53 results about "Mode purity" patented technology

The invention discloses a circular waveguide TE01 mode mode converter, which comprises a rectangular waveguide power division structure unit, a mode conversion structure unit and a waveguide gradient structure unit, the rectangular waveguide power division structure unit is connected with the mode conversion structure unit, and the mode conversion structure unit is connected with the mode conversion structure unit The waveguide gradient structure unit is connected; when the rectangular waveguide power division structure unit includes a two-level branch waveguide structure, the electromagnetic wave TE10 mode first enters through the rectangular waveguide power division structure unit, and forms two channels of equal amplitude power division through the two first-level branch waveguide structures. TE10 modes with equal amplitude and phase, and then two channels of TE10 modes with equal amplitude and phase are divided into four channels of TE10 modes with equal amplitude and phase through the second-stage branch waveguide structure. The structure unit is converted, and after the conversion, the circular waveguide is obtained through the waveguide gradual change structure unit and the TE01 mode is output; the invention has the advantages of high mode purity, wide working bandwidth and easy processing.

The invention discloses a vortex beam self-adaptive pre-correction method and system based on GS algorithm. The vortex beam adaptive pre-correction system provided by the present invention is composed of a transmitting module, a receiving module, a data transmission module and a host. Based on the GS algorithm, the invention calculates the pre-correction phase screen by detecting the light intensity distribution of the Gaussian probe beam, and loads the pre-correction phase into the vortex beam of the transmitting module, thereby compensating the phase distortion caused by the inhomogeneity of the medium. Its principle can be understood as the "distortion" introduced by the pre-correction screen, and the "distortion" is "compensated" by the inhomogeneous medium. Experiments show that after the adaptive pre-correction system, the mode purity of the vortex beam has been significantly improved. The system structure of the invention is stable, easy to operate, and can realize real-time correction of phase distortion. At the same time, the wavefront analyzer and other devices are omitted in the system, which greatly reduces the cost.

The invention discloses an all-fiber scroll optical laser based on the orbital angular momentum mode resonance, which has a ring cavity structure, and comprises a narrow linewidth pump laser, an optical amplifier, an orbital angular momentum mode generator, a first polarization controller, an optical fiber ring, an optical fiber coupler, a second polarization controller and a scroll optical fiber.The orbital angular momentum mode generator converts the fundamental transverse mode of a single-mode optical fiber into the orbital angular momentum mode of a specific topological charge in a vortexoptical fiber. The fiber coupler can realize the directional coupling of the orbital angular momentum mode in one scroll fiber to the orbital angular momentum mode in another scroll fiber. Vortex optical fiber is a kind of optical fiber which supports orbital angular momentum mode stable transmission. Based on Brillouin nonlinear gain of vortex fiber in ring cavity, the resonant amplification oforbital angular momentum mode in cavity is realized and vortex laser is output. The invention adopts an all-optical fiber structure, has good output vortex laser stability, narrow line width and highorbital angular momentum mode purity.

The invention discloses a TE10 mode-to-TE20 mode broadband mode converter of a rectangular waveguide. The mode converter disclosed by the invention is characterized in that a linear slow transition structure is adopted, so that traveling wave state propagation can be implemented basically; waveguide boundary restriction conditions are used to control mode components in each segment of structure of the mode converter; the length of the second segment of T-shaped uniform transition waveguide is one fourth of an operating wavelength of center frequency, plays a role in impedance matching, can effectively restrain electromagnetic wave reflection caused by impedance mismatching, and can guarantee mode purity and high conversion efficiency of the mode converter to a certain extent; and meanwhile, optimal simulation is carried out to the lengths of the first segment and the third segment of the mode converter, so that good performance of the mode converter within a wide operating bandwidth is ensured.

The invention discloses a method for improving the mode purity and collection efficiency of a quantum-correlated photon pair. The method includes the following steps that a cascade structure sequentially composed of a nonlinear medium, a dispersion medium and a nonlinear medium is adopted; pumping is conducted on the cascade structure by using pulse laser, and the quantum-correlated photon pair is generated through the cascade spontaneous parametric process in the cascade structure; the periodic constructive interference and destructive interference of the quantum-correlated photon pair intensity at different wavelengths occur; the wavelengths corresponding to the constructive interference and the destructive interference can be subjected to tuning by changing the length of a dispersive medium; by using a filtering and collecting device, the quantum-correlated photon pair at the wavelengths corresponding to the constructive interference are collected and output. Based on the cascade structure composed of the nonlinear medium, the dispersion medium and the nonlinear medium sequentially, through the cascade spontaneous parametric process during pulse laser pumping, the mode purity and collection efficiency of the quantum-correlated photon pair is improved.

The invention provides a mode coupler with a wavelength-division multiplexing function, and a preparation method thereof. The coupler is manufactured by a plurality of optical fibers through a thermalisolation biconical taper and a fused biconical taper so as to realize the simultaneous multiplexing of multiple wavelengths and multiple modes. The thermal isolation fused biconical taper is performed on the optical fiber, the phase matching is realized between the fine-drawn optical fiber cladding, and the wavelength multiplexing is realized by adjusting stretching distance. The mode coupler issimple in operation and high in accuracy. The simultaneous multiplexing of the wavelength and mode is small in loss, high in mode purity, small in inter-mode cross-talking, large in work bandwidth, and stable in performance, and has extensive application prospect in the field of the high-order mode production, the mode conversion, the mode-division multiplexing, the wavelength-division multiplexing, the few-mode optical fiber laser and like fields.

The invention discloses a waveguide multi-path power distributor / synthesizer applicable to a millimeter wave frequency high end. A fan-shaped waveguide-based power distributor / synthesizer comprises a rectangular waveguide input port, a mode exciter, a 180-degree fan-shaped waveguide, a matching structure and a plurality of (n is greater than or equal to 2) rectangular waveguide output ports, wherein a TE10 mode in the rectangular waveguide excites a TE01 mode in the fan-shaped waveguide through a mode converter (a rectangular waveguide feed source or a Y-type waveguide feed source, the rectangular waveguide feed source is used when the fan angle is smaller than 90 degrees, and the Y-type waveguide feed source is used when the fan angle is between 90 degrees and 180 degrees), and achieves inhibition on other modes. Mode conversion and energy distribution of the fan-shaped waveguide to the TE10 modes of n rectangular waveguides are achieved through the multi-path power distributor; and a signal of each output port is equal in amplitude and phase. Compared with a round waveguide, the fan-shaped waveguide excitation mode is free of polarization degeneracy, higher in mode purity and higher in bandwidth; and compared with a TEM mode with a coaxial line, the fan-shaped waveguide excitation mode is smaller in loss, higher in power capacity, larger in circuit dimension and lower in processing cost and processing difficulty.

Disclosed are a fractal-based coherent optical fiber laser array and a generation system thereof. The coherent optical fiber laser array comprises N circles of light beams annularly arranged around the center of an array optical fiber from inside to outside, each circle of light beams comprises the same number of sub-light beams, and the sub-light beams in the same circle of light beams have the same optical parameters and are uniformly arranged in the angular direction. At least two or more continuous circles of light beams in the N circles of light beams form a fractal arrangement laser array; any two adjacent circles of light beams in the fractal arrangement laser array are separated from each other; and the beam waist radius, the beam caliber and the distance between the beam center and the center of the array optical fiber of each sub-beam in the circle of light beams close to the inner side are reduced in an equal ratio relative to the beam waist radius, the beam caliber and thedistance between the beam center and the center of the array optical fiber of each sub-beam in the circle of light beams close to the outer side. According to the invention, the array filling mode ofthe system can be expanded, and the optical parameter regulation and control capability of the laser array is improved, so that the synthesis efficiency and mode purity of structured light generated by the coherent optical fiber laser array are improved.

The invention provides a novel ultra wide band box type output window which is used for solving the problem that the existing box type output window is narrow in relative working band width. The ultra wide band box type output window comprises a rectangular waveguide, a round waveguide and a round medium window piece welded in the middle of the round waveguide in a sealing mode. Two ends of the round waveguide are connected the rectangular waveguide, and the rectangular waveguide is connected right in the middle of the section of the round waveguide. The novel ultra wide band box type output window is characterized in that the round waveguide is a similar O-shaped waveguide, the length is 0.25*sigma, and sigma is TE11 waveguide wavelength. The novel ultra wide band box type output window adopts the mixed mode transmission of TE11 and TM11, the working bandwidth is effectively expanded to 45%, and drifting of a center frequency point is effectively avoided. The similar O-shaped round waveguide effectively improves the transmission mode purity and further optimizes the transmission characteristic parameters of the box type output window. The box type output window is compact in structure and good in air tightness, has high power capacity, still has good transmission performance under certain machining errors and reduces machining difficulty.

The invention discloses a compact rectangular TE10-circular waveguide TM01 mode conversion device, and belongs to the technical field of microwave millimeter waves. The device comprises a rectangularwaveguide, a coaxial waveguide, a stepped coaxial waveguide and a stepped circular waveguide. A TE10 mode input from a standard rectangular waveguide is converted into a flat waveguide TE10 mode through a step. After that, the feed-in of the coaxial waveguide is realized through a side wall, and then a coaxial TEM mode is generated. The generated coaxial TEM mode is inputted into the subsequentlyconnected stepped coaxial waveguide. After entering the stepped coaxial waveguide, the TEM mode is subjected to the step-by-step transition of the stepped coaxial waveguide. After that, a circular waveguide TM01 mode is excited at the tail end of the TEM mode. The stepped circular waveguide structure is adopted at the output end of the device. In this way, on the premise that the output purity ofthe TM01 is ensured, the outer diameter of the coaxial waveguide is transited to an output port in a step-by-step mode. As a result, the coaxial waveguide is matched with the output port. The device can realize the output of the TM01 mode with the mode purity thereof larger than 99.5% in the BJ 100 full-waveguide bandwidth. Moreover, the length of a rectangular waveguide section is smaller than 95mm and the length of a circular waveguide section is smaller than 90 mm. An intermediate conversion structure adopts a non-supporting coarse coaxial transition design, and the device is small in insertion loss.

A polarized antenna for sending and receiving polarized radio frequency signals is disclosed which includes a dipole and a reflector plate. The dipole is formed as a single part including the radiating arms and feeding structures, thereby requiring minimum assembly. This dipole can be formed by molding conventional materials, such as copper, aluminum, and plastic, which can then be plated. The feeding structure through which the cable passes features a slotted aperture. The impedance of the dipole is based on the width of these apertures and the size of the cable conductor. By having a single-body construction, the dipole of the present invention provides, good impedance, low intermodulation distortion, good port-to-port isolation, and good pattern purity. <IMAGE>

The invention discloses a design method of an electromagnetic ultrasonic body wave transducer, relating to a design method of an electromagnetic ultrasonic body wave transducer, solving the problems of the weak excited body wave signal of the existing electromagnetic ultrasonic body wave transducer and more wave modes in the excited body wave signal. The design method comprises the main steps of: defining parameters required by modeling; establishing a geometric model of each part; setting material attributes; dividing a physical field solving region; modeling an emitting process; modeling a receiving process; partitioning a net of a finite element and solving the finite element; and finding out key parameters influencing induction voltage signal strength and sound wave mode purity in an electromagnetic ultrasonic body wave transducer coil 2, calculating a transducer parameter when the signal of the electromagnetic ultrasonic body wave transducer is strongest and the sound wave mode is optimal, and designing the electromagnetic ultrasonic body wave transducer. The design method has the characteristics that the simplicity is achieved in operation and the influence of the parameters of the electromagnetic ultrasonic body wave transducer to the induction voltage signal is easily analyzed. The design method can be widely applied to the design of the infinite element of any electromagnetic ultrasonic body wave transducer.

A light beam quality evaluation method based on vortex light beams generated by an optical fiber laser array comprises the following steps: generating vortex light beams with topological charges m based on the optical fiber laser array, and obtaining light intensity distribution of target plane synthetic vortex light beams at a distance z = L from an emitting surface; obtaining m-order orbital angular momentum mode purity in a circular domain of the target plane synthetic vortex light beam at the distance of z = L from the emitting surface; calculating a high-order light beam transmission factor; and determining that when the closer the high-order light beam transmission factor is to 1, the better the light beam quality of the vortex light beam with the topological charge number of m generated based on the fiber laser array is. The high-order light beam transmission factor can effectively describe the energy concentration degree of the synthesized vortex light beam, considers the modepurity of the synthesized vortex light beam, and can accurately evaluate the light beam quality of the synthesized vortex light beam.

The invention discloses a high-power overmode microwave elbow with controllable polarization, and belongs to the technical field of high-power microwave transmission devices. The external integral structure of the elbow is a 90-degree bending rectangular shell with two ends symmetrically extending outwards, and the internal cavity structure of the elbow comprises a 90-degree bending square waveguide and a second transition section, an elliptical waveguide, a first transition section and a circular waveguide which are communicated with the two ends of the 90-degree bending square waveguide in sequence respectively, wherein all joints of the internal cavity are in smooth transition, and two ends of the elbow are symmetrical. According to the high-power overmode microwave elbow, the amount of functional devices in a transmission system is reduced as much as possible under the precondition that application requirements of turning and polarization change for a high-power microwave transmission system are met, and the compact degree, transmission efficiency and mode purity of the system are improved. Moreover, the provided high-power elbow realizes the conversion of wave beam linear polarization and circular polarization states according to the application requirements while wave beam high-efficiency turning is guided.

The invention relates to a feed network-based low-frequency compact range feed source, which comprises an ultra-broadband orthogonal dipole antenna (1), a feed network (2), a reflective plate (3), an elliptic cylinder opening surface (4), a support structure (5), a flange plate (6) and a wave-absorbing material (7). The feed source constructs a relatively stable feed source radiation pattern by the elliptic opening surface with a specific length-width ratio, and achieves the characteristics of relatively large 3dB beam width of a horizontal direction pattern and relatively small 3dB beam width of a vertical direction pattern on two different incident polarizations. By introducing a broadband feed network, the length of a feed source horn is greatly reduced. Ultra-broadband oscillators are excited through the feed network; and <e>TE<11> and <o>TE<11> modes with higher mode purity are excited. A support post with a certain length is configured behind the horn antenna of the feed source; the opening surface of the horn antenna is far away from a feed source bracket; a wave-absorbing material with a specific size is added to the bottom part of the support post; and multiple radiation caused by a complicated metal structure of the feed source bracket is inhibited. The feed source mainly works at a low frequency; and the specific frequency range is (300MHz-500MHz).

The invention discloses a low-crosstalk and high-performance photon lantern type mode multiplexer optimization method, and belongs to the technical field of optical fiber communication. The low-crosstalk and high-performance photon lantern type mode multiplexer optimization method comprises the steps of: determining a photon lantern model and performing parameter scanning on the inner diameter ofa glass sleeve at the tail end of a photon lantern and a refractive index of the glass sleeve; analyzing and calculating a relationship between mode crosstalk and mode purity of the photon lantern; performing parameter scanning on the inner diameter of the glass sleeve at the tail end of the photon lantern and the refractive index of the glass sleeve again; and comprehensively analyzing the two parameter intervals, and determining the optimal inner diameter of the glass sleeve at the tail end of the photon lantern and the optimal refractive index of the glass sleeve, so that the optimal innerdiameter and the optimal refractive index meet the photon lantern with low crosstalk, high coupling efficiency and high mode purity simultaneously. By optimizing the inner diameter of the glass sleeveat the output tail end of the photon lantern and the refractive index of the glass sleeve, crosstalk among all modes of the photon lantern is reduced, and the mode purity and the coupling efficiencyof all the modes of the photon lantern are improved. The optimization method provided by the invention is compatible with an existing manufacturing process and can be realized in actual manufacturing.

The invention provides a mode purity optimization method and system for a vortex light beam generated through optical fiber laser coherent combination. The mode purity optimization method comprises the steps of: generating an array light beam with a topological charge number and a radial order number as expected values based on optical fiber laser coherent combination; and designing a spatial filtering module, outputting the array light beam after being subjected to spatial filtering by a spatial filtering module, and transmitting output laser to a far field to form a high-mode-purity vortex light beam with a topological charge number and a radial order number being expected values. According to the mode purity optimization method and the system, mode purification processing is carried out on the array light beam output by an optical fiber laser coherent combination system before emission, side lobes of vortex light beams generated based on optical fiber laser coherent combination and other airspace high-frequency noise components are filtered out through a spatial filtering mode, unnecessary energy loss is avoided, and the mode purity of the vortex light beam generated by the target plane is optimized under the condition that the synthesis efficiency is ensured.

The embodiment of the invention provides a gyrotron energy coupling window. The gyrotron energy coupling window comprises a window support cylinder, a window positioning flange adapter plate, a windowsealing cylinder and cooling water joints, wherein the window support cylinder is arranged at the bottom of the window sealing cylinder, the window positioning flange adapter plate is connected to the window positioning flange adapter plate in a sleeving mode, and the window support cylinder, the window sealing cylinder and the window positioning flange adapter plate are welded in an airtight mode; and at least two cooling water joints communicated with the interior of the window positioning flange adapter plate are further arranged on an outer side of the window positioning flange adapter plate. The gyrotron energy coupling window overcomes the problems that in the prior art, when a gyrotron works at high power and continuous waves, due to electron energy consumption, a large amount of heat energy is deposited on a cavity wall and an energy coupling window, the temperature of a window piece is too high, the thermal stress is too large, the output power, the mode purity and the stability of the gyrotron are reduced, and the gyrotron is scrapped due to the fact that the window piece is broken under severe conditions.

The invention discloses a narrow-linewidth frequency doubling vortex light laser, which comprises a pumping source, a pumping conversion device, a coupling lens group, a laser crystal, a temperature control device, a Brewster plate, a full-wave plate, a nonlinear optical crystal, a diaphragm and an output mirror which are sequentially arranged in the light propagation direction, wherein the pumping source outputs non-uniform pumping light after being coupled by the pumping conversion device and the coupling lens group; the left end face of the laser crystal and the output mirror form an optical resonant cavity, the Brewster plate is inserted into the cavity to polarize fundamental frequency vortex light, polarization selectivity loss is introduced by combining the full-wave plate and the nonlinear optical crystal to force the laser to operate in a single longitudinal mode, and the nonlinear optical crystal is used for frequency doubling of the vortex light in the cavity; and the outputmirror is slightly inclined. The narrow linewidth frequency doubling vortex light laser provided by the invention has the advantages of narrow linewidth, high mode purity, good light beam quality, simple structure, small size, convenience for system integration and the like.

The invention discloses a novel coaxial plugboard high-order mode exciter and belongs to the field of mode exciters. The novel coaxial plugboard high-order mode exciter comprises a coaxial TEM (transverse electric and magnetic field)-fan-shaped coaxial TE10 power divider, a fan-shaped coaxial TE10-coaxial TE61 mode converter, a coaxial TE61-circular waveguide TE61 mode converter and a circular waveguide TE61-circular waveguide TE62 mode converter. A mode conversion process includes: TEM-fan-shaped coaxial TE10-fan-shaped coaxial TE20-coaxial TE61-circular TE61-circular TE62. A wave beating coupling method of cosine metal walls is utilized to realize mode conversion from fan-shaped coaxial TE10 to coaxial TE61, small reflection, high conversion efficiency and large bandwidth are realized, and the novel coaxial plugboard high-order mode exciter is compact in integral structure, capable of inhibiting parasitic modes by every part, high in conversion efficiency and mode purity and promising in application prospect.

The invention discloses a Ka wave-band circular waveguide TE01 mode exciter. The exciter is formed by an orthogonal waveguide, a rectangular step waveguide, a uniform square waveguide, a bone-shaped step waveguide and a uniform circular waveguide. One port of the orthogonal waveguide forms an input port of the mode exciter. The other port of the orthogonal waveguide is connected to the port of the rectangular step waveguide, wherein the port of the rectangular step waveguide has a small size. The port of the rectangular step waveguide is connected to one port of the uniform square waveguide, wherein the port of the rectangular step waveguide has a large size. The other port of the uniform square waveguide is connected to the port of the bone-shaped step waveguide, wherein the port of the bone-shaped step waveguide has a small size. The port of the bone-shaped step waveguide is connected to one port of the uniform circular waveguide, wherein the port of the bone-shaped step waveguide has a large size. The other port of the uniform circular waveguide forms an output port of the mode exciter. The exciter possesses characteristics that conversion efficiency is high; a mode purity is high; the structure is compact; and easy processing and a broadband are achieved.

The invention relates to a vortex light mode detection method based on a three-step phase shift method. Vortex light is a special light field with a spiral wave front, and the three-step phase shift method is a phase measurement method. The method comprises the steps of firstly, preparing a hologram of target vortex light; superposing three beams of one-dimensional gratings with phase shifts of 0,0.5 pi and pi on the basis to obtain three new holograms; sequentially recording the intensity distribution of the initial vortex light and the interference distribution of the three beams of phase shift vortex light on the same plane through a spatial light modulator method, and obtaining the complex amplitude distribution of the vortex light in combination with a phase formula; and secondly, carrying out convolution operation on the complex amplitude distribution and standard vortex light bases with different topological charges through a computer to acquire the mode degree and the mode purity of the target vortex light and achieve mode analysis of the target vortex light. The method provided by the invention is simple in optical path and high in flexibility, belongs to the field of vortex light detection, and can be applied to mode detection of complex vortex light.

The invention discloses a low-crosstalk, high-performance photon lantern-type mode multiplexer optimization method, which belongs to the technical field of optical fiber communication. The photon lantern model is determined, and the parameters of the inner diameter of the glass casing at the tail end of the photon lantern and the refractive index of the glass casing are determined. Scanning; analyze and calculate the relationship between the crosstalk of the photon lantern mode and the mode purity; perform a parameter scan on the inner diameter of the glass sleeve at the end of the photon lantern and the refractive index of the glass sleeve again; comprehensively analyze the above two parameter intervals to determine the optimal photon lantern The inner diameter of the glass tube at the end and the refractive index of the glass tube make it satisfy the photonic lantern with low crosstalk, high coupling efficiency and high mode purity at the same time. By optimizing the inner diameter of the glass sleeve at the output end of the photon lantern and the refractive index of the glass sleeve, the crosstalk between the various modes of the photon lantern is reduced, and the mode purity and coupling efficiency of each mode of the photon lantern are improved. The optimization method provided by the invention is compatible with the existing manufacturing process and can be realized in actual manufacturing.

The invention discloses a mode converter from a rectangular waveguide TE10 mode to a circular waveguide rotating TE11 mode. The mode converter comprises a coplanar magic T structure, a four-path synthesizer, a plurality of bent waveguides, two 3dB couplers and four 90-degree waveguide twisters. Two output ports of the coplanar magic T structure are respectively bent by 180 degrees through the corresponding bent waveguides and are connected to the input ends of the corresponding 3dB couplers; the two 3dB couplers are in central symmetry about the central axis of the four-path synthesizer, and the straight-through ends and the coupling ends of the 3dB couplers are connected to the input ends of the four-path synthesizer through the corresponding 90-degree waveguide twisters respectively. The two 90-degree waveguide twisters connected with the same 3dB coupler are in 180-degree rotational symmetry about the central axis of the 3dB coupler along the electromagnetic signal transmission direction; and the two pairs of 90-degree waveguide twisters connected with the different 3dB couplers are in plane symmetry about the symmetry plane of the four-path synthesizer. The mode converter has the advantages of simplicity and convenience in design, high mode purity, easiness in processing and manufacturing and high conversion efficiency.

The invention discloses a cascade type long-time cycle fiber grating filter ejector, wherein the filter ejector is a segment of few-mode fiber based on multi-cascade long-time cycle fiber grating; write in multi-segment long-time cycle fiber grating in a fiber core; the few-mode fiber comprises the fiber core and a cladding; the outside of the fiber is made of a low-index material; the coating of the few-mode fiber is made of a high-index material. The low-index material is a kind of material that has a refractive index lower than the cladding; each segment of long-time cycle fiber grating satisfies the phase match condition between a fiber-based mode (LP01) and a cladding mode coupling under different wavelength. The long-time cycle fiber grating structure makes the fiber-based mode and the cladding mode couple, and other high order modes have no coupling or the energy can be transferred back after coupling, thereby realizing the purpose of filtering the fundamental mode and reserving the high order modes. According to the invention, work band width can be effectively increased; a mode reuse system using few-mode fiber communication can be used to improve mode purity and reduce mode crosstalk.

The invention discloses an axial cascade relativistic magnetron based on frequency locking and phase locking of a full-cavity coupling structure, and belongs to the technical field of microwaves. The magnetron comprises a plurality of high-frequency systems which have the same structure and are axially cascaded; an annular columnar isolation structure is arranged between the adjacent high-frequency systems; a full-cavity coupling structure shell is arranged on the outer side of the anode shell; an annular columnar cavity between the full-cavity coupling structure shell and the anode shell is divided into four fan-shaped waveguide cavities with the same size through four fan-shaped insertion pieces; linear transition structures are arranged at two ends of the fan-shaped waveguide cavity, and the other ends of the linear transition structures are connected with the rectangular waveguide; energy in the resonant cavity is coupled to the four fan-shaped waveguide cavities through the coupling gaps and finally output from the eight rectangular waveguides. Electromagnetic fields in the adjacent high-frequency system resonant cavities are coupled through the full-cavity coupling structures, and the cascade phase locking effect is enhanced; and through full-cavity extraction and multi-port axial output, the radial space compactness is improved, and the mode purity and the working stability are also improved.

The invention discloses a photonic crystal fiber capable of actively filtering a high-order radial mode. The photonic crystal fiber comprises a first air circular hole, a high-refractive-index ring, a second air circular hole, a third air circular hole, a fourth air circular hole and a fiber cladding which are sequentially arranged from inside to outside, the first air circular hole is located in the center of the fiber cross section; the number of the second air round holes, the third air round holes and the fourth air round holes in each layer is the same, and the air holes are nested from small to large. According to the invention, 226 OAM modes are supported at the position of the working wavelength of 1.5 microns, 208 OAM modes are supported at the position of the working wavelength of 1.55 microns, and the capacity of a communication system is greatly increased; by increasing the radius of the cladding and keeping the thickness of the transmission layer unchanged, the high-order radial mode can be effectively inhibited, and the influence on the OAM mode purity can be reduced; the method has the advantages of inhibiting inter-mode crosstalk, being low in nonlinear coefficient and the like, is suitable for a high-capacity OAM mode division multiplexing communication system, and has good application value.

The invention discloses a vortex light beam wavefront phase correction method based on a Gerchberg-Saxton algorithm. The method comprises the following steps: firstly, constructing an adaptive optical system transmission model based on a vortex beam, and simulating phase disturbance caused by atmospheric turbulence to obtain field intensity distribution of a distorted transmission beam and a detection beam in a time domain; and then taking the distorted detection light beam as the input of a vortex light beam wavefront phase correction method based on a Gerchberg-Saxton algorithm, iteratively calculating a random phase similar to atmospheric turbulence, and further obtaining a corrected phase mask. A spatial light modulator is loaded on a distorted OAM light beam, so that OAM light beam inter-mode crosstalk caused by atmospheric turbulence is relieved. The wavefront phase correction method is good in correction effect and can effectively improve the mode purity of transmitted LG light beams.