the invention, the implementation mode of the auxiliary feedback module is not limited, and the auxiliary feedback module can be feedback devices such as fiber gratings, sagnac rings and the like, and also can be random feedback devices such as random dynamic fiber gratings and the like. The auxiliary feedback module can also comprise a plurality of feedback devices, and can realize high-power and low-noise random fiber laser output or high-power, low-noise and multi-wavelength random fiber laser output with different wavelengths by utilizing auxiliary feedback, distributed Raman gain and random Rayleigh scattering feedback for a plurality of times.
5. In the invention, the matrix material of the gain-feedback optical fiber is selected variously, and can be a silicon dioxide hard glass matrix material or a soft glass mechanism material such as silicate, phosphate, sulfide and the like.
6. The invention can enlarge the wavelength range and has expansibility: by changing the matrix material of the gain-feedback optical fiber, the center wavelength of the excitation source seed or the reflection peak of the auxiliary feedback module, the method can be used for generating random fiber laser in the near infrared band, and also can be used for generating random fiber laser in the middle and far infrared bands or other bands.
Drawings
Fig. 1 is a schematic structural diagram of the general technical scheme of the present invention.
Fig. 2 is a schematic structural diagram of embodiment 1 of the present invention.
Fig. 3 is a schematic structural diagram of embodiment 2 of the present invention.
Detailed Description
The general embodiment of the present invention will be described in further detail with reference to fig. 1.
FIG. 1 is a schematic diagram of the overall technical scheme of a random fiber laser generating system according to the invention, as shown in FIG. 1, the random fiber laser generating system comprises an excitation source seed 1-1, an all-fiber beam splitter array 1-2, an excitation source seed amplifying array 1-3, an excitation beam combining array 1-4, an excitation-signal beam combining module 1-5, a random fiber laser resonant cavity 1-6 and an output port module 1-7.
Wherein: the excitation source seed amplification array 1-3 comprises two amplification submodules 1-3-1 and 1-3-2; the amplifying sub-module 1-3-1 comprises n paths of all-fiber amplifiers 1-3-1 and 1-3-1-2 … … 1-3-1-n, and the amplifying sub-module 1-3-2 comprises n paths of all-fiber amplifiers 1-3-2-1 and 1-3-2- … … 1-3-2-n; the excitation light beam combination array 1-4 comprises two all-fiber excitation light beam combination devices 1-4-1 and 1-4-2; the excitation-signal beam combination module 1-5 comprises two all-fiber excitation-signal beam combiners 1-5-1 and 1-5-2; the output port module 1-7 includes front output ports 1-7-1 and rear output ports 1-7-2.
The excitation source seed 1-1 can be (1) a time domain stable single-frequency laser or (2) multiple single-frequency lasers generated by the time domain stable single-frequency laser through external phase modulation or (3) time domain stable multiple single-frequency lasers generated by combining multiple time domain stable single-frequency lasers with different wavelengths. Wherein: the single-frequency laser with stable time domain can be a solid laser which is output through optical fiber coupling, a semiconductor laser which is output through optical fiber coupling, or a single-frequency optical fiber laser such as a distributed Bragg reflection type single-frequency optical fiber laser, a distributed feedback type single-frequency optical fiber laser, a ring cavity single-frequency optical fiber laser and the like. If the excitation source seed 1-1 is multi-single-frequency laser generated by an external phase modulation of a single-frequency laser with stable time domain, the implementation mode is as follows: the output optical fiber end of the single-frequency laser with stable time domain is connected with an optical fiber coupling type phase modulation device, and an external electric phase modulation signal is applied to the phase modulation device, so that single-frequency laser can be widened into multiple single-frequency laser outputs. The optical fiber coupling type phase modulation device is generally an electro-optic modulator, and the electro-optic modulator can be a lithium niobate material, a graphene material or other two-dimensional materials capable of realizing electro-optic modulation. The applied external electrical phase modulation signal may be a sinusoidal signal, a white noise signal, a rectangular pulse signal, a triangular pulse signal, a hyperbolic secant pulse signal, a binary pseudo-random phase encoded signal, or the like. If the excitation source seed 1-1 is multiple single-frequency lasers generated by combining multiple single-frequency lasers with different wavelengths and stable in time domain, an all-fiber power combiner or an all-fiber wavelength division multiplexer is generally adopted to combine the multiple single-frequency lasers with different wavelengths into one beam of laser output.
In fig. 1, the single-frequency laser or the multi-single-frequency laser generated by the excitation source seed 1-1 and stable in time domain is divided into 2n sub-lasers after passing through the all-fiber beam splitter array 1-2. The split 2n sub-laser is injected into the excitation source seed amplification arrays 1-3. The excitation source seed amplification array 1-3 comprises two amplification submodules 1-3-1 and 1-3-2; the amplifying sub-module 1-3-1 comprises n paths of all-fiber amplifiers 1-3-1 and 1-3-1-2 … … 1-3-1-n, and the amplifying sub-module 1-3-2 comprises n paths of all-fiber amplifiers 1-3-2-1 and 1-3-2- … … 1-3-2-n for amplifying the power of 2n sub-excitation lasers. The excitation light amplified and output by the excitation source seed amplification array 1-3 is incident to the excitation light combining beam array 1-4. The excitation light beam combination array 1-4 comprises two all-fiber excitation light beam combination devices 1-4-1 and 1-4-2, and the two all-fiber excitation light beam combination devices 1-4-1 and 1-4-2 respectively combine n paths of amplified excitation light into a beam of high-power excitation light output. The excitation-signal beam combination module 1-5 is composed of two all-fiber excitation-signal beam combiners 1-5-1 and 1-5-2. The two paths of high-power excitation light synthesized and output by the two all-fiber excitation beam combiners 1-4-1 and 1-4-2 in the excitation beam combiners 1-4 are respectively injected into the resonant cavity 1-6 of the random fiber laser from front to back through the excitation light incidence ends of the two all-fiber excitation-signal beam combiners 1-5-1 and 1-5-2 of the excitation-signal beam combiners 1-5. The random fiber laser resonant cavities 1-6 realize random fiber laser generation under pumping of excitation light by relying on distributed Raman gain and random Rayleigh scattering feedback. The signal output ends of the two all-fiber excitation-signal beam combiners 1-5-1 and 1-5-2 of the excitation-signal beam combiners 1-5 form an output port module 1-7 of the random fiber laser generating system. The output port module 1-7 includes front output ports 1-7-1 and rear output ports 1-7-2. Laser generated by the random fiber laser resonant cavity 1-6 is led out to a free space after passing through the front output port 1-7-1 and the rear output port 1-7-2 respectively.
A detailed description of a specific embodiment of the fully-open cavity high-power, low-noise random fiber laser generation system is provided below in conjunction with fig. 2.
FIG. 2 is a schematic diagram of a full-open cavity high-power low-noise random fiber laser generating system, as shown in FIG. 2, comprising an excitation source seed 1-1, an all-fiber beam splitter array 1-2, an excitation source seed amplifying array 1-3, an excitation beam combining array 1-4, an excitation-signal beam combining module 1-5, a random fiber laser resonant cavity 1-6 and an output port module 1-7.
Wherein: the excitation source seed amplification array 1-3 comprises two amplification submodules 1-3-1 and 1-3-2; the amplifying sub-module 1-3-1 comprises n paths of all-fiber amplifiers 1-3-1 and 1-3-1-2 … … 1-3-1-n, and the amplifying sub-module 1-3-2 comprises n paths of all-fiber amplifiers 1-3-2-1 and 1-3-2- … … 1-3-2-n; the excitation light beam combination array 1-4 comprises two all-fiber excitation light beam combination devices 1-4-1 and 1-4-2; the excitation-signal beam combination module 1-5 comprises two all-fiber excitation-signal beam combiners 1-5-1 and 1-5-2; the random fiber laser resonant cavity 1-6 is only composed of gain-feedback fibers 1-6-1; the output port module 1-7 includes front output ports 1-7-1 and rear output ports 1-7-2.
The excitation source seed 1-1 can be (1) a time domain stable single-frequency laser or (2) a multi-single-frequency laser generated by external phase modulation with the stable single-frequency laser or (3) a time domain stable multi-single-frequency laser generated by combining a plurality of different wavelength time domain stable single-frequency lasers. Wherein: the single-frequency laser with stable time domain can be a solid laser which is output through optical fiber coupling, a semiconductor laser which is output through optical fiber coupling, or a single-frequency optical fiber laser such as a distributed Bragg reflection type single-frequency optical fiber laser, a distributed feedback type single-frequency optical fiber laser, a ring cavity single-frequency optical fiber laser and the like. If the excitation source seed 1-1 is multi-single-frequency laser generated by an external phase modulation of a single-frequency laser with stable time domain, the implementation mode is as follows: the output optical fiber end of the single-frequency laser with stable time domain is connected with an optical fiber coupling type phase modulation device, and an external electric phase modulation signal is applied to the phase modulation device, so that single-frequency laser can be widened into multiple single-frequency laser outputs. The optical fiber coupling type phase modulation device is generally an electro-optic modulator, and the electro-optic modulator can be a lithium niobate material, a graphene material or other two-dimensional materials capable of realizing electro-optic modulation. The applied external electrical phase modulation signal may be a sinusoidal signal, a white noise signal, a rectangular pulse signal, a triangular pulse signal, a hyperbolic secant pulse signal, a binary pseudo-random phase encoded signal, or the like. If the excitation source seed 1-1 is multiple single-frequency lasers generated by combining multiple single-frequency lasers with different wavelengths and stable in time domain, an all-fiber power combiner or an all-fiber wavelength division multiplexer is generally adopted to combine the multiple single-frequency lasers with different wavelengths into one beam of laser output.
In FIG. 2, the excitation source seed 1-1 is first divided into 2n sub-lasers after passing through the all-fiber beam splitter array 1-2. The split 2n sub-laser is injected into the excitation source seed amplification arrays 1-3. The excitation source seed amplification array 1-3 comprises two amplification submodules 1-3-1 and 1-3-2; the amplifying sub-module 1-3-1 comprises n paths of all-fiber amplifiers 1-3-1 and 1-3-1-2 … … 1-3-1-n, and the amplifying sub-module 1-3-2 comprises n paths of all-fiber amplifiers 1-3-2-1 and 1-3-2- … … 1-3-2-n for amplifying the power of 2n sub-excitation lasers. The excitation light amplified and output by the excitation source seed amplification array 1-3 is incident to the excitation light combining beam array 1-4. The excitation light beam combining array comprises two all-fiber excitation light beam combiners 1-4-1 and 1-4-2, and the two all-fiber excitation light beam combiners 1-4-1 and 1-4-2 respectively combine n paths of amplified excitation light into a beam of high-power excitation light output. The excitation-signal beam combination module 1-5 is composed of two all-fiber excitation-signal beam combiners 1-5-1 and 1-5-2. The two paths of high-power excitation light synthesized and output by the two all-fiber excitation beam combiners 1-4-1 and 1-4-2 in the excitation beam combiners 1-4 are respectively injected into the resonant cavity 1-6 of the random fiber laser from front to back through the excitation light incidence ends of the two all-fiber excitation-signal beam combiners 1-5-1 and 1-5-2 of the excitation-signal beam combiners 1-5. The random fiber laser cavity 1-6 is composed of only the gain-feedback fiber 1-6-1. The gain-feedback optical fiber 1-6-1 simultaneously provides distributed Raman gain and random Rayleigh scattering feedback to realize random fiber laser generation; specifically, the excitation light has a center wavelength λ 0 The frequency shift of the Raman Stokes random fiber laser corresponding to the gain-feedback fiber matrix material in the wavelength domain is delta lambda, and the center wavelength is lambda in the random fiber laser generation process 0 Serves as excitation light having a center wavelength lambda 1 (λ 1 ＝λ 0 +Δλ) 1 st order raman stokes random fiber laser pumping light with center wavelength λ achieved by distributed raman gain and random rayleigh scattering feedback 1 (λ 1 ＝λ 0 +Δλ) 1 st order raman stokes random fiber laser generation and amplification. The signal output ends of the two all-fiber excitation-signal beam combiners 1-5-1 and 1-5-2 of the excitation-signal beam combiners 1-5 form an output port module 1-7 of the random fiber laser generation system. The output port module 1-7 includes front output ports 1-7-1 and rear output ports 1-7-2. Laser generated by the random fiber laser resonant cavity 1-6 is led out to a free space after passing through the front output port 1-7-1 and the rear output port 1-7-2 respectively.
A detailed description of a specific embodiment of a half-open cavity high power, low noise random fiber laser generation system is provided below in conjunction with fig. 3.
FIG. 3 is a schematic diagram of a semi-open cavity high-power low-noise random fiber laser generating system, which is shown in FIG. 3, and comprises an excitation source seed 1-1, a full fiber beam splitter array 1-2, an excitation source seed amplifying array 1-3, an excitation beam combining array 1-4, an excitation-signal beam combining module 1-5, a random fiber laser resonant cavity 1-6 and an output port module 1-7.
Wherein: the excitation source seed amplification array 1-3 comprises two amplification submodules 1-3-1 and 1-3-2; the amplifying sub-module 1-3-1 comprises n paths of all-fiber amplifiers 1-3-1 and 1-3-1-2 … … 1-3-1-n, and the amplifying sub-module 1-3-2 comprises n paths of all-fiber amplifiers 1-3-2-1 and 1-3-2- … … 1-3-2-n; the excitation light beam combination array 1-4 comprises two all-fiber excitation light beam combination devices 1-4-1 and 1-4-2; the excitation-signal beam combination module 1-5 comprises two all-fiber excitation-signal beam combiners 1-5-1 and 1-5-2; the random fiber laser resonant cavity 1-6 is composed of an auxiliary feedback module 1-6-2 and a gain-feedback fiber 1-6-1. The auxiliary feedback module 1-6-2 comprises k feedback devices 1-6-2-1, 1-6-2 … … 1-6-2-k-1 and 1-6-2-k; the reflection peak of the ith feedback device (i is more than or equal to 1 and less than or equal to k) corresponds to the center wavelength lambda 0 The ith order raman stokes random fiber laser peak of the excitation light of (a); each feedback device may be a fiber grating, a Sagnac loop, or a random dynamic fiber grating. The output port module 1-7 includes front output ports 1-7-1 and rear output ports 1-7-2.
The excitation source seed 1-1 can be (1) a time domain stable single-frequency laser or (2) multiple single-frequency lasers generated by the time domain stable single-frequency laser through external phase modulation or (3) time domain stable multiple single-frequency lasers generated by combining multiple time domain stable single-frequency lasers with different wavelengths. Wherein: the single-frequency laser with stable time domain can be a solid laser which is output through optical fiber coupling, a semiconductor laser which is output through optical fiber coupling, or a single-frequency optical fiber laser such as a distributed Bragg reflection type single-frequency optical fiber laser, a distributed feedback type single-frequency optical fiber laser, a ring cavity single-frequency optical fiber laser and the like. If the excitation source seed 1-1 is multi-single-frequency laser generated by an external phase modulation of a single-frequency laser with stable time domain, the implementation mode is as follows: the output optical fiber end of the single-frequency laser with stable time domain is connected with an optical fiber coupling type phase modulation device, and an external electric phase modulation signal is applied to the phase modulation device, so that single-frequency laser can be widened into multiple single-frequency laser outputs. The optical fiber coupling type phase modulation device is generally an electro-optic modulator, and the electro-optic modulator can be a lithium niobate material, a graphene material or other two-dimensional materials capable of realizing electro-optic modulation. The applied external electrical phase modulation signal may be a sinusoidal signal, a white noise signal, a rectangular pulse signal, a triangular pulse signal, a hyperbolic secant pulse signal, a binary pseudo-random phase encoded signal, or the like. If the excitation source seed 1-1 is multiple single-frequency lasers generated by combining multiple single-frequency lasers with different wavelengths and stable in time domain, an all-fiber power combiner or an all-fiber wavelength division multiplexer is generally adopted to combine the multiple single-frequency lasers with different wavelengths into one beam of laser output.
In FIG. 3, the excitation source seed 1-1 is first divided into 2n sub-lasers after passing through the all-fiber beam splitter array 1-2. The split 2n sub-laser is injected into the excitation source seed amplification arrays 1-3. The excitation source seed amplification array 1-3 comprises two amplification submodules 1-3-1 and 1-3-2; the amplifying sub-module 1-3-1 comprises n paths of all-fiber amplifiers 1-3-1 and 1-3-1-2 … … 1-3-1-n, and the amplifying sub-module 1-3-2 comprises n paths of all-fiber amplifiers 1-3-2-1 and 1-3-2- … … 1-3-2-n for amplifying the power of 2n sub-excitation lasers. The excitation light amplified and output by the excitation source seed amplification array 1-3 is incident to the excitation light combining beam array 1-4. The excitation photosynthetic beam array comprises twoAll-fiber excitation beam combiners 1-4 to 1 and 1-4 to 2 respectively combine n paths of amplified excitation light into a beam of high-power excitation light to be output. The excitation-signal beam combination module 1-5 is composed of two all-fiber excitation-signal beam combiners 1-5-1 and 1-5-2. The two paths of high-power excitation light synthesized and output by the two all-fiber excitation beam combiners 1-4-1 and 1-4-2 in the excitation beam combiners 1-4 are respectively injected into the resonant cavity 1-6 of the random fiber laser from front to back through the excitation light incidence ends of the two all-fiber excitation-signal beam combiners 1-5-1 and 1-5-2 of the excitation-signal beam combiners 1-5. The random fiber laser resonant cavity 1-6 is composed of an auxiliary feedback module 1-6-2 and a gain-feedback fiber 1-6-1. The auxiliary feedback module 1-6-2 comprises k feedback devices 1-6-2-1, 1-6-2 … … 1-6-2-k; the reflection peak of the ith feedback device (i is more than or equal to 1 and less than or equal to k) corresponds to the center wavelength lambda 0 The ith order raman stokes random fiber laser peak of the excitation light of (a); let the center wavelength of the excitation light be lambda 0 The frequency shift of Raman Stokes random fiber laser corresponding to the 1-6-1 matrix material of the gain-feedback fiber in the wavelength domain is delta lambda, and the i (i is more than or equal to 1 and less than or equal to k) th order Raman Stokes random fiber laser peak is positioned at lambda i ＝λ i-1 +Δλ (1.ltoreq.i.ltoreq.k). Furthermore, each feedback device may be a fiber grating, a Sagnac loop, or a random dynamic fiber grating. It should be noted that the auxiliary feedback modules 1-6-2 may also be a single feedback module having a center wavelength lambda 1 To lambda k A feedback device or a random feedback device for realizing high reflection. The auxiliary feedback module 1-6-2 provides auxiliary feedback of the forward end face, the gain-feedback optical fiber 1-6-1 provides distributed Raman amplification gain and random Rayleigh scattering feedback, and the two function together to realize random fiber laser output. Specifically, if the final center wavelength is λ k The amplification of the kth order raman stokes random fiber laser of (2) has a center wavelength of lambda 0 The exciting light power of the (1) is converted into the center wavelength lambda through the distributed Raman gain and random Rayleigh scattering feedback provided by the 1 st feedback device 1-6-2-1 and the gain-feedback optical fiber 1-6-1 1 (λ 1 ＝λ 0 +Δλ) 1 st order ramanA tokes random fiber laser; the amplified center wavelength is lambda 1 (λ 1 ＝λ 0 +Δλ) the 1 st order raman stokes random fiber laser is further converted into a distributed raman gain and random rayleigh scattering feedback having a center wavelength λ by the 2 nd feedback device 1-6-2 and the gain-feedback fiber 1-6-1 as pumping light of the 2 nd order raman stokes random fiber laser 2 (λ 2 ＝λ 1 +Δλ) 2-order raman stokes random fiber lasers; sequentially recursively, the amplified center wavelength is lambda k-1 (λ k-1 ＝λ k-2 +Δλ) will be the center wavelength λ of the k-1 order raman stokes random fiber laser k The pumping light of the kth order Raman Stokes random fiber laser is converted into the central wavelength lambda through the distributed Raman gain and random Rayleigh scattering feedback provided by the kth auxiliary device 1-6-2-k and the gain-feedback fiber 1-6-1 k (λ k ＝λ k-1 +Δλ). The signal output ends of the two all-fiber excitation-signal beam combiners 1-5-1 and 1-5-2 of the excitation-signal beam combiners 1-5 form an output port module 1-7 of the random fiber laser generation system. The output port module 1-7 includes front output ports 1-7-1 and rear output ports 1-7-2. Laser generated by the random fiber laser resonant cavity 1-6 is led out to a free space after passing through the front output port 1-7-1 and the rear output port 1-7-2 respectively.
The above description is only of specific embodiments of the present invention and is not intended to limit the present invention, and various modifications and variations of the present invention will be apparent to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. A random fiber laser generation method is characterized in that: injecting two paths of time domain stable excitation light into a random fiber laser resonant cavity from front to back respectively, wherein the random fiber laser resonant cavity realizes random fiber laser generation under pumping of the excitation light by relying on distributed Raman gain and random Rayleigh scattering feedback, and the random fiber laser resonant cavity is a full-cavity random fiber laser resonant cavity or a half-cavity random fiber laser resonant cavity;
the full-open cavity random fiber laser resonant cavity is formed by a gain-feedback fiber, and the gain-feedback fiber simultaneously provides distributed Raman gain and random Rayleigh scattering feedback to realize random fiber laser generation; the center wavelength of the exciting light is lambda 0 The frequency shift of the Raman Stokes random fiber laser corresponding to the matrix material of the gain-feedback fiber in the wavelength domain is delta lambda, and the center wavelength is lambda in the random fiber laser generation process 0 Serves as excitation light having a center wavelength lambda 1 Pumping light of 1-order Raman Stokes random fiber laser, realizing center wavelength lambda through distributed Raman gain and random Rayleigh scattering feedback 1 Is a 1-order Raman Stokes random fiber laser, wherein lambda 1 ＝λ 0 +Δλ；
The half-open cavity random fiber laser resonant cavity comprises an auxiliary feedback module and a gain-feedback fiber, wherein the auxiliary feedback module provides auxiliary feedback of a forward end face, the gain-feedback fiber provides distributed Raman amplification gain and random Rayleigh scattering feedback, and the distributed Raman amplification gain and the random Rayleigh scattering feedback work together to realize random fiber laser output; wherein the auxiliary feedback module consists of k feedback devices, and the reflection peak of the ith feedback device corresponds to the center wavelength lambda 0 I < th > order raman stokes random fiber laser peak of excitation light of (1) is equal to or more than i is equal to or less than k; let the center wavelength of the exciting light output by the all-fiber exciting beam combiner be lambda 0 The frequency shift of the Raman Stokes random fiber laser corresponding to the matrix material of the gain-feedback fiber in the wavelength domain is delta lambda, and the ith Raman Stokes random fiber laser peak is positioned at lambda i ＝λ i-1 +Δλ; the center wavelength is lambda 0 First converted to a center wavelength lambda by distributed raman gain and random rayleigh scattering feedback provided by a 1 st feedback device and a gain-feedback fiber 1 1-order raman stokes random fiber laser of (c), wherein lambda 1 ＝λ 0 +Δλ; the amplified center wavelength is lambda 1 The 1-order Raman Stokes random fiber laser of (2) order Raman Stokes random fiber laser is used as pumping light of the 2 nd order Raman Stokes random fiber laser, and distributed Raman gain and random Rayleigh scattering feedback provided by the 2 nd feedback device and the gain-feedback fiber are further converted into a central wavelength lambda 2 2-order raman stokes random fiber laser of (c), wherein lambda 2 ＝λ 1 +Δλ; sequentially recursively, the amplified center wavelength is lambda k-1 The k-1 order Raman Stokes random fiber laser of (2) will be taken as the center wavelength lambda k The pumping light of the kth order raman stokes random fiber laser is converted into a distributed raman gain and random rayleigh scattering feedback provided by the kth feedback device and the gain-feedback fiber into a central wavelength lambda k Is a Raman Stokes random fiber laser of the kth order, wherein lambda k-1 ＝λ k-2 +Δλ，λ k ＝λ k-1 +Δλ。
2. The random fiber laser generation method of claim 1, wherein: the method for generating the time-domain stable excitation light comprises the following steps: the single-frequency laser or the multi-single-frequency laser with stable time domain generates exciting light with stable time domain after beam splitting, power amplification and beam combination.
3. The random fiber laser generation method of claim 1, wherein: the feedback device is a fiber grating, a Sagnac loop, or a random dynamic fiber grating.
4. A random fiber laser generation system, characterized by: comprises an excitation light generation subsystem and a random fiber laser resonant cavity;
the excitation light generation subsystem generates two paths of time-domain stable excitation light; two paths of time-domain stable excitation light are respectively injected into a random fiber laser resonant cavity from front to back, and the random fiber laser resonant cavity generates random fiber laser and outputs the random fiber laser;
the random fiber laser resonant cavity is a full-open cavity random fiber laser resonant cavity or a half-open cavity random fiber laser resonant cavity;
the full-open cavity random fiber laser resonant cavity is formed by a gain-feedback fiber, and the gain-feedback fiber simultaneously provides distributed Raman gain and random Rayleigh scattering feedback to realize random fiber laser generation; the center wavelength of the exciting light is lambda 0 The frequency shift of the Raman Stokes random fiber laser corresponding to the matrix material of the gain-feedback fiber in the wavelength domain is delta lambda, and the center wavelength is lambda in the random fiber laser generation process 0 Serves as excitation light having a center wavelength lambda 1 Pumping light of 1-order Raman Stokes random fiber laser, realizing center wavelength lambda through distributed Raman gain and random Rayleigh scattering feedback 1 Is a 1-order Raman Stokes random fiber laser, wherein lambda 1 ＝λ 0 +Δλ；
The half-open cavity random fiber laser resonant cavity comprises an auxiliary feedback module and a gain-feedback fiber, wherein the auxiliary feedback module provides auxiliary feedback of a forward end face, the gain-feedback fiber provides distributed Raman amplification gain and random Rayleigh scattering feedback, and the distributed Raman amplification gain and the random Rayleigh scattering feedback work together to realize random fiber laser output; wherein the auxiliary feedback module consists of k feedback devices, and the reflection peak of the ith feedback device corresponds to the center wavelength lambda 0 I < th > order raman stokes random fiber laser peak of excitation light of (1) is equal to or more than i is equal to or less than k; let the center wavelength of the exciting light output by the all-fiber exciting beam combiner be lambda 0 The frequency shift of the Raman Stokes random fiber laser corresponding to the matrix material of the gain-feedback fiber in the wavelength domain is delta lambda, and the ith Raman Stokes random fiber laser peak is positioned at lambda i ＝λ i-1 +Δλ; the center wavelength is lambda 0 First converted to a center wavelength lambda by distributed raman gain and random rayleigh scattering feedback provided by a 1 st feedback device and a gain-feedback fiber 1 1-order raman stokes random fiber laser of (c), wherein lambda 1 ＝λ 0 +Δλ; the amplified center wavelength is lambda 1 The 1 st order raman stokes random fiber laser of (2) will be provided as pumping light of the 2 nd order raman stokes random fiber laser by the 2 nd feedback device and the gain-feedback fiberFurther converting the distributed raman gain and random rayleigh scattering feedback to a center wavelength λ 2 2-order raman stokes random fiber laser of (c), wherein lambda 2 ＝λ 1 +Δλ; sequentially recursively, the amplified center wavelength is lambda k-1 The k-1 order Raman Stokes random fiber laser of (2) will be taken as the center wavelength lambda k The pumping light of the kth order raman stokes random fiber laser is converted into a distributed raman gain and random rayleigh scattering feedback provided by the kth feedback device and the gain-feedback fiber into a central wavelength lambda k Is a Raman Stokes random fiber laser of the kth order, wherein lambda k-1 ＝λ k-2 +Δλ，λ k ＝λ k-1 +Δλ。
5. The random fiber laser generation system of claim 4, wherein: the excitation light generation subsystem comprises an excitation source seed, an all-fiber beam splitter array, an excitation source seed amplification array, an excitation beam combining array and an excitation-signal beam combining module;
the excitation source seeds generate single-frequency fiber laser or multi-single-frequency fiber laser with stable time domain;
The all-fiber beam splitter array divides the laser emitted by the excitation source seed into 2n sub-lasers;
the excitation source seed amplification array comprises two amplification submodules, wherein each amplification submodule comprises n paths of all-fiber amplifiers which are respectively used for amplifying the power of n-path excitation lasers;
the excitation light beam combining array comprises two all-fiber excitation light beam combining devices, and each all-fiber excitation light beam combining device combines n paths of amplified excitation light into one beam of high-power excitation light output;
the excitation-signal beam combiner module consists of two all-fiber excitation-signal beam combiners; two paths of high-power excitation light synthesized and output by the two all-fiber excitation beam combiners are respectively injected into a random fiber laser resonant cavity from front to back through excitation light incidence ends of the two all-fiber excitation-signal beam combiners;
the signal output ends of the two all-fiber excitation-signal beam combiners of the excitation-signal beam combiners form an output port module of the random fiber laser generating system, and random fiber laser generated by the resonant cavity of the fiber laser is led out to a free space after passing through the output port module.
6. The random fiber laser generation system of claim 5, wherein: the feedback device is a fiber grating, a Sagnac loop, or a random dynamic fiber grating.
7. A random fiber laser generation system according to claim 5 or 6, wherein: the excitation source seed is a single-frequency laser with stable time domain, and the single-frequency laser with stable time domain is a solid laser which is output through optical fiber coupling, or a semiconductor laser which is output through optical fiber coupling, or a distributed Bragg reflection type single-frequency optical fiber laser, or a distributed feedback type single-frequency optical fiber laser, or a ring cavity single-frequency optical fiber laser.
8. A random fiber laser generation system according to claim 5 or 6, wherein: the excitation source seed is a time-domain stable multi-single-frequency laser generated by a time-domain stable single-frequency laser through external phase modulation, and the implementation mode is as follows: the output optical fiber of the single-frequency laser with stable time domain is connected to the optical fiber coupling type phase modulation device, and an external electric phase modulation signal is applied to the phase modulation device to broaden the single-frequency laser into multiple single-frequency laser outputs.
9. A random fiber laser generation system according to claim 5 or 6, wherein: the excitation source seed is a time-domain stable multi-single-frequency laser generated by combining a plurality of time-domain stable single-frequency lasers with different wavelengths, and the implementation mode is as follows: and synthesizing a plurality of time-domain stable single-frequency lasers with different wavelengths into a beam of time-domain stable multi-single-frequency laser output by an all-fiber power beam combiner or an all-fiber wavelength division multiplexer.
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