5097 results about "Resonant cavity" patented technology

The invention relates to the technical field of water-based paint production, in particular to a water-based paint stirring device with a viscosity detection function, which comprises a mounting seat, a stirring tank is arranged at one corner of the top of the mounting seat, and a tank cover is arranged at the top of the stirring tank; the stirring assembly is arranged in the stirring tank; the bubble adsorption assembly is arranged at the other corner of the mounting seat; the detection assembly comprises a high-frequency ultrasonic probe arranged on the inner wall of the stirring tank, a micro torque sensor and a temperature compensation module which are integrated in the stirring assembly, and a microwave resonant cavity sensor located on the bubble adsorption assembly. Compared with the prior art, the multi-mode viscosity accurate detection and bubble dynamic control of the water-based paint coating in the stirring process are realized through the arrangement of the detection assembly and the cooperative work of the high-frequency ultrasonic probe, the micro torque sensor, the temperature compensation module and the microwave resonant cavity sensor.

The invention relates to the technical field of metasurface antennas, and provides a metasurface antenna parameter optimization method and system based on a convolutional neural network, and the method comprises the steps: collecting metasurface sample data; extracting a comprehensive electromagnetic feature set, and establishing a nonlinear mapping relation model; constructing an antenna performance comprehensive evaluation function, inputting the nonlinear mapping relation model and the antenna performance comprehensive evaluation function into a hybrid optimization algorithm to generate a parameter candidate set, and performing local optimization on the parameter candidate set by using a particle swarm algorithm to obtain a metasurface antenna parameter combination; and extracting electromagnetic characteristics of the metasurface antenna parameter combination, iteratively adjusting the height parameter of the resonant cavity until the height parameter meets a threshold value to obtain an electromagnetic simulation verification result, and feeding back the electromagnetic simulation verification result to the deep Q neural network model for parameter updating to obtain an optimal metasurface antenna parameter combination. According to the method, the optimization of antenna parameters is realized, the design efficiency of the metasurface antenna is improved, and the consumption of electromagnetic simulation calculation resources is reduced.

The invention relates to a continuous domain bound state metasurface microcavity structure based on symmetric protection and a design method. The structure comprises a substrate layer, a low-refractive-index material layer and a metasurface array structure which are sequentially stacked in the z-axis direction. The metasurface array structure is composed of a plurality of square block structures which are periodically arranged in the x-axis direction and the y-axis direction respectively, and the circle centers of round holes formed in the square block structures deviate relative to the centers of the square block structures. The structures of the square blocks and the positions, the sizes and the shapes of the round holes formed in the square blocks are the same; the metasurface array structure provided with the position offset circular holes is used for exciting dipole moment in the z-axis direction when plane waves polarized in the y-axis direction are normally incident, a bound state in a quasi-continuous domain is formed, and the bound state in the quasi-continuous domain is used for forming a resonant cavity with a high Q value. By breaking the internal rotational symmetry of the structure, an ideal BIC is converted into a quasi-BIC state with an extremely high Q value and limited service life, high-performance optical constraint is obtained, the emission performance of various low-dimensional gain material devices is improved, and the development of integrated and miniaturized optical devices is promoted.

The invention discloses a relativistic magnetron with angular slotting coupling output, the magnetron adopts a radial extraction rectangular output structure, the magnetron comprises an anode, a cathode and a magnet, the anode comprises a long anode block and a short anode block, the end part of the short anode block is provided with an angular coupling slot, the end part of the long anode block is provided with a reflection ring, and the end part of the short anode block is provided with an angular coupling slot. A high-frequency magnetic field is distributed in a fan-shaped cavity formed among the short anode block, the long anode block and the reflecting ring, and the high-frequency magnetic field is coupled into an external waveguide through the angular coupling slot to realize output; according to the relativistic magnetron disclosed by the invention, the adopted output structure is positioned at the end part of the anode block, and all the resonant cavities participate in microwave energy extraction, so that the angular periodic symmetry of the resonant cavities is hardly influenced by the output structure; and the coupling output structure and the output structure are axially separated from the resonant cavity area, the external space of the resonant cavity can be used for arranging magnets, the excitation space is small, and the realization of light and small size of the system is facilitated.

The invention belongs to the technical field of lasers, and discloses a 9-shaped hybrid mode-locked fiber laser, which comprises a pumping source, a 2 * 2 polarization-maintaining fiber coupler, a nonlinear amplification loop mirror loop connected with the first side of the polarization-maintaining fiber coupler, and a chirp fiber Bragg grating connected with the second side of the polarization-maintaining fiber coupler, the polarization maintaining optical fiber coupler is located at the connecting position of the nonlinear amplification annular mirror loop and a linear arm of the laser resonant cavity and used for coupling laser of the nonlinear amplification annular mirror loop to the linear arm, and after being reflected by the chirp fiber bragg grating, the laser is output to the nonlinear amplification annular mirror loop through the chirp fiber bragg grating. And then the laser on the linear arm is split into two beams of light which are transmitted clockwise and anticlockwise in a loop of the nonlinear amplification annular mirror. Two passive mode locking technologies are combined, rapid and stable mode locking can be achieved, the influence of the environment on the operation state is small, the signal-to-noise ratio of output laser pulses can be increased, and ultra-short pulses with narrower pulse width can be achieved.

The invention discloses a method for dynamically adjusting the frequency of a resonant cavity of a cyclotron and a tuning circuit, which are applied to the field of cyclotrons and solve the problem that when the frequency of the resonant cavity of the cyclotron is adjusted by judging the magnitude of reflection power, due to the fact that the reflection power can change in multiple stages in a single macro pulse period, the frequency of the resonant cavity of the cyclotron is adjusted. And an accurate numerical value is difficult to obtain through a simple amplitude sampling circuit. According to the invention, through determining the stable resonance time period of the resonant cavity, the phase difference between the incident power signal and the reflection power signal is sampled in the corresponding stable resonance time period of the resonant cavity, and the change value of the phase difference between the incident power signal and the reflection power signal is dynamically compared. According to the conversion relation between the phase difference change value and the frequency change value, the resonant cavity frequency change value is obtained through conversion, then the resonant cavity tuning device is adjusted to enable the resonant cavity frequency to be consistent with the frequency of the incident power signal all the time, and the dynamic tuning method of the resonant cavity is achieved.

The invention provides a tunable micro-nano laser based on a perovskite phase change material and a preparation method thereof, and belongs to the technical field of micro-nano photoelectron, the tunable micro-nano laser comprises a substrate, and a distributed Bragg reflector, a gain dielectric layer and a reflector which are sequentially arranged on the substrate from bottom to top; wherein the gain medium is a perovskite material with a crystal phase transition characteristic. The substrate is made of a material which is transparent or low in loss to pump light and emitted light; the distributed Bragg reflector is formed by alternately arranging high-refractive-index layers and low-refractive-index layers; the gain dielectric layer is a perovskite thin film layer with a crystal phase transition characteristic, and a perovskite material has a spectrum tuning function in the laser resonant cavity; the reflecting mirror is composed of a metal film. According to the invention, the perovskite material is used as a gain medium and a phase change material at the same time, the wide-range tuning of laser wavelength is realized, and the tuning range can reach several nanometers or even wider; the energy utilization efficiency can be improved, the stability is high, and the method is suitable for various types of tunable micro-nano laser applications.

The embodiment of the invention relates to a multi-junction VCSEL device, a VCSEL chip, a laser radar system and a light source of the laser radar system. The multi-junction VCSEL device comprises a substrate; the bottom reflecting mirror structure and the top reflecting mirror structure are stacked on the substrate; the bottom reflector structure and the top reflector structure define a resonant cavity structure used for generating standing waves. The resonant cavity structure comprises a plurality of active regions and a plurality of photoelectric limiting layers, each photoelectric limiting layer is located at one side, far away from the substrate, of the corresponding active region, and the photoelectric limiting layers are located at wave troughs of standing waves and are used for limiting a light emitting region of the multi-junction VCSEL device; and the light field regulation and control layers are arranged adjacent to the photoelectric limiting layer, the light field regulation and control layers are configured to divide the light field in the resonant cavity structure into at least three sections, and the intensity of each section of the light field is different.

The invention belongs to the technical field of water treatment and wastewater treatment, and provides an ultraviolet-ozone water disinfection device and method for cooling a lamp tube and synchronously generating ozone. The water disinfection device comprises an electrodeless ultraviolet disinfection unit, a synchronous cooling ozone generation unit, an ozone disinfection unit and a control unit, the electrodeless ultraviolet disinfection unit comprises a microwave generator, a waveguide, a microwave resonant cavity and a 185 / 254 nm dual-wavelength electrodeless ultraviolet lamp tube, and the synchronous cooling ozone generation unit comprises an air blower, an air inlet pipe, an air outlet pipe, a quartz sleeve and oxygen supply equipment. The ozone disinfection unit comprises a microporous aeration disc, and the control unit comprises a control box, a temperature sensor, an electromagnetic valve and an ozone concentration monitor. According to the invention, the dual-wavelength ultraviolet lamp tube is cooled by using large-flow air or air / oxygen mixed gas, and ozone is synchronously and efficiently generated, so that an ultraviolet-ozone combined water disinfection process is constructed, the promotion effect of ozone on water disinfection is fully utilized, the water disinfection effect is enhanced, and the applicability of the method to water bodies with different water qualities is improved.

The embodiment of the invention provides a gap waveguide cavity filtering power divider, and belongs to the technical field of filtering power dividers, the gap waveguide cavity filtering power divider comprises a device body, a first slot, at least two second slots and a cover plate, the device body is provided with an input waveguide interface and at least two output waveguide interfaces; the first slot is arranged on the device body, and the first slot is connected with the input waveguide interface; the at least two second open slots are formed in the device body, the second open slots are connected with the output waveguide interfaces in a one-to-one correspondence mode, the first open slots are connected with the second open slots respectively, and the opening directions of the first open slots and the second open slots are located on the same side of the device body; the cover plate is arranged on the device body, and is configured to define a first waveguide resonant cavity with the first slot and define a second waveguide resonant cavity with the second slot. The gap waveguide cavity filtering power divider provided by the embodiment of the invention is simple in structure, can reduce the insertion loss, and has better stop-band performance.

The invention provides a bulk acoustic wave resonator, a filter and a manufacturing method thereof. The bulk acoustic wave resonator comprises a bulk acoustic wave resonator carrier with a first resonant cavity, a first electrode layer, a piezoelectric layer, a second electrode layer and a bulk acoustic wave resonator cover body with a second resonant cavity and a heat dissipation layer, the heat dissipation layer is provided with at least one protrusion. The second electrode layer covers a first area of the first surface of the piezoelectric layer, and the first area is the surface, close to one side of the bulk acoustic resonator cover body, of the piezoelectric layer; the first electrode layer covers a second area of the second surface of the piezoelectric layer, and the second area is the surface, close to one side of the bulk acoustic resonator carrier, of the piezoelectric layer; the orthographic projection of the second area on the bulk acoustic wave resonator carrier is at least partially overlapped with the orthographic projection of the first area on the bulk acoustic wave resonator carrier. The heat dissipation layer with a special structure is arranged at a proper position, so that the heat dissipation area can be increased, the heat dissipation efficiency is improved, and the problems of poor heat dissipation effect, poor performance and the like of the bulk acoustic wave resonator are solved.

The invention discloses an ultra-low phase noise harmonic wave type four-core voltage-controlled oscillator. The ultra-low phase noise harmonic wave type four-core voltage-controlled oscillator is composed of a transformer T1, a transformer T2, a transformer T3, a transformer T4, a head oscillator HR1, a head oscillator HR2, a head oscillator HR3, a head oscillator HR4, a resistor R1, a resistor R2, a resistor R3, a resistor R4 and a plurality of decoupling capacitors Cecap. According to the voltage-controlled oscillator, noise is prevented from being converted into phase noise by means of second and third harmonic impedance broadening, inductance loss reduction, reduction of the sensitive time of the resonant cavity to the noise and the like, the phase noise generated by the voltage-controlled oscillator can be effectively reduced, and excellent noise performance is obtained.

The invention provides an active regulation and control device for a microwave resonant cavity based on Rydberg atoms. The microwave resonant cavity comprises a protective shell, an atomic gas chamber and a photoelectric detector, the active regulation and control device comprises a PID control module and piezoelectric ceramics, the PID control module is used for processing a received EIT transmission spectrum signal after generating a modulation signal to carry out atomic resonant frequency scanning on the atomic gas chamber, obtaining a target resonant frequency through a current feedback zero crossing point corresponding to an EIT transmission spectrum valley bottom value, and generating a deviation correction signal; and the piezoelectric ceramic is used for adjusting the length of a protective shell of the microwave resonant cavity according to the received correction signal, so that the atomic resonant frequency is locked as the target resonant frequency. The invention further provides an active regulation and control method for the microwave resonant cavity based on the Rydberg atoms. According to the invention, the resonant frequency of the microwave resonant cavity can be rectified in real time, and the optimal and most stable resonant mode of the local oscillation microwave frequency responding to atoms is kept.

The invention relates to the technical field of filters, in particular to a dual-mode resonator and a dual-mode filter. The dual-mode resonator comprises a metal cavity and a medium resonance body; the number of the metal cavities is two, and the two metal cavities are arranged on the two opposite sides of the medium resonance body respectively. The opening end of the metal cavity faces one end of the dielectric resonator; a conducting ring is arranged between the metal cavity and the dielectric resonant body, and the metal cavity and the conducting ring form a resonant cavity. The dual-mode filter comprises a first resonator and a second resonator; the first resonator is a dual-mode resonator; the first resonator and the second resonator are connected in series through a coupling structure. The conducting rings and the metal cavities are arranged on the two opposite sides of the dielectric resonance body, the conducting rings and the metal cavities form the resonance cavities, and the dual-mode resonance effect is achieved. The overall size is small, the space utilization rate is high, and production is easy.

The invention provides a quasi-continuous thulium-doped fiber laser capable of synchronously suppressing relaxation oscillation and self-pulse, relates to the technical field of fiber laser, and is used for simultaneously realizing suppression of a self-pulse effect and a relaxation oscillation peak. Comprising a continuous driving module, a pulse driving module, a semiconductor laser pumping source, a high-reflectivity fiber bragg grating, a low-reflectivity fiber bragg grating, a beam combiner, a thulium-doped gain fiber, a passive fiber, a cladding pumping stripper and a laser output port, the continuous pump light and the pulse pump light are respectively driven by the continuous driving module and the pulse driving module to output continuous pump light and pulse pump light; the high-reflectivity fiber bragg grating and the low-reflectivity fiber bragg grating form a resonant cavity structure, the thulium-doped gain fiber serves as a gain medium of the thulium-doped fiber laser and absorbs pump light to generate population inversion, laser oscillation is formed by combining the resonant cavity of the laser, relaxation oscillation suppression is achieved, and meanwhile longitudinal mode distribution of the laser is effectively disrupted.

A pulsed laser source device configured to a plurality of Fabry Perot resonant cavities. The pulsed laser source device provides a frequency, a wavelength, and a phase, each of which is matched with a plurality of laser beams configured, respectively, with the plurality of Fabry Perot resonant cavities to generate a high intensity beam for laser fusion.

The multifunctional acoustic device is formed by periodically arranging unit cells in the horizontal direction, and each unit cell comprises an upper frame body, a lower frame body and a vibration absorption sandwich layer located between the upper frame body and the lower frame body; the upper frame body is provided with a through hole; the vibration absorption sandwich layer comprises a central cantilever beam located at the transverse center position, a sandwich plate surrounding the periphery of the central cantilever beam and fixed between the upper frame body and the lower frame body, and vibrator mass blocks arranged above and below the central cantilever beam; the sandwich plate is connected with the central cantilever beam through a plurality of L-shaped beams; and the plurality of L-shaped beams surround the periphery of the central cantilever beam. The lattice sandwich structure is used as a basic frame, a local resonance system with a spring mass part is formed, a sub-wavelength elastic wave band gap frequency band is obtained, a low-frequency vibration reduction effect is generated, holes are formed in the upper frame body, the remaining part in the structure is used as an air spring, a Helmholtz resonant cavity is formed, and meanwhile low-frequency vibration reduction and broadband sound absorption are achieved.

The invention is suitable for the technical field of filters, and particularly relates to a manufacturing method of a linear gradient filter and the linear gradient filter. The manufacturing method of the linear gradient filter comprises the following steps that a glass wafer serves as a substrate, and a lower reflecting layer is plated on the surface of the glass wafer; wherein the lower reflecting layer is formed by alternately stacking a plurality of layers of low-refractive-index materials and a plurality of layers of high-refractive-index materials; coating a resonant cavity layer on one side, far away from the glass wafer, of the lower reflecting layer through a stepped coating process; plating a reflecting layer on one side, far away from the glass wafer, of the resonant cavity layer; and plating a long-wave-pass layer on one side, far away from the glass wafer, of the upper reflecting layer and in an area larger than the central wavelength to obtain the linear gradient filter. Compared with the prior art, the linear gradient filter provided by the invention is better in spectral resolution in a long wave band, smaller in energy difference of channels, excellent in wavelength selection performance and capable of being applied to spectrum applications such as a miniaturized infrared spectrometer and the like.

The invention discloses a CLLLC converter light load efficiency improvement and load expansion circuit based on variable resonant cavity regulation and control and a control method thereof. The circuit comprises a primary side full bridge, a variable resonant cavity, a secondary side rectifier and an output loop, the digital control unit detects the load in real time, and drives and switches the parallel or series capacitor branch to adjust the equivalent resonant capacitor; and the auxiliary buffer branch is used for soft start and sudden change buffer. According to the control method, capacitance is reduced during light load, efficiency is improved, capacitance is increased during heavy load, gain linearity is kept, the load range is widened, and smooth starting is achieved. The device is compact in structure and easy to control, the light load efficiency can be remarkably improved, the load application range is expanded, and the device has high reliability and good industrialization prospects.

The invention relates to an all-welded Ramsey microwave resonant cavity for a cold atom fountain clock, the all-welded Ramsey microwave resonant cavity comprises a Ramsey resonant cavity, a flying area waveguide, a cut-off waveguide and a microwave feed-in system, the flying area waveguide is arranged above the Ramsey resonant cavity, and a non-closed atom free flight channel is formed above the flying area waveguide; the flying area waveguide is connected with the cut-off waveguide through welding; the cut-off waveguide is integrally connected with the Ramsey resonant cavity; the microwave feed-in system is connected with the Ramsey resonant cavity through welding. According to the invention, a full-cavity integrated structure is realized through an integrated welding process, the hidden danger of microwave leakage is thoroughly eliminated, repeated debugging is not needed after welding is completed, the tuning period of the resonant cavity is shortened, and the resonant cavity is especially suitable for a low-temperature working environment scene. Meanwhile, through a non-closed atom free flight channel, a vacuum system can conveniently keep a high vacuum state in a flight area, so that the loss of cold atom cohesion is reduced, and an atom signal is relatively large.

The invention relates to the technical field of noise control, and discloses a combined noise reduction and sound absorption unit and a sound absorption board, sound absorption unit structures are periodically arranged and combined to form the sound absorption board with a large area, the sound absorption board is installed on an indoor wall or ceiling of a gas power plant, and indoor low-frequency broadband sound absorption and noise reduction are achieved. The sound absorption device comprises a first sound absorption assembly, the first sound absorption assembly comprises a first shell and a first micro-perforated plate arranged on the first shell, and the first micro-perforated plate is arranged on the first shell; the second sound absorption assembly comprises a second shell, a second micro-perforated plate arranged above the second shell and a second Helmholtz resonant cavity arranged below the first shell; the third sound absorption assembly comprises a third shell, a third micro-perforated plate arranged above the second shell and a plurality of third Helmholtz resonant cavities arranged below the first shell; the first sound absorption assembly, the second sound absorption assembly and the third sound absorption assembly are distributed in parallel.

The invention provides a near-infrared perovskite laser and a preparation method thereof. The near-infrared perovskite laser includes: a substrate; the perovskite gain dielectric layer is arranged on the substrate, a microcrystalline structure is formed on the perovskite gain dielectric layer, and the microcrystalline structure is a resonant cavity of the perovskite gain dielectric layer. The near-infrared perovskite laser provided by the invention can realize lasing under optical pumping at room temperature without adopting an additional resonant cavity, so that the device structure is greatly simplified, and the integration of the laser is improved; by regulating and controlling the components and the preparation process, the regulation of the lasing peak can be realized, the regulation precision is high, and the use requirements of multiple wavelengths can be met; a full-solution method can be adopted for preparation, the process is simple, and the cost is low.

The invention discloses a compact monolithic dual-wavelength distributed feedback laser device and a manufacturing method thereof, and belongs to the technical field of laser, the laser device is composed of a front part, a middle part and a rear part, and the middle part comprises two equivalent Pi phase shift chirp sampling gratings. The laser is based on a reconstruction equivalent chirp technology and has a tunable wavelength interval. A chirp sampling grating with two equivalent phase shifts is arranged in the laser, and the grating is composed of a front part, a middle part and a rear part. Phase matching is achieved through the microstructure quasi-phase matching technology, it is ensured that a laser resonant cavity reaches the phase matching condition at the phase shift position, and wide-range adjustment expanded from 59.50 GHz to 116.25 GHz can be effectively achieved by changing injection current. The invention has the advantages of accurate wavelength control, simple structure, low power consumption, high integration level and the like.

The invention discloses a double-resonant-cavity Q-switched laser, two resonant cavities which share a laser crystal and a Q-switched switch but have different cavity lengths are formed through a rotatable half-wave plate, and the polarization state of light is changed by rotating the half-wave plate, so that the light is converted between the two resonant cavities; under the condition that a gain medium or a device structure is not changed, half-wave plate rotation is provided, and pulse width conversion can be simply achieved.

The invention provides a pilot frequency combiner and a multi-system access platform, the pilot frequency combiner comprises a first substrate waveguide resonant cavity, the first substrate waveguide resonant cavity is provided with at least two input feed line ends, the at least two input feed line ends are used for introducing excitation signals of different information sources, a second substrate waveguide resonant cavity is stacked on the first substrate waveguide resonant cavity, and the second substrate waveguide resonant cavity is used for feeding excitation signals of different information sources. The second substrate waveguide resonant cavity is provided with an output feeder end, and the second substrate waveguide resonant cavity and the first substrate waveguide resonant cavity share a cavity wall; the common cavity wall is provided with at least two through coupling holes, and the coupling holes are communicated with the first substrate waveguide resonant cavity and the second substrate waveguide resonant cavity, so that excitation signals input by the at least two input feeder line ends are transmitted to the second substrate waveguide resonant cavity, and are output to an external antenna radiation end after being combined by the output feeder line end. According to the pilot frequency combiner provided by the invention, the isolation degree of multi-band signals is relatively good, the frequency expansibility is also good, and the design flexibility is relatively high.

The invention discloses a laser-induced Raman and fluorescence spectrum testing system, which relates to the technical field of spectrum testing and comprises a laser module, a harmonic separation mirror, a frequency doubling crystal, a first cavity mirror, a sample pool, a second cavity mirror and a spectrum detection unit, laser output by the laser module sequentially passes through the harmonic separation mirror, the frequency doubling crystal and the first cavity mirror; a high-transmittance film and a high-reflection film are respectively plated on two surfaces of the harmonic separation mirror, and the harmonic separation mirror reflects the laser with the required wavelength to the sample cell; the second cavity mirror is used for turning back the laser from the sample cell; a harmonic separation mirror, a first cavity mirror, a second focusing lens and a second cavity mirror form a double-beam-waist laser resonant cavity. The first cavity mirror and the second cavity mirror are spherical reflectors and are respectively plated with high-reflection films. The first cavity mirror and the first focusing lens are confocal, and the second cavity mirror and the focusing lens are confocal. And two beam waist focuses of the laser resonant cavity are respectively arranged at the positions of the frequency doubling crystal and the sample pool, so that the optimal frequency doubling efficiency and sample excitation efficiency are realized.

The invention provides a cavity adjusting method and device for a laser gyroscope resonant cavity, and the method comprises the following steps: building a light beam loop: horizontally placing a resonant cavity substrate on a supporting seat, and forming the light beam loop with two plane reflectors and two spherical reflectors; light beam introduction: starting a sweep frequency laser assembly, and enabling the reference light beam to enter a resonant cavity light path after passing through a light beam collimation system; light spot form monitoring and coarse adjustment: after a light beam emitted by the resonant cavity is collected by an image collector, the main control computer analyzes the light spot form and judges the imbalance state, evaluation information is fed back to the control system, the control system adjusts the inclination amount of the horizontal dimension and the pitching dimension of the light beam in the light beam collimation system according to the feedback information, and the light spot form is obtained. And the light spot is located at the center of the cavity mirror to finish coarse adjustment of the cavity. According to the method, coarse cavity adjustment can be completed without depending on a complex optical cavity technology, the cavity adjustment time is greatly shortened, the overall operation is simple, and the cavity adjustment efficiency is improved.

The invention provides an underwater broadband sound absorption metamaterial based on a Helmholtz resonant cavity and a design method thereof. The sound absorption metamaterial comprises a frame and a cover plate. A resonant cavity is arranged in the frame, one end of the frame is open, and the inner wall of the frame is coated with a damping material coating. The cover plate is connected to the open end of the frame to seal the frame, the cover plate is provided with a plurality of parallel necks vertically extending into the resonant cavity from the cover plate, the necks are in a hollow cylindrical shape, and sound waves enter from one end of each neck and enter the resonant cavity from the other end of each neck. The metamaterial is simple in structure; the sound absorption peak value at the frequency point below 1000Hz can reach more than 0.99, and the thickness is only 1 / 125-1 / 45 of the corresponding perfect sound absorption wavelength; in the range of 0-2000Hz, the sound absorption coefficient can reach more than 0.5, the effective sound absorption bandwidth can reach 127.9%, and the thickness of the metamaterial is within 1 / 45 of the wavelength, so that the metamaterial is an underwater low-frequency perfect sound absorption metamaterial with the deep sub-wavelength scale, has excellent low-frequency sound absorption performance, is wide in sound absorption frequency band, and can meet the low-frequency sound absorption requirement by being small in size.

The invention provides a distributed feedback laser with a double-layer grating structure, and relates to the technical field of lasers, the laser forms an InGaAlAs multi-quantum well active region, an upper sampling grating layer and a lower phase shift grating layer on an n-type InP substrate in sequence, the upper grating layer is designed based on a reconstruction equivalent chirp technology, and the lower phase shift grating layer is designed based on a reconstruction equivalent chirp technology. Two sections of asymmetric modulation areas with sampling periods linearly gradually changing in opposite directions are arranged in the axial direction of the resonant cavity, and the lower grating layer is a quarter-wave phase shift grating matched with the period of the upper seed grating. Through the synergistic effect of equivalent phase modulation and phase shift generated by the double-layer grating, the photon density distribution in the cavity can be improved, the longitudinal space hole burning effect can be weakened, the sensitivity to end face phase fluctuation can be reduced, high single-mode power and large modulation bandwidth can be realized in a wide temperature range, and the double-layer grating is suitable for a high-speed optical communication and coarse wavelength division multiplexing transmission system.

The invention provides a method for measuring the temperature gradient between an optical pressure standard FP resonant cavity and a temperature control copper cavity. Comprises: determining sample data; fitting the sample data to obtain a first frequency change coefficient of the frequency change quantity of the measurement cavity along with the temperature change and a second frequency change coefficient of the frequency change quantity of the reference cavity along with the temperature change; determining a plurality of first thermal expansion coefficients of the measurement cavity, and determining a plurality of second thermal expansion coefficients of the reference cavity; determining a plurality of first temperature-induced frequency change rates of the measurement cavity, and determining a plurality of second temperature-induced frequency change rates of the reference cavity; a first temperature gradient between the measuring cavity and the copper cavity is determined, and a second temperature gradient between the reference cavity and the copper cavity is determined. According to the scheme, fitting processing and calculation are performed on the sample data to obtain the temperature gradient of the FP resonant cavity and the copper cavity, so that the actual temperature of the gas in the FP resonant cavity is corrected according to the temperature gradient, and the accuracy of substituting the gas temperature into the incidence relation to measure the pressure is improved.