56 results about "Refractive index modulation" patented technology

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 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 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 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.

The invention relates to the technical field of multimode interference, and provides a central wavelength tunable multimode interference device which comprises an input waveguide region, a multimode interference region and an output waveguide region which are connected in sequence, the multimode interference region comprises a core layer, the core layer is made of a high-refractive-index material, and the output waveguide region is made of a high-refractive-index material. And a modulation electrode structure for modulating the refractive index of the core layer is arranged on the multimode interference region. The invention further provides a manufacturing method of the multimode interference device with the tunable central wavelength and a coherent modulator. Refractive index modulation is carried out on the core layer of the multi-mode interference area through the modulation electrode structure, in the multi-mode interference area, the effective refractive index directly determines the self-mapping point positions of different wavelengths, therefore, the effect of tunable central wavelength can be achieved through refractive index modulation, and through selection of different bias voltages, the tunable wavelength of the multi-mode interference area can be achieved. And the output effect of the optical power in the output waveguide is tuned.

The application discloses a kind of optical fiber side light extraction structure and method, belong to optical fiber side light extraction technical field, structure has including femtosecond grating light extraction component, filter component including filter layer and with slit light shielding layer, and detection component.The method includes: with grating diffraction separation optical signal in fiber core, with filter component filters optical signal, with detector receives signal.The application is by femtosecond laser in fiber core and writes small refractive index modulation area, with diffraction effect will transport light be introduced with specific angle to side, again cooperate external filter and metal slit and constitute spatial filter, physically block the stray light deviating from preset angle.This internal diffraction+external filter synergic mechanism avoids physical damage optical fiber surface, and realizes high purity, high directional signal extraction under micro size.

The application discloses a phase mask plate preparation method for inhibiting a Fabry-Perot effect, and comprises the following steps: a dispersion fiber grating model is established, and reflection spectrum, transmission spectrum and group delay curve of the dispersion fiber grating are obtained through simulation; an ultra-Gaussian cut-off function model is established; according to the reflection spectrum and the transmission spectrum of the dispersion fiber grating and the ultra-Gaussian cut-off function, the reflection spectrum, the transmission spectrum and the group delay curve of the optimized dispersion fiber grating are obtained through simulation, and then a refractive index modulation depth distribution curve of a grating area of the phase mask plate is obtained; the refractive index modulation depth distribution curve of the grating area of the phase mask plate is optimized to obtain an optimized refractive index modulation depth distribution curve; a diffraction efficiency distribution curve and a groove depth of the phase mask plate are calculated; and the phase mask plate is obtained according to the groove depth of the phase mask plate. According to the application, the groove depth distribution of the phase mask plate used for writing is only adjusted, the Fabry-Perot effect can be effectively inhibited, and therefore the reflection spectrum flatness of the dispersion fiber grating is improved.

The invention belongs to the field related to information security and identity authentication, and particularly relates to a reconfigurable optical PUF (Physical Unclonable Function) based on a photorefractive effect and an authentication system and method thereof, the reconfigurable optical PUF has the stable cross-linked structure characteristic of a solid optical PUF, and a reconfiguration principle based on refractive index modulation of the photorefractive effect is fused. On the basis, the authentication method and system of the reconfigurable optical PUF based on the photorefractive effect are constructed; in the system, two paths of laser illumination PUF (Physical Unclonable Function) of detection and pumping are coupled from a light path structure by adopting a coupling device, an arranged laser power regulation module can regulate the power of the pumping laser, control the total energy of pumping photons injected into the optical PUF, excite a carrier self-built field to modulate the carrier self-built field or other polar molecules, and control the light path of the optical PUF. Therefore, the scattering characteristic of the optical PUF can be dynamically reconstructed in a controllable state. The PUF is illuminated by detection laser to form speckles to generate a key for identity authentication. The method has the advantages of high safety, high reliability and the like, and is suitable for the field with high safety requirements.

The invention discloses a photopolymer material, application thereof and a volume holographic grating, and relates to the technical field of polymer photosensitive materials. The photopolymer material comprises the following raw materials: a binder, an active monomer, a photoinitiator, a photosensitizer, a hydrogen donor and a sensitizer, the molar ratio of the active monomer to the photoinitiator is (8-12): 1; the molar ratio of the photosensitizer to the photoinitiator is 1: (15-25); the active monomer comprises a high-refractive-index monomer with the refractive index of 1.55-1.72 and a low-refractive-index monomer with the refractive index of 1.44-1.50, and the molar ratio of the high-refractive-index monomer to the low-refractive-index monomer is (0.7-1.3): 1. The photopolymer material meeting holographic recording can be prepared, and the prepared material is good in heat resistance, rapid in film forming, short in oxygen isolation exposure response time (as long as several seconds), high in refractive index modulation degree, high in sensitivity, high in diffraction efficiency, good in mechanical property and high in transmittance and can be prepared in a large area.

The invention concerns a hybrid optical device combining a silicon-on-insulator (SOI) waveguide platform (1) comprising a silicon waveguide (1a) with a thin-film electro-optical (EO) material such as lithium niobate or barium titanate forming a waveguide structure (2). The EO material waveguide structure (2) is bonded in optical contact with the SOI waveguide (1a), and electrodes (6) on its sides enable refractive index modulation via the electro-optical material Pockels effect. A coupling section (7), preferably comprising a tapered SOI waveguide (7a), transfers light between the SOI and EO structures with low loss. The device may include Bragg gratings (4a) or periodically poled sections (4b) in the EO layer for tunable or wavelength-selective modulation. The structure allows fast, reconfigurable light modulation, filtering, and signal routing on a CMOS-compatible platform, suitable for high-speed communication, optical computing, and sensing, offering a compact and efficient electro-optic integration solution.

The invention relates to the technical field of fiber bragg grating preparation, in particular to a method for preparing a fiber bragg grating through longitudinal line-by-line cold machining based on femtosecond laser direct writing, which comprises the following steps of: S10, controlling a femtosecond laser spot to move point by point along the axial direction of an optical fiber by taking a grating period as a step length, and applying a laser pulse at a corresponding position of each grating period, a local refractive index modulation area is formed; the at least m local refractive index modulation areas are periodically arranged in the axial direction of the optical fiber to form a longitudinal modulation track; s20, the femtosecond laser spot is controlled to move by a preset distance in the first direction perpendicular to the axial direction of the optical fiber; and the steps S10 and S20 are repeated until n longitudinal modulation tracks are formed, so that the local refractive index modulation areas located in the same cross section of the optical fiber can form a refractive index modulation plane, m refractive index modulation planes are obtained, and processing of the optical fiber grating is completed. Energy relaxation of the optical fiber material is facilitated, and a refractive index modulation structure is stably formed.

This invention provides a photopolymer composition, a holographic film, and a volume holographic grating. The photopolymer composition of this invention comprises a polymer matrix, a photopolymerizable monomer, and a photoinitiator; the polymer matrix comprises linear polyurethane, and the photopolymerizable monomer comprises a compound represented by Formula I. By using linear polyurethane as the polyurethane matrix and a compound represented by Formula I as the photopolymerizable monomer, the photopolymer composition of this invention possesses high refractive index modulation capability and low viscosity, enabling the formation of a holographic film with uniform material distribution, thereby achieving high diffraction efficiency in the volume holographic grating.

Disclosed is a surface etched grating semiconductor laser with periodic pumping structure. The structure includes a lower doped dielectric layer, a multiple quantum well active layer, a ridge-shaped doped dielectric layer, periodic grating grooves formed on the ridge-shaped doped dielectric layer and a top electrical contact layer forming ohmic electrical contact with electrical contact regions between the grating grooves. Carriers are injected through the periodic electrical contact layer, flow through the electrical contact regions, spread laterally when reaching the bottom of the grating grooves, and then continue to spread to the multiple quantum well active layer. In a case of uniform distribution, a laser based on refractive index modulation is realized. In a case of non-uniform distribution, a laser with mixed modulation is realized by introducing additional gain modulation.

This application relates to the field of optical device technology, and provides a method, device and equipment for preparing a polymer holographic optical device. The method includes: mixing a photosensitive polymer holographic material with preset nanoparticles to obtain a mixed material; the preset nanoparticles have photosensitive active groups; covering the mixed material onto a substrate; subjecting the mixed material on the substrate to a thermosetting treatment; and irradiating the thermosetting mixed material with coherent light to obtain a polymer holographic optical device, thereby improving the refractive index modulation of the polymer holographic optical device.

The invention discloses a high-power grating carrier optical fiber and a preparation method thereof, and relates to the technical field of laser manufacturing equipment. The high-power grating carrier optical fiber comprises a fiber core, and an inner cladding, a quartz outer cladding and an organic resin coating which are sequentially sleeved on the surface of the fiber core, the fiber core is composed of a core layer with a concave central refractive index and a germanium-doped core layer which is sleeved on the core layer with the concave central refractive index and is concentric with the core layer. And the inner cladding consists of five layers of refractive index modulated germanium-fluorine-doped quartz claddings of which the refractive indexes are alternated from high to low. The high-power grating carrier optical fiber not only has good photosensitivity and does not need hydrogen-loading sensitization, but also can inhibit different high-order modes to different extents under different wavelengths, effectively solves the problem that the endurance capacity is reduced due to heating of the carrier optical fiber in a laser working state, and improves the stability of the high-power grating carrier optical fiber due to regulation and control of a mode coupling state. And the output beam quality of the laser is greatly improved.

The invention discloses a red-sensitive holographic photopolymer based on an acrylate-acetate copolymerization system and a preparation method of the red-sensitive holographic photopolymer. According to the method, the influence of exposure and post-processing parameters on the holographic recording performance of the red-sensitive photopolymer is systematically studied, the diffraction efficiency of the red-sensitive photopolymer is more than 95%, the refractive index modulation (RIM) reaches 0.03, the sensitivity (S) is 4.87 * 1cm / mJ, the spatial frequency (SF) reaches 4757 lp / mm, and the performance of the red-sensitive photopolymer is superior to that of the existing red-sensitive photopolymer; a one-step single-beam exposure method and a two-step double-beam exposure method are respectively adopted to prepare the reflective Denisyuk hologram, and the light intensity ratio of parameters is researched to obtain the high-quality hologram, so that the application potential in the fields of anti-counterfeiting, holographic three-dimensional imaging, AR display and the like is shown. According to the invention, high performance of the red-sensitive holographic photopolymer is realized, and a high-quality material and technical support are provided for related holographic application.

The application discloses a high-sensitivity high-temperature high-pressure sensor based on a high-birefringence grating, which comprises a microstructure optical fiber, the microstructure optical fiber comprises a fiber core and a cladding layer, the fiber core is located at the center of the cladding layer, the microstructure optical fiber has a first polarization direction and a second polarization direction on a radial plane, the first polarization direction is perpendicular to the second polarization direction, symmetrical air hole channels are arranged in the cladding layer on both sides of the fiber core along the first polarization direction, and the air hole channels are parallel to the fiber core; and a high-birefringence grating is formed in the fiber core or the cladding layer of the microstructure optical fiber through periodic refractive index modulation. The high-sensitivity high-temperature high-pressure sensor can directly form two separated Bragg resonance peaks, does not need to use any polarization device for demodulation, and can simultaneously measure temperature and pressure, has high sensitivity to pressure, and can work in a high-temperature environment.

The invention provides a macromolecular photoinitiator composition, a photopolymer composition, a holographic grating and a holographic display system. The macromolecular photoinitiator composition provided by the invention is prepared from the following components in percentage by mass: 5 to 15 percent of isocyanate compound, 0.1 to 5 percent of photosensitive dye, 5 to 20 percent of coinitiator, 10 to 30 percent of acrylate compound, 1 to 15 percent of fluorine-containing compound, 20 to 60 percent of first solvent and 0.1 to 2 percent of catalyst. The macromolecular photoinitiator composition can react to form a polyurethane photoinitiator grafted with a photosensitive dye, a coinitiator, an acrylic acid compound and a fluorine-containing compound, so that not only can the solubility of the photoinitiator in an organic system be effectively improved, but also the photosensitivity and the diffusion rate of the photoinitiator can be improved; therefore, the uniformity, the light sensitivity, the resolution ratio, the diffraction efficiency and the refractive index modulation degree of the formed holographic grating can be greatly improved.

Photonic crystal layer, PC layer, (100), for a surface-emitting photonic crystal laser, PCSEL, (200), comprising a semiconductor layer (10) consisting of a first semiconductor material and including a structured region (12) in which a plurality of adjacent square PC unit cells (20) with a common side length A form a periodic refractive index modulation grating structure, wherein each PC unit cell (20) comprises a symmetrical elongated isosceles triangle, SIT, (30) of a second semiconductor material having a lower or higher refractive index than the first semiconductor material, wherein the SIT (30) has a base length B and a base angle θ, the upper corner (31) of the SIT (30) coinciding with a corner (21) of the PC unit cells (20), the base length B being between 0.60A and 0.85A and the base angle θ is between 60° and 80°,and wherein the first base corner (32) of the SIT (30) and the second base corner (33) of the SIT (30) are located outside the PC unit cell (20) or each coincide with a side of the PC unit cell (20).

The application relates to the technical field of blue-sensitive photopolymer photosensitive materials, in particular to a blue-sensitive photopolymer film and a preparation method and application thereof. The blue-sensitive photopolymer film comprises the following preparation raw materials in parts by mass: 40-45 parts of writing monomers, 20-25 parts of polyester polyols, 14-16 parts of aliphatic isocyanate, 1-2 parts of blue light photosensitizer, 2-4 parts of photoinitiator, 5-10 parts of crosslinking agent, 5-10 parts of anti-oxidation inhibitor, 0.4-0.6 parts of catalyst, 0.5-0.6 parts of defoaming agent and 5-9 parts of solvent. The blue-sensitive photopolymer film has the characteristics of good moisture-proof effect, long storage time, high diffraction efficiency, high refractive index modulation, high sensitivity and low exposure energy, and is an ideal holographic recording material.

The invention relates to a fluorinated biuret borate nonlinear optical crystal and a preparation method and application thereof, the chemical formula of the crystal is [C2N3O2BF2H5] [BF4], the molecular weight is 238.71, and the crystal is prepared by a hydrothermal method or a room temperature solution method; the crystal belongs to a monoclinic system, the space group is P21, and the cell parameters are as follows: a = 6.0521 (11), b = 9.4651 (18), c = 7.1398 (12), beta = 91.267 (7), Z = 2, and V = 408.90 (13) 3. The [C2N3O2BF2H5] [BF4] nonlinear optical crystal obtained by the method is used for manufacturing a second harmonic generator, an upper frequency converter, a lower frequency converter, an optical parametric oscillator and the like; meanwhile, the crystal can also be used as a birefringent crystal for manufacturing a refractive index modulator, a phase modulator and a polarization device.

The invention relates to the technical field of surgical instruments, and discloses a medical optical fiber capable of emitting light laterally, an annular chirp grating structure is arranged in a section of area, closest to the end face of the optical fiber, on the medical optical fiber, the annular chirp grating structure can realize uniform scattering of laser in the optical fiber from the side face of the optical fiber, and the end face of the optical fiber is a flush matte surface. And the forward radiation distribution of the optical fiber is more dispersed and uniform. Through the femtosecond laser direct writing technology, the annular chirp grating structure is machined on the end face of the medical optical fiber in the radial direction. Through periodic refractive index modulation of the annular chirp grating structure, laser in the optical fiber can be uniformly scattered from the side face of the optical fiber, the lateral radiation area of the laser is increased, and large-range uniform irradiation of deep tissue is achieved.

This invention relates to the field of fiber optic temperature measurement technology, specifically to a high-temperature sensor based on a torsion-type long-period fiber grating and its fabrication method. The fabrication process includes: fixing an optical fiber to a rotating fixture and rotating it by a preset angle to prepare an optical fiber with a preset torsional stress field; controlling a laser and a displacement platform to alternately perform fixed-point pulse irradiation and step-by-step movement to induce thermal relaxation of the stress field to prepare the grating; collecting transmission spectral data and controlling the processing equipment based on power loss values; and calculating the temperature sensitivity coefficient. In this invention, by pre-setting a torsional stress field and inducing periodic thermal relaxation of stress, dependence on photosensitive doping materials is eliminated, mechanical strength is maintained, and efficient refractive index modulation is achieved, resulting in excellent thermal stability. Combined with real-time spectral acquisition and loss analysis, a closed-loop feedback is constructed to precisely adjust irradiation parameters, improving temperature sensitivity and linearity, and solving the problems of low yield and poor long-term stability associated with traditional processes.

The invention discloses a high-refractive-index 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. The molecular arrangement mode of the high-refractive-index composition provided by the invention is obviously different from the texture of a conventional liquid crystal nematic phase, and the diffraction efficiency and the refractive index modulation degree of the holographic polymer dispersed grating containing the composition can be improved. The invention also provides a holographic polymer dispersed grating which comprises a photoinitiator system, a polymer system and the high-refractive-index composition. The holographic polymer dispersed grating provided by the invention is obviously different from an existing liquid crystal composition by selecting the high-refractive-index composition, can have relatively high diffraction efficiency on S light and P light, has relatively high intersolubility with a polymer system, has a relatively high refractive index modulation degree, and is convenient for practical application of the grating.

The invention provides a phenyl sulfide monomer as well as a preparation method and application thereof. The phenyl sulfide monomer has a structure as shown in a formula G1. The phenyl sulfide monomer has a high refractive index, is presented in a liquid form at room temperature, and is easy to diffuse and migrate in an exposure process, and the photopolymer material prepared from the phenyl sulfide monomer has excellent properties of high sensitivity, high recording grating diffraction efficiency, high refractive index modulation degree and the like.

The invention provides an alkenyl monomer and a preparation method and application thereof, the alkenyl monomer has a structure as shown in a structural general formula G1, the alkenyl monomer is a liquid monomer with a high refractive index, so that a holographic recording medium has high sensitivity, and a recording grating has excellent properties such as high diffraction efficiency, low shrinkage, high refractive index modulation degree and the like.

The invention provides a photo-initiation system and application thereof. The photo-initiation system comprises a photosensitizer and a co-initiator, wherein the photosensitizer is obtained by modifying a basic dye by using a modifier; the modifying agent is prepared from a C6-C20 alkyl sodium sulfosuccinate compound; the basic dye comprises at least one of ethyl violet, navy T, basic violet 7, basic fuchsin, methylene blue, neomethylene blue and azure A. The photosensitizer in the photo-initiation system provided by the invention is obtained by modifying the basic dye by using the modifier, and the types of the modifier and the basic dye are limited, so that when the photo-initiation system is used for preparing the holographic grating, the photosensitizer is easily dispersed in a solution, is not easy to form a precipitate and is more easily bleached by visible light; therefore, the diffraction efficiency, the refractive index modulation degree and the transmittance of the holographic grating can be improved.

The present application discloses a photopolymer-based holographic recording medium, a volume holographic grating and a preparation method therefor, and a holographic device. The photopolymer-based holographic recording medium at least comprises a compound having a plurality of isocyanate reactive functional groups and a polyisocyanate-based compound, wherein the number of the isocyanate reactive functional groups is different from the number of isocyanate groups. The volume holographic grating prepared in the present application has a relatively high refractive index modulation for red, green and blue light.

A distributed feedback laser (DFB) is a type of laser diode in which the active region of the device contains a periodically structured element or diffraction grating, which may include periodic changes in refractive index that cause reflection back into the laser cavity. Conventional DFB lasers used in optical networks may exploit either loss-modulated or index-modulated gratings. In the case of complex-coupling, index-modulated and loss-modulated gratings may be combined together.