111 results about "Refractive index contrast" patented technology

Composite optical waveguide structures or mode transformers and their methods of fabrication and integration are disclosed, wherein the structures or mode transformers are capable of bi-directional light beam transformation between a small mode size waveguide and a large mode size waveguide. One aspect of the present invention is directed to an optical mode transformer comprising a waveguide core having a high refractive index contrast between the waveguide core and the cladding, the optical mode transformer being configured such that the waveguide core has a taper wherein a thickness of the waveguide core tapers down to a critical thickness value, the critical thickness value being defined as a thickness value below which a significant portion of the energy of a light beam penetrates into the cladding layers surrounding the taper structure thereby enlarging the small mode size. This primary tapered core structure may be present in either a vertical or horizontal direction and may be combined with further up taper or down taper structures in the directions transverse to the primary taper direction. Another aspect of the present invention is directed to a non-cylindrical graduated refractive index (GRID) lens structure. The non-cylindrical GRIN structure has a graded refractive index having a maximum value at its core and a minimum value at its outer edges. The grading of the refractive index is provided in a either the vertical or horizontal directions and may have either a fixed refractive index or a graded refractive index in the transverse directions. Yet another aspect of the present invention is directed to composite optical mode transformers that are combinations of the taper waveguide structures and the non-cylindrical graduated refractive index structures. Yet another aspect of the present invention is the further integration of the mode transformers with V-grooves for multiple input / output fibers and alignment platform for multiple input / output photonic chips or devices.

An optical mode transformer comprises a first waveguide including a first core, a first cladding and an end facet configured to be coupled to an optical fiber. The transformer further includes a second waveguide comprising a second core, a second cladding and an end directly coupled to an end of the first waveguide. A third waveguide comprises a third core and a third cladding, and is arranged with respect to the second waveguide so as to realize an evanescent optical coupling with the second waveguide. The third core includes a tapered region wherein evanescent coupling takes place, and wherein a refractive index contrast of the first waveguide is less than a refractive index contrast of the second waveguide, the refractive index contrast of the second waveguide is less than a refractive index contrast of the third waveguide, and the refractive index contrast of the third waveguide is not less than 18%.

An optical mode transformer comprises a first waveguide including a first core, a first cladding and an end facet configured to be coupled to an optical fiber. The transformer further includes a second waveguide comprising a second core, a second cladding and an end directly coupled to an end of the first waveguide. A third waveguide comprises a third core and a third cladding, and is arranged with respect to the second waveguide so as to realize an evanescent optical coupling with the second waveguide. The third core includes a tapered region wherein evanescent coupling takes place, and wherein a refractive index contrast of the first waveguide is less than a refractive index contrast of the second waveguide, the refractive index contrast of the second waveguide is less than a refractive index contrast of the third waveguide, and the refractive index contrast of the third waveguide is not less than 18%.

An optical arrangement includes a plurality of planar substrates with at least one planar integrated optical waveguide on each planar substrate. At least one optical waveguide structure has at least one end connected via an optical connecting structure to one of the planar integrated optical waveguides. The optical waveguide structure is positioned at least partly outside the integration plane for the planar integrated optical waveguide and a refractive index contrast between a core region and a cladding region of the optical waveguide structure is at least 0.01.

An optical mode transformer comprises a first waveguide including a first core, a first cladding and an end facet configured to be coupled to an optical fiber. A second waveguide comprises a second core and a second cladding, and is arranged with respect to the first waveguide so as to realize an evanescent optical coupling with the first waveguide. The second core comprises a tapered region, in at least a portion of which the evanescent coupling takes place.The first core and the second core are separated by a gap. A first refractive index contrast of the first waveguide is less than a second refractive index contrast of the second waveguide.

A method of forming a waveguide including a core region, a cladding region, and an index contrast region situated therebetween includes depositing a polymerizable composite on a substrate to form a layer, patterning the layer to define an exposed area and an unexposed area of the layer, irradiating the exposed area of the layer, and volatilizing the uncured monomer to form the waveguide, wherein the polymerizable composite includes a polymer binder and sufficient quantities of an uncured monomer to diffuse into the exposed area of the layer and form the index contrast region. The resulting waveguide includes an index contrast region which has a lower index of refraction than that of the core and cladding regions.

A quantum logic gate for qubits, suitable for receiving as inputs at least two polarization-encoded qubits, includes at least one partially polarizing beam splitter (PPBS), the beam splitter comprising a first waveguide and a second waveguide which are constructed in integrated optics, the first and second waveguides having a refractive index contrast of between 0.1% and 6% and a birefringence of between 10−6 and 6*10−5.

An optical arrangement includes a plurality of planar substrates with at least one planar integrated optical waveguide on each planar substrate. At least one optical waveguide structure has at least one end connected via an optical connecting structure to one of the planar integrated optical waveguides. The optical waveguide structure is positioned at least partly outside the integration plane for the planar integrated optical waveguide and a refractive index contrast between a core region and a cladding region of the optical waveguide structure is at least 0.01.

Disclosed is a photovoltaic solar cell and method for producing same for conversion of light into electric power using a composite film having micron sized down to nanometer sized particles sufficiently sized for precise light scattering. A matrix material is further provided having a substantially different refractive index to provide a refractive index contrast for light scattering.

Composite optical waveguide structures or mode transformers and their methods of fabrication and integration are disclosed, wherein the structures or mode transformers are capable of bidirectional light beam transformation between a small mode size waveguide and a large mode size waveguide. One aspect of the present invention is directed to an optical mode transformer comprising a waveguide core having a high refractive index contrast between the waveguide core and the cladding, the optical mode transformer being configured such that the waveguide core has a taper wherein a thickness of the waveguide core tapers down to a critical thickness value, the critical thickness value being defined as a thickness value below which a significant portion of the energy of a light beam penetrates into the cladding layers surrounding the taper structure thereby enlarging the small mode size.

High-quality Al1-xInxN layers and AlInN / GaN Bragg mirrors near lattice-matched to GaN layers are grown by metalorganic vapor-phase epitaxy on a GaN buffer layer with no cracks over full 2-inch sapphire wafers. The index contrast relative to GaN is 6.5% to 11% for wavelengths ranging from 950 nm to 380 nm. A crack-free, 20 pairs Al0.84In0.16N / GaN distributed Bragg reflector is grown, centered at 515 nm with over 90% reflectivity and a 35 nm stopband. High-quality AlInN lattice matched to GaN can be used in GaN-based optoelectronics, for waveguides and for mirror structures in resonant-cavity light-emitting diodes and monolithic Fabry-Pérot cavities, for example.

Holographic optical elements, devices and methods are disclosed. The holographic optical elements include calamitic materials. This is advantageous because the holographic medium in which the holographic image is formed is latent or very nearly latent, has little or no Rayleigh scattering, has high refractive index contrast, and is fabricated with mild post-processing conditions.

An optoelectronic transducer comprises a unipolar, intraband active region and a micro-cavity resonator. The resonator includes a 2D array of essentially equally spaced regions that exhibits resonant modes. Each of the spaced regions has a depth that extends through the active region and has an average refractive index that is different from that of the active region. The refractive index contrast, the spacing of the spaced regions, and the dimensions of the spaced regions are mutually adapted so that the array acts as a micro-cavity resonator and so that at least one frequency of the resonant modes of the array falls within the spectrum of an optoelectronic parameter of the active region (i.e., the gain spectrum where the transducer is a laser; the absorption spectrum where the transducer is a photodetector). In a first embodiment, the transducer is an ISB laser, whereas in a second embodiment it is a unipolar, intraband photodetector. In other embodiments, the laser is a surface-emitting ISB laser and the photodetector is a vertically-illuminated detector. In another embodiment, a nonlinear optical material is optically coupled to the micro-cavity resonator, which in one case allows an ISB laser to exhibit bistable operation.

Novel processing methods for production of high-refractive index contrast and low loss optical waveguides are disclosed. In one embodiment, a “channel” waveguide is produced by first depositing a lower cladding material layer with a low refractive index on a base substrate and a refractory metal layer. Then, an etch mask layer is deposited on the refractory layer, followed by selective etching of the refractory metal layer with a dry-etch tool with high selectivity to the etch mask layer. Then, the refractory metal layer is oxidized to form an oxidized refractory metal region, and a top cladding layer made of a second low refractive index material to encapsulate the oxidized refractory metal region. In another embodiment, a “ridge” waveguide is produced by using similar process steps with an added step of depositing a high-refractive-index material layer and an optional optically-transparent layer.

The present invention provides a method for fast switching of optical properties in photonic crystals using pulsed / modulated free-carrier injection. The results disclosed herein indicate that several types of photonic crystal devices can be designed in which free carriers are used to vary dispersion curves, stop gaps in materials with photonic bandgaps to vary the bandgaps, reflection, transmission, absorption, gain, or phase. The use of pulsed free carrier injection to control the properties of photonic crystals on fast timescales forms the basis for all-optical switching using photonic crystals. Ultrafast switching of the band edge of a two-dimensional silicon photonic crystal is demonstrated near a wavelength of 1.9 μm. Changes in the refractive index are optically induced by injecting free carriers with 800 nm, 300 fs pulses. Band-edge shifts have been induced in silicon photonic crystals of up to 29 nm that occurs on the time-scale of the pump pulse. The present invention also provides a method of producing a virtual or temporary photonic crystal using free carrier injection into pure semiconductors, bulk or thin film, in which the carriers are generated in patterns which create a patterned refractive index contrast used to steer light beams in the semiconductor while it is being pulsed.

A high-index contrast waveguide component is presented, which is based on the fast changing of the transmission properties of an optical waveguide by applying electric voltages, or by embossing electric currents. The waveguide consists of a high-refractive waveguide core surrounded by a low-refractive surrounding material, which at least area by area has electro-optical properties. By applying a voltage to completely or partially optically transparent electrodes, an electric field is generated having a strong overlap with the optical mode, being in interaction with it, and therefore changing the transmission properties of the waveguide. The transparent electrodes or supply line areas are laminar, connected at low resistance with conductor paths of high conductivity by means of structures continually repeated along the propagation direction. Thus, it is possible for example to very fast load the capacity being effective between the electrodes, and to thus achieve a high electric band width. In certain embodiments, the waveguide core itself consists of one or more electrically conductive stripes being used as electrodes at the same time. These embodiments make especially small switching voltages possible.For example, the presented component makes fast electro-optical modulators with small switching voltages possible, which modulators may be integrated together with electronic components on a common semiconductor substrate (e.g. silicon).

A low-loss photonic waveguide in the form of a Bragg optical fiber is provided that includes a dielectric core region extending along a waveguide axis that is characterized by a low amount of Rayleigh scattering, and a dielectric confinement region surrounding the dielectric core region that includes alternating layers of different glass compositions having relative refractive index differences that are at least 0.10, and preferably at least 0.30. The core region may be formed from air. The confinement region includes alternating high and low index glass layers wherein the high index layers are substantially pure silica mixed with index raising dopants that form enough % of the high index glass layers by weight to achieve the aforementioned 0.10 difference in indices of refraction, while the low index glass layers may be either substantially pure silica, or silica mixed with index lowering dopants to increase the index contrast between the layers. The use of alternating high and low index glass layers to form the dielectric confinement region allows the Bragg fiber to be usually manufactured on a large scale via conventional fiber optic fabricating techniques with relatively few steps. The resulting fiber is capable of conducting high photonic power levels, and is particularly compatible with short photonic wavelengths, such as ultraviolet light.

A high-index contrast waveguide component is presented, which is based on the fast changing of the transmission properties of an optical waveguide by applying electric voltages, or by embossing electric currents. The waveguide consists of a high-refractive waveguide core surrounded by a low-refractive surrounding material, which at least area by area has electro-optical properties. By applying a voltage to completely or partially optically transparent electrodes, an electric field is generated having a strong overlap with the optical mode, being in interaction with it, and therefore changing the transmission properties of the waveguide. The transparent electrodes or supply line areas are laminar, connected at low resistance with conductor paths of high conductivity by means of structures continually repeated along the propagation direction. Thus, it is possible for example to very fast load the capacity being effective between the electrodes, and to thus achieve a high electric band width. In certain embodiments, the waveguide core itself consists of one or more electrically conductive stripes being used as electrodes at the same time. These embodiments make especially small switching voltages possible.For example, the presented component makes fast electro-optical modulators with small switching voltages possible, which modulators may be integrated together with electronic components on a common semiconductor substrate (e.g. silicon).

The present invention provides a composition comprising at least one a photoactive index-contrasting polymerizable material, wherein the photoactive polymerizable material comprises at least one reactive functional group and at least one index-contrasting group, and wherein the photoactive polymerizable material includes one or more of the following parameters: (1) a distance between at least one reactive group and at least one index-contrasting group which is at least to the average radius of the index-contrasting group; (2) two or more reactive groups per photoactive polymerizable materials; (3) an index-contrasting group having a strong chromophore absorption at a wavelength shorter than the recording wavelength, and (4) the photoactive polymerizable material comprises a reactive nanoparticle. The photoactive polymerizable material may be used to prepare an article by, for example, dispersion thereof in a support matrix, which may be used, for example, to record holograms.

A method of forming a waveguide including a core region, a cladding region, and an index contrast region situated therebetween includes depositing a polymerizable composite on a substrate to form a layer, patterning the layer to define an exposed area and an unexposed area of the layer, irradiating the exposed area of the layer, and volatilizing the uncured monomer to form the waveguide, wherein the polymerizable composite includes a polymer binder and sufficient quantities of an uncured monomer to diffuse into the exposed area of the layer and form the index contrast region. The resulting waveguide includes an index contrast region which has a lower index of refraction than that of the core and cladding regions.

A hybrid waveguide structure having a combination of buried waveguide sections and ridge waveguide sections on the same substrate, share a common core layer. The buried waveguide sections provide the low index contrast desirable for couplers and other device components. The ridge waveguide sections provide the high index contrast needed for efficient low-loss tightly curved waveguides. The devices are fabricated starting from a low index contrast buried waveguide. Cladding material is then selectively removed by etching down from an upper surface either side of the waveguide core to a lower surface. This forms an enhanced index contrast ridge section of the waveguide. The other sections of the waveguide core remain buried and thus retain lower index contrast. Using this approach, a variety of optical devices, such as add / drop or add-after-drop multiplexers for WDM applications based on microrings or Mach-Zehnder interferometers, can be made with large feature sizes of several microns using silica-on-glass or silica-on-silicon technology, for example, and without having to use nanofabricated semiconductor structures.

A method of growing semiconductor materials in the Indium, Aluminium, Gallium Nitride (InAlGaN) material system and to devices made therefrom, in particular optical devices in the ultraviolet to green region of the visible spectrum. Certain optical devices, for example Vertical Cavity Surface Emitting Lasers (VCSELs) require great precision in the thickness of certain semiconductor layers. One aspect of the present invention provides a gallium-rich group III nitride layer (200, 201) and an adjacent layer of AlxInyGa1-x-yN layer (202). The AlxInyGa1-x-yN layer (202) acts as a fabrication facilitation layer and is selected to provide a good lattice match and high refractive index contrast with the gallium-rich group III nitride layer (200, 201). The high refractive index contrast permits in-situ optical monitoring. The extra layer (202) can be used as an etch marker or etch stop layer in subsequent processing and may be used in a lift-off process.

A method of forming a waveguide including a core region, a cladding region, and an index contrast region situated therebetween includes depositing a polymerizable composite on a substrate to form a layer, patterning the layer to define an exposed area and an unexposed area of the layer, irradiating the exposed area of the layer, and volatilizing the uncured monomer to form the waveguide, wherein the polymerizable composite includes a polymer binder and sufficient quantities of an uncured monomer to diffuse into the exposed area of the layer and form the index contrast region. The resulting waveguide includes an index contrast region which has a lower index of refraction than that of the core and cladding regions.

A system in one general embodiment includes a waveguide structure comprising a core of an alloy of Group III-V materials surrounded by an oxide (which may include one or more Group III-V metals), wherein an interface of the oxide and core is characterized by oxidation of the alloy for defining the core. A method in one general approach includes oxidizing a waveguide structure comprising an alloy of Group III-V materials for forming a core of the alloy surrounded by an oxide.

A waveguide structure according to the invention comprises a core layer (10), having a refractive index ncore, and an array of rods (11) in the core layer having a refractive index nrods. The refractive indices satisfy the inequality: nrods>ncore. In a planar waveguide structure buffer (12) and cladding (13) layers are included, having a refractive index nbuffer and ncladding respectively. The refractive indices then satisfy the inequality: nrods>ncore>ncladding and nbuffer. This condition provides greater vertical confinement of the E-field of an optical signal passing through the waveguide. Furthermore, it allows waveguides to be formed of a glassy material having a similar refractive index and core dimensions to that of a fiber. A high refractive index contrast within the photonic crystal region is used while totally eliminating the need for mode conversion to launch light in and out of the waveguide.