478 results about "Photonic bandgap" patented technology

This invention relates to processes for the assembly of three-dimensional structures having periodicities on the scale of optical wavelengths, and at both smaller and larger dimensions, as well as compositions and applications therefore. Invention embodiments involve the self assembly of three-dimensionally periodic arrays of spherical particles, the processing of these arrays so that both infiltration and extraction processes can occur, one or more infiltration steps for these periodic arrays, and, in some instances, extraction steps. The product articles are three-dimensionally periodic on a scale where conventional processing methods cannot be used. Articles and materials made by these processes are useful as thermoelectrics and thermionics, electrochromic display elements, low dielectric constant electronic substrate materials, electron emitters (particularly for displays), piezoelectric sensors and actuators, electrostrictive actuators, piezochromic rubbers, gas storage materials, chromatographic separation materials, catalyst support materials, photonic bandgap materials for optical circuitry, and opalescent colorants for the ultraviolet, visible, and infrared regions.

On-chip multispectral imaging and data management is provided in the form of an Adaptive Focal Plane Array (AFPA) that is capable of spectral tunability at the pixel level. Layers of photonic crystals are registered with pixels of a broadband focal plane array. Spectral tuning is accomplished by switching the photonic crystal layers on/off and/or by changing their material structure to tune their photonic band gaps and provide a passband for incident photons. The photonic crystal layers are preferably segmented to independently address different regions or “cells” of pixels down to a pixel-by-pixel resolution. The AFPA may simultaneously sense different regions of a scene at different spectral wavelengths, spatial resolutions and sensitivities.

The invention consists in structuring scintillation radiation detectors as Photonic Bandgap Crystals or 3D layers of thin filaments, thus enabling extremely high spatial resolutions and achieving virtual voxellation of the radiation detector without physical separating walls. The ability to precisely measure the recoil electron track in a Compton camera enables to assess the directions of the gamma rays hitting the detector and consequently dispensing with collimators that strongly reduce the intensity of radiation detected by gamma cameras. The invention enables great enhancements of the capabilities of gamma cameras, SPECT, PET, CT and DR machines as well as their use in Homeland Security applications. Methods of fabrication of such radiation detectors are decribed.

An optical fiber having a longitudinal direction and a cross-section perpendicular thereto, the optical fiber includes a core region; and a micro-structured cladding region, the cladding region surrounding the core region and having longitudinally extending micro-structure cladding elements arranged in a background cladding material, the micro-structured cladding elements having cross-sectional sizes which are equal or different, at least a number of the cladding elements being arranged in a substantially two dimensional periodic manner or a Bragg-type of manner, such as concentric rings of cladding elements surrounding the core, and the at least a number of the cladding elements are filled in at least one longitudinally extending section of the optical fiber with a liquid crystal material. The at least one filled section exhibits a photonic bandgap effect for at least one phase state of the liquid crystal.

A light emitting structure includes a semiconductor light emitting device capable of emitting first light having a first peak wavelength, a luminescent material capable of emitting second light having a second peak wavelength disposed over the semiconductor light emitting device, and a photonic band gap material disposed between the light emitting device and the luminescent material. The photonic band gap material is capable of transmitting the first light and reflecting the second light, regardless of the angle of incidence of the first and second light.

An active photonic crystal device for controlling an optical signal is disclosed. The device includes a planar photonic crystal with a defect waveguide bounded on the top and bottom by an upper cladding region and a lower cladding region. An optical signal propagating in the defect waveguide is confined in the plane of the photonic crystal by the photonic bandgap, and in the direction normal to the photonic crystal by the upper clad region and the lower clad region. The propagation of the optical signal in the defect waveguide is controlled by varying the optical properties at least one of the upper clad region or the lower clad region. The variation of the optical properties of the controllable regions may be achieved using a thermo-optic effect, an electro-optic effect, a stress-optic effect, or a mechano-optic effect, or by moving a material into or out of the controllable region.

A new class of processes suited to the fabrication of layered material compositions is disclosed. Layered material compositions are typically three-dimensional structures which can be decomposed into a stack of structured layers. The best known examples are the photonic lattices. The present invention combines the characteristic features of photolithography and chemical-mechanical polishing to permit the direct and facile fabrication of, e.g., photonic lattices having photonic bandgaps in the 0.1-20.mu. spectral range.

A reflector, a method of producing same and a method of creating high omnidirectional reflection for a predetermined range of frequencies of incident electromagnetic energy for any angle of incidence and any polarization. The reflector includes a structure with a surface and a refractive index variation along the direction perpendicular to the surface while remaining nearly uniform along the surface. The structure is configured such that i) a range of frequencies exists defining a photonic band gap for electromagnetic energy incident along the perpendicular direction of said surface, ii) a range of frequencies exists defining a photonic band gap for electromagnetic energy incident along a direction approximately 90° from the perpendicular direction of said surface, and iii) a range of frequencies exists which is common to both of said photonic band gaps. In an exemplary embodiment, the reflector is configured as a photonic crystal.

A non-imaging optical collecting and concentrating apparatus for use in i.e., optical communications, passive lighting, and solar power applications that is relatively immune from optical incidence angle(s) and therefore does not need to track the movement of the sun to efficiently collect and concentrate optical energy. The apparatus includes a non-planar support structure having a source-facing entrance and an energy-outputting exit. An interior surface of the structure includes a scattering, reflecting and/or diffractive medium such as a photonic bandgap structure to enhance the collection and concentration efficiency.

Included among the many structures described herein are photonic bandgap fibers designed to provide a desired dispersion spectrum. Additionally, designs for achieving wide transmission bands and lower transmission loss are also discussed. For example, in some fiber designs, smaller dimensions of high index material in the cladding and large core size provide small flat dispersion over a wide spectral range. In other examples, the thickness of the high index ring-shaped region closest to the core has sufficiently large dimensions to provide negative dispersion or zero dispersion at a desired wavelength. Additionally, low index cladding features distributed along concentric rings or circles may be used for achieving wide bandgaps.

An optical fiber that exhibits reduced mode distortions as the fiber is bent is formed by properly defining its refractive index profile during fabrication. The as-fabricated profile is defined as a “pre-distorted” profile that takes into account the gradient introduced by bending the fiber. A parabolic index profile is one exemplary bend-resistant profile that exhibits a quadratic form. A raised-cone index is another profile that may be used as the “as-fabricated” profile. In any properly configured form, factors such as bend loss and mode distortion are significantly reduced, since the profile undergoes a shift of essentially constant gradient as a bend is introduced. The resultant effective area of the inventive fiber is substantially improved over state-of-the-art fiber that is subjected to bending during installation. The as-fabricated profile may be incorporated into various types of fibers (birefringent, photonic bandgap, etc.), and is particularly well-suited for use in a fiber amplifier arrangement.

The present invention deals with optical systems for providing short laser pulses. An object of the invention is to provide an optical system providing compact and cost-effective short laser-pulses using fibers with anomalous dispersion and high non-linear thresholds. The object is achieved by a short pulse optical system for generating or processing short laser-pulses, said optical system comprises an optical fiber in the form of a photonic crystal fiber arranged to provide guidance of light in the core region due to the photonic bandgap effect (PBG), where light propagates in a hollow or solid core surrounded by a Silica cladding comprising a substantially periodic distribution of micro-structural elements, and where the refractive index of the core is lower than the effective refractive index of the cladding. The invention may be useful in applications such as laser-based micromachining, thin-film formation, laser cleaning, in medicine and biology.

A photonic bandgap device has a lattice structure, with a waveguide formed by a mesh of defects in the lattice, the defects being located discontinuously, but sufficiently close to each other to provide coupling between overlapping evanescent defect modes. By changing shape and configuration of the mesh and varying the types of defects, it is easier to control the width and position of the transmission band, in wavelength terms, compared to a waveguide formed only from a planar defect, i.e. a single line of defects. Multiplexers, demultiplexers, filters, switches, combiners, and splitters may be created. Many devices and different types of devices can be integrated onto the same crystal lattice, with far greater compactness than planar waveguide technology. The mesh can have a periodic structure of lines of defects, or periodic spacing between defects to reduce loss.

The invention relates to processes for the synthesis of 2-D and 3-D periodic porous silicon structures and composites with improved properties having the advantages of porous silicon and photonic bandgap materials. Photonic crystals comprise a two dimensionally periodic or three dimensionally periodic microporous structural matrix of interconnecting, crystallographically oriented, monodispersed members having voids between adjacent members, and said members additionally having randomly nanoporous surface porosity. The silicon nanofoam material shows enhanced and spectrally controlled/tunable photoluminescence and electroluminesce and finds use as transparent electrodes, high-lumonosity light emitting diodes (LEDs), wavelength division multiplexors, high-active-area catalyst supports, photonic bandgap lasers, silicon-based UV detectors, displays, gas sensors, and the like.

An infrared emitter, which utilizes a photonic bandgap (PBG) structure to produce electromagnetic emissions with a narrow band of wavelengths, includes a semiconductor material layer, a dielectric material layer overlaying the semiconductor material layer, and a metallic material layer having an inner side overlaying the dielectric material layer. The semiconductor material layer is capable of being coupled to an energy source for introducing energy to the semiconductor material layer. An array of holes are defined in the device in a periodic manner, wherein each hole extends at least partially through the metallic material layer. The three material layers are adapted to transfer energy from the semiconductor material layer to the outer side of the metallic material layer and emit electromagnetic energy in a narrow band of wavelengths from the outer side of the metallic material layer.

A microstructured fiber having a cladding comprising a number of elongated features that are arranged to provide concentric circular or polygonial regions surrounding the fiber core. The cladding comprises a plurality of concentric cladding regions, at least some of which comprising cladding features. Cladding regions comprising cladding features of a relatively low index type are arranged alternatingly with cladding regions of a relatively high index type. The cladding features are arranged in a non-periodic manner when viewed in a cross section of the fiber. The cladding enables waveguidance by photonic bandgap effects in the fiber core. An optical fiber of this type may be used for light guidance in hollow core fibers for high power transmission. The special cladding structure may also provide strong positive or negative dispersion of light guided through the fiber-making the fiber useful for telecommunication applications.

A photonic crystal having reversibly tunable photonic properties. The photonic crystal includes a phase change material having a plurality of structural states that vary with respect to fractional crystallinity. Optical constants including refractive index, extinction coefficient and permittivity vary as the fractional crystallinity of the phase change material is varied thereby providing tunability of photonic crystal properties. Variations among the structural states of the phase change material are reversibly effected through the addition of energy in forms including optical or electrical energy. The photonic crystals may include defects that provide photonic states within the photonic band gap. The position of these states is tunable through the control of the fractional crystallinity of the phase change material included in the photonic crystal. Electromagnetic radiation resonators including photonic crystals having photonic states in the photonic band gap are further provided. These resonators may be used for frequency selective filtering or routing of electromagnetic radiation and permit tunable variation in the frequency and decay rates of resonant modes through control of the structural state of the phase change material. These resonators are further coupled to waveguides to provide tunable channel drop filters and narrowband reflectors.

A Fabry-Perot cavity comprised of three-dimensional photonic crystal structures is disclosed. The self-assembly of purified and highly monodispersed microspheres is one approach to the successful operation of the device for creating highly ordered colloidal crystal coatings of high structural and optical quality. Such colloidal crystal film mirrors offer high reflection with low losses in the spectral window of the photonic band gap that permit Fabry-Perot resonators to be constructed with high resolving power, for example, greater than 1000 or sharp fringes that are spectrally narrower than 1.0 nm. The three-dimensional photonic crystals that constitute the Fabry-Perot invention are not restricted to any one fabrication method, and may include self-assembly of colloids, layer-by-layer lithographic construction, inversion, and laser holography. Such photonic crystal Fabry-Perot resonators offer the same benefits of high reflection and narrow spectral band responses available from the use of multi-layer dielectric coatings. However, the open structure of three-dimensional photonic crystal films affords the unique ability for external media to access the critical reflection layers and dramatically alter the Fabry-Perot spectrum, and provide means for crafting novel laser, sensor, and nonlinear optical devices. This open structure enables the penetration of gas and liquid substances, or entrainment of nano-particles or biological analytes in gases and liquids, to create subtle changes to the colloidal mirror responses that manifest in strong spectral responses in reflection and transmission of the collective Fabry Perot response.

In order to create an optical device with a photonic band gap extending in two dimensions and with very uniform properties in any direction and for any polarisation state, to within 1%, air holes are etched within a substrate of low refractive index material such silicon oxynitride or silica glass. The ratio of air hole area to the remainder of the substrate is low, being less than 35%. The air holes define a quasicrystal structure, having twelve fold symmetry, being based on a square-triangle system. In another development, an etched substrate with a regular crystal structure or quasicrystal structure exhibits a non-linear refractive index. Two adjacent areas in such a substrate have different lattice properties, or have defects in the lattices, to create a unidirectional transmission path (diode action). A further beam of light may be used to modulate the transmission path by reason of the non-linear refractive index.

A device includes a photonic crystal having a plurality of voids disposed in a periodic lattice throughout a dielectric material. Each void is at least partially defined by a surface of the dielectric material. The photonic crystal also includes a waveguide. Gain material is disposed within at least one void located proximate the waveguide. The gain material may emit radiation having a wavelength within a photonic bandgap of the photonic crystal and corresponding to an allowable mode of the waveguide. A method for coupling radiation to a waveguide includes providing a photonic crystal having a plurality of voids disposed in a periodic lattice throughout a dielectric material and a waveguide. Each void is at least partially defined by at least one surface of the dielectric material. Gain material is provided within at least one void located proximate the waveguide and stimulated to emit electromagnetic radiation.

A microstrip patch antenna utilizes a microstrip patch antenna substrate formed of photonic bandgap material. One or more periodic patterns may be used therewith to produce multiple bandgaps into the photonic bandgap material. The periodic patterns may be produced by introducing periodic defects into the dielectric material substrate with drilled holes, slots, shorted vias, blind vias, buried vias, and/or plated or unplated patterns, such as plated patterns on the groundplane or on internally positioned surfaces, or on the surface adjacent the radiating elements. One or more radiating elements are used on an upper surface of said microstrip patch antenna substrate, and a groundplane is formed on a lower surface of said microstrip patch antenna substrate.