270 results about "Refractive index modulation" patented technology

Described herein are the materials, mechanisms and procedures for optimizing various performance parameters of HPDLC optical devices in order to meet differing performance requirements. These optimization tailoring techniques include control and independent optimization of switchable HPDLC optical devices to meet the demanding requirements of anticipated applications for, inter alia, the telecommunications and display industries. These techniques include optimization of diffraction efficiency, i.e., index modulation, polarization dependence control, haze, cosmetic quality, control of response and relaxation time, voltage driving for on and off switching, and material uniformity. This control and independent optimization tailors properties of switchable HPDLC optical devices according to the specific requirements of the application of the switchable HPDLC optical device. The invention disclosed herein retains the desirable attributes of the multi-functional acrylate system for forming HPDLC optical devices, but adds new materials to the acrylate system and / or new process control to the recording to optimize performance parameters as may be needed for specific applications. This results in high optical quality switchable holograms with good diffraction efficiency and low, stable switching voltage.

Fused ring bridge, ring locked dyes that form thermally stable photorfractive compositions. The fused ring bridge structures are pi -conjugated bonds in benzene-, naphthalene- or anthracene-derived fused ring systems that connect donor and acceptor groups. The donor and acceptor groups contribute to a high molecular dipole moment and linear polarizability anisotropy. The polarization characteristics of the dye molecules are stabilized since the bonds in the fused ring bridge are not susceptible to rotation, reducing the opportunity for photoisomerization. The dyes are compatible with polymeric compositions, including thermoplastics. The dyes are electrically neutral but have charge transport, electronic and orientational properties such that upon illumination of a composition containing the dye, the dye facilitates refractive index modulation and a photorefractive effect that can be utilized advantageously in numerous applications such as in optical quality devices and biological imaging.

A holographic recording apparatus having a source of illumination, a master hologram containing at least one hologram lamina overlaying, a copy substrate containing a holographic recording medium, and a voltage generator for applied a voltage across at least one of the master hologram and the copy substrate. The master hologram diffracts the illumination light into zero order light and diffracted light which interfere in the copy substrate to form a copy of the master hologram. The source of illumination is applied for a predefined exposure time during which the voltage varies the refractive index modulation of at least one of the master hologram and the copy hologram.

Described herein are the materials, mechanisms and procedures for optimizing various performance parameters of HPDLC optical devices in order to meet differing performance requirements. These optimization tailoring techniques include control and independent optimization of switchable HPDLC optical devices to meet the demanding requirements of anticipated applications for, inter alia, the telecommunications and display industries. These techniques include optimization of diffraction efficiency, i.e., index modulation, polarization dependence control, haze, cosmetic quality, control of response and relaxation time, voltage driving for on and off switching, and material uniformity. This control and independent optimization tailors properties of switchable HPDLC optical devices according to the specific requirements of the application of the switchable HPDLC optical device. The invention disclosed herein retains the desirable attributes of the multi-functional acrylate system for forming HPDLC optical devices, but adds new materials to the acrylate system and / or new process control to the recording to optimize performance parameters as may be needed for specific applications. This results in high optical quality switchable holograms with good diffraction efficiency and low, stable switching voltage.

Described herein are the materials, mechanisms and procedures for optimizing various performance parameters of HPDLC optical devices in order to meet differing performance requirements. These optimization tailoring techniques include control and independent optimization of switchable HPDLC optical devices to meet the demanding requirements of anticipated applications for, inter alia, the telecommunications and display industries. These techniques include optimization of diffraction efficiency, i.e., index modulation, polarization dependence control, haze, cosmetic quality, control of response and relaxation time, voltage driving for on and off switching, and material uniformity. This control and independent optimization tailors properties of switchable HPDLC optical devices according to the specific requirements of the application of the switchable HPDLC optical device. The invention disclosed herein retains the desirable attributes of the multi-functional acrylate system for forming HPDLC optical devices, but adds new materials to the acrylate system and / or new process control to the recording to optimize performance parameters as may be needed for specific applications. This results in high optical quality switchable holograms with good diffraction efficiency and low, stable switching voltage.

Plural p-n junctions are formed in a waveguide such that they have junction interfaces in a normal direction to a surface of a substrate (to an extending direction of the substrate). Accordingly, a doping concentration changes in only a horizontal direction in the substrate, and it is possible to fabricate using the same processes as those for silicon electronic devices and to perform device fabricating at a low cost. Moreover, two or more junction interfaces are formed in the waveguide and thus an occupied area of the waveguide in a refractive index modulation region expands. Therefore, the efficiency of the refractive index modulation can be improved and a low-voltage operation is possible.

A method for fabricating fiber Bragg gratings including: scanning a photosensitive optical fiber with ultraviolet laser light in a longitudinal direction of the optical fiber by means of a phase mask method, thereby forming periodic refractive index modulation structure in a core of the optical fiber in the longitudinal direction; and instantaneously moving a phase mask used in the phase mask method by a predetermined distance in the longitudinal direction, thereby forming a phase shift portion in the periodic refractive index modulation structure formed in the core of the optical fiber, when a radiation position of the ultraviolet laser light reaches a predetermined position, in the middle of the scanning step using the ultraviolet laser light.

A two-photon absorption decolorizable material comprising: a two-photon absorption dye executing a two-photon absorption; and a decolorizable dye having a molar absorption coefficient equal to or less than 100 at a wavelength of a light irradiated at the two-photon absorption, wherein the decolorizable dye is decolorized by an electron transfer or an energy transfer utilizing an excitation energy obtained by the two-photon absorption of the two-photon absorption dye.

A hologram recording material is provided and has: an optical refractive index-modulating component; and a curable polymer. The optical refractive index-modulating component performs at least one of: (1) a color development reaction; (2) a color development reaction amplified by a self-sensitization with a coloring material of a latent image; (3) a color development reaction amplified by a self-sensitization with a coloring material of a latent image; (4) an alignment change in a compound having a birefringence; (5) a dye discoloration reaction; and (6) a latent image-sensitized polymerization reaction sensitized by a latent image of a residual of a discolorable dye, to record interference fringes providing a refractive index modulation.

Light pulses can be stopped and stored coherently, with an all-optical process that involves an adiabatic and reversible pulse bandwidth compression occurring entirely in the optical domain. Such a process overcomes the fundamental bandwidth-delay constraint in optics, and can generate arbitrarily small group velocities for light pulses with a given bandwidth, without the use of any coherent or resonant light-matter interactions. This is accomplished only by small refractive index modulations performed at moderate speeds and has applications ranging from quantum communications and computing to coherent all-optical memory devices. A complete time reversal and / or temporal / spectral compression and expansion operation on any electromagnetic field is accomplished using only small refractive index modulations and linear optical elements. This process does not require any nonlinear multi-photon processes such as four-wave mixing and thus can be implemented using on-chip tunable microcavity complexes in photonic crystals. The tuning process requires only small refractive index modulations, and moderate modulation speeds without requiring any high-speed electronic sampling.

An optical fiber 4 having a clad diameter of 125 μm is made by adding Ge to a core 41 having a core diameter of 8 μm and a relative refractive index difference of 0.3 %, and two refractive index grating portions 41a and 41b having a slant angle of 2° are formed in series in the optical fiber 4 by a phase mask method using KrF excimer laser (λ=248 nm). The central period (2Λ) of the phase mask of a chirped grating is 1,140 nm, the chip rate (C) of the period is 1.2 nm / mm, the length (G) of the first and second index grating portions 41a and 41b is 8 mm, the effective refractive index of the first and second index grating portions 41a and 41b is 1.447, the refractive index modulation is 3×10−3, and the gap between the first and second index grating portions 41a and 41b is 1 mm.

The present invention provides a direct laser writing fabrication method and system for devices having periodic refractive index modulation structures, for example, Bragg gratings. By focusing a modulated pulsed laser beam into a transparent material substrate, a path of laser modified volumes can be formed with modified refractive index compared with the unprocessed material. Modulation of exposure conditions provides periodic or modified periodic waveguide structures such that the waveguide structures exhibit grating responses and can be used for a variety of optical applications, for example, as spectral filters, Bragg reflectors, grating couplers, grating sensors, or other devices. The method enables direct one-step fabrication and integration of periodic or modified periodic refractive-index modulation devices together with other optical waveguiding devices to enable low-cost, multifunctional one-dimensional, two-dimensional or three-dimensional optical circuit fabrication of simple and complex optical systems.

The invention discloses a multiplexed volume holographic grating. The multiplexed volume holographic grating respectively records red, green and blue three holograms on the same dielectric layer by exposing for three times; volume holographic gratings formed by exposure of different wavelengths are the same in inclination angle and are different in period; by controlling exposure time, refractive index modulation depths corresponding to red, green and blue light after exposure accords with the relation that delta n red light is greater than delta n green light, and delta n green light is greater than delta n blue light, and peak diffraction efficiencies corresponding to the red, green and blue light after exposure are similar. The multiplexed volume holographic grating can effectively balance irradiating energy of red, green and blue light waves and avoid color offset.

The invention relates to devices having periodic refractive index modulation structures and fabrication methods for the devices using a laser means. By focusing a pulsed laser beam into a transparent material substrate, a path of laser modified volumes can be formed with modified refractive index compared with the unprocessed material. By selecting appropriate laser parameters and relative scan speed, the laser modified path defines an optical waveguide. Separation distance of the individual modified volumes define a periodic modification pattern along the waveguide path, so that the waveguide structures also exhibit grating responses, for example, as spectral filters, Bragg reflectors, grating couplers, grating sensors, or other devices. This method of direct laser fabrication enables one-step fabrication and integration of periodic or aperiodic refractive-index modulation devices together with optical waveguiding properties to enable low-cost, multifunctional I D, 2D or 3D optical circuit fabrication for simple and complex applications.

Disclosed are a planar waveguide Bragg grating and a laser thereof based on reconstruction-equivalent chirp and equivalent apodization; the grating adopts sampling structure, the real phase shift or real chirp of the grating is fabricated through reconstruction-equivalent chirp technology; meanwhile, the equivalent apodization is also introduced to the sampling structure to change the sampling duty cycle Gamma along the cavity length direction to realize apodization. The invention combines the equivalent apodization technology in FBG design with the reconstruction-equivalent chirp technology to design a planar waveguide Bragg grating device and a high-performance DFB semiconductor laser. The invention maintains the cycle and refractive index modulation of a seed grating constant, utilizes the sampling structure of gradient duty cycle to effectively introduce the apodization to the planar waveguide Bragg grating, accordingly eliminates the sidelobe of the transmission spectrum of the planar waveguide Bragg grating and ensures the time delay spectrum to be smooth so that planar waveguide Bragg grating devices with high performance are designed.

The invention provides a reflection holographic thin membrane and a preparation method thereof. The reflection holography membrane comprises a basement membrane, a buffer layer which is coated at one side of the basement membrane, a photopolymer coating which is coated at the other side of the buffer layer and formed by the holographic polymer paints, and a protective membrane which is covered on the surface of the photopolymer; wherein, hologram images or the interference fringes of double discoloration pictures are recorded on the photopolymer coating; the photopolymer coating comprises film-forming agents, a nano-composite pre-polymer, a monomer, photo initiators, chain transfer agents and photo sensitizers; the nano-composite pre-polymer is a product which is prepared by alkenyl unsaturated monomer with an unsaturated group at the terminal position and nano-particles. The invention has high sensitivity, high reflection efficiency, high refractivity modulation value, long storage life and little influence of the environment on the hologram images; the recorded images are treated by photo-curing and heat-enhancement and can reach reflected images and double discoloration images with the reflection efficiency of more than 99.9 precent, so mass production is available.

In accordance with one exemplary embodiment the invention provides a multi-parameter fiber optic sensing system with an aperiodic sapphire fiber grating as sensing element for simultaneous temperature, strain, NOx, CO, O2 and H2 gas detection. The exemplary sensing system includes an aperiodic fiber grating with an alternative refractive index modulation for such multi-function sensing and determination. Fabrication of such quasiperiodic grating structures can be made with point-by-point UV laser inscribing, diamond saw micromachining, and phase mask-based coating and chemical etching methods. In the exemplary embodiment, simultaneous detections on multi-parameter can be distributed, but not limited, in gas / steam turbine exhaust, in combustion and compressor, and in coal fired boilers etc. Advantageously, the mapping of multiple parameters such as temperature, strain, and gas using sapphire aperiodic gratings improves control and optimization of such systems directed to improve efficiency and output and reduce emissions.

To provide a two-photon absorption dye-containing material having a great off-resonant two-photon absorption cross section and comprising a two-photon absorption dye capable of decoloring itself through off-resonant two-photon absorption, useful for a three-dimensional refractive index or absorption index modulation material, a three-dimensional optical recording medium, three-dimensional refractive index modulation method and recording and reproducing method for a three-dimensional optical recording medium a two-photon absorption dye-containing material comprising at least a two-photon absorption dye capable of decoloring itself through two-photon absorption.

A chemical sensing device comprises a fiber core and a fiber cladding. The fiber core comprises an index-modulated grating region having an apodized profile configured for increasing shedding of light into the fiber cladding, and the fiber cladding of the chemical sensing device is configured for reflecting at least some of the deflected light back towards the fiber core. The sensing device is applicable in methods and systems for sensing chemicals.

The invention provides a water nano compound photosensitive coating and a preparation method thereof and a photosensitive film formed by the coating. The water nano composite photosensitive coating is formed by the way that nano material with excellent properties is compounded with film forming agent, thus refractive index modulation degree of photosensitive coating is improved. The coating comprises the following components (by weight percent): 10-50% of film forming agent, 15-30% of monomer, 20-50% of photoinitiator, 0.05-1% of photosensitizer, 2-10% of crosslinking agent and 0.1-1% of nano material. The holographic photosensitive film of the invention comprises a base film, a photosensitive nano compound polymer coating and a surface protective film. The reflecting holographic photosensitive film has higher luminous sensitivity, reflection efficiency and refractive index modulation degree, storage life is long, and hologram is stable.

A hologram recording material is provided and includes at least a sensitizing dye capable of absorbing light having a hologram recording wavelength to generate an excited state thereof, and an interference fringe-recording component capable of recording interference fringes providing a refractive index modulation by an electron transfer or an energy transfer from the excited state, in which the sensitizing dye in the hologram recording material has a molar absorption coefficient within a range of 1 to 10,000 at the hologram recording wavelength.

The planar polarization transformer for a normally incident optical wave or beam having a given vacuum wavelength λ comprises an optical planar grating between a cover medium of refractive index nc and an optical substrate of refractive index ns, this planar grating defining a binary index modulation or corrugation of substantially rectangular profile with periodic ridges. This polarization transformer is characterized in that the ridge refractive index nr is larger than the substrate refractive index ns, the grating period Λ is larger than 0.4·λ / nc, the substrate refractive index ns is smaller than 2.7·nc, and the index modulation or corrugation is designed such that, according to the grating mode dispersion equation, the effective index of the mode TE0 is larger than the substrate index ns and the effective index of the mode TM0 is larger than the cover refractive index and smaller than the substrate index.

A hologram recording material is provided and has: a sensitizing dye absorbing light upon hologram exposure to generate an excited state thereof, and an interference fringes-recording component capable of causing color development reaction or discoloration by an electron or energy transfer (movement) form the excited state to record interference fringes providing a refractive index modulation. At least one of the sensitizing dye one the interference fringes-recording component is one a polymer and an oligomer.

The invention relates to a fiber grating which can realize any target response, which belongs to fiber communication, optical sensor and other relative light signal processing fields. The product is a fiber grating of sampling structure realized with phase model scanning method; the period and phase function of the initial end of the fiber grating, As, Phi s (z) and A s (z) are period, phase function and apodization function of any given fiber grating initial end. And it can acquires distance Zk from the K ultraviolet exposure position to the sample fiber grating initial end and the amplitude Ak of refraction rate modulation leaded in at the Zk. The character of the invention is: its reflection spectrum has multi-channel type, and some special reflection peak in them has the demanded target reflection response, or has the character of target phase shift.

A hologram recording method is provided and includes: a first step of forming a latent image in a hologram recording material by holographic exposure; a second step of subjecting the hologram recording material having the latent image to heat treatment so as to form interference fringes providing a refractive index modulation; and a third step of irradiating the hologram recording material entirely with light to fix the interference fringes. A hologram recorded by the hologram recording method can be reproduced without erasing the refractive index modulation.

The invention relates to devices having periodic refractive index modulation structures and fabrication methods for the devices using a laser means. By focusing a pulsed laser beam into a transparent material substrate, a path of laser modified volumes can be formed with modified refractive index compared with the unprocessed material. By selecting appropriate laser parameters and relative scan speed, the laser modified path defines an optical waveguide. Separation distance of the individual modified volumes define a periodic modification pattern along the waveguide path, so that the waveguide structures also exhibit grating responses, for example, as spectral filters, Bragg reflectors, grating couplers, grating sensors, or other devices. This method of direct laser fabrication enables one-step fabrication and integration of periodic or aperiodic refractive-index modulation devices together with optical waveguiding properties to enable low-cost, multifunctional 1D, 2D or 3D optical circuit fabrication for simple and complex applications.

To overcome problems of fabricating conventional core-clad optical fibre from non-silica based (compound) glass, it is proposed to fabricate non-silica based (compound) glass optical fibre as holey fibre i.e. one contining Longitudinal holes in the cladding. This removes the conventional problems associated with mismatch of the physical properties of the core and clad compound glasses, since a holey fibre can be made of a single glass composition. With a holey fibre, it is not necessary to have different glasses for the core and cladding, since the necessary refractive index modulation between core and cladding is provided by the microstructure of the clad, i.e. its holes, rather than by a difference in materials properties between the clad and core glasses. Specifically, the conventional thermal mismatch problems between core and clad are circumvented. A variety of fibre types can be fabricated from non-silica based (compounds) glasses, for example: single-mode fibre; photonic band gap fibre; highly non-linear fibre; fibre with photosensitivity written gratings and other refractive index profile structures; and rare-earth doped fibres (e.g. Er, Nd, Pr) to provide gain media for fibre amplifiers and lasers.