Showing papers on "Radiation mode published in 1999"

Theory and modelling of optical waveguide sensors utilising surface plasmon resonance

Abstract: A theoretical analysis of the phenomenon of excitation of surface plasma waves in integrated-optical waveguide structures is carried out. Rigorous approach to analysis of light propagation through a waveguide structure with a thin metal overlayer supporting surface plasma waves is formulated using a bi-directional mode expansion and propagation method. It is demonstrated that because the back-reflections in the structure are very weak and most of optical power is transmitted by only a limited number of modes of the sensing structure, the method can be considerably simplified.

Leaky cladding mode propagation in long-period fiber grating devices

Abstract: We investigate leaky-mode propagation of the cladding modes of an optical fiber through coupling with a long-period fiber grating. A one-dimensional ray propagation model is applied. Experimental measurements are compared to a transfer-matrix model to estimate the cladding mode losses. Losses are also measured using an all-fiber Mach-Zehnder mode interferometer. The measured losses are somewhat greater than predicted by the simple theory.

Tapered polymer single-mode waveguides for mode transformation

Abstract: This paper presents a tapered polymer waveguide structure for coupling light between optical waveguides with differing geometries. Optical fibers, lasers, and other photonic integrated circuit components can be coupled with tapered waveguides. The polymer waveguide performs a mode transformation between different mode shapes and sizes. For example, the mode transformation can be from an elliptical laser diode mode to that of a circular optical fiber mode. The input and output of a tapered waveguide structure are analyzed, for the case of laser to fiber coupling, in order to determine the effect of misalignments on the coupling efficiency. Adiabaticity in waveguide propagation is discussed. The fabrication of our polymer waveguides is also described.

Polymeric waveguide polarization splitter with a buried birefringent polymer

Abstract: A waveguide polarization splitter is demonstrated based on a low-loss polymer waveguide and a birefringent polyimide. Crosslinkable fluorinated polymers with an excellent stability and a low absorption loss are utilized for the device. The polyimide is buried under one branch of the Y-branch waveguide to enhance the birefringence between the TE and TM modes. By the adiabatic mode evolution, the TE mode is coupled to the branch with the polyimide strip, while the TM mode propagates through the other branch without the polyimide. For the device with a branch angle of 1/400 rad, we obtained a crosstalk less than -20 dB and a fiber-to-fiber insertion loss of 3.8 dB.

Twin waveguide based design for photonic integrated circuits

Abstract: An asymmetric twin waveguide (ATG) structure is disclosed that significantly reduces the negative effects of inter-modal interference in symmetric twin-waveguide structures and which can be effectively used to implement a variety of optical devices. The ATG structure of the invention can be monolithically fabricated on a single epitaxial structure without the necessity of epitaxial re-growth. To achieve the ATG structure of the invention, the effective index of the passive waveguide in the ATG is varied from that of a symmetric twin waveguide such that one mode of the even and odd modes of propagation is primarily confined to the passive waveguide and the other to the active waveguide. The different effective indices of the two coupled waveguides result in the even and odd modes becoming highly asymmetric. As a result, the mode with the larger confinement factor in the active waveguide experiences higher gain and becomes dominant. In a further embodiment, the active waveguide is tapered to reduce coupling losses of the optical energy between the passive waveguide and the active waveguide. In a further embodiment, a grating region is incorporated atop the passive waveguide to select certain frequencies for transmission of light through the passive waveguide.

Tapered optical waveguide coupler

Abstract: A tapered waveguide couples optical waveguides of different sizes in a multi-chip optical assembly. In a particular embodiment, a resonator containing a semiconductor diode amplifier is coupled to a planar waveguide structure that optically couples to an optical fiber. A single-mode semiconductor laser waveguide is flip-chip bonded to a substrate and couples to a silica waveguide structure that couples to a single-mode tantala waveguide. In a further embodiment, high-index material is provided in a gap between chips. In another embodiment, polymer material is used in the waveguide structure to modify thermal characteristics of the waveguide structure.

Dispersion managed optical waveguide and system with distributed amplification

Abstract: A unitary dispersion managed waveguide fiber with distributed amplification and a system incorporating the waveguide fiber are disclosed. Total dispersion along the waveguide fiber changes from positive to negative along the length of the waveguide over a transmission wavelength range. Distributed amplification is provided by stimulated emission of a dilute concentration of a rare earth dopant in the waveguide, by Raman effects or by both.

Optical waveguide crossings

Abstract: An optical waveguide structure including a first waveguide (1104), a second waveguide (1106) that intersects with the first waveguide, and a resonant cavity at the intersection of the first and second waveguides. The resonant cavity is designed so that the resonant modes that are excited from the input port are prevented by symmetry from decaying into the transverse ports. Thereby cross talk is substantially reduced. A realization of the resonant cavity is a photonic crystal.

Optical functional devices, their manufacturing method and optical communication system

Abstract: In order to realize an optical functional device like a DFB laser in which the radiation mode loss is small and the threshold current is low even when high-order gratings easy to process are used, the gratings are configured to be asymmetric in its cross-sectional structure. Then, by partly varying the asymmetry (blaze angle) of the cross-sectional structure of the gratings along the cavity lengthwise direction, the cavity-lengthwise profile of radiation modes from the high-order gratings is controlled. It is also controlled by using a relationship between a phase shift of the gratings and the asymmetry. In a edge emitting DFB laser, by utilizing destructive interference among radiation modes, the radiation mode loss is reduced, and the threshold can be decreased. When a radiation mode is used as an output, the radiation mode can be reinforced to increase the output by utilizing constructive interference.

High power fiber ribbon laser and amplifier

Abstract: A single-mode fiber laser (66) that provides increased power. The fiber laser (66) includes a fiber ribbon (30) having a plurality of parallel waveguides (10). Each waveguide (10) includes a rectangular shaped core (12) that has a relatively thin dimension in one direction and a relatively wide dimension in an orthogonal direction. A step-index cladding (14, 16) is provided in the thin direction to limit the propagation of light in the core (12) to a single mode in that direction. Mode filters (18, 20) are provided adjacent the ends of the core (12) in the thickness direction and the various propagation modes in the core (12) enter the mode filters (18, 20). The mode filters (18, 20) guide the desirable single-mode back into the core (12) and reject the other modes away from the core (12). Light absorbing layers (22, 24) are provided adjacent the mode filters (18, 20) and opposite the core (12) to absorb the undesirable propagation modes of light. Therefore, the main propagation mode in the core (12) is a single low order mode, but the cross-sectional area of the core (12) is increased to provide more power. Each of the cores (12) in the ribbon (30) are optically pumped form the side by a bar (40) of diode arrays (42) positioned at strategic locations along the length of the ribbon (30) relative to the waveguides (10). Various transmission gratings (48) and/or reflection gratings (50) can be provided within a ribbon jacket (32) to launch the optical pump light down the waveguide (10). The ribbon (30) can be wrapped around a mandrel (68) and a cooling fluid can be introduced through the mandrel (68) to cool the ribbon (30) during laser operation.

Optical functional element and transmission device

Abstract: A distributed feedback laser comprising: waveguide (4) having a hologram (10) capable of emitting radiation mode light in upper and lower directions; first reflector (20) provided below said waveguide for returning said radiation mode light back to said waveguide; and second reflector (21A, 21B, 21C, 21D, 21E) provided above said waveguide for returning said radiation mode light back to said waveguide, intensity profile of said radiation mode light on said waveguide being non-uniform is disclosed. Also, by using 2nd- or higher-order diffraction gratings having an asymmetric cross-sectional configuration together with a reflection structure located at one side thereof, a highly directional optical isolator can be provided. Further, the present invention provides an optical functional element comprising: first waveguide which guides optical waves and has a gain or a loss, said waveguide having a hologram (202) capable of coupling with said optical waves guided by said waveguide to generate radiation mode light; amplifier (203) for amplifying said radiation mode light released from said first waveguide and releasing it; and first reflector (204) for reflecting said radiation mode light emitted from said amplifier back to said first waveguide.

Semiconductor optical component comprising a spot-size converter

Abstract: A semiconductor optical component, comprising a spot-size converter to deconfine the optical mode, comprises an active waveguide and a passive waveguide that are superimposed and buried in a sheathing layer. The component successively comprises a damped coupling section in which the width of the active waveguide tapers down and the width of the passive waveguide increases, and a mode expansion section comprising only the passive waveguide whose width tapers down.

Y branching optical waveguide and optical integrated circuit

Abstract: The present application provides an asymmetric Y branch optical waveguide capable of obtaining an asymmetric branching ratio stably with a low radiation loss, and a lightwave circuit and an optical transmission system both using the asymmetric Y branch optical waveguide. The asymmetric Y branch optical waveguide according to the present application has a waveguide (I) for input, two waveguides (III) for output, and a multi-mode waveguide (II) disposed between the waveguides (I) and (II). The present Y branch optical waveguide is constructed in such a manner that the width of the multi-mode waveguide, extending in the direction intersecting with an optical axis changes discontinuously at a portion where the input waveguide and the multi-mode waveguide are connected to each other, and the multi-mode waveguide is asymmetric with respect to a center line extending in the direction of the optical axis to allow optical peaks to respectively appear in each individuals of the two output waveguides. Thus, a difference occurs between peak's heights in each light-intensity distribution having two peaks, which appears due to mode interference, so that the asymmetry of a branching ratio can be implemented.

Optical waveguide photosensitization

Abstract: The present invention is directed to a method of enhancing the photosensitivity of an optical waveguide and an optical waveguide having persistent UV photosensitivity following out diffusion of a loading gas such as H 2 or D 2 . The optical waveguide is loaded with a gas such as H 2 or D 2 to form an associated baseline refractive index. At least a portion of the loaded optical waveguide is exposed to UV radiation to induce a change in the baseline refractive index and the waveguide is annealed to diffuse the gas from the loaded optical waveguide and to stabilize the change in refractive index. Following annealing the optical waveguide retains a UV photosensitivity sufficient to produce significant refractive index changes relative to the induced change in baseline refractive index. The method of the present invention is particularly well suited for designing and fabricating grating devices, tuning grating strength and wavelength, and for providing accurate spatial control of waveguide photosensitivity. Waveguides having complex photosensitivity profiles as a function of length are also disclosed.

Positive dispersion low dispersion slope fiber

Abstract: Disclosed is a single mode optical waveguide having a segmented core of at least two segments. The relative refractive index, the index profile and the radial dimensions of the core segments are selected to provide an optical waveguide fiber having properties suitable for a high performance telecommunication system operating in the wavelength window of about 1530 nm to 1570 nm. Embodiments of the invention having two, three and four segments are described to eliminate non-linear effects, such as FWM and SPM, which occur in a high performance, high rate systems, the effective area of the waveguide is made to be greater than about 60 νm2, more preferably greater than 65 νm2, and most preferably greater than 70 νm2. The total dispersion is preferably positive and equal to at least 2 ps/nm-km at 1530 nm. This total dispersion together with a total dispersion slope less than about 0.1 ps/nm2-km insures a minimum FWM effect over the wavelength window.

Structural radiation mode sensing for active control of sound radiation into enclosed spaces

Abstract: In the recent article by Cazzolato and Hansen [J. Acoust. Soc. Am. 104, 2878–2889 (1998)] it was shown that it is possible to derive for a structure some set of surface velocity distributions, referred to as radiation modes, which are orthogonal in terms of their contributions to the acoustic potential energy of a coupled cavity. The technique used an orthonormal decomposition to derive an expression for the radiation modes which was based on prior work for free-field sound radiation. It will be shown in the following letter that for the special case involving the calculation of global internal potential energy it is possible to use a simple approach which requires no orthonormal decomposition since the expression for the global potential energy is already in a form that can be easily diagonalized.

Transverse electric or quasi-transverse electric mode to waveguide mode transformer

Abstract: A transverse electric or quasi-transverse electric mode to rectangular waveguide mode transformer converts an electrical signal propagating in a transmission line from the TE or quasi-TEM transmission mode to a rectangular waveguide transmission mode for propagating in a waveguide. The transformer comprises a trace printed on a substrate, the substrate having first and second major surfaces and first, second, third, and fourth minor surfaces. The transformer is logically divided into a quasi-TEM mode portion, a conversion portion, and a waveguide mode portion. The quasi-TEM mode comprises a length of microstrip. The microstrip widens to a conversion trace in the conversion portion where there is one or more converting fins oriented perpendicularly to the direction of signal propagation. The conversion portion is adjacent the waveguide mode portion comprising metalized first and second major surfaces and third and fourth minor surfaces. The fins direct the quasi-TEM energy into waveguide mode energy in the substrate for propagation through the substrate.

Tapered optical fiber grating devices with variable index coatings for modifying guide properties of the fundamental mode

Abstract: An optical fiber grating device including a length of optical fiber having a predetermined fundamental mode effective guide index and a longitudinally tapered region for accessing a fundamental mode of light. The tapered region has a grating with a predetermined light spectral shaping property that shapes the light spectrum of the fundamental mode. A coating surrounds the tapered region of the fiber for modifying the fundamental mode effective guide index of the fiber in order to change the spectral shaping property of the grating.

Merging optical waveguides having branch angle within a specific range

Abstract: An optical waveguide device having a folded waveguide structure on a semiconductor substrate. The optical waveguide device includes first and second single mode optical waveguides formed on a semiconductor substrate. The first and second optical waveguides merge together into a merging optical waveguide. A reflector is positioned so that light travelling through the first optical waveguide into the merging optical waveguide is reflected by the reflector to travel through the second optical waveguide. A total reflection complementary angle for the light traveling through the first optical waveguide is θ c , and a branch angle θ b of the first and second optical waveguides is less than or equal to 0.55θ c .

On probing molecular monolayers: a spectroscopic optical waveguide approach of ultra-sensitivity

Abstract: A broadband, multichannel, single-mode, planar waveguide based spectrometer was developed for probing molecular monolayers. A protein sub-monolayer (thickness h @ 3 nm, imaginary part of refractive index kl oe 0.01) immobilized on the waveguide surface was characterized by the waveguide attenuated total reflection (ATR) spectrometer. A sensitivity enhancement of 4 orders of magnitude, compared to conventional transmission measurements, has been experimentally achieved in the characterization of ultra-thin films. In addition, polarized spectroscopic measurements at the TE and TM waveguide modes were implemented to determine the average orientation angle of the adsorbed molecules. The work developed here is a new research tool for the investigation of some fundamental aspects of molecular films and a novel platform to develop new technological devices of high sensitivity and selectivity such as biosensors.

Hollow optical waveguide for trace analysis in aqueous solutions

Abstract: Low concentrations of substances dissolved in liquids are detected by coupling analysis/excitation light into the liquid core of an optical waveguide in the form of a capillary. When the substance of interest is to be excited to cause the emission of fluorescent light, the excitation light is transversely coupled into the hollow core of the waveguide and the generated fluorescent light is kept in the optical path of the waveguide for as long as possible. The invention also contemplates the use, in either an absorption or fluorescence mode, of specially treated fused silica fibers to deliver analysis/excitation light with very short wavelengths into the liquid core of an optical waveguide.

Optical waveguide with dissimilar core and cladding materials, and light emitting device employing the same

Abstract: An optical waveguide, radiation emitting device employing the same, and process for fabricating the radiation emitting device are provided. The optical waveguide has a core (12) fabricated of a first material with a first index of refraction and cladding (14) surrounding the core (12) fabricated of a second material with a second index of refraction. The core is an active material which emits radiation at a desired wavelength when pumped with radiation of a predetermined wavelength, and the first material and second material are dissimilar materials (R1, R2), having been separately fabricated and subsequently physically assembled as the waveguide. The light emitting device employing the optical waveguide is configured either as an amplified spontaneous emission (ASE) source or laser source employing appropriate reflective materials at the ends of the optical waveguide.

Waveguides and backplane systems with at least one mode suppression gap

Abstract: Waveguides and backplanes systems are disclosed. A waveguide according to the present invention includes a first conductive channel, and a second conductive channel disposed generally parallel to the first channel. A gap is defined between the first and second channels that allows propagation along a waveguide axis of electromagnetic waves in a TE n,0 mode, wherein n is an odd number, but suppresses electromagnetic waves in a TE m,0 mode, wherein m is an even number. An NRD waveguide is disclosed that includes an upper conductive plate and a lower conductive plate, with a dielectric channel disposed between the conductive plates. A second channel is disposed adjacent to the dielectric channel between the conductive plates. The upper conductive plate has a gap above the dielectric channel that allows propagation along a waveguide axis of electromagnetic waves in an odd longitudinal magnetic mode, but suppresses electromagnetic waves in an even longitudinal magnetic mode. A backplane system according to the invention includes a substrate with a waveguide connected thereto. The backplane system includes at least one transmitter connected to the waveguide for sending an electrical signal along the waveguide, and at least one receiver connected to the waveguide for accepting the electrical signal.

Optical wavelength multiplexer/demultiplexer with uniform loss

Abstract: Disclosed is an optical wavelength multiplexer/demultiplexer with uniform loss. The optical wavelength multiplexer/demultiplexer includes a first star coupler for dividing optical power of input optical signals received from input optical waveguides, an arrayed waveguide grating for guiding the optical signals outputted from the first star coupler therethrough in such a fashion that the optical signals have different phases, respectively, a second star coupler for coupling or dividing the wavelengths of the optical signals outputted from the arrayed waveguide grating, and outputting the resultant optical signals to output waveguides, respectively, and a waveguide mode controller for controlling the profile of a waveguide mode of the optical signals outputted from the arrayed waveguide grating, thereby allowing the optical signals focused at an output terminal of the second star coupler to have flat amplitude distributions. The waveguide mode controller maintains the main peak of the output waveguide mode while phase-shifting tails of the output waveguide mode. By virtue of the mode controller, it is possible to form a diffraction pattern with flat amplitude distribution. Accordingly, an uniformity of loss among channels is obtained.

Semiconductor-solid state laser optical waveguide pump

Abstract: The invention includes a solid state laser which outputs wavelength emission λss centered about 946 nm, combined with a lasing waveguide which includes a Yb doped optical waveguide such that when the λss output is inputted into the lasing waveguide the lasing waveguide produces a wavelength emission λy centered about 980 nm. The invention further includes the utilization of pump light with optical waveguide amplifying devices.

Method for compensating polarization mode dispersion in a waveguide and a polarization mode dispersion compensator

Abstract: A polarization mode dispersion compensator including a number of polarization mode converters. At least three mode converters, or at least three groups of mode converters, are individually actuated by at least three control voltages to compensate for PMD.

Semiconductor-solid state laser optical waveguide pump device and method

Abstract: The invention includes a solid state laser (22) which outputs wavelength emission μss centered about 946 nm, combined with a lasering waveguide (24) which includes a Yb doped optical waveguide (26) such that when the μss output is inputted into the lasing waveguide (24) the lasing waveguide produces a wavelength emission μy centered about 980 nm. The invention further includes the utilization of pump light with optical waveguide amplifying device.

Manufacture of optical waveguide device, and optical waveguide device

Abstract: PROBLEM TO BE SOLVED: To obtain an optical waveguide device which has practically a small optical connection loss and is easily manufactured. SOLUTION: In the manufacture of the optical waveguide device having an optical connection structure between an optical waveguide composed of a core 6 and clad layers 4, 5, and 8 and an optical element formed on a platform, a core end part is positioned nearby the end part of a flat surface of the platform 3 when the core 6 of the optical waveguide is patterned and after an upper clad layer 8 is formed, an end surface is formed by etching the flat part of the upper clad layer 8 where the influence of a projection of the core 6 is eliminated to guide light in and out of the core 6 through the upper clad layer 8. Consequently, the etching time needed to form the end surface of the optical waveguide is shortened.