186 results about "Refractive index modulation" patented technology

The invention discloses a holographic sight based on a volume Bragg grating, and belongs to the field of holographic optics. The holographic sight comprises a sight housing, a semiconductor laser, a wave-locking element, a beam expander, an off-axis parabolic reflector and a holographic grating. The wave-locking element is a reflective volume Bragg grating, and the holographic grating is a transmissive volume Bragg grating. Both have excellent selectivity for the wavelength and incident angle of light. At the same time, both are made of photothermorefractive glass, which is less affected by the external temperature and can effectively reduce the deviation of the output wavelength, thereby reducing the deviation of the holographic grating mark image and increasing the accuracy and stability of the holographic sight. The photothermorefractive glass has a high refractive index modulation degree, which achieves a higher holographic diffraction efficiency, making the displayed holographic image brighter and more recognizable. In addition, the components of the beam expander and the off-axis parabolic reflector are used to shorten the optical path and reduce the overall structural size of the sight.

The invention discloses a photopolymer type holographic recording medium and a preparation method and application thereof.The photopolymer type holographic recording medium comprises a writing monomer, film-forming resin, a photosensitive initiation combination agent and a catalyst, the writing monomer comprises nanoparticles and a polymerizable monomer, and the film-forming resin is prepared from the nanoparticles and the polymerizable monomer; the refractive index of the polymerizable monomer is smaller than that of the nanoparticles, and the difference between the refractive index of the nanoparticles and the refractive index of the polymerizable monomer is larger than 0.5. The film-forming resin includes a polyol compound and an isocyanate-based compound. The catalyst is used for catalyzing a polyol compound and an isocyanate compound to react to form a film. The photosensitive initiation combination agent is used for sensing light and inducing polymerization of the polymerizable monomer. According to the photopolymer type holographic recording medium disclosed by the invention, after exposure, the polymerizable monomers located in the bright area and the nanoparticles extruded to the dark area have relatively large refractive index difference, so that the refractive index modulation degree of the recording grating can be improved; the film-forming resin provides effective support for the nanoparticles, and the nanoparticles are not agglomerated.

The invention provides a chirped fiber bragg grating manufacturing method based on asymmetric apodization, which is applied to the technical field of fiber bragg grating preparation, and the method comprises the steps: determining a target asymmetric envelope function corresponding to a target chirped fiber bragg grating based on the parameter requirements of the target chirped fiber bragg grating; adjusting the pulse number of laser output by the femtosecond laser based on the target asymmetric envelope function; laser is controlled to irradiate a target area in the optical fiber, a target chirped fiber grating is formed, and the pulse number of the laser changes according to a target asymmetric envelope function and is gradually reduced from the center of the grating to the two ends. According to the method, the femtosecond laser pulse number is adjusted based on the asymmetric envelope function, so that the distribution gradient of refractive index modulation is finely adjusted, better reflection spectrum and time delay characteristics are obtained, the high-precision requirements for laser energy adjustment and displacement platform movement are reduced, and the apodization machining precision of the chirped fiber grating is effectively improved.

The invention discloses a fiber bragg grating femtosecond laser direct writing system and method based on light field regulation and control. The system comprises a femtosecond laser source, a polarization control module, a light beam expanding module, a light field modulation module, a 4f filtering imaging module, an oil immersed objective lens, a precision positioning and optical fiber clamping module, an observation module and a computer control module. The method comprises the following steps: firstly, fixing a standard single-mode optical fiber to be processed on a three-dimensional precision displacement platform; then programmable wavefront modulation is carried out on the femtosecond laser through a light field modulation module, and a multi-focus array is generated; then focusing the multi-focus array into the fiber core through an oil-immersed objective lens to realize one-time parallel inscribing of a plurality of refractive index modulation RIM regions; and finally, the computer control module controls the three-dimensional precision displacement platform to move at a constant speed in the axial direction of the optical fiber, and parallel integrated inscribing of a plurality of FBG structures is completed. According to the invention, the inscribing precision and inscribing efficiency of fiber bragg grating femtosecond laser direct writing are improved.

The invention discloses a preparation method of a polymer dispersed liquid crystal holographic grating with s polarization high diffraction characteristics, and belongs to the technical field of holographic optics. Raw materials comprise 60-90% of a thiol-ene monomer, 10-40% of liquid crystals, a photoinitiator accounting for 1.25% of the mass of the monomer, and a coinitiator accounting for 1.56% of the mass of the monomer. Light with the wavelength of 532 nm and the light intensity of 5-30 mW / cm < 2 > is used for carrying out double-interference photoetching to generate photochemical reaction so as to generate the polymer grating film, and the light is s polarized light. Under the optimal recording condition, delta n under s polarization can reach 1.93 * 10, and delta n under p polarization can reach 1.21 * 10. In combination with morphology analysis, it is found that refractive index modulation strongly depends on the proportion of a liquid crystal-rich phase to a polymer-rich phase in the grating. It is proved that the size of liquid crystal microdroplets formed by holographic recording is larger due to low recording intensity, and therefore the threshold driving voltage of the HPDLC grating is reduced.

The invention provides an acrylate monomer with a high refractive index and a preparation method and application thereof, the acrylate monomer has a structure as shown in a formula G1, G2 or G3, the refractive index of the acrylate monomer is 1.75 or above, so that a holographic recording medium has higher sensitivity and higher diffraction efficiency, and the holographic recording medium can be applied to the field of holographic recording. The holographic recording medium is used for a holographic grating, so that the holographic grating has high diffraction efficiency and high refractive index modulation degree.

The invention discloses a thiophene monomer, a holographic recording medium, a preparation method and a related device, the structural general formula of the thiophene monomer is shown in the specification, the refractive index of the monomer is larger than 1.8 and smaller than 1.9, the diffraction efficiency can be remarkably improved, the thiophene monomer is applied to preparation of a photopolymer type holographic recording medium, and the photopolymer type holographic recording medium with the sensitivity larger than 100 cm / mJ can be obtained. According to the holographic recording medium, the diffraction efficiency of the recording grating is larger than 95%, the refractive index modulation degree is larger than 0.1, and the shrinkage rate is lower than 1%, and further, the holographic recording medium can be used for preparing a volume holographic grating, a holographic optical element and an optical device.

The invention discloses a grating waveguide device and waveguide system based on a polarization volume grating technology, and belongs to the technical field of augmented reality display. The device comprises a waveguide substrate and a grating structure, the grating structure adopts a liquid crystal material to form a periodic refractive index modulated PVG through a light-induced orientation and self-assembly process, the polarization state of a light beam can be selectively regulated and controlled, and the rainbow pattern phenomenon caused by ambient light diffraction is inhibited. The efficient diffraction and total internal reflection transmission of the multi-wavelength light beam are realized by optimizing the grating period, the Bragg inclination angle and the waveguide matrix parameters and combining Zemax simulation to optimize the light beam propagation path. The waveguide system can be matched with AR glasses, a head-mounted display and other devices, the intensity of the rainbow lines is remarkably reduced under the complex ambient light condition, and high-definition and distortion-free visual experience is provided.

The invention relates to the technical field of optical fiber device manufacturing, and discloses a femtosecond laser inscribing low-polarization-dependent-loss optical fiber grating method and system, and the method comprises the steps: firstly, synthesizing an initial phase comprising a flat-topped beam phase, an astigmatism correction phase and a defocus phase, and loading the initial phase to a spatial light phase modulator; therefore, a preset circular flat-top focusing light spot is generated. Secondly, collecting a three-dimensional light field image sequence of a focusing light spot in a low-power detection mode, reconstructing light intensity distribution, extracting effective focal depth and ovality characteristic parameters, dynamically optimizing a phase through a closed-loop feedback mechanism until light field characteristics reach a preset target, and obtaining an optimized phase; and finally, loading an optimized phase in a high-power inscribing mode, and controlling the axial scanning of the optical fiber to inscribe the grating. Accurate active regulation and control of the three-dimensional shape of the focused light field and closed-loop self-optimization of process parameters are realized, birefringence caused by anisotropy of a refractive index modulation area is inhibited from a physical mechanism, and polarization dependent loss of the fiber bragg grating is fundamentally reduced.

The invention provides a polymerizable monomer with the refractive index larger than 1.7 and a preparation method and application thereof.The polymerizable monomer has the structure shown in the formula G1 or G2 or G3 or G4 or G5 or G6, the refractive index of the polymerizable monomer is 1.7 or above, and therefore a holographic recording medium has various excellent characteristics such as high sensitivity, high diffraction efficiency and high refractive index modulation degree; the holographic recording medium is used for a holographic grating, so that the holographic grating has high diffraction efficiency and high refractive index modulation degree.

The invention discloses a 4, 4 '-bis (omega-alkenyl thioether) diphenyl sulfide monomer and a preparation method, the structural general formula of the 4, 4'-bis (omega-alkenyl thioether) diphenyl sulfide monomer is shown in the specification, n represents the number of methylene and is a positive integer, n = 1-10, the refractive index of a polymer obtained after the monomer and 4 '4-dimercapto diphenyl sulfide are polymerized is larger than 1.65 and smaller than 1.8, diffraction efficiency is remarkably improved, the preparation method is easy to operate, and the preparation method is suitable for industrial production. The invention further provides a photopolymer type holographic recording medium containing the monomer and a preparation method of the photopolymer type holographic recording medium, the sensitivity of the holographic recording medium is larger than 100 cm / mJ, the diffraction efficiency of a recording grating is larger than 95%, the refractive index modulation degree is larger than 0.1, the shrinkage rate is lower than 1%, and the preparation method is simple, controllable and suitable for industrial production. The invention also provides a volume holographic grating containing the holographic recording medium, a holographic optical element and an optical device.

The present invention belongs to the technical field of optical fiber sensing. Provided are a ring-type small-period long-period fiber grating sensor, and a preparation method therefor and the application thereof. A ring-type small-period long-period fiber grating provided in the present invention matches the cross-sectional shape of an optical fiber, and rings can more effectively expand the area of each refractive index modulation region in the cross section of the optical fiber, such that the ring-type grating has large refractive index modulation regions in both the axial direction and longitudinal direction of the optical fiber, and the intensities of a Bragg resonance peak and a cladding mode resonance peak can thus be simultaneously enhanced. Therefore, the Bragg resonance peak and the cladding mode resonance peak can be simultaneously observed in a transmission spectrum of the ring-type grating, such that simultaneous measurement of an ambient refractive index and temperature can be realized, and there is no longer a need to observe a reflection peak, thereby simplifying multi-parameter sensing test steps of the small-period long-period fiber grating.

The invention provides a preparation method of a reflective volume Bragg grating optical filter with a high signal-to-noise ratio. Through the light intensity modulation plate, the refractive index modulation degree presents any function distribution with a high center and gradually reduced two sides in the thickness direction of the volume grating optical filter, so that the distribution of the refractive index modulation degree is optimized, the signal-to-noise ratio is remarkably improved, the inter-channel crosstalk is effectively inhibited, the signal-to-noise ratio exceeds 60dB in the spectral range of 3nm, and the volume grating optical filter has a wide application prospect. And important application values are shown in the fields of optical communication, spectral filtering, optical display and the like.

The invention discloses a dithiocarbamate monomer, a holographic recording medium, a preparation method and a related device, the structural general formula of the monomer is as shown in G1 and G2, R1 represents any one of hydrogen, halogen and C1-C4 alkyl, R3 represents any one of hydrogen, halogen and C1-C4 alkyl, A1 represents C1-C4 alkyl, A2 represents hydrogen or methyl, n is a positive integer, and n = 1-10. The dithiocarbamate monomer provided by the invention has high refractive index, and the holographic recording medium with high sensitivity, high diffraction efficiency and high refractive index modulation degree can be obtained by applying the dithiocarbamate monomer to preparation of the photopolymer holographic recording medium; holographic recording media can be used to prepare volume holographic gratings, holographic optical elements, and optical devices.

The invention provides a photopolymer system, a grating device containing a chirp structure and a preparation method of the grating device. Visible light and ultraviolet light dual initiators and azobenzene polymerizable acrylate monomers are introduced into the photopolymer system; by utilizing the characteristics that an acrylate group can be used as a writing monomer to participate in a copolymerization process and an azobenzene group can be subjected to continuous photoisomerization during holographic exposure, a visible light photoinitiator and an ultraviolet light initiator driving system are reacted and cross-linked in sequence; a chirp structure is induced to be generated in the formed volume holographic grating while the photopolymer system records interference fringes, so that grating period change caused by material shrinkage is effectively compensated, the angle response bandwidth of the grating is remarkably widened, the requirement for refractive index modulation of the photopolymer system is reduced, and the optical grating has a wide application prospect. According to the invention, the selection range of the photopolymer system is widened, the overall aging resistance of the material system is improved, and the service life of the grating device is prolonged.

The invention discloses an acrylate monomer and a preparation method thereof, a photopolymer composition and a volume holographic grating and a preparation method thereof, the acrylate monomer provided by the invention is simple in structure and rich in expandable structure, so that the synthesis steps are simple and convenient, the cost is reduced, a relatively high refractive index of the monomer is realized on the basis of introduction of more sulfur atoms into the monomer, and the volume holographic grating has a good application prospect. In the subsequent photopolymerization process, the difference between the refractive index of the generated polymer and the refractive index of the common matrix is larger, so that the preparation of the holographic grating with high-refractive-index modulation degree can be realized.

The invention relates to a quaii-BIC chiral metasurface device based on refractive index modulation and a preparation method and application thereof.The chiral metasurface device comprises a plurality of sub-wavelength structure partitions which are sequentially arranged along the X axis, and every two adjacent sub-wavelength structure partitions are rotationally and symmetrically arranged relative to the Y axis; a sub-wavelength structure in the sub-wavelength structure partition comprises at least two optical dielectric layers which are stacked along the Z axis, at least one sub-wavelength structure in the sub-wavelength structure partition is obliquely arranged relative to the Y axis, and a refractive index difference exists between the at least two optical dielectric layers, so that the metasurface device realizes intrinsic chirality. The metasurface device realizes tunable strong intrinsic chirality at multiple wavelengths, and the preparation method has the advantages that the processing difficulty is low, the thickness of the optical dielectric layer is low, the thickness and the inclination angle of the optical dielectric layer do not need to be accurately controlled, the lift-off process is compatible, and high-precision large-area metasurface device preparation can be realized.

The invention discloses a chirp grating design method and device, equipment and a storage medium, and relates to the technical field of optical fibers, and the disclosed chirp grating design method comprises the steps: analyzing a preset target spectrum function to obtain a target grating structure parameter; layering the initial grating into a plurality of sub-grating regions with uniform periods based on the target grating structure parameters, and establishing a layered transmission matrix model; determining a refractive index modulation depth range of each sub-gate region according to the layered transmission matrix model; and performing iterative optimization on grating structure parameters of the initial grating according to the layered transmission matrix model, the target spectral function, the refractive index modulation depth range and a preset error function to obtain a target grating. The performance of the chirp grating can be optimized.

The invention relates to the technical field of display, in particular to a volume holographic grating raw material system, a volume holographic grating and a preparation method of the volume holographic grating. The volume holographic grating raw material system comprises a photopolymerizable monomer, a liquid crystal, an organic additive and a photoinitiator, the structural formula of the organic additive is A-B, A is a photopolymerizable monomer affinity group, and B is a liquid crystal affinity group. On the basis of a raw material system composed of a photopolymerizable monomer, liquid crystal and a photoinitiator, a novel organic additive is introduced, and the organic additive is beneficial to good phase separation of a PDLC system and increase of the refractive index difference between a bright area and a dark area, so that the refractive index modulation degree of the volume holographic grating is improved, and the display application in the AR / VR field is met.

The invention discloses a dual-channel all-optical switch device based on two-dimensional Bi2O2Se and a design method of the dual-channel all-optical switch device. The core of the device is an optical interference structure formed by two-dimensional Bi2O2Se nanosheets arranged on a mica substrate. The same group of transient absorption spectrum data is obtained through a pumping-detection system, and is decoupled into two independent switching channels: a channel I is based on carrier relaxation dynamics, and switching is realized by detecting a ground state bleaching signal at a wave band of 560-670 nm; the channel II is based on refractive index modulation caused by a Kramers-Kronig relationship, and realizes switching by analyzing interference fringe signals formed by probe light between the upper surface of the nanosheet and the lower surface of the mica substrate. The invention also provides a quantitative design method of the device, and the method achieves the fitting of an interference fringe signal through building a transient refractive index model, and precisely solves the relative refractive index change dynamics. The dual-channel device realizes picosecond-level ultrafast response (the channel I is 38.1 ps, and the channel II is 65.8 ps) and low-power-consumption operation (mJ / cm < 2 > magnitude), and the channel switch ratios respectively reach 1.74 and 1.93.

The invention provides a controllable processing method for a photoetching single crystal optical fiber multi-ring cladding based on femtosecond laser and a multi-ring mask plate. The technical bottlenecks that in the prior art, the processing efficiency is low, the processing length is limited, and the structural precision is insufficient are effectively solved. The core of the method is that high-energy ultrashort pulse laser generated by a femtosecond laser is combined with a spatial light modulation technology of a programmable multi-ring mask plate to generate multi-layer femtosecond laser spots in specific annular distribution. Micron-scale focusing of multi-ring femtosecond laser beams can be achieved through a precisely-designed optical system, and precise spatial selective refractive index modulation is achieved on the cross section of the single-crystal optical fiber. Compared with a single-crystal optical fiber with a single-multi-ring annular cladding structure, the multi-ring annular cladding structure can further enhance the suppression capability of the multi-ring annular cladding structure on a high-order mode, realizes flexible regulation and control of a light wave transmission mode field, effectively reduces the influence of a multi-mode interference problem in the single-crystal optical fiber on the signal quality, and improves the signal quality. The stability of signal transmission and the quality of sensing signals are improved, and the application requirements of different scenes are met.

The invention provides a femtosecond laser inscribing system used for manufacturing an apodized fiber bragg grating, which is applied to the technical field of fiber bragg grating preparation, and comprises a femtosecond laser used for outputting laser, the laser is used for adjusting the refractive index of an optical fiber, and the number of laser pulses corresponding to each refractive index modulation point in the optical fiber is different; wherein the laser pulse number is determined based on a preset apodization envelope function; the adjusting module is used for adjusting the propagation direction and the laser parameters of the output laser; the displacement platform is used for moving the optical fiber to enable the laser to accurately irradiate a corresponding refractive index modulation point in the optical fiber so as to modulate the refractive index and obtain an apodized fiber grating; and the control module is used for determining the number of laser pulses corresponding to each refractive index modulation point based on a preset apodization envelope function, adjusting the laser output parameters of the femtosecond laser and controlling the movement parameters of the displacement platform.

The invention provides a polymer composition, a polymer film material, a holographic grating, a preparation method of the holographic grating, an optical film material and display equipment. The polymer composition comprises a first polymerizable monomer, a second polymerizable monomer and a film-forming resin. The first polymerizable monomer is a non-liquid crystal monomer; the second polymerizable monomer is a liquid crystal monomer, the second polymerizable monomer comprises an active group, and the second polymerizable monomer can be subjected to a copolymerization reaction with the first polymerizable monomer through the active group under illumination. The refractive index modulation degree of the optical film material can be improved by using the polymer composition.

The invention relates to the technical field of holographic gratings, in particular to a holographic grating with a high refractive index modulation degree and a preparation method thereof, and the preparation method comprises the steps: coating a grating substrate with a precursor material to form a coating, and preparing a holographic dry plate with a holographic material layer; performing interference exposure on the holographic plate to obtain a semi-finished grating; bleaching the semi-finished product grating, and soaking the semi-finished product grating in an extraction liquid to obtain a grating precursor with a groove; and filling the groove with a fluorine-containing polymer dopant to obtain the holographic grating. The part, corresponding to the exposure bright area, of the grating precursor with the grooves is a polymer with a high refractive index, the inert body in the exposure dark area is removed, air is left, the grooves are formed in the surface of the grating, the appearance of the grooves fluctuates, the grooves are filled with low-refractive-index substances, and finally the high-refractive-index substances in the bright area are formed. The dark area is of a grating structure made of a low-refractive-index material; by adopting a two-step processing method, the holographic grating without light leakage in the reverse direction can be manufactured.

A dynamically tunable optical mirror named as a resonant cavity switching (RCS) device and a refractive index modulating (RIM) device are disclosed. The RCS device is comprising a nanoporous piezoelectric III-nitride material layer, such as GaN, AlN, AlScN, AlGaScN or their alloys sandwiched between a high-reflectivity distributed Bragg reflector (DBR) and a lower-reflectivity output DBR. The RIM devise is comprising the nanoporous III-nitride material layer. The nanoporous layer, patterned with interdigital transducers (IDTs), is actuated via surface acoustic waves (SAWs) or electric fields to induce rapid, reversible modulation of its effective refractive index. This enables sub-nanosecond switching between resonant and off-resonant optical states, facilitating efficient energy extraction, optical pulse carving, or phase control.

The invention discloses an unsaturated phenyl ether monomer, a holographic recording medium, a preparation method and a related device, the structural general formula of the monomer is as shown in G1 and G2, R1 represents any one of R2, A1 and A2 independently represent any one of hydrogen and phenyl, A3 represents hydrogen or methyl, A4 represents C1-C4 alkyl or phenyl, n is a positive integer and n = 1-5. The unsaturated phenyl ether monomer provided by the invention has high refractive index and is in a liquid state, and the holographic recording medium with high sensitivity, high diffraction efficiency and high refractive index modulation degree can be obtained by applying the unsaturated phenyl ether monomer to preparation of the photopolymer type holographic recording medium.

This optical integrated circuit comprises an optical waveguide device, a light-emitting device, and a support unit. The optical waveguide device includes a substrate, and an optical waveguide layer that is disposed on the substrate and includes an input coupler and an optical waveguide. The light-emitting device is spaced apart from the optical waveguide device. The light-emitting device includes a light-emitting layer and a phase modulation layer. The phase modulation layer includes a base layer and a plurality of different refractive index regions. The support unit includes a first support portion in which one device is disposed, and a second support portion that supports the other device. The distance between the optical waveguide device and the light-emitting device is smaller than the width of the second support portion in the direction in which the one device and the second support portion are lined up.

The invention relates to the technical field of optical fiber sensing and optical fiber device manufacturing, and discloses a femtosecond laser-inscribing polarization-maintaining fiber grating method and system for vector sensing, and the method comprises the following steps: obtaining a stress region image of a polarization-maintaining fiber through a CCD camera, recognizing the slow axis direction of the fiber through image processing, rotating the fiber, and obtaining the stress region image of the polarization-maintaining fiber; an included angle of 45 degrees is formed between the slow axis direction and a preset incident plane of the femtosecond laser; calculating a conjugate phase of wavefront aberration generated when femtosecond laser penetrates through a fiber coating layer and a cladding and is focused to a fiber core, and generating a phase diagram for loading a spatial light modulator; after being modulated by the spatial light modulator, a light beam emitted by the femtosecond laser enters and is focused on the fiber core along the direction of an included angle of 45 degrees, and a grating structure is formed by combining axial scanning and inscribing. Accurate automatic alignment in the fast and slow axis direction and active compensation of transmission aberration are achieved, refractive index modulation birefringence forming a specific included angle with the inherent birefringence axis of the optical fiber can be effectively induced, and therefore the polarization-maintaining fiber grating with the highly controllable reflection spectrum and the asymmetric double-peak characteristic is engraved.

The invention discloses a grating preparation system, a grating preparation method and a controller, and belongs to the technical field of photosensitive materials. The grating preparation system comprises a rotary table used for placing photopolymers with different concentration ratios; the light source system comprises an exposure light path system, an infrared real-time monitoring light path system and a diffraction efficiency testing light path system; the controller is electrically connected with the rotary table and the light source system, the controller is used for receiving change data sent by the infrared real-time monitoring light path system and diffraction efficiency data sent by the diffraction efficiency testing light path system, and the controller constructs a refractive index modulation degree model based on the change data and the diffraction efficiency data; and outputting a target exposure parameter and a target material concentration ratio based on the target refractive index modulation degree and the refractive index modulation degree model, and controlling the turntable to rotate and an exposure light path corresponding to the exposure light path system based on the target exposure parameter. The grating preparation system saves time and is high in preparation efficiency.

The invention discloses a liquid crystal composition which comprises at least one of compounds in a general formula I, at least one of compounds in a general formula II and at least one of compounds in a general formula III. According to the invention, the liquid crystal composition has a high refractive index. Specifically, the compound as shown in the general formula I can increase the intersolubility of the liquid crystal composition while providing a relatively high refractive index for the liquid crystal composition, and has good stability to both photoelectricity and thermoelectricity; the compound in the general formula II can keep good solubility with other compounds while providing a relatively high refractive index for the liquid crystal composition; and the compound in the general formula III is an ester liquid crystal monomer compound, so that the liquid crystal composition has more diversity, and the stability of the whole liquid crystal system is higher. The invention also discloses a holographic polymer dispersed liquid crystal grating which has higher diffraction efficiency and refractive index modulation degree.