64 results about "Optical limiter" patented technology

An intracavity resonant Fabry-Perot saturable absorber (R-FPSA) induces modelocking in a laser such as a fiber laser. An optical limiter such as a two photon absorber (TPA) can be used in conjunction with the R-FPSA, so that Q-switching is inhibited, resulting in laser output that is cw modelocked. By using both an R-FPSA and a TPA, the Q-switched modelocked behavior of a fiber laser is observed to evolve into cw modelocking.

There is provided an optical limiter device for protecting an object from incident light having a wavelength in the visible, infrared or ultraviolet spectrum. The device comprises a plurality of nanoparticles of a metallic material including free electrons that undergo collective oscillations when exposed to the incident light. The plurality of nanoparticles of the metallic material include a plurality of nanoparticles of a non-spherical particle geometry, which may include a geometry having a plurality of sharp protrusions on a spherical body. The metallic material may include gold, silver, aluminum, indium or copper. The device further comprises a structurally rigid transparent medium in which the plurality of nanoparticles of the metallic material are embedded; and a mechanical support mounting the transparent medium between the incident light and the object.

An optical system comprising a concave primary mirror reflects light through an intermediate focus to a secondary mirror. The secondary mirror re-focuses the image to a final image plane. Optical limiter material is placed near the intermediate focus to optically limit the intensity of light so that downstream components of the optical system are protected from intense optical transients. Additional lenses before and / or after the intermediate focus correct optical aberrations.

The present invention relates to optical power-limiting devices, and more particularly, to an optical power-limiting passive (self-adaptive) device and to a method for limiting solar power transmission in devices such as windows, using scattering level changes in a novel thermotropic composition that contains salt nano or microparticles embedded in a solid transparent host layer, where temperature change induces change in the refraction index of the matrix as well as of the embedded particles, creating a scattering layer, substantially reflecting the incident light thus limiting the amount of light passing through the window, green house covers, car sun roofs, solar panel windows and protection layers on housing roofs and walls, as a function of ambient temperature.

Inorganic crystals having one or more species of dopant ions which are photo-reactive are used as visible and or infrared light optical limiters to protect against laser radiation exposure while permitting passage of the visible and or infrared light spectrum at least until exposed to high energy laser radiation. The dopant ions are selected from ions of transition metals. The exposure of these ions within the transparent crystalline matrix either photo-ionize or are elevated to an excited state and thereby absorb or otherwise attenuate the passage of the laser beam radiation sufficiently to protect human eyes or photo-sensitive equipment. The crystals may be fabricated into such items as lenses for use in eyeglasses or on shields of flight helmets to protect the eyes of aircraft pilots.

The present invention in one aspect relates to a low-cost, nano-graphene based broadband optical limiter with limiting properties superior to current standards, carbon fullerenes (C60) solutions and carbon black suspensions. The broadband optical limiter includes a plurality of graphene nano-sheets, and a base material in which the plurality of graphene nano-sheets is distributed. The base material can be liquid or gel matrix.

An optical power limiter comprises an input optical transmission element, an output optical transmission element, and a power-limiting element disposed between the input and output elements for transmitting optical signals from the input element to the output element. The power-limiting element comprises an optical-limiting solid mixture containing particles of at least one material that produces reversible thermal changes in response to light above a predetermined optical power level, thereby changing the optical transmission properties of the power-limiting element.

A reversible optical energy limiting device comprises a waveguide forming an optical path between an input end and an output end, and an optical energy responsive material located in the optical path for reflecting at least a portion of optical energy received from the input end back toward the input end when the optical energy exceeds a predetermined threshold. The optical energy responsive material does not reflect optical energy when it drops below the predetermined threshold, and thus propagation of optical energy from the input end to the output end is automatically resumed when the optical energy drops below the predetermined threshold. The optical energy responsive material may extend across the optical path an acute angle relative to the longitudinal axis of the optical path so that back-reflected light does not re-enter the optical system.

The invention relates to an optical limiter with adjustable threshold, comprising a nonlinear refractive material, a diaphragm and a supporting encapsulation device; the nonlinear refractive material and the diaphragm are arranged in the supporting encapsulation device; wherein, the nonlinear refractive material is arranged in front of the diaphragm; the incident laser beam sequentially passes through the nonlinear refractive material and the diaphragm; the diaphragm is provided with a clear aperture with changeable size; and the position of the diaphragm corresponding to the nonlinear refractive material is changed by an adjusting device. Compared with the prior art, the optical limiter utilizes the combination of the thermal lens effect of the nonlinear refractive material and the changeable diaphragm, realizes the optical limiter with adjustable threshold, has simple structure, easy preparation and low cost, has convenient, online and real-time adjustment of the limiting threshold, can be applied to various situations, provides guarantee for the safe use of precise optical devices (including human eyes), and prompting the improvement of the laser protection technique.

Method for limiting amount of radiation impinging on a radiation-sensitive detector device by directing radiation toward the detector, permitting the radiation to impinge upon the detector device when the radiation is below a predetermined threshold, and utilizing radiation having wavelengths different from signals of interest to initiate limiting of the radiation impinging upon the detector when the predetermined threshold is exceeded. The optical limiter includes an IR limiting layer pair selected so that energy from visible and near infrared radiation activates the optical limiter. The limiting layer pair may includes a layer closer to the source of radiation of e.g. vanadium dioxide, vanadium sesquioxide, or germanium crystal and a layer further from the source of radiation of e.g. chalcogenide glass, germanium crystal, or sodium chloride crystal.

A pneumatic-control optical limiter comprises a sealing cavity and a decompress system. Characteristics that nonlinear scattering effect of nonlinear scattering media is relative to solvent boiling point are adopted by the optical limiter; and by means of adjusting air pressure around the nonlinear scattering media, real-time control on response of optical limiting is realized. Real-time and quantitative adjustment on the response of optical limiting can be realized with the pneumatic-control optical limiter which can be applicable to laser protection and laser control of sensitive optical elements.

An IR limiting device for a detector that is based on a micro-optomechanical cantilever array is disclosed. In the normal state, each microcantilever device in the array behaves like a mirror that reflects the infrared signal to the detector. The microcantilever device absorbs radiation outside the desired infrared region. When the radiation is stronger than a predetermined threshold, the microcantilever device bends as a result of thermo-mechanical forces, and it reflects the signal away from the detector, thereby limiting the radiation. The advantage of such a system is that each pixel in the detector can be addressed individually, and the limiting is localized.

A system and method for producing bulk GaAs with an increased carrier lifetime of at least 10 microseconds is provided. The system and method of producing the GaAs crystal involves using a technique called low pressure hydride vapor phase epitaxy (LP-HVPE). In this technique, a gas containing Ga (typically GaCl) is reacted with a gas containing As (typically AsH3) at the surface of a GaAs substrate. When grown under the proper conditions, the epitaxial, vapor grown GaAs crystal has ultra-long free carrier lifetimes of at least one order of magnitude greater than that of the previous lifetime of 1 microsecond. This very long free carrier lifetime GaAs will be particularly useful as a semiconductor radiation detector material and is also expected to be useful for many other applications than include medical imaging, solar cells, diode lasers, and optical limiters and other applications.

A composite optical limiter comprises a first quartz cuvette and a second quartz cuvette that are sequentially arranged in the incidence direction of an incident light, wherein the emergent surface of an incident light of the first quartz cuvette is in contact with the incident surface of an incident light of the second quartz cuvette, a single walled carbon nanotube dispersion liquid is contained in the first quartz cuvette, and a single-layer graphene dispersion liquid is contained in the second quartz cuvette. The limiter has an amplitude limiting protection role within a macro-energy dynamic scope due to the action of the single walled carbon nanotube dispersion liquid with a high damage threshold; and the limiter is guaranteed to have an ultralow amplitude-limited output after two stages of amplitude limiting actions due to the action of the single-layer graphene dispersion liquid with a strong amplitude limiting capability. According to the invention, the advantages of low amplitude limiting threshold of the single-layer graphene and high damage threshold of a single walled carbon nanotube are combined, and the composite optical limiter has the advantages of low amplitude limiting threshold, wide dynamic scope, and wide applicable spectral scope. The composite optical limiter has the characteristics of simple structure and low cost.

An optical limiter comprises a glass backing, a glass cover, and a layer of a phase changing material placed between said glass backing and said glass cover, the phase changing material comprising a transparent matrix having embedded particles of material that changes its optical properties due to temperature induced phase change of said material. The optical properties may change from transparent to reflective, from transparent to refractive or from transparent to scattering. The phase changing material is preferably at least one material selected from the group consisting of the elements Antimony, Bismuth, Cadmium, Lead, Tin and Indium and low-melting-point alloys of two or more of these elements. Two or more layers of phase changing materials may be used in a stack configuration, with each of the phase changing materials having a unique melting temperature.

An optical device may include a sacrificial limiter filter including at least one layer of graphene disposed on a substrate. The at least one layer of graphene may be configured to absorb and scatter at least a portion of electromagnetic radiation incident on the at least one layer of graphene.

According to some aspects, a transmissive and all-dielectric optical component / limiter with great cutoff efficiency using Vanadium Dioxide (VO2) as the active component is disclosed. In some embodiments, Vanadium dioxide is used for an optical limiter due to the large contrast in optical constants upon undergoing the semiconductor to metal phase transition. When triggered optically, this transition occurs within 60 fs, making the device suitable for an ultrafast laser environment. In addition, the phase transition threshold is tunable by applying stress or doping; therefore, the device cutoff intensity can be adjusted to fulfill specific requirements.

The invention discloses an ultrashort pulse optical limiter based on an optical Kerr effect. The ultrashort pulse optical limiter comprises a polarizer, a first quarter-wave plate, a first lens, optical Kerr media, a second lens, a second quarter-wave plate, a polarization analyzer and a diaphragm which are sequentially arranged in the direction of incident light. The first quarter-wave plate and the second quarter-wave plate are orthogonal in the long axis direction, and the polarization detection direction of the polarization analyzer is parallel to the polarization direction of the polarizer. According to the ultrashort pulse optical limiter based on the optical Kerr effect, the polarizer and the first quarter-wave plate are combined to generate elliptically polarized light, the optical Kerr effect generated in the optical Kerr media is further utilized, the polarization ellipse rotation and self-focusing effect are generated through abduction, part of incident light is intercepted when passing through the polarization analyzer and the diaphragm, and accordingly light amplitude limiting output can be achieved. The ultrashort pulse optical limiter based on the optical Kerr effect has the advantages of being high in linear transmissivity, high in response speed, extremely wide in bandwidth, simple in structure and low in cost, thereby being quite suitable for designing and manufacturing ultrashort pulse broadband laser protection devices.

The invention relates to a passive optical limiter having a nonlinear material capable of switching in a predetermined optical band from a transparent state to an opaque state as a function of the power of an incident laser beam. The nonlinear material is an organic dye which comprises molecules derived from 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene into which a nitrogen atom is inserted at the meso position, referred to as aza-bodipy molecules, and which have conjugated π chains functionalized so as to exhibit absorption for two photons around an incident beam wavelength lying between 1.45 μm and 1.6 μm.

An image sensing device with a wide dynamic range by using an optical limiter, and an image pickup apparatus using the same. The image sensing device includes an optical limiter for converting an input image into a non-linear image at an intensity greater than a threshold intensity, and an image sensor for converting the non-linear input image into an electrical signal. By forming the optical limiter capable of outputting a non-linear image with respect to the intensity of light on the image pickup surface of the image sensor, the dynamic range of the image sensing device can be expanded without using a separate device.

The invention relates to new application of a Te / TeO2-SiO2 composite film, namely, the application of the Te / TeO2-SiO2 composite film as an optical limiting material. The Te / TeO2-SiO2 composite film is a composite film in which TeO2 and / or Te is embedded among SiO2 particles and the Te / TeO2-SiO2 composite film is generated by carrying out constant-potential electrochemical induction on transparent TeO2-SiO2 composite sol under -0.1 to -1.5V. According to the invention, optical limiting experiments are carried out by selecting Te / TeO2-SiO2 composite film samples prepared under different voltages, the Te / TeO2-SiO2 composite film is proved to have a better optical limiting property, and the application value of the Te / TeO2-SiO2 composite film in optical limiting is revealed. Therefore, the Te / TeO2-SiO2 composite film can be applied as the optical limiting material and can be applied to an optical limiter.

A novel bulk GaAs with an increased carrier lifetime of at least 10 microseconds has been produced. This novel GaAs has many uses to improve optical and electrical devices. The method of producing the GaAs crystal involves using a technique called low pressure hydride phase epitaxy (LP-HVPE). In this technique, a gas containing Ga (typically GaCl) is reacted with a gas containing As (typically AsH3) at the surface of a GaAs substrate. When grown under the proper conditions, the epitaxial, vapor grown GaAs crystal has ultra-long free carrier lifetimes of at least one order of magnitude greater than that of the previous art of 1 microsecond. This very long free carrier lifetime GaAs will be particularly useful as a semiconductor radiation detector material and is also expected to be useful for many other applications than include medical imaging, solar cells, diode lasers, and optical limiters and other applications.

The present invention relates to optical power-limiting devices, and more particularly, to an optical power-limiting passive (self-adaptive) device and to a method for limiting solar power transmission in devices such as windows, using scattering level changes in a novel thermotropic composition that contains salt nano or microparticles embedded in a solid transparent host layer, where temperature change induces change in the refraction index of the matrix as well as of the embedded particles, creating a scattering layer, substantially reflecting the incident light thus limiting the amount of light passing through the window, green house covers, car sun roofs, solar panel windows and protection layers on housing roofs and walls, as a function of ambient temperature.

A material is composed of at least one spin transition compound that corresponds to the formula Fe1-mMm(R-Trz)3XbYc (I) in which M is a metal having a 3d4, 3d5, 3d6 or 3d7 configuration, other than Fe; 0≦m≦1; R-Trz represents a 1,2,4-triazole ligand carrying an R substituent on the nitrogen in the 4 position; R is an alkyl group or an R1R2N— group in which R1 and R2 represent, each independently of the other, H or an alkyl radical; X represents at least one noncoloring monovalent or divalent anion; Y represents at least one anion which has a coloring group; and b and c are chosen so that the electrical neutrality of the compound (I) is adhered to. A process for the preparation of this material and to its use as thermochromic pigment, as support for data storage or as optical limiter.