Abstract: A tunable optical filter is based on a conventional thin film optical filter. The thickness of the thin film optical filter determines the optical properties of the filter, specifically the pass band. The thin film optical filter is arranged within a hole extending through a layer of piezoelectric material such that the periphery of the thin film optical filter is secured to the periphery of the hole. Electrodes are provided on opposite surfaces of the piezoelectric layer such that different voltage levels can be applied. The resulting deformation of the piezoelectric layer causes a difference in the thickness of the thin film optical filter thereby permitting tuning of the optical filter.

Abstract: The present invention relates to an electrical field absorbing semiconductor optical modulator, more particularly, to a high speed semiconductor optical modulator and a fabricating method thereof. The present invention includes a high speed semiconductor optical modulator, the optical modulator formed by stacking an n-type light-wave guiding layer, a light absorbing layer, a p-type light-wave guiding layer, a p-type clad layer, and a p-type ohmic contact layer on a substrate successively, the optical modulator having a ridge structure wherein the optical modulator is an electric-field absorbing type, and wherein width W3 of the light absorbing layer is less than the width W1 of the p-type ohmic contact layer. Accordingly, the present invention enables to provide high speed optical modulation of tens of giga rate of which modulating characteristics are excellent by reducing contact resistance and capacitance, which are the major problems of ruining the characteristics of an optical modulator, simultaneously.

Abstract: Disclosed is an optical modulating device capable of use as a light-valve, display, optical filter or Fabry-Perot cavity, for example. The device lends itself to batch processing, and is compatible with monolithic integration with silicon, silicon-germanium, silicon-on-sapphire (SOS) or silicon-on-quartz (SOQ) advanced microelectronic technology (NMOS, PMOS and CMOS) for integrated control circuitry, electrical addressing, system interfacing, and the like. The device forgoes the complexities of liquid crystal constructions, and avoids the need to position and fix piezoelectric spacers within layers of the device. The invention includes first and second transparent layers that are disposed to oppose one another. Metallic layers are disposed upon the inwardly facing surfaces of the transparent layers and these are arranged to oppose each other. Spectral coupling layers are disposed upon the outwardly facing surfaces of the transparent layers opposite of the metallic layers.

Abstract: A high-precision etalon and novel method of construction thereof is presented. The etalon comprises a pair of plane-parallel flat mirrors spaced a first distance apart, a pair of plane-parallel spacers transversely attached to the pair of mirrors which operate to fix the first distance between the pair of mirrors, and a thin film mirror layer deposited on at least one of the pair of plane-parallel flat mirrors to form a laser cavity therein of a precise second distance apart. The method of constructing an etalon in accordance with the invention includes the steps of fabricating one or more spacers, measuring the length of the spacer(s), and deriving a dimensional deviation of the spacer length from a nominal cavity dimension specified for the etalon. A thin-film pedestal is then deposited on one, the other, or both of a first and second substrate and then coated with a reflective coating. The etalon is then assembled using the spacer(s) and first and second substrates.

Abstract: A process for configuring a tunable MOEMS filter train comprises determining a spectral response of a MOEMS tunable filter. A spectral separation between different order modes, or free spectral range, is then determined for the filter. This information is then related to a mode size of a desired mode of the tunable filter. With this information, lenses for the optical train are provisioned, and then installed so that light is launched into the optical filter at the desired mode size to thereby maximize the SMSR of the filter train.

Abstract: A semiconductor device is provided with at least two photodetectors and an interposed etalon. Signals from the photodetectors may be compared to generate a control signal. The control signal may be used for wavelength control and/or stabilization and for other purposes. According to a preferred embodiment, the etalon is formed of at least two distributed Bragg reflectors. The etalon provides high discrimination power. In addition, the etalon has a periodic discrimination function that may be matched to the periodic channels of a dense wavelength division multiplexing system. According to one aspect of the invention, electrical current may be applied to selected layers of the device to tune and/or shift the response of the device. If desired, the invention may be incorporated into a waveguide structure, such as an optical fiber. The present invention also relates to a wafer fusion technique for making integrated devices.

Abstract: A method of fabricating optical filter is disclosed. The method includes providing the substrate and selectively etching the substrate to form a plurality of freestanding layers. A plurality of dielectric layers is disposed over an outer surface of each of the freestanding layers. The resultant optical filters may be used in a variety of applications including etalon applications.

Abstract: An optical modulation element is capable of forming a reflective diffraction grating in which heights of a plurality of elements each having a reflecting surface periodically change. The reflecting surfaces of at least one of the plurality of elements are driven in a direction of height by piezoelectric elements. The plurality of elements each having the surface as the reflecting surface are two-dimensionally arrayed by juxtaposing long sides. A rear surface side of an effective reflecting portion of each of the elements is fixed to the piezoelectric element.

Abstract: An optical image shutter is provided having a multiplicity of thin layers of alternating narrow and wide gap semiconductor material stacked to form an MQW structure and electrodes located on at least two semiconductor surfaces of the image shutter, wherein the electrodes are configured so that a voltage difference applied between them produces an electric field that is temporally and spatially substantially uniform in the volume of the MQW structure and wherein the aperture of the image shutter is greater than 4 square mm.

Abstract: A multi-wavelength etalon suitable for tuning and maintaining the operating frequency of a laser used in an optical communication system is disclosed. The communication system has a representative channel wavelength and a channel spacing. The etalon has a plurality of steps on one of the sides with a step size that is a fraction of the channel spacing. The nominal thickness of the etalon is chosen so that a transmission peak occurs at a wavelength substantially equal to the representative channel wavelength and a next peak occurs at the wavelength of an adjacent channel. The step size is a fraction of the channel separation and is substantially optimized so that a peak or trough in the transmission curve in the region of one step overlaps a steep portion of the transmission curve for one or more other steps.

Abstract: The invention provides tunable optical filters in which operating characteristics such as initial cavity length and mirror tilt, affecting passband wavelength position and filter finesse, respectively, can be controlled independently of membrane tuning bias. An illustrative embodiment incorporates a surface-micromachined plate with an opening in which a moveable frame is supported by, e.g., flexure bars or support arms. A moveable membrane with a high reflective (HR) coated mirror is supported in an opening in the moveable frame. The mirror defines one side of a Fabry-Perot (FP) filter cavity and is movable in a direction along an axis of the filter cavity. The other side of the filter cavity is defined by a second HR-coated mirror. The moveable frame has a number of electrodes arranged on a surface thereof, such that an operating characteristic of the filter, e.g.

Abstract: A solid state device used to modulate the intensity of reflected or transmitted light by modulating with an external voltage the optical thickness of a thin film ferroelectric placed in an etalon cavity is disclosed. The device is constructed by selecting a generally planar supporting substrate, preferably silicon or sapphire in order to be compatible with silicon integrated circuits. A dielectric stack consisting of alternating layers of different index of refraction materials, also specifically selected to be compatible with later growth of the thin film ferroelectric, is deposited thereon to form a partially reflective and partially transmitting mirror, followed by a transparent electrically conductive layer. The thin film ferroelectric is deposited on the conductive layer, followed by a second transparent conductive layer and a second dielectric stack. Leads are connected to the conductive layers and in turn to a voltage generator.

Abstract: Light in the visible spectrum is modulated using an array of modulation elements, and control circuitry connected to the array for controlling each of the modulation elements independently, each of the modulation elements having a surface which is caused to exhibit a predetermined impedance characteristic to particular frequencies of light. The amplitude of light delivered by each of the modulation elements is controlled independently by pulse code modulation. Each modulation element has a deformable portion held under tensile stress, and the control circuitry controls the deformation of the deformable portion. Each deformable element has a deformation mechanism and an optical portion, the deformation mechanism and the optical portion independently imparting to the element respectively a controlled deformation characteristic and a controlled modulation characteristic. The deformable modulation element may be a non-metal.

Abstract: An optical filter having broad resonant frequency passbands for filtering an optical input including a plurality of multiplexed optical wavelengths into a first set of transmitted wavelengths and a second set of reflected wavelenghts. The filter has first and second inner mirrors separated substantially by an inner spacer, a first outer mirror separated from the first inner mirror substantially by a first outer spacer, and a second outer mirror separated from the second inner mirror substantially by a second outer spacer. The inner mirrors have reflectivity which is greater than the reflectivity of the outer mirrors, and are formed from layers of alternating high and low refractive index materials. The optical thicknesses of the spacers are substantially identical, and are sized to align the resonant frequency passbands of the filter with the first set of transmitted wavelengths.

Abstract: A solid state device used to modulate the intensity of reflected or transmitted light by modulating with an external voltage the optical thickness of a thin film ferroelectric placed in an etalon cavity is disclosed. The device is constructed by selecting a generally planar supporting substrate, preferably silicon or sapphire in order to be compatible with silicon integrated circuits. A dielectric stack consisting of alternating layers of different index of refraction materials, also specifically selected to be compatible with later growth of the thin film ferroelectric, is deposited thereon to form a partially reflective and partially transmitting mirror, followed by a transparent electrically conductive layer. The thin film ferroelectric is deposited on the conductive layer, followed by a second transparent conductive layer and a second dielectric stack. Leads are connected to the conductive layers and in turn to a voltage generator.

Abstract: A method for tuning a dielectric filter comprises determining filter characteristics of a filter including a cut-on wavelength and a cut-off wavelength taken at a selected gain level. The filter is rotatably attached to a collimator assembly and a light source having a wavelength approximately equal to the cut-on frequency is applied to the filter and rotated to adjust the filter to the cut-on wavelength, and the spectral performance is measured and compared with a cut-on rating value. The method further includes applying a light signal having a wavelength set to a cut-off wavelength, to the filter rotating the filter relative to the collimator assembly, measuring spectral performance, and comparing the measured spectral performance with a cut-off rating value.

Abstract: Active phase-shift control is achieved in a hybrid etalon by selecting appropriate elements in the photodiode array 22, 22' of FIG. 2 for a prescribed phase-shift. A negative lens 20, (20") is used to expand the beam spot of the output beams P.sub.2 16, (P.sub.1 18) to the line length of the photodiode array 22, (22'). The signal beam 14 and the LO (local oscillator) beam 12 are angularly misaligned by the incident beam angle .delta. 26 to the 2-face 8 and .delta.' 26' to the 1-face 10 (.delta.'.noteq..delta.), thus resulting in the misaligned signal and LO beamlets inside the etalon 6. The beamlets from the 2-face 8 comprise the P.sub.2 beam 16 and the beamlets from the 1-face 10 comprise the P.sub.1 beam 18. The photodiode array 22, 22' detects an interference fringe pattern in the output beams P.sub.1 18 and P.sub.2 16 due to the misaligned input beams. The beamlets from the 2-face 8 and the 1-face 10 have been expanded for illustrative purposes in FIG.

Abstract: An eye protection arrangement for protection against multispectral laser threats includes goggles or spectacles with a tunable etalon optical filter. In one embodiment, the optical filter is fixed-tuned to a safe frequency. In another embodiment, light from the laser being used is sensed, and used to set the protective goggles to a different wavelength than the laser. In yet another embodiment of the invention, the protective optical filters have a comb response, and additional protection is provided by optically cascading two filters, each having a somewhat different comb response, so as to reduce the number of transmission spectra.

Abstract: A far-infrared image is directed onto a transducer having a planar array of absorbing discs on one side. The discs are supported by a thin membrane ich expands and bulges as the discs heat up. The discs thus change their spacing with respect to a partially reflective mirror. The nominal spacing between the discs and mirror is about 1/4 wavelength of the infrared radiation, such that absorption is enhanced. The mirror is supported on a transparent substrate through which visible or near-infrared light is shown, and carries a perforated mask atop an insulating layer and in registration with the discs. The mirror/discs thus establish a Fabry-Perot cavity for the visible or near-infrared light, whereby a visible or near-infrared image may be observed or detected as the various discs establish various spacings in accordance with incremental variations in the infrared image. An electrostatic field is established between the mirror and the shield by a voltage source.

Abstract: By applying a photonic signal to a microresonator that includes a photonic bandgap delay apparatus having a photonic band edge transmission resonance at the frequency of the photonic signal, the microresonator imparts a predetermined delay to the photonic signal. The photonic bandgap delay apparatus also preferably has a photonic band edge transmission resonance bandwidth which is at least as wide as the bandwidth of the photonic signal such that a uniform delay is imparted over the entire bandwidth of the photonic signal. The microresonator also includes a microresonator cavity, typically defined by a pair of switchable mirrors, within which the photonic bandgap delay apparatus is disposed. By requiring the photonic signal to oscillate within the microresonator cavity so as to pass through the photonic bandgap delay apparatus several times, the microresonator can controllably impart an adjustable delay to the photonic signal.

Abstract: Light in the visible spectrum is modulated using an array of modulation elements, and control circuitry connected to the array for controlling each of the modulation elements independently, each of the modulation elements having a surface which is caused to exhibit a predetermined impedance characteristic to particular frequencies of light. The amplitude of light delivered by each of the modulation elements is controlled independently by pulse code modulation. Each modulation element has a deformable portion held under tensile stress, and the control circuitry controls the deformation of the deformable portion. Each deformable element has a deformation mechanism and an optical portion, the deformation mechanism and the optical portion independently imparting to the element respectively a controlled deformation characteristic and a controlled modulation characteristic. The deformable modulation element may be a non-metal.

Abstract: A reversible and conservative photon routing switch is implemented as a room temperature, optical, vertical cavity X-gate (also sometimes known as a Fredkin gate). Such gates are primitive structures into which all logic functions can be decomposed. The construction of the device makes it uniquely suited to dense packed arrays of optoelectronic components for optical routing and logic. In one of the switching states, light incident on the device from either side of the wafer will pass through the device (the device is bi-directionally transmissive). In the other switching state, light incident from either side of the wafer will be reflected. Switching can be performed using either electrical or optical control. Thus incident photons are either routed through the device or reflected from the device.

Abstract: A photonic band gap structure device and method for delaying photonic signals of a predetermined frequency and a predetermined bandwidth by a predetermined delay is provided. A Fabry-Perot delay line device has several regions of periodically alternating refractive material layers which exhibit a series of photonic band gaps and a periodicity defect region, interposed between the regions of periodically alternating refractive material layers. The Fabry-Perot delay line device imparts a predetermined delay to photonic signals that pass therethrough. The introduction of the periodicity defect region into this photonic band gap structure creates a sharp transmission resonance within the corresponding photonic band gap of the structure and causes at least an order of magnitude improvement in photonic signal delay for a band-edge delay line device of similar size. Variable photonic delays to multiple photonic signals are also generated by this Fabry-Perot delay line device.

Abstract: A method and device for wavelength locking is provided, wherein an element having a wavelength dependent characteristic such as a Fabry Perot etalon is used to provide an output signal having an intensity that varies with wavelength. The intensity of a reference signal derived from an input signal is compared with an output from the Fabry Perot etalon to provide a feedback signal that corresponds to the frequency of the input signal. The system is calibrated before wavelength locking is performed to determine a ratio of intensities that determines a locked state or condition.

Abstract: An electro-absorption optical modulator, where a waveguide length of the absorption layer is denoted by L, a light confinement coefficient thereof is denoted by .GAMMA., and a performance factor of the absorption layer at an applied voltage V to an absorption layer is denoted by K(V), has design parameters selected so that a relationship .vertline.K(V)-.GAMMA..multidot.L.vertline. .ltoreq.0.005 cm is satisfied in a continuous operation range of a quenching ration T.sub.Att. The waveguide length L is preferably optimizrd so as to satisfy K(V).apprxeq..GAMMA..multidot.L in the operation range.

Abstract: An electro-optic modulator and a method for its use, in which an optical carrier is effectively suppressed for transmission of a radio-frequency (rf) modulating signal over an optical communication link, to provide improved demodulator performance. A carrier component is recovered from the modulator, amplified, and reused, to minimize the effect of optical carrier losses. In one embodiment of the invention, a modulator (10) with complementary output ports (20 and 22) generates a carrier-suppressed output (FIG. 2B) containing rf sidebands from one port (20) and a strong carrier component (FIG. 2C) from the other output port (22). The carrier component is filtered in a residual sideband filter (14), amplified in an optical amplifying medium (12) and returned to the modulator (10) as its carrier input. In a second embodiment of the invention, a modulator (30) with a single output port produces rf sidebands and a suppressed carrier component (FIG.

Abstract: A photonic signal is applied to a photonic bandgap structure having a photonic band edge transmission resonance at the frequency of the photonic signal and having a photonic band edge transmission resonance bandwidth which is at least as wide as the bandwidth of the photonic signal. When a photonic band edge transmission resonance is matched to the photonic signal which is being transmitted, a controllable delay is imparted to the photonic signal without significantly altering the photonic signal itself.

Abstract: An electrically-controllable liquid crystal filter device comprises two partially-reflecting substrate structures mounted substantially parallel to each other with a space therebetween to form a Fabry-Perot filter. A layer of ferroelectric liquid crystal material is disposed in the space, the liquid crystal material being switchable, by application of an electric field, between different refractive index values whereby the device is switchable between transmissive and reflective states for light of a particular narrow wavelength band. The spacing of the substrate structures is selected in relation to the wavelength of light to be transmitted, such that the Fabry-Perot filter operates in a low order state, which may be the first order.

Abstract: A cavity thickness compensated etalon filter. A tuning medium is placed in a Fabry-Perot etalon cavity. The index of refraction of the tuning medium varies as a function of voltage applied across the medium. The etalon is formed of two generally flat substrates disposed substantially parallel to one another. Each substrate has a layer of conductive material within the cavity adjacent the substrate. Each substrate also has a layer of reflective material within the cavity adjacent the substrate. At least one layer of reflective material is only partially reflective so as to enable light to pass into and out of the cavity. Liquid crystal material may be used as a tuning medium in the cavity. In the case of liquid crystal material, the etalon also comprises an alignment layer disposed within the cavity adjacent each substrate to pre-order the liquid crystal material.

Abstract: This invention concerns an electrochromic pane comprising a principal functional film constituted of a material which, under the effect of an electric current, is capable of reversibly inserting cations and which has characteristics of coloration and/or transmission in certain wavelengths of electromagnetic radiation that differ for its inserted and deinserted states. Said principal functional film has a quasi-columnar structure, with axes of growth of the columns parallel to straight lines contained within a dihedron, the opening of which is less than 20.degree., and the bisector plane of which makes an acute angle with the substrate.

Abstract: A single-channel gas concentration measurement method and apparatus. According to the method, a radiant source is employed to generate a measuring signal, the measuring signal is subsequently directed to a measurement object containing a gas mixture to be measured, the measuring signal is subsequently bandpass filtered using at least two passband wavelengths, and the filtered measuring signals are detected by a detector. According to the invention, the bandpass filtering step is implemented by a single electrostatically tunable, short-resonator Fabry-Perot interferometer.

Abstract: A rhodopsin family protein is inserted into an etalon type cavity having partially reflecting mirrors as principal components having a reflectivity of 50% to less than 100% for light having a wavelength in the 650-800 nm region and a transmissivity of 30% or more for light having a wavelength in the 400-600 nm region to form a photo-controlled spatial modulator. By utilizing a change in the refractive index by light of the photo-sensitive protein, near infrared light of a stronger intensity can be controlled by weaker visible light, and the information contained in the light signal on a two-dimension plane can be rapidly controlled by a light signal of weaker intensity of another two-dimension plane by using an optical switch of a simple construction.

Abstract: This invention provides analog phase modulators comprising smetic liquid crystal cells wherein the layers are specifically not aligned perpendicular to the cell walls. The layers are either tilted with respect to the substrate or are in a chevron structure. Application of an analog electric field perpendicular to the cell walls bends the molecules in an analog fashion in a plane not parallel to the cell walls and thereby provides analog phase modulation of incident light. Analog phase modulation can not be directly provided by the surface-stabilized smectic liquid crystal cells known in the art, nor can analog tilting of SmC* liquid crystals be achieved. This invention further provides Fabry-Perot devices containing these analog phase modulators within the resonance cavity. The filter of this invention is optimally suited for wavelength-division multiplexing in photonic networks. It has high throughput, large tuning range, high resolution, and high modulation speed.

Abstract: An asymmetric Fabry-Perot modulator (AFPM) is disclosed having an operating wavelength in the 1.5 .mu.m region used for long-haul optical transmission. The AFPM includes electro-absorption material consisting of an Al.sub.x In.sub.y Ga.sub.1-x-y As multiple quantum well structure. An amplitude modulated optical signal is produced by modulating the bias voltage across the electro-absorption material between zero bias and the matching voltage that gives zero reflectivity from the cavity formed by the electro-absorption material and top and bottom reflectors. An amplitude modulated optical signal having a negative chirp parameter is produced by coating the top of the modulator with a high-reflectivity coating to reduce the voltage required to achieve the matching condition and then modulating the electro-absorption material between the matching voltage and a higher voltage.

Abstract: This invention provides a multipass Solc filter which utilizes liquid crystal variable retarders to provide high resolution and tunability. The Solc polarization-interference effects are used synergistically with the Fabry-Perot cavity resonances. The cavity comprises a central retarder, two quarter wave plates, and an optional isotropic spacer. The central retarder or the isotropic spacer can include liquid crystal cells to provide tuning of the Solc envelope or the cavity resonances respectively. In one embodiment the variable retarder is a three element quarter-half-quarter device with a liquid crystal electro-optically rotatable half-wave plate. Reflection mode configurations are introduced wherein, because of the bilateral symmetry of the Solc filter, it is possible to use only half of the intracavity elements. Criteria for designing filter parameters to meet resolution, out-of-band discrimination, and tuning range requirements are provided.

Abstract: A variable spectral resolution agile filter has instantly adjustable spectral resolution with no required mechanical motion and a quickly adjustable center wavelength. Adjustment of the center wavelength is accomplished by reliable piezoelectric actuators. Adjustment of the spectral resolution is achieved by changing the finesse of the system, the finesse being governed by the reflectivity of the faces. By making one of the faces exhibit electrically variable reflectivity, the finesse of the system is instantly changeable, and thus the spectral resolution is also instantly changeable.

Abstract: A photo isolator transmits light of a frequency fo in the normal direction and substantially intercepts the light in the reverse direction. A phase modulator comprising an optical crystal having a refractive index, counter faces and counter electrodes formed on the counter faces. The phase modulator receives an electrical signal having a frequency of .DELTA.f or higher and changes the refractive index of the optical crystal by the Pockels effect. A narrow band pass filter has a half band width of .DELTA.f, is mounted on an optical axis, and substantially transmits light having frequency of from (fo-.DELTA.f) to (fo+.DELTA.f). The phase modulator is juxtaposed with the narrow band pass filter on the optical axis.

Abstract: Photocurrent suppression is achieved without deleteriously affecting modulation performance in a surface normal, electro-absorption, quantum well modulator by introducing a sufficient number of non-radiative recombination centers in the quantum well region of the modulator. The presence of the non-radiative recombination centers significantly shortens the lifetime of photogenerated carriers and, thereby, suppresses the photocurrent. Modulation performance characteristics such as contrast ratio are maintained at acceptable levels even though exciton broadening occurs in the quantum wells. The present modulator exhibits a careful balance between defect density in the quantum wells and the acceptable degree of exciton broadening necessary to preserve quantum effects.

Abstract: A process and apparatus for the modulation and amplification of light beams having at least one input light beam (8) supplied to at least one Fabry-Perot resonator having at least one resonance mode, and defined by two mirrors (M1,M2) and produced by stacking layers on a substrate (4). At least one of the layers form an active medium (6) able to amplify the input light beam by stimulated emission, the wavelength thereof being around the resonance of the resonator and the density of free charge carriers in the active medium being varied in such a way as to make the latter sometimes absorbent and sometimes an amplifying with respect to the input beam and thus obtain at least one output light beam (10) whose intensity is modulated and amplified relative to the input beam. Application to optical telecommunications and to optical interconnections.

Abstract: A laminated glazing unit has controllable transparency to visible light and a solar load reduction element which preferentially excludes infrared radiation while being substantially transparent to visible light. Electro-active material for controlling the transmission of visible light through the glazing unit is sandwiched between electrodes deposited on facing surfaces of plys or layers of an inextensible polymeric material, such as polyethylene terephthalate. One or both electrodes comprises a solar load reduction ("SLR") element, i.e., a Fabry-Perot interference filter which includes preferably at least one silver metal film sandwiched between zinc oxide films.

Abstract: The present invention provides optical modulators which comprise aligned chiral smectic liquid crystal cells within an optical resonance cavity. The cavity configurations include symmetric and asymmetric Fabry-Perot etalons. The liquid crystal cells can be planar- or homeotropically-aligned and can be discrete state or analog cells. The device configurations of the present invention provide discrete or continuous optical modulation of the phase, intensity, and wavelength of elliptically polarized light, without requiring polarization analyzers. The modulators are optically or electronically addressable in single pixels or arrays of multiple pixels. Certain homeotropically-aligned cells are provided as an aspect of this invention, as are certain variable retarders comprised of planar-aligned cells in combination with birefringent elements.

Abstract: A wide band optical modulator is grown on a substrate as tandem Fabry-Perot resonators including three mirrors spaced by two cavities. The absorption of one cavity is changed relative to the absorption of the other cavity by an applied electric field, to cause a change in total reflected light, as light reflecting from the outer mirrors is in phase and light reflecting from the inner mirror is out of phase with light from the outer mirrors.

Abstract: An asymmetric Fabry-Perot reflectance modulator (AFPM) consists of an active region between top and bottom mirrors, the bottom mirror being affixed to a substrate by a buffer layer. The active region comprises a strained-layer region having a bandgap and thickness chosen for resonance at the Fabry-Perot frequency. The mirrors are lattice matched to the active region, and the buffer layer is lattice matched to the mirror at the interface. The device operates at wavelengths of commercially available semiconductor lasers.

Abstract: Simple polarization independent wavelength tuning components (filters) employ a filter element, such as a Fabry-Perot etalon element, which is such that light input thereto undergoes two element transitions with orthogonal polarization states before being output, in order to suppress polarization noise. The element may be mounted for rotation about a single axis. In one arrangement, two etalon filters (20, 21), are separated by a half wave plate (22) providing the necessary polarization rotation. The two etalon filters and the half wave plate comprise a single element rotatable about the single axis.

Abstract: The present invention relates to a novel spatial light modulator comprising a plurality of individual pixels that each contain separate detectors, electronic circuitry, and optical modulators. A primary application of such a spatial light modulator is to provide the requisite nonlinear relationship between a plurality of optical beams fanned in to each detector on the one hand, and a plurality of optical beams fanned out from such modulator on the other, on a pixel-by-pixel basis. In one embodiment, the spatial light modulator is configured to differentially amplify the inputs to two separate detectors within each pixel, and to transform iORIGIN OF INVENTIONThe U.S. Government has certain rights in this invention pursuant to Contract No. F49620-87-C0007, awarded by the Department of the Air Force, and to Grant No. AFOSR-89-0466, awarded by the Defense Advanced Research Projects Agency through the Department of the Air Force.

Abstract: In a reflective optical modulator light enters through an optical waveguide into a detunable optical resonator which couples it back into the optical waveguide, the modulation being effected by detuning the resonator. The resonator includes the end face of the optical waveguide through which the light enters and is coupled back, and a first reflective surface disposed opposite this face.

Abstract: A photodiode array composed of sharply tuned at consecutively different wavelengths are disclosed with the vertical resonance cavity. Semiconductor superlattice distributed Bragg reflectors can be used as the resonance cavity to achieve sharp tuning and monolithic integration, and the wedged distributed Bragg reflector configuration resonance cavity provides a sequential wavelength detection range. A linear array having resolution a fraction of the photodiodes bandwidth and a square-matrix array with a wedged etalon for high resolution, are disclosed. The disclosed photodiode array make a pocket-type wavelength meter feasible and can be used as a substitute for a spectrometer.

Abstract: A tunable etalon filter is formed by placing mirrors on either side of a spacer of a material which has a relatively large rate of change of refractive index with temperature, and coupling the filter to a thermoelectric cooler to control the temperature of the spacer and, therefore, the index of refraction of the spacer. More specifically, the spacer can be a silicon wafer, or a wafer of zinc sulfide or zinc selenide. The mirrors can be formed of quarter wavelength layer pairs of dielectric coatings of high and low refractive index material. The thermoelectric cooler, which can be coupled to a heat sink, controls the temperature of the spacer by either heating or cooling the spacer. In operation the filter is coarse tuned by adjusting its angle relative to the angle of a received optical signal. It is then fine tuned to the signal by adjusting the temperature of the spacer.

Abstract: The liquid crystal device has a pair of flat glass substrates, a pair of dielectric multilayer film mirror, a plurality of transparent electrodes arranged in a matrix, a plurality of minute insulating films formed on inner face of the glass substrates, and a liquid crystal layer. A pair of dielectric multilayer film mirror constitute a Fabry-Perot etalon via the liquid crystal layer and enhance a contrast ratio. The minute insulating films are formed by physical vapor deposition and attain a uniform thickness, so that a liquid crystal device having a uniform cell gap is obtained.

Abstract: In an optosemiconductor device including a superlattice configuration (TBQ) of first and second quantum well layers and a potential barrier therebetween, photo-excited carriers are formed in the first quantum well layer and are tunnelled through the potential barrier toward the second quantum well layer, so that the tunneled carriers are accumulated in the second quantum well layer. An electric field is applied to the superlattice configuration to expel the tunneled carriers from the second quantum well layer.