32 results about "Population inversion" patented technology

This invention discloses a 2.3 μm fiber laser based on 980 nm laser pumping, relating to the field of mid-infrared fiber laser technology. This fiber laser utilizes fluorotellurate glass fiber co-doped with thulium and erbium ions as the gain medium. It absorbs the 980 nm pump light energy by introducing erbium ion doping, and then achieves Tm through the energy transfer process between erbium and thulium ions. 3+ of 3 H4- 3 The population inversion of the H5 energy level ultimately yields laser output in the 2.3 μm band. This invention utilizes a high-power 980 nm laser as the pump source and a thulium-erbium co-doped fluorotellurate glass fiber prepared by the rod-tube method as the gain medium. By writing fiber gratings with appropriate reflectivity at both ends of the fiber, a resonant cavity with a reflection wavelength of 2.3 μm is constructed, enabling the development of a high-power 2.3 μm laser that can operate stably for a long time.

The invention relates to the technical field of solid laser, and discloses a quasi-three-level laser with end-side composite pumping, which comprises a quasi-three-level laser crystal, an end-side pumping assembly, a side pumping module and a laser resonant cavity. The end face pumping assembly is used for injecting end face pumping light to the end face of the crystal. The side pumping module is used for injecting side pumping light to the side face of the crystal, and the laser resonant cavity and the quasi-three-level laser crystal are matched to form a laser oscillation circuit. Through the arrangement, the end face pumping assembly is used for providing high-power-density pumping light, the problem of high excitation threshold of the quasi-three-level laser crystal is solved, and population inversion and laser gain are effectively established; and meanwhile, large-area and high-pumping power input is carried out by virtue of the side pumping module, so that uniform allocation of a pumping heat load, reduction of a temperature gradient and end surface stress in the crystal and inhibition of a thermal lens effect are effectively realized, consideration of high-power density excitation of the crystal, low thermal stress and uniform thermal distribution is realized, and high-efficiency and high-power laser output of the laser is ensured.

According to the gallium nitride-based semiconductor laser with the gradually-changed hole mobility waveguide layer, a fitting curve of In ion strength distribution or In atom concentration distribution, a fitting curve of valence band effective state density distribution and a fitting curve of hole mobility distribution of an upper waveguide layer and a lower waveguide layer which are tested by SIMS all meet any function distribution of ExpGrow1, ExpGrow2, Lorentz and Bradley; energy band degeneracy is improved, ionization impurities, polarization charges and energy band bending restriction are reduced, coupling of a heavy hole band and a light hole band with an SO band is regulated and controlled, valence band effective state density is improved, population inversion and laser gain are enhanced, hole mobility distribution of a waveguide layer is controlled to be in splayed distribution, interface scattering and ionization impurity scattering are inhibited, and the performance of the laser is improved. The hole mobility and the thermal stability are improved, the hole transport efficiency is enhanced, the hole leakage is reduced, and the slope efficiency, the optical power, the aging life and the temperature quenching ratio of the laser are improved.

The invention provides an optical fiber amplifier which comprises a gain light path used for amplifying signal light; the first filter is used for filtering backward spontaneous radiation light generated when the gain light path amplifies the signal light and retaining auxiliary light meeting preset requirements; and the coupler is used for combining the auxiliary light and the new signal light to be amplified by the gain light path so as to enhance population inversion generated by amplifying the new signal light by the gain light path after beam combination. When the optical fiber amplifier amplifies the signal light, the signal light can generate stronger population inversion, so that the noise coefficient is effectively reduced, and the transmission quality of the signal light can be improved after the optical fiber amplifier is deployed to an optical communication network.

The application provides a multi-wavelength output double-circulation optical pumping Xe laser, which uses metastable Kr generated by gas discharge as an energy source, transmits energy by collision with ground state Xe to realize inversion in Xe system; meanwhile, uses two laser beams of 882nm and 828nm as pumping sources to maintain particle number inversion of Xe system and output multiple laser wavelengths. The application fully utilizes the effect of buffer gas Kr, realizes acceleration of collision relaxation process between energy levels and also plays a role in resonance energy transmission; the method effectively improves the utilization rate of Xe primary discharge particles, further improves the efficiency of optical pumping inert gas metastable state laser, and realizes primary electric pumping and multiple optical circulation.

The present application provides an optical fiber amplifier, comprising: a gain optical path, configured to amplify signal light; a first filter, configured to filter backward spontaneous emission light generated by the amplification of the signal light by the gain optical path, and retain auxiliary light that meets a preset requirement; and a coupler, configured to combine the auxiliary light with new signal light to be amplified by the gain optical path, so as to enhance population inversion generated when the combined new signal light is amplified by the gain optical path.

The invention relates to a method for amplification of a forward-propagating laser pulse (16) and lower amplification of a backward-propagating laser pulse (20), wherein the laser pulses (16, 20) pass through a pumped laser amplifier (14), the method having the following method steps: A) switching on or increasing the pump power provided by a pump source for the laser amplifier (14) before the passage of the forward-propagating laser pulse (16) and switching off or decreasing the pump power provided by the pump source for the laser amplifier (14) before the passage of the backward-propagating laser pulse (20); and / or B) operating the laser amplifier (14) with a high small-signal amplification factor and / or a low saturation power, such that the forward-propagating laser pulse (16) reduces the population inversion of the laser amplifier (14) to a maximum extent for the backward-propagating laser pulse (20).

The application discloses a high-power continuous-wave single-frequency tunable titanium sapphire laser, which comprises a resonant cavity and at least two titanium sapphire crystals, the resonant cavity comprises at least one adjacent concave-convex mirror pair in an optical path and an output coupling mirror, the titanium sapphire crystals are arranged at waist spots between the concave-convex mirror pair, and each titanium sapphire crystal has an independent pump source. The application inserts multiple titanium sapphire crystals with independent pump sources into the resonant cavity, and arranges the titanium sapphire crystals at the waist spots between the two concave-convex mirrors to realize population inversion, solves the problem that the output power of the titanium sapphire laser is limited due to the limited output power of the pump source through multi-end pumping, meanwhile, the multiple concave-convex mirrors effectively expand the pumpable ports, avoid crystal damage caused by a titanium sapphire crystal driven by a very high-power pump source, and provide an effective way for realizing high-power continuous-wave single-frequency titanium sapphire laser output.

The invention relates to a method for generating and amplifying laser pulses (12, 14) by means of an optical amplifier (32), the optical amplifier (32) comprising a laser-active solid body (34) for amplifying the laser pulses (12, 14). The method comprises: generating a laser pulse of a first type (12); generating a laser pulse of a second type (14); generating a population inversion in the laser-active solid body (34); and amplifying the laser pulse of the first type (12) and the laser pulse of the second type (14) by means of the optical amplifier (32) by causing the laser pulse of the first type (12) and the laser pulse of the second type (14) to pass through the laser-active solid body (34) while the laser-active solid body (34) is in the state of population inversion. The laser pulse of the first type (12) and the laser pulse of the second type (14) differ from one another in terms of their wavelength.

The application discloses a kind of based on ground state association's superlinear infrared confocal stimulated radiation super-resolution system and method.The application builds the up-conversion superlinear stimulated radiation loss super-resolution imaging system under the guidance of confocal, by constructing ground state association's dynamic cross relaxation energy transfer model, to accurately obtain the light loss process of the rare earth particles under the action of superlinearity, and can accurately predict the ideal excitation power under high loss efficiency.Based on the super-resolution imaging method under the guidance of the theory, by infrared confocal module, two-photon scanning module, photoelectric detection module Microscopic imaging device, simultaneously utilize the double infrared excitation response of rare earth nanoparticles, the light path precision calibration of stimulated radiation super-resolution imaging process is realized.Using rare earth doped up-conversion nanoparticles and rate equation model accurately simulates the particle number distribution of each energy state of up-conversion nanoparticles, explores the influence of cross relaxation energy transfer process in rare earth nanometer material on the formation process of high-efficiency particle number inversion.Finally, the application can realize the up-conversion stimulated radiation super-resolution imaging system of low loss, high resolution, high signal-to-noise ratio and low system calibration complexity.

The application discloses an all-fiber time-space mode-locked laser, which comprises a pump source, a beam combiner, a multimode gain optical fiber, a coupler, a filter, an isolator and a mode-locked device, the beam combiner, the multimode gain optical fiber, the coupler, the filter, the isolator and the mode-locked device are sequentially arranged and fused to form a ring-shaped laser resonant cavity; the pump light emitted by the pump source is coupled into the multimode gain optical fiber through the beam combiner; the multimode gain optical fiber absorbs the pump light, forms population inversion and generates a laser beam; the laser beam is coupled out to the filter through the coupler, the filter transmits the laser beam to the isolator after performing spectral filtering on the laser beam; the laser beam is transmitted to the mode-locked device after passing through the isolator, and the laser beam realizes time-space mode locking through the mode-locked device. Through the multimode gain optical fiber, the mode-locked device, the filter, the isolator, the beam combiner, the coupler and other devices, high-power, high-beam-quality and stable time-space mode-locked laser output is realized.

The application discloses a kind of all-optical pumping gas laser, including harmonic cavity, extreme ultraviolet laser system, auxiliary pumping semiconductor laser system and main pumping semiconductor laser system;Extreme ultraviolet laser system generates extreme ultraviolet laser, realizes extreme ultraviolet pumping process and generates laser metastable gas particles transition energy state, and auxiliary pumping process and fluorescence transition process are combined with the auxiliary pumping process of auxiliary pumping semiconductor laser system, and generate metastable gas particles, as the effective working material of laser;The main pumping semiconductor laser generated by main pumping semiconductor laser system is transmitted and injected into the resonant cavity, realizes the particle number inversion between laser upper and lower energy levels, and obtains output laser after oscillation amplification.The application has the characteristics of high conversion efficiency, compact structure, small size, high pumping efficiency, etc., which can effectively improve the conversion efficiency of the existing gas laser by electric excitation to generate effective gas working medium.

An all-fiber laser system includes a gain fiber and a fiber-based optical coupling structure configured to introduce pump light into a signal fiber. The optical coupling structure provides intrinsic isolation of pump fibers from backward-propagating optical radiation generated in the gain fiber, including backward-propagating signal light and stimulated Raman scattering (SRS) light. By structurally suppressing coupling of the backward-propagating optical radiation into the pump fibers, the laser system mitigates population inversion collapse and suppresses laser instability and self-pulsation induced by optical back reflection during processing of reflective materials. The system enables stable continuous operation at multi-kilowatt output power without reliance on free-space optical isolators, circulators, or active shutdown mechanisms, thereby improving reliability of pump light sources and protecting an output fiber during high-power laser operation.

The application discloses a compact long-cavity-path multi-path pumped alkali laser, which comprises a cross-flow alkali metal vapor cell, an alkali laser resonant cavity mirror, at least two 45-degree dichroic mirrors and a semiconductor laser pumping source, the cross-flow alkali metal vapor cell is used for providing a gain medium for the alkali laser, the alkali laser resonant cavity mirror is used for forming a laser resonant cavity and selecting a mode, the 45-degree dichroic mirror is used for folding and separating a pumping beam and a laser beam, and the semiconductor laser pumping source is a narrow-wavelength semiconductor laser adopting a line width compression technology, which is used for exciting alkali metal vapor atoms, forming population inversion and being one of three elements of laser. The compact long-cavity-path multi-path pumped alkali laser scheme disclosed by the application can select a proper number of pumping modules according to power level, volume and weight requirements of a laser system.

An erbium fiber laser produces a beam of ultrashort laser pulses having a center wavelength greater than 780 nanometers, an average power greater than 0.5 watt, and a spectral bandwidth compressible to a pulse duration of less than 200 femtoseconds. The laser includes a fiber preamplifier that is energized by a counter-propagating pump beam, has relatively low population inversion in a relatively long optical gain fiber, and provides a spectrally-shaped beam for further amplification. Wavelength dependent gain and absorption within the optical gain fiber enhances longer wavelengths relative to shorter wavelengths in the spectrally-shaped beam. The spectral shaping is sufficient to overcome gain narrowing and gain shifting in a subsequent high-gain fiber amplifier.

The invention relates to the technical field of integrated optoelectronic chips, and discloses a setting method for on-chip laser generation of a micron-thickness lithium niobate film, and the method comprises the steps: preparing a micron-thickness erbium-doped lithium niobate film waveguide on an erbium-doped lithium niobate film substrate as a gain medium, so as to enlarge the mode field area and gain volume, and improve the laser output power; sagnac annular reflectors are integrated at the two ends of the erbium-doped lithium niobate film waveguide respectively to form a Fabry-Perot resonant cavity, and the optical feedback efficiency of the resonant cavity is optimized; a pump light source is efficiently coupled to a waveguide input end through a conical lens optical fiber, erbium ions are excited to realize population inversion, and stimulated radiation light is generated; stimulated radiation light is subjected to multiple reflection resonance enhancement in the Fabry-Perot resonant cavity to form laser oscillation, laser generated by the laser oscillation is transmitted through the erbium-doped lithium niobate film waveguide and is coupled and output through the output end, and on-chip laser output of 0.36 mW or above and chip external coupling power of 114 mu W or above are achieved.

The invention discloses an integrated waveguide device for generating 2.7 [mu] m mid-infrared laser and a laser generation method thereof, and relates to the technical field of on-chip integrated optics. The integrated waveguide device comprises an erbium-doped lithium niobate film waveguide, the cross section area of the erbium-doped lithium niobate film waveguide is smaller than 1 [mu] m, and the erbium-doped lithium niobate film waveguide is bonded on a silicon dioxide insulating layer; the silicon dioxide insulating layer is deposited on the lithium niobate substrate; the incident end of the erbium-doped lithium niobate thin-film waveguide is plated with a high-reflection film, the output end of the erbium-doped lithium niobate thin-film waveguide is provided with a Bragg grating, the high-reflection film and the Bragg grating jointly form a resonant cavity, and a cavity body of the resonant cavity is formed by an erbium-doped lithium niobate thin-film waveguide area located between the high-reflection film and the Bragg grating and serves as a gain area. The erbium-doped lithium niobate film integrated photonics are used for realizing population inversion between a second excited state and a first excited state of erbium ions under the excitation of 1480nm pump light, so that 2.7 mu m intermediate infrared laser is obtained, and the blank of research and application of erbium-doped lithium niobate film integrated photonics in the field related to intermediate infrared bands is filled.

The present disclosure discloses a kind of laser and method based on cavity emptying group realizes pulse group laser output, in the laser: fast photoelectric detector, first all-reflection mirror, electro-optic switch, quarter-wave plate, polaroid, gain medium, second output mirror are sequentially placed from left to right;Pump source is placed below the gain medium, for using the pump light emitted by it to pump the gain medium, so that gain medium realizes enough particle number inversion;Electro-optic switch voltage waveform controller is electrically connected with the electro-optic switch, for the electro-optic switch power supply, control the voltage of electro-optic crystal inside the electro-optic switch, the electro-optic switch voltage waveform controller is also connected with the fast photoelectric detector, for receiving the electrical signal generated by the fast photoelectric detector, after this signal triggers electro-optic switch voltage waveform controller, output multiple high level as quarter-wave electro-optic crystal voltage square wave signal.

The invention discloses a dye with a Donor-Acceptor (D-A) structure, a laser gain medium containing the dye and application of the dye, and aims to solve the key technical problem that the gain capacity of the existing dye is reduced due to aggregation quenching under high concentration. The structural general formula of the organic dye molecules is shown in the specification. R1 is selected from alkyl, hydroxyl-substituted alkyl, sulfonic acid-substituted alkyl, carboxylic acid-substituted alkyl, alkylene and phenyl, R2 is selected from alkyl, phenyl, alkoxy phenyl and alkylphenyl, X is selected from S or O, and n is selected from 1, 2 and 3; the dye can form an aggregate through intermolecular interaction under high concentration, two new energy levels independent of a single-molecule excited state are generated, a four-energy-level system beneficial to population inversion is constructed, and low-threshold amplified spontaneous emission (ASE) can still be achieved even if the quantum yield is lower than 0.49%; the macrocyclic ligand can regulate and control the microenvironment of the cavity to inhibit aggregation and quenching among dye molecules, improve the solubility of the dye, optimize the excited state behavior and further reduce the ASE threshold value. Meanwhile, accurate regulation and control of ASE emission wavelength can be realized by adjusting electron-donating groups in dye molecules.

The invention discloses a laser molecule with cascade excited state double proton transfer activity, a single crystal material and a preparation method and application of the laser molecule and the single crystal material. According to the invention, the laser molecule with a specific structure and cascade excited state double proton transfer activity is designed, so that the J-type aggregate can be spontaneously formed; by utilizing the intermolecular coupling effect of J-type aggregation, the excited state energy of the tautomer B is effectively reduced, and two times of proton transfer are promoted to be completely completed in thermodynamics. The thorough cascade excited state double-proton transfer process can avoid excited state particle shunting loss and promote excitons to release energy through an excited radiation channel, so that the utilization rate of the excitons is remarkably improved, sufficient population inversion intensity and optical gain are guaranteed, and the photoelectric conversion efficiency is improved. Finally, the core problems that an existing near-infrared organic solid laser is low in exciton utilization rate and insufficient in optical gain are solved, and ultralow-threshold near-infrared laser emission is achieved.

The application discloses a wavelength-switchable and tunable dual-wavelength single-frequency fiber laser based on birefringence effect, which comprises a partially reflective polarization maintaining fiber grating, a gain fiber, a wavelength division multiplexer, a pump source, a 3dB fiber coupler and an unpumped active fiber; the partially reflective polarization maintaining fiber grating is used as a reflective cavity mirror and simultaneously realizes laser output; the birefringence effect of the fiber is utilized to generate dual-wavelength laser, and wavelength tuning and wavelength switching are realized under the action of longitudinal stress; the 3dB fiber coupler and the unpumped active fiber form a Sagnac loop reflector, which provides feedback for the laser and realizes single longitudinal mode operation as a frequency selection device; the gain fiber absorbs the pump laser injected by the pump source to form particle number inversion and provide gain for the laser. The application utilizes the unpumped active fiber as a saturated absorber for frequency selection and combines the birefringence effect of the partially reflective polarization maintaining fiber grating to realize watt-level dual-wavelength single-frequency laser.

The application provides a diamond color center microwave generator and a preparation method thereof. The diamond color center microwave generator is composed of arrayed diamond color center columns, laser diodes, sapphire resonant cavities, copper resonant cavities and microwave antennas. The diamond color center columns of each array unit can realize energy level deflection under the action of an external magnetic field, particle number inversion under the action of laser excitation, stimulated radiation under the action of external microwave particles received by the microwave antennas, and avalanche microwave particle amplification after resonance of the sapphire resonant cavities and the copper resonant cavities. The output powers of the array units are accumulated, and the microwave output power of the diamond color center microwave generator is increased.

The application discloses a laser containing a particle number inversion structure, which comprises, from bottom to top, a substrate, a lower limiting layer, a first lower waveguide layer, a second lower waveguide layer, an active layer, an upper waveguide layer and an upper limiting layer; the first lower waveguide layer and the second lower waveguide layer form a lower waveguide layer; the upper limiting layer, the upper waveguide layer, the active layer, the first lower waveguide layer and the second lower waveguide layer form a particle number inversion structure; in the particle number inversion structure, the upper waveguide layer steep Mg-doped concentration interface, the active layer steep Si-doped concentration interface, the lower waveguide layer steep Si-doped concentration interface, the upper waveguide layer steep Al content interface and the lower waveguide layer steep Al content interface jointly make the electron number of the active layer much larger than the hole number, thereby forming particle number inversion; with continuous input of an excitation source, hole radiation recombination is greater than loss, laser generation is accelerated, the threshold of the laser is reduced, and laser power and efficiency are improved.

The invention discloses a 195 nm femtosecond laser capable of outputting high power, which relates to the technical field of laser, and comprises a femtosecond laser seed source, a seed optical coupling system, a Ti: sappfire single crystal optical fiber, a pump light focusing mirror, a double-color sheet, a collimating mirror, a pump source, an amplification optical coupling system, a frequency doubling crystal, a frequency quadruplicating crystal and a triangular prism, 532nm pump light generated by the pump source sequentially passes through the collimating mirror, the double-color plate and the pump light focusing mirror and enters the Ti: sapphile single crystal optical fiber to generate population inversion; seed light generated by the femtosecond laser seed source passes through the seed light coupling system and enters the Ti: sapphile single crystal optical fiber generating population inversion to amplify the optical power of the Ti: sapphile single crystal optical fiber, and 780nm power amplified light is output; 780nm power amplification light is output through the pump light focus lens and the double-color sheet in sequence, enters the frequency doubling crystal and the frequency quadruplicating crystal through the amplification light coupling system for cascade frequency doubling, and is finally split through the triangular prism to obtain 195 nm deep ultraviolet laser. And the 195 nm deep ultraviolet laser with the power of W magnitude is obtained.

The application discloses a chip active optical clock based on a MEMS atomic gas chamber and an implementation method thereof. The application pumps the gain medium in the MEMS atomic gas chamber by laser, establishes population inversion, and through the cavity feedback of the resonant cavity, continuously amplifies the spontaneous radiation to reach the laser threshold, and then outputs the active lasing signal. Since the resonant cavity for generating the active lasing signal is a bad cavity, the gain line width is much smaller than the cavity mode line width, the noise caused by the cavity dragging effect can be greatly suppressed, and the output laser can be directly used as an optical frequency standard signal without the need of a servo circuit to stabilize the resonant cavity length, thereby reducing the volume and power consumption of the system. Meanwhile, the MEMS atomic gas chamber is used as a core component, various optoelectronic components are assembled in a stacking mode and integrated on a silicon-based chip, and the chip microcavity optical comb is combined to perform frequency down-conversion, so that the chip active optical clock with a narrow line width and high stability is realized. The application provides a new way for the deployment of the active optical clock in miniaturized and portable time-frequency devices.

The invention discloses an argon laser excitation method and system for generating third harmonics based on femtosecond laser filamentation. The method comprises the following steps: generating femtosecond laser pulses and transmitting the femtosecond laser pulses in the atmosphere in a long distance; focusing the pulse in the atmosphere to form a laser filamentation, and generating a third harmonic at the filamentation position; the generated third harmonic is used as pump light, population inversion of the target energy level of atmospheric argon atoms is achieved through a three-photon resonance excitation mechanism, and finally bidirectional and multi-wavelength cascade laser output is achieved. Remote transmission is carried out through near-infrared laser, third harmonics are generated at the position of the light filament, the problems of transmission loss and efficiency reduction caused by strong air absorption when ultraviolet pump light is directly used are solved, and therefore high-efficiency argon laser output is achieved. The system is simple in structure and high in environmental adaptability, and has important application value in the fields of remote sensing, spectral analysis and the like.

This invention proposes a gallium nitride-based semiconductor laser with a hole-burning suppression layer, comprising, from bottom to top, a substrate, a lower confinement layer, a lower waveguide layer, an active layer, an upper waveguide layer, an electron blocking layer, and an upper confinement layer. This invention sets the distribution and variation trend of Al or In element concentrations in the hole-burning suppression layer, the upper confinement layer, the upper waveguide layer, and the lower waveguide layer, thereby controlling the uniformity of interface strain, the uniformity of interface Al element concentration distribution, and the interface quality of the laser structure. This improves the quantization of injected carrier energy, increases the carrier utilization rate in the injected active region, reduces the coupling time constant between electrons and photons in the active layer, reduces the number of interface states, and reduces the standing wave reduction caused by stimulated emission and the interaction between defects and interface states, as well as the population inversion distribution of standing wave interference particles excited by the laser resonator. This suppresses abrupt drops in the gain curve at any frequency position, suppresses the hole-burning effect, and improves slope efficiency.

An optical cavity resonator, comprising a transparent or nearly transparent dielectric, and having gas or plasma provided thereabout, the resonator constructed to have an optical resonance that extends to partially spatially overlap with said gas or plasma, the gas or plasma providing an optical gain at a frequency overlapping a resonant frequency of said resonator, wherein the optical cavity, with plasma, is constructed to be pumped so that the plasma is able to amplify light at a frequency approximately related to an atomic transition of said gas or plasma.

The application discloses a kind of based on single-double mode optical fiber laser's ultra-short pulse generation method and device, method includes: pump light enters erbium-doped optical fiber by double-mode wavelength division multiplexer, excitation erbium ion to upper level and form particle number inversion, produce stimulated emission, amplify laser signal;Pass through double-mode optical fiber coupler, a small amount of laser output to outside cavity and measure, remaining laser continues to oscillate in cavity;Remaining laser passes through polarization controller and adjusts the polarization state in resonant cavity, to ensure that laser is stably transmitted in cavity, utilize carbon nanotube saturable absorber to realize the mode locking of laser, ensure that stable ultra-short pulse is generated;Laser passes through double-mode isolator and ensures that optical pulse is unidirectional operation in resonant cavity, re-enters double-mode wavelength division multiplexer and forms circulation;After periodic mode coupling, finally form stable mode-locked pulse.The application is suitable for few-mode fiber mode-locked laser, with simple structure, easy to construct and maintain, with very high stability and reliability.