Showing papers on "Radiation mode published in 1995"

Wavelength division optical multiplexing elements.

Abstract: The present invention relates to methods and apparatus for wavelength division multiplexing (WDM) using arrays of optical filtering elements to create a desired wavelength passband in an optical filter. In one aspect of the invention, an optical demultiplexer is formed using an input waveguide, such as a planar waveguide or an optical fiber, coupled to plural output waveguides. Each output waveguide includes a wavelength selective configuration of optical filtering elements formed within a contiguous portion of the waveguide forming an optical channel-selective filter having spectral regions having an optical transmission passband and spectral regions of low transmissivity. Exemplary optical filtering elements are Bragg gratings formed into an optical filter which transmits a characteristic wavelength band.

Single-mode waveguide structure for optoelectronic integrated circuits and method of making same

Abstract: An optical waveguide for use in an optoelectronic integrated circuit and the associated method of manufacturing such a waveguide. The waveguide is formed by the successive layering of varied waveguide materials on a III-V semiconductor substrate, thereby producing a slab waveguide. The various layers within the slab waveguide are relatively thick, thereby producing a slab waveguide that is sized to be more compatible with an optical fiber and therefore more readily coupled to an optical fiber. The larger slab waveguide structure broadens the fundamental mode of the optical signal. However, multiple modes are also produced in the thicker slab waveguide that include higher order modes. A ridge structure is etched into the slab waveguide, wherein the width and height of the ridge structure are selected to impose lateral confinements on the higher order slab modes. The result is a waveguide that has a broadened fundamental mode yet is essentially single-mode. The resulting broadened fundamental mode is closer in symmetry to the mode of standard optical fibers, thereby enabling the waveguide to be more efficiently coupled to an optical fiber.

Increased capacity optical waveguide

Abstract: An compound core optical waveguide fiber designed for high data rate or single channel or WDM systems which may include optical amplifiers. The waveguide is characterized by a core having two or three regions wherein the refractive index can be varied. The relative size of the regions may also be varied. By adjusting these variables, the desired mode field diameter, zero dispersion wavelength, dispersion slope and cut off wavelength were obtained. The optical properties are chosen to limit non-linear effects while maintaining low attenuation and acceptable bend performance. In addition, the residual stress within the waveguide is maintained at a low level to limit stress induced birefringence. The low residual stress in the uncoated waveguide, together with a dual coating system having selected moduli and glass transition temperatures results in low polarization mode dispersion.

Diamond-like carbon optical waveguide

Abstract: An optical circuit device has a carbon optical waveguide structure which has a substrate. A first carbon layer is atop the substrate and has a first refractive index. A carbon optical waveguide core is positioned atop the first layer and has a second refractive index different than the first refractive index. A cladding layer of carbon is positioned atop the first layer and the waveguide core and has a third refractive index different than the refractive index of the waveguide core.

Controlled dispersion optical waveguide

Abstract: A single mode optical waveguide fiber having low, non-zero dispersion over a pre-selected wavelength range is disclosed. The refractive index profile of the core is characterized in that the core includes a plurality of distinct regions, each having an index profile, and a radius or width. By adjusting the index profile sizes and shapes of the plurality of core regions, a waveguide fiber may be made having a set of properties tailored for a high performance telecommunication system. In particular, dispersion slope can be maintained less than 0.05 ps/nm2 -km and absolute magnitude of total dispersion maintained in the range of 0.5 to 3.5 ps/nm-km over a pre-selected wavelength range. The zero dispersion wavelength is outside the pre-selected wavelength range and the cut off wavelength and mode field diameter are controlled to target values.

Optical fiber design for strong gratings photoimprinting with radiation mode suppression

Abstract: The performances of fiber gratings can be impaired by coupling to cladding modes, especially for applications in multiplexed systems. This coupling is due to a non-zero weighted overlap integral between the guided mode and the cladding modes. It can generate transmission losses larger than 3 dB over more than 20 nm on the blue side of the resonance wavelength and are commonly observed in high reflectivity gratings (> 50%) (see for example transmission curves of figures 2 and 7 of reference [1]). From a perturbation theory, it comes that, for a tensorial perturbation Δe of the permittivity, the coupling coefficient is proportionnai to the quantity ∬ E g Δ e E c * d S, where Eg is the guided mode field and Ec a cladding mode field. In the case of a circularly symmetrical perturbation (generally assumed in photowritten gratings), the coupling is limited to cladding modes of LP0 symmetry. The above integral can be nulled if Δe is constant over the area where the guided mode field is confined [2]. This is not usely the case of the refractive index difference associated to gratings, since the cladding is far less photorefractive than the germanium-doped core. One way to solve the problem is to obtain the same refractivity in a region of a few core diameters and to ensure a constant UV illumination intensity in the same volume. This implies to modify the dopant concentration profiles of the fiber.

Optical waveguide and process for producing it

Abstract: This invention provides an optical waveguide having diffraction gratings with sufficiently high reflectivity, a waveguide member for obtaining the optical waveguide, and a production process thereof. An optical waveguide in which desired diffraction gratings are formed in a core and in a cladding at a predetermined portion by using a waveguide member in which germanium dioxide is added in the core and in the cladding and irradiating the predetermined portion of the waveguide member with interference fringes of ultraviolet light. By this, the optical waveguide according to the present invention reflects guided light throughout the entire mode field region, thus having a high reflectivity.

Radiation-mode coupling loss in tilted fiber phase gratings.

Abstract: We demonstrate that grating tilt is an important adjustable parameter that can be utilized in addition to the more familiar parameters of grating length and index change to tune the spectral shapes of fiber phase gratings designed to perform demanding filter applications through guided-mode to radiation-mode coupling loss. A comparison is made between calculated transmission spectra obtained from a coupled-mode-theory analysis and measured spectra obtained from strong gratings written by ultraviolet irradiation of deuterium-sensitized fiber with grating tilt angles ranging from 0 degrees to 15 degrees . We show that good agreement is obtained between the experimental measurements and the theoretical predictions.

The bidirectional mode expansion method for two-dimensional waveguides: the TM case

Abstract: The mode expansion propagation method is a modelling technique for a large variety of waveguide components. Until now only the case with TE modes has been reported; we give details on the mode expansion propagation method for TM modes. Instead of one type of overlap integral in the TE case, a TM analysis requires two kinds of overlap integrals. The inclusion of radiation modes in this method is discussed. The modifications in the algorithm to include waveguides with gain or loss structures are also considered.

Hybrid all optical silica waveguide modulator using non-linear electro-optic components

Abstract: Generally, the present invention is an optically controlled optical waveguide circuit comprising a substrate 30, an inorganic waveguide core 34 disposed within one or more cladding layers 36 upon the substrate 30 and an active cladding drop-in component 40 comprising a non-linear optical material adjacent to the waveguide core wherein the phase of an optical signal within the waveguide core may be modulated by controlling the index of refraction of the active cladding region. An embodiment of the present invention uses an inorganic optical waveguide 34 with a drop-in component of non-linear silica 40 as an active cladding to provide a phase modulator for a Mach-Zender interferometer which can be used to implement high speed low loss switching of optical signals.

Simplified tracking antenna

Abstract: An antenna pointing detection system for use with circularly polarized electromagnetic radiation comprises a horn (10) for receiving radiation in a primary mode from a source; a waveguide (12) coupled to the horn (10) for receiving the received radiation from the horn (10), the waveguide (12) supporting only radiation in the primary mode and the next order TE mode, and at least one mode switching arm (14) extending from the waveguide for stimulating only radiation of the next order TE mode in the waveguide (12), the arm (14) having a switchable plurality of different effective lengths for causing a phase alteration in said next order TE mode radiation and thereby causing a deflection of the effective pointing direction of the horn (10) (Fig. 1).

All fiber in-line optical isolator

Abstract: The present invention is directed at an all-fiber in line isolator. The basic isolator includes a single-mode optical fiber, a multimode waveguide, a coil or other traditional means to generate a magnetic field, and a fiber block or other traditional means to couple the fiber to the waveguide. In one embodiment, the fiber has a core and a cladding, and maintains a circular state of light polarization. The fiber has a coupling region where the cladding is partially removed. The waveguide evanescently couples to the fiber along the coupling region. The waveguide has magneto-optical properties such that applying a magnetic field along it causes backward propagating light to transfer to the waveguide with minimal disturbance to forward propagating light. Other embodiments using birefringent optical fibers are disclosed as well.

Optical waveguide mode coupling using mechanical wave interference

Abstract: Apparatus for mode coupling in a waveguide that includes an engagement substrate arranged for intimate contact with a waveguide, and at least two actuators coupled to the engagement substrate and operative to create an interference pattern in the engagement substrate for producing a periodic deformation of the waveguide.

Polyimide optical waveguide having electrical conductivity

Abstract: A light transmitting structure or optical waveguide (47) of the present invention can provide both optical and electrical conductivity. The optical waveguide (47) is capable of simultaneously transmitting multiple optical and electrical signals. The optical waveguide (47) has several cladding layers (40, 41, 42, 43, 44) which optically isolate several different regions of waveguide core material (45, 46) through which the multiple optical signals are transmitted. To provide a compact structure, portions of the cladding layers (42, 43, 44) of the optical waveguide (47) are used as electrical conductors while the waveguide core material (45, 46) is used as an electrical insulator for the electrical conductors.

Easily manufacturable optical self-imaging waveguide

Abstract: An optical waveguide device based on the self-imaging (Talbot) effect is closed. An induced mode index difference between the device's multimode propagation (MMP) region and its surrounding host region forms a total internal reflection (TIR) interface. A pair of TIR interfaces result in lateral waveguide mode confinement and self-imaging formation. Also disclosed is an improved method of manufacturing the waveguide device.

Dispersion shifted optical waveguide

Abstract: A novel optical waveguide fiber having low total dispersion slope, relatively large mode field diameter, larger effective area, and a relatively simple core profile design is disclosed. The core refractive index profile comprises three segments. The adjustability of the height, width and location of the three core index profile segments, provides sufficient flexibility to meet a specification which calls for a dispersion shifted waveguide fiber capable of limiting four photon mixing or self phase modulation. The novel waveguide is characterized by a mode field diameter ≧7.5 microns and a total dispersion slope ≦0.070 ps/nm 2 -km.

Polimide optical waveguide

Abstract: A polyimide optical waveguide comprising a core made of polyimide whose refractive index is controlled to a predetermined value by electron beam irradiation, and a cladding set in contact with the core and having a refractive index lower than that of the core.

Plasma generator with mode restricting means

Abstract: A plasma processing apparatus has a waveguide along which microwaves are propagated from a microwave generator to a plasma-forming region in a low-pressure processing chamber. The waveguide has a large cross-sectional area, to enable a large region of plasma to be achieved. Uniformity and stability of the plasma are improved by a mode restrictor which inhibits mixing of propagation modes which is otherwise liable to occur in a wide waveguide. The mode restrictor consists of electrically conductive dividers which divide the waveguide cross-section into an array of sub-guides before the plasma-forming region.

Semiconductor optical waveguide-integrated light-receiving device

Abstract: Disclosed herein is a semiconductor optical waveguide-integrated light-receiving device comprising a waveguide-type photodetector and a passive optical waveguide which are selectively formed on the same substrate, wherein the width of mask for a selective growth is varied along the waveguiding direction so as to simultaneously form core layers which differ from each other in absorption edge wavelength. The core layer may be formed with an MQW layer. It is also featured that waveguide width of the photodetector is made larger than the waveguide width of the optical waveguide. The photodetector and the optical waveguide may be buried by an n--InP layer.

Low-power excitation of gyrotron-type modes in a cylindrical waveguide using quasi-optical techniques

Abstract: Experimental results of low-power excitation of a 118 GHz TE(22,6) rotating mode are presented. A rectangular waveguide is converted to a TE(22,6) circular waveguide mode using quasi-optical techniques. A good conversion efficiency is measured and the experimentally-observed field intensity profiles show the percentage of unwanted modes to be small.

Polarisation and wavelength independent optical power splitting circuit

Abstract: An optical waveguide circuit comprises a mode splitter and an input guide (1/4/6.1) and first and second output guides (6.2/2, 6.3/3), and a mode converter (5) incorporated in the input guide for converting a fraction of an optical signal (Ii), entering via the input waveguide, of a first propagation mode into a second propagation mode having mutually different order. The mode converter (5) has a first waveguiding section (5.1) and a second waveguiding section (5.2), which adjoin each other via a single discontinuity (7). The first and second sections (5.1 and 5.2) have propagation modalities, as a result of which, at the discontinuity, a coupling can take place between two propagation modes of different order, whereas the extent (x) of discontinuity determines the fraction of conversion for obtaining a desired splitting ratio in emitting signals (Io1, Io2).

Waveguide coupling device including tapered waveguide with a particular tapered angle to reduce coupling loss

Abstract: A waveguide device comprising a cladding layer having a refractive index ncl, a first waveguide having a refractive index ng (ng >ncl) formed on said cladding layer, and a second waveguide having a refractive index ncp (ncp >ng) formed on said first waveguide, wherein the sectional shape of said second waveguide has a tapered structure in which a layer thickness of said second waveguide reduces as the distance from the end face of the waveguide increases, and a tapering angle Θ in said tapered structure satisfies the following conditions: Θa ={90°-arcsin (neff /ncp)}/2 (1) Θ<2.0 Θa (2) wherein neff represents an effective refractive index of said first waveguide. This waveguide device has a high resistance against the deviation in the positions of the light exit face of an LD or an optical fiber and the light entrance face of a waveguide and thus enables an optical coupling at a high efficiency.

Planar Fresnel lens photoimprinted in a germanium-doped silica optical waveguide.

Abstract: A gradient-thickness Fresnel lens was photoimprinted in the germanium-doped core layer of a single-mode planar waveguide on silica by exposure to ultraviolet light through a mask, which increases the refractive index in the lens region by approximately 5 x 10(-3). The lens is used to collimate the output of a standard single-mode optical fiber butt coupled to the waveguide at a wavelength of 1.3 microm. The method is applicable to the mass production of complex diffractive elements in a planar waveguide geometry.

Method of determining the zero dispersion wavelength of an optical waveguide

Abstract: It is necessary to know the zero dispersion wavelength .lambda.0, to ensure the reliable transmission of high bit-rate frequency signals via remote transmissionpaths. The method for determining the zero dispersion wavelength of an optical waveguide knowingly utilizes a disturbing effect that is undesirable in optical communications transmission techniques, which is able to lower the transmission quality. This effect is the so-called four-wave mixing, or in special cases a partially degenerated four-wave mixing. The method couples two light signals of different wavelengths (.lambda.1, .lambda.2) into an optical waveguide (4). A mixing product which occurs in the optical waveguide as a result of a partially degenerated four-wave mixing is evaluated by an analyzer (3). The wavelength of one of the two light signals is selectively varied until the optical output of the mixing product reaches a maximum. At that point the wavelength of this light signal coincides with the zero dispersion wavelength .lambdaO

Generalized scattering matrix of waveguide corners distorted by discontinuities in the resonator region

Abstract: A new generalized scattering matrix formulation is presented for the calculation of waveguide corners distorted by discontinuities. The novel approach lies in the fact that the introduction of shorting planes some distance away from the actual discontinuity-as is common practise in analyses known so far-is entirely avoided. Therefore, this method allows the computation of components in which other structures are connected as closely as possible to the waveguide corner. This follows directly from the rigorous incorporation of higher-order mode interactions. Previously, only fundamental-mode scattering parameters could be calculated and, therefore, connected components had to be far enough away from the waveguide corner in order to avoid interference of reactive fields. Consequently, the theory presented in this paper will, first, allow the calculation and design of more complex waveguide components and, secondly, contribute to a more efficient use of component space. For the examples of 90- and 18O-degree waveguide bends, the theoretical model is compared with measurements and a finite-element analysis. Results are found to be in good agreement. >

Band pass filter device

Abstract: PROBLEM TO BE SOLVED: To easily manufacture a single mechanical structure although it has ≥2 resonance modes by coupling a 1st resonance mode connected to an external circuit and a 3rd resonance mode which is connected to the external circuit with a 2nd resonance mode which is not connected to the external circuit. SOLUTION: The sectional shape of the resonance structure body 1 cut with planes parallel to the electric field vectors of the 1st resonance mode and 2nd resonance mode is made not square and, for example, some corners are chambered 12a and 12b to couple the 1st resonance mode and 2nd resonance mode with each other. Similarly, the sectional shape of the resonance structure 1 cut with planes parallel to the electric field vectors of the 2nd resonance mode and 3rd resonance mode is made not square and, for example, some corners are chambered 13a and 13b to couple the 2nd resonance mode and 3rd resonance mode with each other. Then the 1st resonance mode and 3rd resonance mode are not practically coupled with each other. COPYRIGHT: (C)1997,JPO

Fabrication of TE/TM mode splitter using completely buried GaAs/GaAlAs waveguide

Abstract: A GaAs/GaAlAs-system TE/TM mode splitter using the mode interference principle is described. Single- and double-mode waveguides are patterned by reactive ion etching after the first molecular beam epitaxy. They are then completely buried by liquid-phase epitaxy, which enables low loss propagation due to side-wall smoothness, because of the thermal deformation effect. For achieving low loss characteristics in this mode splitter, the surface treatment process before crystal growth and S-bend waveguide mask formation procedure are also optimized. Propagation loss of the single-mode waveguide is less than 1.0 dB/cm. In order to secure birefringence of the waveguide for mode splitting, upper and lower GaAlAs-cladding mol fractions are different. Finally, the fabricated device achieves the TE/TM mode splitting ratio of 8.2 dB for both polarizations.

Light sensitive semiconductor device integrated with an optical waveguide

Abstract: Disclosed herein is a semiconductor optical waveguide-integrated light-receiving device comprising a waveguide-type photodetector and a passive optical waveguide which are selectively formed on the same substrate, wherein the width of mask for a selective growth is varied along the waveguiding direction so as to simultaneously form core layers which differ from each other in absorption edge wavelength. The core layer may be formed with an MQW layer. It is also featured that waveguide width of the photodetector is made larger than the waveguide width of the optical waveguide. The photodetector and the optical waveguide may be buried by an n--InP layer.

Adiabatic reflection Y-coupler apparatus

Abstract: A wavelength selective structure is coupled to an adiabatic Y-coupler via a multimode section which supports both symmetric and antisymmetric modes. One single mode branch of the coupler converts guided light to a symmetric mode, whereas the other single mode branch converts guided light to an anti-symmetric mode. The structure, which includes a pair of single mode waveguide arms coupled to the common section and a reflection device (such as a grating or ROR) located in each arm, converts reflected light from a symmetric mode to an anti-symmetric mode and conversely. Applications described include a channel dropping fiber and channel balancing apparatus for WDM systems, and a dispersion compensator for fiber optic systems.