Abstract: An ultrasonic receiving apparatus is equipped with such a condition capable of obtaining superior sensitivities. This ultrasonic receiving apparatus includes: an ultrasonic detecting element for modulating light on the basis of ultrasonic waves applied thereto, the ultrasonic detecting element including an ultrasonic sensible portion having a length not larger than ¾ of a wavelength of ultrasonic waves propagated therethrough; and a photodetector for detecting light output from the ultrasonic detecting element.

Abstract: An optical apparatus (spectral filter, temporal encoder, or other) comprises a planar optical waveguide having at least one set of diffractive elements. Each diffractive element set routes by diffraction therefrom a portion of the optical signal propagating in the planar waveguide. The planar waveguide includes at least one material having thermo-optic properties chosen so as to yield a designed temperature dependence of spectral and/or temporal characteristics of the diffracted portion of the optical signal. Variations of material refractive indices, physical dimensions, and/or optical mode distributions with temperature may at least partly compensate one another to yield the designed temperature dependence. Optical materials with ?n/?T of various magnitudes and signs may be variously incorporated into the waveguide core and/or cladding.

Abstract: A diffraction device using a photonic crystal includes a diffraction grating, which has a period and periodically divides electromagnetic waves, and an input medium and an output medium, which contact the diffraction grating. The input medium is air, and the output medium is a one-dimensional layer having a periodic characteristic in a single direction (Z axis direction). The photonic crystal is formed by a periodic multilayer film having a period corresponding to the sum of the thickness of a first substance and the thickness of a second substance, which are superimposed. The diffraction device drastically decreases the resolution corresponding to the difference of the separated frequencies.

Abstract: A distributed optical structure comprises a set of diffractive elements. Individual diffractive element transfer functions collectively yield an overall transfer function between entrance and exit ports. Diffractive elements are defined relative to virtual contours and include diffracting region(s) altered to diffract, reflect, and/or scatter incident optical fields (altered index, surface, etc). Element and/or overall set transfer functions (amplitude and/or phase) are determined by: longitudinal and/or angular displacement of diffracting region(s) relative to a virtual contour (facet-displacement grayscale); longitudinal displacement of diffractive elements relative to a virtual contour (element-displacement grayscale); and/or virtual contour(s) lacking a diffractive element (proportional-line-density gray scale).

Abstract: An optical apparatus comprises an optical element having at least one set of diffractive elements and multiple channel optical waveguides. Diffractive elements of each set are distributed among diffractive element subsets corresponding to each of the multiple channel waveguides. Each diffractive element set routes, between a corresponding pair of optical ports, those corresponding portions of an optical signal propagating within the optical element that are received by multiple channel waveguides and back-diffracted within the receiving channel waveguides by corresponding diffractive element subsets. The channel optical waveguides are arranged so that optical signals propagate through regions of the optical element between the ports and the first ends of the channel waveguides.

Abstract: The present invention is directed to a gain equalizer having a preferable equalization characteristic and a structure that can be easily fabricated. The gain equalizer flattens a spectrum of light in a predetermined wavelength range inputted through an input terminal and outputs the light from an output terminal, and comprises a coarse-tunable equalizing section and a fine-tunable equalizing section connected in series. The coarse-tunable equalizing section coarsely flattens the spectrum of the light in the predetermined wavelength range, and includes a plurality of filters each having a large loss and a small reflectance as compared with the fine-tunable equalizing section. The fine-tunable equalizing section flattens the spectrum of the light in a wavelength range where the coarse-tunable equalizing section can not flatten at a predetermined value or less among the predetermined wavelength range.

Abstract: A tunable Bragg grating method and apparatus. In one aspect of the present invention, a method according to an embodiment of the present invention includes directing an optical beam into a first end of an optical path having the first end and a second end disposed in a semiconductor substrate, reflecting a first portion of the optical beam having a first center wavelength back out from the first end of the optical path and tuning the optical path to reflect a second portion of the optical beam having a second center wavelength back out from the first end of the optical path. In one embodiment, the Bragg grating is tuned with a heater used to adjust a temperature of the semiconductor substrate. In another embodiment, charge in charge modulated regions along the optical path is modulated to tune the Bragg grating.

Abstract: A planar lightwave circuit includes at least one optical waveguide core, and at least one feature proximate the core having a stress-engineered property to balance stress and therefore minimize birefringence affecting the core. A protective passivation layer is formed over the core and the feature to be substantially non-interfering with the balanced stress provided by the feature. The stress balancing feature may be an overcladding layer formed over the core, doped to have a coefficient of thermal expansion approximately matched to that of an underlying substrate, to symmetrically distribute stress in an undercladding between the overcladding and the substrate, away from the core. The protective passivation layer is formed to have a coefficient of thermal expansion approximately matched to that of the overcladding. In one exemplary embodiment, the passivation layer is formed from silicon nitride. Related concepts of stress release grooves, and core overetching, are also disclosed.

Abstract: A tunable optical structure and devices based thereon for the compensation of chromatic dispersion in a multi-channel light signal are provided. The optical structure includes a waveguide and a Bragg grating provided therein. The Bragg grating has a plurality of grating components, each associated with one or a few of the channels to be compensated. The period of each grating component is selected to allow compensation of chromatic dispersion experienced by this particular channel or these particular channels, thereby taking into account the wavelength-dependent dispersion slope of the light signal. Tuning means are also provided in order to adjust the dispersion of the grating components to the required values.

Abstract: The present invention relates to the tailoring the reflectivity spectrum of a SGDBR by applying digital sampling theory to choose the way each reflector is sampled. The resulting mirror covers a larger wavelength span and has peaks with a larger, more uniform, coupling constant (?) than the mirrors produced using conventional approaches. The improved mirror also retains the benefits of the sample grating approach. Additionally, most of the embodiments are relatively simple to manufacture.

Abstract: A transverse Bragg resonance waveguide is comprised of a waveguiding channel, and on at least two opposing sides of the channel two periodic index media; and a means for providing gain in the periodic index media. In one embodiment the waveguiding channel is planar and is sandwiched on two opposing sides by the periodic index media. In another embodiment the waveguiding channel is cylindrical and is surrounded by the periodic index media. The means for providing gain in the periodic index media is electrical or optical pumping. The periodic index media comprises a periodic lattice of regions having an index of refraction distinct from the channel, such as an array of transverse holes defined in a planar semiconductor substrate in which the channel is also defined, or an array of longitudinal holes defined in a cylindrical semiconductor fiber in which the channel is also longitudinally defined.

Abstract: The present invention provides a controllable double cladding guiding structure for tunable phase delay, dynamic chromatic dispersion and polarization mode dispersion compensation. The device includes an etched fiber, an electro-optic material with index of refraction changing with externally applied stimulus (electric, magnetic or thermal effect) and a fiber Bragg grating (uniform, apodized, linearly or non-linearly chirped).

Abstract: An evanescent filed based sensor uses a detector for sensing variations in properties of a fluid flowing in a boundary layer adjacent to the detector. The detector comprises an optical waveguide in the form of an optical fiber having a core layer covered by a cladding layer and having a substantially D-shaped cross section defining a planar surface with an optical grating pattern thereon. When a beam of laser light is directed through the detector as an input, variations in an output of the beam of laser light are indicative of changes in fluid pressure or density in the boundary layer or immediate region adjacent to the grating of the optical waveguide.

Abstract: A tunable interferometer for creating gratings of variable periodicity in an optical waveguide is disclosed. The interferometer includes a beam splitter for producing first and second write beams from an input beam. First and second reflectors receive the first and second write beams, respectively, from the beam splitter and direct the first and second write beams to intersect at a fixed location. The angle of intersection of the first and second write beams is a function of impingement locations of the first and second write beams on the first and second reflectors. The impingement locations of the first and second write beams on the first and second. reflectors may be varied to vary the angle of intersection at the fixed location.

Abstract: A method and apparatus that microbend a fiber Bragg grating with a transverse acoustic wave. The fiber Bragg grating reflects one or more Nth order sidebands of reflection wavelengths an optical signal in order to couple the band of wavelenghts within from a first mode to a second mode.

Abstract: An optical monitoring arrangement utilizes the properties of a blazed Bragg grating to redirect a portion of an optical signal out of the axial path and into a detecting device. A plurality of blazed Bragg gratings are utilized, each having unique properties, to increase the robustness of the monitor. In particular, by utilizing a plurality of N gratings, the bandwidth of the monitor may be increased N-fold (assuming no overlap in wavelength between gratings). Alternatively, an improvement in resolution can be obtained by utilizing a narrower bandwidth and measuring N times the number of raw data points within that bandwidth. A combination of increase in bandwidth and resolution may be obtained by a comprise between these two extremes. Chirped blazed gratings may also be employed.

Abstract: A method and apparatus is described for controlling the attenuation of multiple wavelengths signals propagating in an optical fiber, that may have a time-dependent power in each signal, to provide an output signal having a desired attenuated power in each of the multiple signals. An equalizer may be used that has various optical elements to focus and disperse light, such as a concave diffraction grating and a modulator array having modulators disposed on a concave surface. The equalizer may also be coupled to various components such as a circulator or thermally expanded core fibers.

Abstract: A system and method for suppressing light scattering in optical fiber transmission systems are disclosed. The system includes an optical fiber assembly having first and second ends and at least one blocking apparatus disposed along the fiber between the first and second ends. The method includes providing a fiber assembly having a first end and a second end; installing a blocking apparatus in the fiber assembly between the first end and the second end; and transmitting light between the first end and the second end. The fiber assembly generates Brillouin and Rayleigh scattering light in a direction opposite the direction of the transmitted light, and the blocking apparatus suppresses the Brillouin and Rayleigh scattering light.

Abstract: A beam refraction apparatus includes an input fiber carrying an input beam. A wavelength dispersive element is coupled to the input fiber. The wavelength dispersive element spreads the input beam in at least one dimension as a function of wavelength and generates a dispersed beam. A controllable grating reflects the dispersed beam to the wavelength dispersive element and generates a recombined beam. The controllable grating provides a controllable reflectivity as a function of wavelength. An output fiber receives the recombined beam. A collimating optical member is coupled to the input and output fibers. The collimating optical member passes the input beam and the recombined beams in parallel and opposite directions.

Abstract: A photonic circuit includes a tunable drop filter arrangement that includes a plurality of resonators. The drop filter arrangement is tuned to remove a selected frequency from an input data stream from a waveguide. A wavelength sensor coupled to the drop filter to monitor the selected frequency to which the drop filter arrangement has been tuned. A tunable laser presents a new signal of a defined frequency indicative of a signal to be added to the input data stream. A modulator coupled to the tunable laser for receiving the new signal and forming a modulated signal. An add filter arrangement coupled to the modulator for receiving the modulated signal and adding the modulated signal to the data stream.

Abstract: A semiconductor-based tunable optical dispersion compensation method and apparatus for multiple channels. In one aspect of the present invention, an apparatus according to an embodiment of the present invention includes a semiconductor material. An optical path through the semiconductor material is included. The optical path is optically coupled to receive an optical beam. A nonlinearly chirped Bragg grating is disposed in the semiconductor material. The optical path includes the nonlinearly chirped Bragg grating to substantially reduce chromatic dispersion in the optical beam.

Abstract: Unique multi-diffraction structures using electronically controlled Bragg diffraction devices such as acousto-optic (AO) devices to accomplish optical beam attenuation control functions. These variable optical attenuator (VOA) modules can be fully inertialess as they can use electronically programmable sub-microsecond speed AO devices to implement optical gain controls. These VOAs deliver desirable capabilities in one optically reversible unit, making high dynamic range, low loss, high power handling, ultra-fast, high optical isolation, broadband operation, self-aligning robust modules. These VOAs can be made essentially independent of the optical polarization of the incident light by the use of a unique fixed waveplate compensation technique within the VOA configuration that suppresses polarization dependent loss. Broadband gain control operation over several wavelengths can be achieved by controlling the frequency and electrical drive power of the chosen frequencies feeding the acousto-optic devices.

Abstract: The present invention relates to a diffraction grating device in which a diffraction grating based on perturbation of refractive index is formed through a predetermined range in a light guide direction in an optical waveguide and in which the diffraction grating selectively reflects light in a reflection band out of light guided through the optical waveguide. In the diffraction grating device, where a first band is defined as a band with a maximum bandwidth out of continuous wavelength bands for which the transmittance is not more than T0 and where a second band is defined as a wavelength band between a maximum wavelength and a minimum wavelength out of wavelengths for which the reflectance is R0, T0 is not more than ?20 dB and R0 is not more than ?20 dB. A ratio (B1/B2) of a width B1, of the first band to a width B2 of the second band is not less than 0.3. A maximum group delay difference caused by reflection of the light in the first band by the diffraction grating is not more than a predetermined limit, 0.

Abstract: This invention provides a novel wavelength-separating-routing (WSR) apparatus that uses a diffraction grating to separate a multi-wavelength optical signal by wavelength into multiple spectral channels, which are then focused onto an array of corresponding channel micromirrors. The channel micromirrors are individually controllable and continuously pivotable to reflect the spectral channels into selected output ports. As such, the inventive WSR apparatus is capable of routing the spectral channels on a channel-by-channel basis and coupling any spectral channel into any one of the output ports. The WSR apparatus of the present invention may be further equipped with servo-control and spectral power-management capabilities, thereby maintaining the coupling efficiencies of the spectral channels into the output ports at desired values.

Abstract: The present invention discloses a drop-before-add optical routing and switching system. The drop-before-add optical routing and switching system includes an input waveguide for carrying a multiplexed optical signal comprising optical signals transmitted over a plurality of wavelength channels represented by ?1, ?2, ?3, . . . , ?N?1 and ?N, where N is a positive integer wherein the input waveguide extending over a first direction. The drop-before-add optical routing and switching system further includes a plurality of second direction waveguides extending over a second direction and intersecting at N intersections with the input waveguide. The drop-before-add optical routing and switching system further includes a plurality of wavelength selective grating switches each disposed on one of the N intersections for selectively transmitting an optical signal of a selected wavelength into an associated one of the second direction waveguide.

Abstract: An optical device including strained and non-strained regions along an optical medium. In one aspect of the present invention, strain-inducing material disposed proximate to the optical medium induces one or more perturbations of a refractive index along the optical medium to selectively reflect an optical beam directed through the optical medium having a first center wavelength back out a first end of an optical path as remaining wavelengths of light are propagated through a second end. In another embodiment, an optical device may include a strained region disposed in a non-strained region so that one or more perturbations of the refractive index compensates for birefringence of an optical beam directed through the optical medium.

Abstract: A tuneable optical fibre comprising a long-period Bragg grating (5) written in a portion of an optical waveguide (10) comprising a core and an optical cladding (11), characterised in that the portion of the waveguide comprising the grating (5) is at least partially immersed in an external environment consisting of two distinct sections, a first section (1) whose refractive index is higher than that of the optical cladding (11) and a second section (2) whose refractive index is lower than that of the optical cladding (11), the long-period grating being at least partially immersed in one of the said sections so as to almost independently tune the wavelength and/or the contrast of the spectral response of the filter.

Abstract: The invention provides a method of photoinducing a Bragg grating in an optical fiber (300) or a waveguide, in which a selected zone of the fiber (300) or waveguide is subjected to a step of being exposed with a source beam (120) using a mirror (200) in such a manner as to fold a portion (122) of the source beam (120) as reflected by the mirror (200) onto a portion (224) of the source beam that is not reflected by the mirror, thereby obtaining a diffraction grating in the fiber (300) or waveguide, the method being characterized in that an additional exposure step is performed on said portion of the fiber (300) or waveguide, and in that relative displacement is imparted between the two exposure steps to elements selected from the beam (120), the fiber (300) or waveguide, and the mirror (200) in such a manner as to cause a same portion of the beam (120) used for photoinduction in both exposure steps to be reflected by the mirror (200) in one of the steps and not reflected by the mirror (200) in the other step.

Abstract: A method and system are disclosed for switching at least part of a light signal out of a first waveguide by a Bragg grating formed from an electro-optic effect in the first waveguide. The Bragg grating is created by turning on a series of electrodes on each side of the first waveguide. The electrodes create electric fields in the core of the first waveguide which raise the refractive index in certain regions of the core. When the electric fields are tilted and evenly spaced apart, at least part of a light signal propagating through the waveguide, at a predetermined wavelength, is reflected out of the first waveguide. The reflected light signal can be switched back into a second waveguide by use of another Bragg grating. When the electric fields are off in the first waveguide the light signal, including the part of the light signal having the predetermined wavelength, continues straight on through the Bragg grating area.

Abstract: A fine-tuning assembly for an optical grating in an optical fiber is provided. The fiber is mounted under tension in a hollow structure which has a sliding member longitudinally slideable therein. The fiber is attached to both the sliding member and hollow structure. A slanted passage is provided in the sliding member, forming a small angle with the transversal, and a wedge member is slideably inserted in this passage. To fine-tune the spectral response of the grating, the wedge member is transversally displaced without any longitudinal displacement, preferably by the action of screws, thereby pushing on its walls to longitudinally slide the sliding member and adjust the tension in the fiber.

Abstract: A tunable optical device for adding or dropping one or more channels in a wavelength division multiplexing communication system is disclosed. The tunable optical device comprises one or more filters, wherein at least one filter comprises (a) one or more elastimers and (b) one or more gratings. An elastimer is a polymer that expands and contracts with a change in a voltage applied across the polymer or when a certain wavelength of light is diffracted from or transmitted through the polymer.

Abstract: Wide range linear tuning of optical gratings is possible by selecting a thin film heater such that the temperature variation in heater's resistivity ? matches the temperature variation in the heat transfer coefficient of air h. A tunable optical device, such as a fiber grating with such a grating heater, exhibits near linear tuning characteristics over a wide range of temperatures and tuning currents. The heater is useable in other heat tunable optical devices such as interferometers.

Abstract: The present invention provides an arrayed waveguide such that each waveguide of the grating has a substantially uniform width, but the width of any single waveguide in the grating is selected based on a predetermined birefringence required for the waveguide. Generally, the narrowest grating waveguide has the longest overall length and the widest grating waveguide has the shortest overall length. The remaining intermediate waveguides have widths that are interpolated between the narrowest and widest waveguide gratings. With an appropriate width for each waveguide, an arrayed waveguide grating is provided that has low polarization dependent wavelength.

Abstract: A temperature sensing and control method and apparatus. In one aspect of the present invention, an apparatus according to the teachings of the present invention includes an optical path disposed in semiconductor material, a grating disposed in the optical path, and a thermal probe including an optical sensor optically coupled to the grating to sense a spectral response of the grating. The thermal probe is adapted to determine a temperature of the optical path in which the grating is disposed in response to the spectral response of the grating.

Abstract: Optoelectronic and photonic devices are formed by employing polymer materials that have a lower glass transition temperature (Tg) than the nominal operating temperature. By using such materials, the local or segmental mobility is increased so that local stress is eliminated or minimized on the polymer material, making performance more robust. The current invention involves use of a polymer in an optical device in an operating temperature range in the region above Tg, where the polymer segments between crosslinks are allowed local freedom of movement; however, large-scale movement of the material may be restricted by the crosslinked structure of the polymer material.

Abstract: A method for making an apodized Bragg grating in a photosensitive, planar, linear waveguide. A photosensitive, planar, linear waveguide is provided on a surface of a substrate. A patterned phase mask is placed between the waveguide and a laser beam. The waveguide is exposed through the phase mask to the laser beam wherein either the laser beam is moving at a substantially constant velocity with respect to the substrate and phase mask, or the substrate and phase mask are moving at a substantially constant velocity with respect to the laser beam. The beam has a smoothly varying intensity profile, and the exposure is conducted at an angle of more than 0° and less than 90° to the longitudinal axis of the waveguide under conditions sufficient to induce a modulation in the index of refraction of the waveguide and impart an apodized Bragg grating in the waveguide corresponding to the phase mask pattern.

Abstract: An arrayed waveguide grating type optical multiplexer/demultiplexer in which the 1 dB band width is large, the ripple is small, and the degradation of the adjacent crosstalk can be controlled. A waveguide forming portion is formed on a substrate. The waveguide forming portion includes an optical input waveguides, a first slab waveguide, an arrayed waveguide including a plurality of channel waveguides arranged side by side and which have different lengths with the differences preset, a second slab waveguide, and a plurality of optical output waveguides arranged side by side, all of the components being connected in the order stated. A single mode straight waveguide narrower than the optical input waveguides is provided at the output end of at least one or more optical input waveguides. A multi-mode trapezoidal waveguide whose width increases toward the arrayed waveguide is provided at the output end of the straight waveguide.

Abstract: In the present invention an optical waveguide grating sensing device for a dual-parameter optical waveguide grating sensor includes a first optical waveguide grating of a first resonant wavelength provided in a first section of an optical waveguide and a second optical waveguide grating of a second resonant wavelength provided in a second of an optical waveguide. The first and second gratings have different coefficients of rate of change of wavelength as a function of temperature and have substantially the same coefficient of rate of change of wavelength as a function of stain.

Abstract: An optical signal amplification device (200) comprises an optical amplifier (210) having a wavelength-dependent gain and an equalization device (100) optically coupled in series to the optical amplifier and having a wavelength-dependent transmission function that substantially equalize the gain of the optical amplifier, the equalization device comprising a waveguide Bragg grating having a substantially constant refractive index envelope and a chirp rate that varies in such a way as to obtain the wavelength-dependent transmission function.

Abstract: A distributed optical structure comprises a set of diffractive elements. Individual diffractive element transfer functions collectively yield an overall transfer function between entrance and exit ports. Diffractive elements are defined relative to virtual contours and include diffracting region(s) altered to diffract, reflect, and/or scatter incident optical fields (altered index, surface, etc). Element and/or overall set transfer functions (amplitude and/or phase) are determined by: longitudinal and/or angular displacement of diffracting region(s) relative to a virtual contour (facet-displacement grayscale); longitudinal displacement of diffractive elements relative to a virtual contour (element-displacement grayscale); and/or virtual contour(s) lacking a diffractive element (proportional-line-density gray scale).

Abstract: An arrayed waveguide grating 101 is shown, which comprises at least one input waveguide 103, a plurality of output waveguides 104, at least one wavelength compensation output waveguide 105 disposed adjacent to the output waveguide 104, a channel waveguide array 107, an input side slab-waveguide 108, and an output side slab-waveguide 109. The wavelength compensation output waveguide 105 has a tapering connecting portion connected to the output side slab-waveguide 105. Thus, the outputted light has a sharp spectrum, thus permitting ready wavelength compensation.

Abstract: The present invention is directed towards dynamic spectral shaping. Using a grating, the spectral band is spread across a MEMS or other suitable device array. The device may be the deformable grating modulator invented by Bloom et. al. (U.S. Pat. No. 5,311,360) or other suitable device. The invention also includes the coupling in and out of the fiber and may use polarization optics to ensure the grating is used in only one polarization where the diffraction efficiency is higher.

Abstract: An optical apparatus comprises an optical element having at least one set of diffractive elements and multiple channel optical waveguides. Diffractive elements of each set are distributed among diffractive element subsets corresponding to each of the multiple channel waveguides. Each diffractive element set routes, between a corresponding pair of optical ports, those corresponding portions of an optical signal propagating within the optical element that are received by multiple channel waveguides and back-diffracted within the receiving channel waveguides by corresponding diffractive element subsets. The channel optical waveguides are arranged so that optical signals propagate through regions of the optical element between the ports and the first ends of the channel waveguides.

Abstract: An optical spectrum analyzer (10), receiving a multi-channel optical signal (12). The optical signal (12) is passed through an optical isolator (14) and a fiber coupler (16) to a tunable optical filter. The tunable optical filter comprises one or more fiber Bragg gratings (18) inscribed in a length of optical fiber. The optical fiber is mounted on a means operable to apply a variable strain to the fiber, to they tune the peak wavelength of the Bragg grating (18) over a desired wavelength range, the tunable optical filter thereby reflecting each channel of the input signal (12) in turn. The detector (20) therefore detects a signal only if the input signal (12) contains wavelengths corresponding to the reflection wavelength of a grating (18).

Abstract: The present invention seeks to provide a GFF with a technique amenable to manufacturing in large volume and having a filter with a more precise control of the spectral response.

Abstract: The invention provides a method of processing an optical signal having a first amplitude frequency or gain frequency profile so as to produce a desired second amplitude frequency or gain frequency profile, the method comprising subjecting the signal to action by a plurality of chirped gratings each of which is designed to act upon a respective wavelength band of said signal and to remove at least a part of the radiation in said band and operating the gratings such that the proportion of the radiation removed from the respective band is such as to alter the first profile to the second profile within that band. The electrodes define a plurality of adjacent independently adjustable filter segments along the waveguide. Each filter segment functions over a specific range of wavelengths, where the center-to-center wavelength difference between adjacent segments and the wavelength bandwidth of each segment are defined in large part by the chirp in the grating.

Abstract: A tunable filter having a top mirror, a bottom mirror, and one or more intervening layers. The one or more intervening layers preferably have a refractive index that changes with temperature. By heating the one or more intervening layers, the wavelength that is selected by the optical filter can be controlled. The one or more intervening layers are preferably heated by passing current through the one or more intervening layers, or by passing current through a separate resistive layer that is thermally coupled to the one or more intervening layers. Such a filter can provide a high degree of wavelength selectivity in a robust and stable manner.

Abstract: A pitch averaging Bragg grating includes a plurality of grating peaks spaced by different pitch values. By selecting the different pitch values to have an average pitch value equal to a target pitch value, the pitch averaging Bragg grating can be made to perform like a constant pitch Bragg grating having a fixed pitch at the target pitch value. The different pitch values can be multiples of the minimum placement resolution of a production tool to be used to produce the Bragg grating. The pitch averaging Bragg grating can be used in place of constant pitch Bragg gratings in optical devices and systems, such as DFB lasers, DBR lasers, optical spectral filters, multi-wavelength laser arrays, and WDM systems.

Abstract: A transverse Bragg resonance waveguide is comprised of a waveguiding channel, and on at least two opposing sides of the channel two periodic index media; and a means for providing gain in the periodic index media. In one embodiment the waveguiding channel is planar and is sandwiched on two opposing sides by the periodic index media. In another embodiment the waveguiding channel is cylindrical and is surrounded by the periodic index media. The means for providing gain in the periodic index media is electrical or optical pumping. The periodic index media comprises a periodic lattice of regions having an index of refraction distinct from the channel, such as an array of transverse holes defined in a planar semiconductor substrate in which the channel is also defined, or an array of longitudinal holes defined in a cylindrical semiconductor fiber in which the channel is also longitudinally defined.

Abstract: An active diffraction grating that has a high degree of freedom in control, small size and high reliability is realized.