Showing papers on "Radiation mode published in 2001"

Dual band multimode coaxial tracking feed

Abstract: A dual band multimode coaxial antenna feed has an inner section of longitudinal hollow waveguide having first and second orthogonal mode transducers that interface first and second orthogonally polarized cylindrical waveguide TE11 mode signals lying in a first upper (e.g.,Ka) frequency band. An outer coaxial waveguide section has a Potter horn surrounding the inner waveguide section, which terminates at a polyrod. The outer section includes third and fourth orthogonal mode transducers that interface orthogonally polarized coaxial waveguide TE11 mode signals lying in a second lower (e.g.,X) frequency band. A tracking port coupled to the outer coaxial waveguide section provides an output representative of the difference pattern of the radiation profile produced by transverse electromagnetic TEM mode signals generated and propagating in the outer coaxial waveguide. A mode supressor in the outer waveguide section adjacent its two orthogonal mode transducers locally supresses TEM signals in their vicinity.

Guided wave spatial filter

Abstract: The invention concerns a guided wave spatial filter (300) for receiving input radiation and outputting corresponding filtered output radiation, the filter comprising first and second waveguide sections (30, L3, L5) connected in series, the sections: (a) mutually matched for transmitting fundamental mode radiation components present in the input radiation therethrough to provide the output radiation; and (b) mutually mismatched for hindering higher-order mode radiation components present in the input radiation from propagating therethrough and contributing to the output radiation. The spatial filter (300) is implemented using rib waveguides (30) for the sections with associated relatively deeply and relatively shallowly etched structures (20, 310, 320) for imparting to the sections their radiation mode filtration characteristics. The spatial filter according to the invention can be incorporated into optical splitters and optical modulators to enhance their performance and desensitise them to higher-order mode radiation injected thereinto.

Optical wavelength converter

Abstract: In accordance with the invention there is provided an optical wavelength conversion device The conversion device comprises a micro-structured optical waveguide, which includes sections with a non-linear material having an index of refraction which changes as a non-linear function of light intensity The optical waveguide includes a light guiding core region, and the waveguide is dimensioned for providing spatial overlap between the sections filled with the non-linear material and light propagating within the waveguide The conversion device further comprises a first optical light source for introducing light into the waveguide in a mode guided along the core, and a second intensity modulated light source for introducing encoding light into the waveguide in such a manner that it illuminates the sections filled with a non-linear material The second light source has an intensity modulation sufficient to change the refractive index of the non-linear material by an amount sufficient to encode or modulate the light from the first optical light source accordingly, whereby the encoding takes place through the effect of leaking light from the first light source from the inside of the guiding core to the outside of the guiding core The micro-structured optical waveguide may comprisean optical fibre, in which the light from the first light source may be guided by different types of waveguiding principles including total internal reflection or by photonic bandgap effects In an alternative embodiment the micro-structured optical waveguide may comprise an optical planar waveguide The conversion device includes embodiments in which the encoding light from the secondlight source and the light to be encoded or modulated from the first light source are co-propagating, are counter-propagating, or where the encoding light has a propagation direction different to the propagation direction of the light to be encoded According to the invention there is also provided a micro-structured optical waveguide, which may have an axial direction, which waveguideincludes sections that are elongated in the axial direction and comprise a non-linear material having an index of refraction whichchanges as a non-linear function of light intensity This optical waveguide, which may be an optical fibre, includes a light guiding core region, and the waveguide is dimensioned for providing spatial overlap between the sections filled with the non-linear material and light propagating within the waveguide There is furthermore provided an optical switching device and an optical intensity limiting device which may be based on the micro-structured optical waveguide of the invention

Mode transformer between low index difference waveguide and high index difference waveguide

Abstract: A mode transformer (100) that enables low-loss coupling between optical modes of two waveguides with different index difference. The mode size and the effective index are gradually changed between two waveguides to gradually transform the mode shape, size, and speed with minimum power loss. The mode transformer is useful for coupling the mode of an optical fiber waveguide with low index difference to the mode of a planar high index difference waveguide, and vice versa.

Broadband mode converter

Abstract: A mode converter for converting an optical signal from a first propagation mode (e.g., LP 01 ) to a second propagation mode (e.g., LP 02 ). The mode converter includes a first waveguide supporting a first mode of propagation. The mode converter also includes a second waveguide supporting a second mode of propagation. The first and second waveguides each having a group index characteristic, wherein the first group index characteristic is matched with the second group index characteristic such that electromagnetic energy propagating through the first waveguide at the first mode couples to the second waveguide at the second mode.

Photonic integrated detector having a plurality of asymmetric waveguides

Abstract: A photonic integrated circuit 'PIC' device comprising two or more vertically stacked asymmetric waveguides is provided. A photo-detector PIC device comprises a first coupling waveguide (114) for providing a low-coupling loss with an external optical fiber and for guiding primarily a first mode of light, a second waveguide (116) vertically coupled to the first waveguide (114) for guiding primarily a second mode of light having an effective index of refraction different from the first mode, and a photo-detector (118) vertically coupled to the second waveguide (116). Light received at the coupling waveguide is moved into the second waveguide via a lateral taper (117) in the second waveguide. The photo-detector PIC may further comprise a third waveguide having an optical amplifier therein and positioned between the coupling waveguide and the second waveguide.

High-Sensitivity Temperature Sensor Using a Side-Polished Single-Mode Fiber Covered With the Polymer

Abstract: A temperature sensor based on evanescent field coupling between a single-mode side-polished fiber and a polymer planar waveguide was demonstrated. Due to thermooptic effects of a polymer planar waveguide, the resonance wavelength of the device is very sensitive to ambient temperature. Two kinds of polymers were used as planar waveguide materials. Fabricated sensors have a sensitivity of 0.37 nm C and 0.71 nm C, respectively. We also measured the thermooptic coefficient of employed polymer approximately.

Numerical analysis of core-mode to radiation-mode coupling in long-period fiber gratings

Abstract: This letter presents, to the best of our knowledge, the first analysis of core-mode to radiation-mode coupling in long-period fiber gratings (LPGs) that are surrounded with dielectric material whose refractive index is higher than that of the cladding. We calculated core-mode transmission spectra through LPGs by integrating numerically the coupled-mode equations between the core mode and a continuum of radiation modes. We show calculated core-mode transmission spectra that exhibit such loss band continuums as have already been observed experimentally but not yet theoretically estimated.

Vertically-tapered optical waveguide and optical spot transformer formed therefrom

Abstract: An optical waveguide is disclosed in which a section of the waveguide core is vertically tapered during formation by spin coating by controlling the width of an underlying mesa structure The optical waveguide can be formed from spin-coatable materials such as polymers, sol-gels and spin-on glasses The vertically-tapered waveguide section can be used to provide a vertical expansion of an optical mode of light within the optical waveguide A laterally-tapered section can be added adjacent to the vertically-tapered section to provide for a lateral expansion of the optical mode, thereby forming an optical spot-size transformer for efficient coupling of light between the optical waveguide and a single-mode optical fiber Such a spot-size transformer can also be added to a III-V semiconductor device by post processing

Hollow Optical Waveguide for Temperature-Insensitive Photonic Integrated Circuits

Abstract: We propose a hollow optical waveguide with metal coating or dielectric multilayer coating to achieve sufficient reflectivity at guiding walls. Low-loss and polarization-insensitive propagation characteristics are predicted. The propagation constant is independent of the temperature, resulting in temperature-insensitive photonic waveguide devices, such as optical filters and grating optical demultiplexers. We demonstrate a hollow optical waveguide with metal-coated walls on a GaAs substrate, which was fabricated using dry etching. The propagation loss including the coupling loss with an input fiber was 2.6 dB/cm and 7.3 dB/cm for transverse electric (TE) mode and transverse magnetic (TM) mode, respectively.

System and method for providing integrated optical waveguide device

Abstract: Optical filters in, for example, a wavelength division multiplexing (WDM) fiber optic system or an optical waveguide device are utilized and provided The optical waveguide device comprises a lower substrate layer, an insulating dielectric layer and a waveguide ribs layer The insulating dielectric layer, having a first refractive index, is positioned above the lower substrate layer The waveguide ribs layer, having a second different refractive index, is positioned above the dielectric layer An optical waveguide is formed from the waveguide ribs layer for transmission of light In the waveguide ribs layer, an optical filter structure formed, wherein the optical filter structure is integrated onto the same substrate as the optical waveguide

Optical waveguide multimode to single mode transformer

Abstract: An optical waveguide mode transformer (2) has a high refractive index core layer (102a) surrouded by lower refractive index cladding (102b). The core layer includes a wide input waveguide section (110) to accept a multimode, including a fundamental mode, light input. The input waveguide section (110) is coupled to a narrow output waveguide section (140) by a tapered region (120) having a taper length enabling adiabatic transfer of the fundamental mode of the multimode light for the wide input waveguide section to the output waveguide section while suppressing (stripping) other modes of the multimode light input. The narrow output waveguide section (140) supports a single mode light output comprising said fundamental mode. In one embodiment, the core layer is contoured, preferably defined by a ridge intermediate the sides of the core layer, to provide an effective index step portion to control lateral waveguiding of light propagated along the waveguide structure, and the output waveguide section (140) includes a portion having a real index step between the core layer and cladding layers, and is functional to output a light beam having similar vertical and horizontal divergences.

Optical waveguide elements, optical wavelength conversion elements, and process for producing optical waveguide elements

Abstract: An optical waveguide element includes a three-dimensional optical waveguide of a bulky non-linear optical crystal, a substrate, and a joining layer made of an amorphous material. The substrate is joined to the optical waveguide via the joining layer.

Arrayed waveguide grating type optical multiplexer/ demultiplexer

Abstract: An arrayed waveguide grating optical multiplexer/demultiplexer includes an arrayed waveguide connected to at least one first optical waveguide via a first slab waveguide, a plurality of second optical waveguides connected to the arrayed waveguide via a second slab waveguide. At least one expanding width waveguide has a first end portion and a second end portion having a second width larger than a first width of the first end portion. Each first end portion is connected to each first optical waveguide. The second end portion is connected to the first slab waveguide. The first width of the first end portion is larger than a first optical waveguide width of the at least one first optical waveguide. The first width of the first end portion satisfies a single mode condition. A width of the expanding width waveguide increases from the first end portion toward the second end portion.

System and method for passively aligning and coupling optical devices

Abstract: An external mode size transformer includes a waveguide having an input section, an output section, and a tapered section disposed between the input and output sections. The cross sections between the input and output sections of the waveguide can vary smoothly throughout the length of the waveguide, similar to a waveguide shaped like a boat hull. By positioning the external mode size transformer between optical devices, coupling between optical devices is substantially improved compared to that of direct coupling. For example, by positioning the external mode size transformer between a laser and an optical fiber, laser to fiber coupling is significantly improved compared to that of direct coupling between these optical devices. The present invention can include a manufacturing method that employs multiple masks with predetermined shapes to fabricate the sections of the waveguide within a planar substrate via an exemplary ion exchange process.

Slab-coupled optical waveguide laser and amplifier

Abstract: A laser and optical amplifier waveguide device with a plurality of layers that supports a single lowest-order optical mode with gain while higher order modes radiate and have a net loss. The supported lowest-order mode which has gain, has a mode cross section which is large compared to the operating optical wavelength in both the transverse and lateral directions. The contours of constant optical intensity of such lowest-order can be nearly circular, having an approximately elliptical shape with a small aspect ratio.

Optical waveguide element, manufacturing method for optical waveguide element, optical deflecting element, and optical switching element

Abstract: An optical waveguide element capable of being coupled with optical fibers at high coupling efficiency is to be provided. Also an optical waveguide element manufacturing method permitting accurate production of such optical waveguide elements is to be provided. The optical waveguide element is provided with a buffer layer formed over a monocrystalline substrate and an optical waveguide layer formed over the buffer layer, and a recess is formed in the buffer layer along the lengthwise direction of the monocrystalline substrate. The optical waveguide layer is provided to fit into this recess to form a channel optical waveguide. Over the upper face of the optical waveguide layer on the light incidence side and the light emission side, a cladding layer whose refractive index is smaller than that of the optical waveguide layer and whose thickness increases towards the end face(s) in a flared shape is provided in the same width as that of the monocrystalline substrate. By providing the cladding layer whose refractive index is smaller than that of the optical waveguide layer, it is made possible to expand the mode field diameter and substantially reduce the coupling loss between the optical fiber and the optical waveguide element. Further by increasing the thickness of the cladding layer in a flared shape toward the end face(s), it is made possible to gradually compress the mode field diameter and to reduce the optical propagation loss within the optical waveguide.

Structure for shielding stray light in optical waveguide module

Abstract: A structure for shielding a stray light in an optical waveguide module is composed of an optical waveguide substrate supported in an optical waveguide module package, an optical waveguide formed on the optical waveguide substrate, a LD mounted on the optical waveguide substrate, an optical fiber-placement section formed on the optical waveguide substrate, an optical fiber situated on the optical fiber-placement section, a WDM filter formed on the optical waveguide substrate, a PD-mounting carrier situated behind the WDM filter, a PD mounted on the PD-mounting carrier, a metallic layer evaporated on the WDM filter, and a pin hole formed on the metallic layer at nearly a center thereof.

Waveguide device with mode control and pump light confinement and method of using same

Abstract: A waveguide device in the form of either a solid-state laser or amplifier is divided into separate pumping and output mode control sections along at least one direction of the device by leaving a portion of a core of the device unclad or by depositing appropriate coatings on different sections of the core or by contacting/bonding materials with different refractive indices to different sections of the core or by a combination of these approaches. The core has a pump input surface for receiving pumping radiation at a pumping wavelength and one or more output surfaces for emitting a laser beam at an output wavelength. When used as an amplifier, the core also has a laser input surface which may be the same as one of the output surfaces.

Arrayed waveguide grating and optical communication system using arrayed waveguide grating

Abstract: An arrayed waveguide element having flat optical frequency characteristics, and an optical communication system using such arrayed waveguide element are realized by providing the arrayed waveguide element that is prepared by forming an inputting channel waveguide as well as an outputting channel waveguide, a channel waveguide array, a first sector form slab waveguide for connecting the inputting channel waveguide with the channel waveguide array, and a second sector form slab waveguide for connecting the outputting channel waveguide with the channel waveguide array on a substrate. A waveguide part wherein the outputting channel waveguide is connected with the second sector form slab waveguide is defined in a parabolic configuration, whereby flat optical frequency characteristics are realized. Furthermore, it is possible that an individual parabolic configuration is adjusted in response to a wavelength, so that it can cope with a trend of broad band in optical signals.

Variable optical attenuators and optical shutters using a coupling layer in proximity to an optical waveguide (II)

Abstract: A controllable variable optical attenuator for attenuating an optical signal is described herein. The attenuator has an optical waveguide made from similar waveguide core and cladding materials and a coupling layer in close proximity to the waveguide which is configured to provide a difference between the refractive index of the coupling layer in proximity to the waveguide and the effective index of the waveguide. The index of the waveguide can be modified such that if the refractive index of the coupling layer is substantially lower than the effective index of the waveguide, minimal attenuation occurs to the light in the waveguide. Furthermore, if the refractive index of the coupling layer is substantially greater than the effective index of the waveguide, light is coupled into the coupling layer out of the waveguide to attenuate the optical signal. The amount of attenuation varies smoothly between these maximum and minimum values.

Wavelength multiplexer and optical unit

Abstract: The subject to be attained by the disclosed technique is to provide an optical unit less expensive than conventional like optical units and having a wavelength multiplexer and optical waveguides. For achieving the above subject there is provided a wavelength multiplexer wherein a light combining/branching section is constituted by a multi-mode interference type optical waveguide, and an incident-side optical waveguide and a reflection-side optical waveguide are spaced a predetermined distance from each other at their connections to the multi-mode interference type optical waveguide. An optical filter is installed in the multi-mode interference type optical waveguide and a multi-mode interference is set so that a peak in a light intensity distribution is formed in the vicinity of an inlet of each of an exit-side optical waveguide and the reflection-side optical waveguide.

Optical fiber having an elevated threshold for stimulated brillouin scattering

Abstract: An optical fiber having an elevated threshold for stimulated Brillouin scattering is provided. The optical fiber includes a core and a cladding surrounding the core with both the core and the cladding designed to guide optical waves through the core while anti-guiding acoustic waves. Moreover, the optical fiber includes other features to alter the mode profile of the acoustic waves and/or to further promote their lateral radiation. For example, the optical fiber can include an irregular coating to alter the mode profile of the acoustic waves. In another example, the optical fiber can include a quarter wave layer surrounding the cladding to promote the lateral radiation of the acoustic waves. In order to further alter the mode profile of the acoustic waves, the cladding can also have a lateral thickness that varies irregularly in a lengthwise direction.

Optical waveguide, optical module, and their fabrication method

Abstract: It is a problem of disclosed technology to provide a polymer optical waveguide substrate having a V-groove for fiber alignment providing optical coupling with an optical fiber with low loss. According to a resolution means therefor, there is provided an optical waveguide member characterized in that an optical waveguide is formed at a portion over a silicon substrate, a core or a clad of the optical waveguide comprises a polymer resin, a groove in a shape of V for positioning and fixing an optical fiber to the optical waveguide is provided to the silicon substrate and a groove in a rectangular shape extended in a direction orthogonal to the groove in the shape of V at a boundary of the V-groove and the optical waveguide, is provided to the silicon substrate, a film thickness of the core or the clad constituting the optical waveguide becomes thinner at a vicinity of the boundary than a film thickness of other portion and the shape of the groove having the shape of V is set such that when the optical fiber is mounted to the V-groove in the shape of V, a height of a center of a core of the optical fiber becomes lower than a height of the core of the optical waveguide at a position sufficiently remote from the boundary and highly efficient optical coupling is achieved between the optical fiber and the optical waveguide.

Variable width waveguide for mode-matching and method for making

Abstract: A variable width waveguide useful for mode matching between dissimilar optical waveguides and optical fibers and a method for making the same is described. In one embodiment, a tapered waveguide is etched in a substrate, a cladding material is laid over the upper surface of the substrate and within the waveguide, and the waveguide is then filled with a core material. The core material may be deposited in a single step, or in successive deposition steps.

Optical communication module and process for producing the same

Abstract: In the production process of an optical send/receive module, parts in each section for two-way communication are constructed on a chip of an optical waveguide substrate, A V groove for installing an optical fiber is formed on the optical waveguide substrate by anisotropic etching. A filter for the transmission and reflection of an optical signal is provided diagonally relative to the V groove. A first optical waveguide and a second optical waveguide as a straight waveguide for send/receive of an optical signal are disposed at respective angles such that an optical signal introduced from the first optical waveguide is reflected from the filter and transmitted to the second optical waveguide and one end of each of the first and second optical waveguides is disposed at a position close to the optical signal reflection point in the filter. The V groove is disposed straightly relative to and in the same direction as the second optical waveguide. A groove for the insertion of the filter and a groove for abutting against the optical fiber provided in each of the optical waveguide substrates are formed at a time for each line of the optical waveguide substrates in the wafer. The above construction can realize an optical send/receive module, which can eliminate the need to provide a bent waveguide, enables all waveguides to be constructed by a straight waveguide, has a small size, and can realize mass production at low cost, and a process for producing the same.

Dispersion of the ordinary refractive-index change in a proton-exchanged LiNbO3 waveguide

Abstract: The wavelength dependence of the ordinary refractive-index change of a proton exchanged LiNbO3 waveguide is determined by applying a recently proposed method based on radiation modes. A peculiar behavior is observed since the absolute value of the ordinary index change increases with the wavelength, while the extraordinary one decreases. The Sellmeier curves for the dispersion of both the index changes are provided in the wavelength range from λ=0.514 μm to λ=1.554 μm.

Dispersion slope compensating optical waveguide fiber

Abstract: Disclosed is a dispersion compensating and dispersion slope compensating single mode optical waveguide fiber. The refractive index profiles of waveguide fibers in accord with the invention are disclosed and described. These index profiles provide a waveguide fiber having negative total dispersion and negative total dispersion slope so that a standard waveguide fiber is compensated over an extended wavelength range. A telecommunications link using the fiber in accord with the invention is also disclosed and described. A standard fiber to compensating fiber length ratio in the range of 1:1 to 3:1 is shown to give optimum link performance with respect to limiting non-linear dispersion effects.

Methods and apparatus for measuring the power spectrum of optical signals

Abstract: A method of measuring a power spectrum of an optical signal. The optical signal is transmitted through an optical fiber. A power of at least one wavelength of the optical signal is coupled from a first mode to a second mode of the waveguide. The power of the optical signal coupled from the first mode to the second mode is measured at a detector.