319 results about "Saturable absorption" patented technology

The invention belongs to the technical field of photoelectronics, and particularly relates to a wide-spectrum narrow-linewidth semiconductor mode-locked laser, and the collaboration of a saturable absorption region SA and a resonator is reflected in time domain-frequency domain dual optimization. And the resonator optimizes the frequency domain characteristics through nonlinear broadening, phase synchronization and mode purification. The SA adjusts a mode locking threshold value in real time through dynamic bias voltage, the pulse energy stability is ensured, dispersion management of the resonator balances the SPM and group velocity dispersion, spectrum splitting is avoided, and the dissipative soliton form is maintained. Besides, due to heterogeneous integration of the InP-based SA and the SiN-based resonator, wafer bonding of the InP-based SA and the SiN-based resonator is realized, high-efficiency energy transfer is realized through the low-loss conical waveguide, a high-performance frequency comb with a wide spectrum and a narrow pulse width is output, and the high-performance frequency comb can be widely applied to the fields of ultrafast optics, coherent light communication and precision spectroscopy.

The invention discloses a high-tolerance synchronous dual-band pulse laser, and relates to the field of lasers, and the laser comprises a first resonant cavity and a second resonant cavity; the first resonant cavity comprises a first pumping source and an optical annular cavity formed by sequentially connecting a first wavelength division multiplexer, a first thulium-doped optical fiber, a first optical coupler, a first isolator, a second wavelength division multiplexer, a high-nonlinearity saturable absorber, a third wavelength division multiplexer and a first polarization controller; the second resonant cavity comprises a second pumping source and an optical annular cavity which is formed by sequentially connecting a fifth wavelength division multiplexer, a second erbium-doped fiber, a second optical coupler, a second wavelength division multiplexer, a high-nonlinearity saturable absorber, a third wavelength division multiplexer, an electric control adjustable delay line, a fourth wavelength division multiplexer, a second polarization controller and a second isolator, and the fifth wavelength division multiplexer, the second erbium-doped fiber, the second optical coupler, the high-nonlinearity saturable absorber, the third wavelength division multiplexer, the electric control adjustable delay line, the fourth wavelength division multiplexer, the second polarization controller and the second isolator; and the first optical coupler and the second optical coupler respectively output synchronization pulses in the wave bands of 2 microns and 1.5 microns. The device is compact in structure, low in manufacturing cost, convenient to operate and capable of covering the mid-infrared band of 2 microns.

The invention discloses a dual-band mode-locked fiber laser based on metasurface polarization control, and belongs to the technical field of fiber lasers. Comprising a first loop, a second loop and a common end, the first loop and the second loop are connected with the gold cross-shaped metasurface through the common end, and the first loop and the second loop are independent of each other and do not affect each other. According to the dual-band ultrafast laser device, based on the metal surface plasmon effect, the gold cross-shaped metasurface mode locking device is prepared, gold cross-shaped metasurface structures which are different in length in the horizontal direction and the vertical direction are designed respectively, the polarization and nonlinear saturable absorption characteristics of the gold cross-shaped metasurface structures are utilized, and the dual-band ultrafast laser device is obtained. And meanwhile, mode-locked laser output in two wavebands is realized, and the lasers in the two wavebands are mutually independent and do not influence each other.

The invention relates to the field of optical calculation and optical signals, in particular to a hybrid photon neural network device and a classification method. Comprising a multi-channel tunable light source, a modulator array, an FPGA and a 4 * 4 MZI array. A DFB-SA array and a PD array; the output end of the multi-channel tunable light source is connected with the input end of the modulator array, the FPGA is connected with the radio frequency end of the modulator array, the output end of the modulator array is connected with the input end of the 4 * 4 MZI array, the output end of the 4 * 4 MZI array is connected with the input end of the DFB-SA array, and the output end of the DFB-SA array is connected with the input end of the PD array. According to the invention, the phase parameters of the 4 * 4 MZI array can be configured through an efficient gradient descent algorithm, so that the device has advantages in the aspect of flexible simulation of neural network synapses; in addition, the device adopts a distributed feedback semiconductor laser array with a saturated absorption region, and the nonlinear activation function of photon neurons is realized by fully utilizing the threshold characteristic of the distributed feedback semiconductor laser array.

Disclosed in the present invention is a near-infrared wavelength scanning pulse fiber laser having a low mode-locking threshold. According to the present invention, a nonlinear amplifying loop mirror and a saturable absorber mirror architecture are used to achieve a low mode-locking threshold and ensure long-term mode-locking stability. After mode-locking self-starting, an automatic control module automatically achieves single-pulse operation by adjusting the intensity of retro-reflected pulses. In the single-pulse operation stage, different frequencies of radio frequency signals and different signal intensities are provided for an acousto-optic tunable filter by means of a radio frequency module to achieve a 1030 nm-1100 nm wavelength scanning and tuning range.

The invention relates to a self-calibration atomic wavelength meter. The self-calibration atomic wavelength meter comprises a saturated absorption spectrum light path for locking a detection laser frequency on a cesium atom energy level transition line based on a saturated absorption spectrum; the double-peak spectrum light path scans the frequency of a coupled laser after the frequency of the detection laser is locked by a saturated absorption spectrum, and when the detection laser and the coupled laser jointly act on alkali metal atoms and are subjected to resonance excitation, an electromagnetic induced transparency effect is generated; when the detection laser is detuned, the detection laser and the combined laser jointly act on the alkali metal atoms to generate non-resonance excitation, a double-peak EIT spectrum with Doppler frequency shift is generated, and the wavelength measurement of the current detection laser can be completed based on the linear relation between the double-peak spectrum interval and the detuning amount of the detection laser. In addition, the double-peak spectrum interval is compared with the atomic energy level transition frequency, the difference between the double-peak spectrum interval and the atomic energy level transition frequency serves as an error signal to be fed back to the control end of the detection laser, the frequency of the detection laser is tuned to the reference frequency standard, and calibration of the wavemeter can be achieved.

The invention relates to the technical field of semiconductor lasers, in particular to a semiconductor laser with an adjustable time domain. According to the time-domain-adjustable semiconductor laser, a mutual injection coupling region and a gain region are arranged on a semiconductor laser chip, the mutual injection coupling region comprises multiple sections of interval units, and the ratio of the length of a saturable absorber region to the length of the gain region in a resonant cavity is controlled by adjusting the absorption / gain characteristics of the interval units. And a plurality of pulse generation mechanisms are switched to adjust the pulse width. On the premise that the structural complexity of the semiconductor laser is reduced, large-range adjustment of laser pulses can be achieved.

The invention discloses a plug-and-play Rydberg atom preparation device based on a three-photon absorption method, which comprises a laser generator, a laser input module, a laser detector, three frequency stabilization modules and a temperature and humidity control module, and is characterized in that the laser generator is used for preparing laser to be measured; the input module is used for transmitting and introducing laser; the saturated absorption frequency stabilization module, the electromagnetic induction transparent frequency stabilization module and the heating electromagnetic induction transparent frequency stabilization module all adopt a glass bonding technology to build frequency stabilization light paths; the laser detection device is used for detecting laser lines in the saturation absorption frequency stabilization module, the electromagnetic induction transparent frequency stabilization module and the heating electromagnetic induction transparent frequency stabilization module and locking the laser frequency corresponding to the specific wavelength. According to the invention, a frequency-stabilized light path is built by using a glass bonding technology, so that devices and the size are greatly reduced, and the integration level of a light path system is greatly improved; moreover, the degree of freedom of device adjustment can be reduced, and the reliability and stability of a laser frequency stabilization optical path are effectively improved.

The invention belongs to the technical field of quantum precision measurement, and particularly discloses a frequency stabilization system and a frequency stabilization method for an external cavity semiconductor laser. The system comprises a saturated absorption spectrum module, a wavelet peak searching module, a modulation and demodulation module, a bias amplification module and a switch module, wherein the saturated absorption spectrum module outputs an electric signal of a saturated absorption spectrum; under the control of the frequency locking instruction, the wavelet peak searching module outputs a target bias voltage signal corresponding to the locking frequency based on the electric signal; the modulation and demodulation module performs signal modulation and demodulation based on the electric signal and a reference signal corresponding to the locking frequency to output a modulation signal and a demodulation signal; and the bias amplification module performs superposition and amplification processing on the modulation signal, the demodulation signal and the target bias voltage signal, and outputs a target superposition signal to a PZT modulation port of the laser, so that the output laser freely operates on the locking frequency. According to the invention, the laser is not liable to generate mode hopping in the frequency locking process, the whole frequency stabilization system is more stable, the structure is simple, and the cost is low.

The invention discloses an automatic frequency stabilization system based on dual-core correlation matching intelligent peak searching. The automatic frequency stabilization system comprises the following steps that S1, a saturated absorption spectrum light path and a circuit are built, debugged and optimized; s2, constructing a double-matching template; s3, triangular wave voltage scanning and clock timing are started, and signals are collected and transmitted; s4, starting a KCF algorithm, applying a template to track model matching, judging a result obtained by matching, finding a peak point and solving a corresponding scanning voltage; and S5, recording a peak point scanning voltage, closing a scanning signal, starting sinusoidal signal modulation, and giving a triangular wave scanning voltage corresponding to a peak value to the sinusoidal signal as an offset. The spectrum line peak value suspected area can be effectively positioned, the double-branch and correlation filtering tracking method can perform precise secondary searching in the suspected area, the locking precision is greatly improved, the long-term stability of 10-12 orders of magnitude is ensured, and meanwhile the good vibration interference resistance can be achieved when a vibration signal occurs.

Aspects of embodiments pertain to an optical mapping device having non-linear optical characteristics. The device may comprise an optical unit that is configured to direct an optical signal from an input interface to an output interface of the optical unit. The device includes a substance causing the optical unit to attain saturable absorber characteristics such that absorption of an optical input signal guided from the input interface to the output interface by the optical unit decreases with an increase in optical signal intensity received by the optical unit. In some examples, the saturable absorber characteristics of the mapping device are selectively adaptable.

The invention discloses an all-fiber structure pulse laser based on a superfine single-crystal fiber and a preparation method thereof. The all-fiber structure pulse laser comprises a gain single-crystal fiber and a pulse modulation single-crystal fiber, and the gain single-crystal fiber and the pulse modulation single-crystal fiber form a superfine single-crystal fiber heterogeneous bonding structure through thermocompression bonding; the gain single-crystal optical fiber serves as a laser gain medium, the pulse modulation single-crystal optical fiber serves as a saturable absorber, the gain single-crystal optical fiber is provided with a high-reflection grating, the high-reflection grating and an oblique-angle low-reflection end arranged at the tail end of the pulse modulation single-crystal optical fiber form a resonant cavity, and pump light is input into the gain single-crystal optical fiber and enters the resonant cavity through the high-reflection grating. And the oblique-angle low-reflection end outputs pulse laser. The gain section and the modulation section are fused into an integrated structure through the superfine single crystal optical fiber bonding technology, the high-reflection grating is inscribed through the femtosecond laser direct writing technology, low-reflection-mirror oblique angle processing is carried out at the output end, space coupling loss is eliminated, and all-optical-fiber monolithic integration is achieved.

The invention belongs to the technical field of lasers, and discloses a fiber laser for promoting generation of a stable soliton attraction state by using a high-birefringence fiber. The optical fiber laser comprises a laser pumping source, a wavelength division multiplexer, an erbium-doped gain optical fiber, a polarization independent isolator, a polarization controller, a polarization maintaining optical fiber, an output coupler and a mode locking device based on a carbon nanotube saturable absorber, and all the components are sequentially connected through single-mode optical fibers. The polarization-maintaining optical fiber is a panda-shaped polarization-maintaining optical fiber with a high birefringence effect. The polarization direction and the polarization state in the cavity are accurately controlled by adjusting the polarization controller, phase synchronization of soliton pulses is achieved when the polarization maintaining optical fiber is output, soliton energy in the cavity is rapidly accumulated, soliton splitting is triggered, and finally a stable multi-pulse soliton attraction state is formed. The design is simple and convenient to operate, and stability and anti-interference capability of soliton transmission are remarkably improved.

The invention discloses a periodic forked near-transformation limit nanosecond pulse mode-locked fiber laser and a generation method. The laser is characterized in that a fiber ring cavity comprises a wavelength division multiplexer, an erbium-doped fiber, a first polarization controller, a polarization analyzer, a dispersion control unit, an output coupler, a fiber isolator and a second polarization controller which are sequentially connected in a closed loop mode. The method comprises the steps that pumping continuous light is coupled into the laser through the wavelength division multiplexer; pumping continuous light is absorbed by using an erbium-doped fiber and is stimulated to radiate a gain pulse with a long wave band, and the generated pulse oscillates in a fiber laser cavity; under the combined action of a first polarization controller, an analyzer and a second polarization controller, an equivalent saturated absorption effect is generated by utilizing nonlinear polarization rotation generated when gain pulses are propagated in an optical fiber, and pulse mode locking is realized; the optical fiber laser works in an abnormal dispersion region, so that generated pulses meet the soliton area theorem, and near-transformation limit pulses are generated. According to the invention, nanosecond pulse period bifurcation output of the short-cavity fiber laser can be realized.

The invention discloses a dual-wavelength mode-locked laser generating device and a dual-wavelength mode-locked laser generating method, and belongs to the technical field of optical communication, and the dual-wavelength mode-locked laser generating device comprises a pumping source, an optical integration module, a gain optical fiber, a saturable absorber and a dual-wavelength pulse independent polarization mode linear coupling regulation and control structure, linear coupling strength of cross-polarization components in two wavelength pulses is independently regulated and controlled by using a structure of a polarization controller and a polarization maintaining optical fiber, and dual-wavelength mode-locked pulse laser of different types of pulse combinations can be obtained. The coherent pulse light source with unique spectral characteristics can provide a low-cost light source for the fields of high repetition frequency optical combs, all-fiber architecture high repetition frequency soliton sequences and microwave photonics.

The invention discloses a high-stability self-mode-locking optical fiber laser based on phase modulation. The high-stability self-mode-locking optical fiber laser is composed of an optical pumping source, a wavelength division multiplexer, an isolator, a coupler, a polarization beam splitter, a 45-degree Faraday rotating mirror, a 90-degree Faraday rotating mirror, a non-polarization-maintaining single-mode optical fiber, a polarization-maintaining single-mode optical fiber and an erbium-doped optical fiber. The wavelength division multiplexer, the isolator and the coupler can be integrated into a three-in-one device and can also be placed separately. The intra-cavity tail fiber and the output end are arranged to be polarization-maintaining single-mode optical fibers and are connected with a pumping source; polarization-maintaining single-mode optical fibers are arranged at the beam combining end and the beam splitting end of the polarization beam splitter; in the 45-degree Faraday rotating mirror, a tail fiber on one side is arranged to be a non-polarization-maintaining single-mode fiber, and a polarization-maintaining single-mode fiber is arranged on the other side. The saturable absorption effect is achieved through polarization state changes related to light intensity when a light field is transmitted in an optical fiber, but different from a traditional NPR, the whole structure does not need interference of a polarization controller, and the expected effect can be achieved only by controlling the input light intensity.

The invention provides a gas saturation absorption optical path structure based on dual optical path enhancement, which belongs to the field of laser optical path design and comprises an optical fiber circulator, a gas absorption chamber and an optical fiber reflector. A first port of the optical fiber circulator is connected with a laser output optical fiber, a second port of the optical fiber circulator is connected with an input collimator of the gas absorption chamber, and a third port of the optical fiber circulator is connected with a detector and is used for providing frequency reference for gas absorption; and the optical fiber reflector is connected with the output end of the gas absorption chamber. According to the invention, the physical contradiction between the air chamber size and the optical path gain is broken through, and a compact frequency stabilization system with miniaturization and high stability is realized.

The utility model discloses an intracavity frequency doubling passive mode-locked laser which comprises a pumping source system, a laser crystal, a resonant cavity and a wavelength conversion structure. The pumping source system pumps the laser crystal to generate fundamental frequency laser; the resonant cavity comprises a plurality of resonant cavity mirrors, the plurality of resonant cavity mirrors are sequentially arranged in the optical path transmission direction of the fundamental frequency laser, a saturable absorber is arranged in the resonant cavity, and the saturable absorber is used for realizing passive mode locking of the fundamental frequency laser in the resonant cavity and generating short-pulse fundamental frequency laser; the wavelength conversion structure is arranged in the resonant cavity, the wavelength conversion structure is located between two adjacent resonant cavity mirrors in the multiple resonant cavity mirrors in the light path transmission direction, and the wavelength conversion structure is used for converting the short-pulse fundamental frequency laser into multi-frequency-doubling short-pulse laser with the preset wavelength. According to the scheme provided by the invention, the frequency doubling conversion efficiency of the laser can be improved, so that the laser output efficiency and power of the laser are improved.

The invention provides a high-efficiency and high-stability space coupling system for a solid-core optical fiber and a hollow-core anti-resonance optical fiber, and belongs to the field of optics. After output information of the hollow-core anti-resonance optical fiber is detected, the output information is transmitted to the instruction input module so as to regulate and control the coupling module, automatic adjustment of the system is achieved, and the system can operate stably. In the coupling module, laser output by a solid optical fiber is subjected to beam shaping through an optical fiber output device and a curvature mirror group, so that the laser is matched with a hollow-core anti-resonance optical fiber mode field, and then the laser is injected into the hollow-core anti-resonance optical fiber after being subjected to stray light absorption and filtration through a gradient saturable absorber diaphragm; besides, the hollow-core anti-resonance optical fiber is clamped by a clamp with a refrigeration function and is placed on a programmable electric control displacement table with a thermal focal movement active compensation function, and high-power, high-efficiency and high-stability coupling is realized through accurate adjustment. The problem that the hollow-core optical fiber is damaged due to stray light, light spot distortion, light beam jitter and the like under high-power laser transmission is effectively solved.

The invention discloses a narrow-linewidth thulium-doped fiber laser oscillator, which is characterized in that a saturable absorption fiber has certain absorption on signal light wavelength and is arranged between a first high-reflectivity fiber bragg grating and a second high-reflectivity fiber bragg grating, and when the laser gain exceeds the loss of a laser resonant cavity formed by the first high-reflectivity fiber bragg grating, the second high-reflectivity fiber bragg grating and a low-reflectivity fiber bragg grating, a thulium-doped fiber is generated; laser oscillation is formed and output through the low-reflection fiber bragg grating; the first and second high-reflectivity fiber gratings form an etalon effect; an etalon effect is formed between the second high-reflectivity fiber bragg grating and the low-reflectivity fiber bragg grating and between the first high-reflectivity fiber bragg grating and the low-reflectivity fiber bragg grating; signal light oscillated between the first high-reflectivity fiber bragg grating and the second high-reflectivity fiber bragg grating can form standing waves, and a dynamic grating is formed in the saturable absorption fiber. Under the action of the resonant cavity vernier effect and the saturable absorption dynamic optical fiber, signal light oscillates in a narrow linewidth mode between the first high-reflectivity fiber bragg grating and the second high-reflectivity fiber bragg grating, and the narrowed signal light is injected into the thulium-doped gain optical fiber through the second high-reflectivity fiber bragg grating, so that the laser maintains narrow spectral linewidth operation.

The invention relates to a nanosecond fiber laser and method for high-order chaotic pulses. A fiber ring cavity of the laser comprises a wavelength division multiplexer, an erbium-doped fiber, a first polarization controller, an analyzer, a second polarization controller, an output coupler, a dispersion control unit, a fiber isolator and a band-pass filter which are connected in sequence. The method comprises the steps that pumping continuous light is coupled into the laser through the wavelength division multiplexer; pumping continuous light is absorbed by using an erbium-doped optical fiber and is stimulated to radiate a long-wave-band gain pulse; under the combined action of the first polarization controller, the polarization analyzer and the second polarization controller, an equivalent saturable absorption effect is generated by utilizing nonlinear polarization rotation generated when gain pulses are propagated in an optical fiber, and large anomalous dispersion is introduced to realize generation of nanosecond pulses; through the band-pass filter, nanosecond pulses are allowed to be generated, and meanwhile, the nonlinear increasing speed of propagation and accumulation of the nanosecond pulses in the cavity is controlled, so that order-by-order generation of high-order chaotic pulses is realized. According to the invention, reliable output of high-order chaotic pulses can be realized.

The invention discloses an ultrashort pulse generation method and device based on a single-mode and dual-mode fiber laser. The method comprises the steps that pump light enters an erbium-doped fiber through a dual-mode wavelength division multiplexer, erbium ions are excited to an upper energy level to form population inversion, stimulated radiation is generated, and a laser signal is amplified; through the dual-mode optical fiber coupler, a small amount of laser is output to the outside of the cavity for measurement, and the remaining laser continues to oscillate in the cavity; the polarization state of the remaining laser in the resonant cavity is adjusted through a polarization controller so as to ensure that the laser is stably transmitted in the resonant cavity, and mode locking of the laser is realized by using a carbon nanotube saturable absorber so as to ensure that stable ultrashort pulses are generated; the laser passes through the dual-mode isolator to ensure that the light pulse runs unidirectionally in the resonant cavity and enters the dual-mode wavelength division multiplexer again to form circulation; and through periodic mode coupling, a stable mode-locked pulse is finally formed. The device is suitable for a few-mode optical fiber mode-locked laser, is simple in structure, is easy to construct and maintain, and is extremely high in stability and reliability.

The invention discloses a reflective pumping detection nondestructive testing device and method capable of saturatively absorbing uniformity in a mirror surface. The device is based on a wavelength degeneracy pumping-detection principle, and comprises a femtosecond laser source, a beam splitter, an optical delay line, a double-frequency optical chopper, a two-dimensional precision translation stage, a coaxial focusing system, a spatial filtering diaphragm arranged in a reflection light path, a photoelectric detector, a lock-in amplifier and a signal processing unit. According to the method, different point positions of a sample are accurately positioned through a two-dimensional translation stage, a nonlinear differential reflectance dynamic curve of each point is measured under low power, the maximum differential reflectance and the carrier lifetime are extracted as characteristic parameters, the spatial relative standard deviation of the characteristic parameters is calculated, and lossless and quantitative in-plane uniformity evaluation is realized. According to the method, the interference of the pump light is effectively filtered through the space filtering diaphragm, the signal-to-noise ratio is remarkably improved in combination with the phase-locked amplification technology, and the problem that the nonlinear optical performance uniformity of the saturable absorber mirror cannot be quantitatively evaluated through a traditional method is solved.

A passively, Q-switched laser is described. The laser may operate at an eye-safe lasing wavelength of 1.34 microns and use a gain element of Nd:YVO4 and a saturable absorber element of V:YAG with a space separating the gain element and saturable absorber element. The Q-switched laser is pumped by a grating stabilized laser diode. The laser may be used in laser ranging applications.

Apparatus, systems, and methods for a bidirectional mode-locked all-polarization maintaining fiber laser with two counter-propagating, orthogonally polarized pulses are applicable in a variety of applications. A mode-locked fiber laser can be realized with a laser cavity including a first polarization maintaining gain fiber, a second polarization maintaining gain fiber, and a saturable absorber. The saturable absorber can be arranged with the first polarization maintaining gain fiber and the second polarization maintaining gain fiber to generate two counter-propagating pulses, being orthogonally polarized with respect to each other. The laser cavity can include a circulator arranged to provide separate paths for the two counter-propagating pulses in a portion of the fiber laser cavity.

The invention provides a slow saturable absorber, a preparation method of a mixed mode locking structure and a pulse laser, and the preparation method of the slow saturable absorber comprises the steps: adding selenium powder, sodium hydroxide and copper nitrate trihydrate into deionized water according to a first preset proportion, and obtaining a colloidal suspension; transferring the colloidal turbid liquid into a stainless steel high-pressure kettle for reaction to obtain copper selenide nanosheets; washing the copper selenide nanosheet by using alcohol; and depositing the washed copper selenide nanosheet on a D-type optical fiber, and coupling a laser to the D-type optical fiber in the deposition process to obtain the slow saturable absorber. According to the scheme, the problems that an existing real saturable absorber is low in anti-damage threshold value, mode-locked laser achieved based on the existing real saturable absorber is low in output power and poor in stability and long-term operation stability are solved, and the problems that an existing artificial saturable absorber is difficult to self-start, low in modulation depth and sensitive to polarization are solved.

A ring resonator (10) and a NALM (20) configured as a saturable absorption mechanism constitute a laser oscillator. A multiport BPF (12) is provided to a path through which light propagates in the laser oscillator, the multiport BPF (12) passing light in a prescribed band of the propagating light, and branching light outside of the prescribed band as monitoring light (L). A photodetector (1) detects the monitoring light (L). A control unit (2) controls the oscillation state of the light propagating through the laser oscillator on the basis of the intensity of the monitoring light (L), thereby controlling the mode synchronization of the light propagating through the laser oscillator.

The invention discloses a mode-locked laser based on cross-polarization feedback injection and a control method thereof, and belongs to the technical field of lasers, a light beam emitted by a VCSEL laser is divided into two beams through an optical splitter, the first beam is divided into a first TM mode light beam and a first TE mode light beam through a first polarization-maintaining beam splitter, the two beams form an annular loop on a light path, and the first TM mode light beam and the first TE mode light beam form an annular loop on the light path; and a half-wave plate is arranged on the loop. And the two beams of light are respectively and oppositely propagated along the annular loop, return to the VCSEL laser after being subjected to polarization state conversion by the half-wave plate, are reflected by a resonant cavity of the VCSEL laser again, are coupled into the resonant cavity after being subjected to secondary polarization state conversion by the half-wave plate, and finally finish the output of the mode-locked laser. The laser reaches a mode-locked state by adjusting the angle of the half-wave plate. The laser uses an orthogonal polarization feedback injection mechanism, does not need to use a saturable absorber and a polarization inverter, is simple in structure and easy to implement, greatly reduces the cost and complexity of a system, and meets the requirements of different application scenes.

A self-calibration atomic wavemeter, including a saturated absorption spectrum optical path based on saturated absorption spectrum to lock the probe laser frequency on cesium atomic energy level transition line; a double-peak spectrum optical path scans the coupling laser frequency after the probe laser frequency is locked by the saturated absorption spectrum, when the probe laser and the coupling laser jointly act on the alkali metal atom and resonantly excite, the electromagnetic induced transparency effect is generated; and when the probe laser is detuned, the probe laser and the coupling laser jointly act on the alkali metal atom to produce non-resonant excitation, and the double-peak EIT spectrum with Doppler frequency shift is generated, based on the linear relationship between the double-peak spectrum interval and the probe laser detuning amount, the wavelength measurement of the current probe laser can be completed, in addition, the double-peak spectrum interval and the atomic energy level transition frequency are compared, and the difference between the two is taken as an error signal feedback to the control end of the probe laser, and the frequency of the probe laser is tuned to the reference frequency benchmark, so that the calibration of the wavemeter can be realized.

This invention discloses a passively mode-locked fiber laser with switchable transverse modes and an optical communication system, relating to the field of ultrafast optical technology. The passively mode-locked fiber laser comprises a pump source and a laser resonator. The laser resonator comprises a wavelength division multiplexer, a gain fiber, a few-mode isolator, a first polarization controller, a saturable absorber, a second polarization controller, a mode-selective photon lantern, and a few-mode coupler, all connected in sequence along the direction of light propagation. Compared to existing technologies, the present invention offers low insertion loss and high spatial mode selection flexibility, making it widely applicable in communications, industrial processing, detection, and other fields.