Abstract: A tunable semiconductor laser comprises a gain section having an MQW active region, a uniform pitch grating DFB region, and first waveguide. A composite reflector, including a second MQW region and a second waveguide, forms a cavity resonator with the DFB region. A tuning voltage applied to the composite reflector induces refractive index changes, thereby allowing the center wavelength to be altered.

Abstract: A method of fabricating an expanded beam optical waveguide device (e.g., a laser), comprises the steps of (a) forming a first semiconductor waveguide region having first and second sections of different thickness and an intermediate vertical taper section of varying thickness coupling the first and second sections to one another, the first waveguide region being effective to expand the size of the beam as it propagates from the first section to the second section, (b) forming a second semiconductor region (e.g., a laser active region) on the first waveguide region, (c) etching the second region so as to form an essentially vertical first surface of length A-B which extends obliquely across the propagation axis of the device, (d) forming a third semiconductor region (e.g.

Abstract: A multiple wavelength quantum cascade (QC) superlattice (SL) light source has at least three energy levels in each radiative transition (RT) region, and electron transitions between the levels give rise to emission lines at different wavelengths. In one embodiment, a lower miniband has at least a first energy level and an upper miniband has at least third and fourth energy levels. In another embodiment, the lower miniband has first and second energy levels. In both cases, electron transitions between a first pair of the upper and lower levels generates light at a first spontaneous emission line having a center wavelength .lambda..sub.1 and a line broadening first energy, and electron transitions between a second pair of the upper and lower levels generates light at a second spontaneous emission line having a center wavelength .lambda..sub.2 and a line broadening second energy.

Abstract: A solid state laser comprises a cavity resonator in the form of a generally cylindrical body and, located within the resonator, an active region which generates lasing light when suitably pumped. The resonator has a relatively high effective refractive index (n>2 and typically n>3) is sufficiently deformed from circularity so as to support at least one librational mode (e.g., a V-shaped or a bow-tie mode, the latter being presently preferred for generating relatively high power, directional outputs). Specifically described is a Group III-V compound semiconductor, quantum cascade (QC), micro-cylinder laser in which the resonator has a flattened quadrupolar deformation from circularity. This laser exhibits both a highly directional output emission and a three-order of magnitude increase in optical output power compared to conventional semiconductor micro-cylinder QC lasers having circularly symmetric resonators.

Abstract: Properly designed optical waveguides exhibit anomalous (positive) dispersion over a continuum of visible and near infrared wavelengths and, in one embodiment, the fiber has zero-dispersion at a visible wavelength (e.g., about 760 nm). Preferably, the zero-dispersion point occurs at a vis-nir wavelength where the normal (negative) material dispersion is relatively high and the effective refractive index difference between the core and the cladding is sufficiently large that the anomalous (positive) waveguide dispersion compensates the normal material dispersion. Illustratively, the optical waveguide is a microstructured fiber comprising a solid silica core surrounded by an inner cladding that includes a plurality of capillary air holes that allow for index-guiding within the core. The pattern formed by the cross-sections of the air holes, typically circles, may take on a variety geometric configurations, such as a closely packed hexagon or triangle.

Abstract: In a WDM fiber-optic network, a unique laser transmitter enables signals to be routed at three hierarchical levels: at one level discrimination among signal paths is based on N WDM wavelength channels, at another level discrimination is based on m AM subcarrier frequency channels, and at a third level discrimination is based on n FM subcarrier frequency channels. Thus, a total of Nmn distinguishable optical channels can be accommodated and a like number of users served. The laser transmitter comprises a broadband, tunable semiconductor laser which includes an intracavity, integrated composite reflector to which a tuning voltage and a FM dither signal are applied, an intracavity gain section to which drive current is applied, and an extracavity, integrated electroabsorption modulator to which an information (e.g., data, voice, video) signal and an AM dither signal are applied.

Abstract: An optical fiber amplifier is pumped by a fiber pump laser which has a pair of separate active media within a common resonator. The fiber gain section of the amplifier is also located within the resonator.

Abstract: In a DH-PHEMT the channel layer comprises InGaAs, the donor layers comprise In.sub.y Ga.sub.1-y P(0.15.ltoreq.y.ltoreq.0.85), and each of the spacer layers comprises an In.sub.0.5-q (Al.sub.x Ga.sub.1-x).sub.0.5+q P outer spacer layer (0.2.ltoreq.x) and an Al.sub.r Ga.sub.1-r As (0.ltoreq.r.ltoreq.0.3) inner spacer layer. In another embodiment, a similar InAlGaP layer forms a Schottky barrier gate contact with a barrier height of at least 1.0 eV and hence low leakage current. The devices exhibit the capability for both low noise and high power operation at low supply voltages.

Abstract: An optical transceiver assembly for use in a bidirectional system includes a beam splitter to direct an incoming signal to a photodiode. An outgoing signal from a laser diode is partially transmitted and partially reflected by the splitter. The reflected signal, which may reach the photodiode, constitutes crosstalk which is reduced by means of a cavity positioned to receive the reflected signal and an oblique surface within the cavity adapted to prevent much of the reflected signal from reaching the photodiode.

Abstract: Stability of a pump laser for activating an erbium amplifier is enhanced by a grating which results in laser operation in the coherence collapse regime.

Abstract: In an optical fiber light source a section of multimode fiber is interposed between an energizing laser (e.g,, a diode laser) and a single mode fiber active medium. In a preferred embodiment the single mode fiber active medium is surrounded by a multimode cladding coupled to the multimode fiber. The source may serve as a pump laser for a fiber amplifier or as an amplified spontaneous emission source. Arrangements for coupling several energizing lasers to the active medium are also described.

Abstract: A Si IC includes an Al-based layer which is deposited as a composite of sublayers of different composition Al-based materials. In one embodiment a first sublayer comprises an Al-Si-based alloy disposed so as to prevent substantial Si migration into the first sublayer, and a second sublayer, above the first, comprises an Al-based alloy with substantially no Si to alleviate precipitation-induced problems.

Abstract: A power converter with a self synchronized synchronous rectifier includes one or two drive windings to provide positive drive to the control electrodes of the controlled switches (FETs) of a self synchronized synchronous rectifier. The polarities of these windings are selected so that the switched devices are driven appropriately to rectify the periodic signal output of the secondary winding of the power transformer of the converter. In some arrangements one or two drive windings are included as extra windings in the power transformer and connected to provide the proper polarity drive signals. The turn ratios of the drive windings to the other windings are selected to provide the proper gate drive signal levels. In an alternative arrangement a separate drive transformer may be provided to supply the gate drive signals.

Abstract: The base layer of high quality spacers, such as those used on the sidewalls of the gate stack of submicron devices (e.g., MOSFETs, EPROMs), are formed as composite, multi-layered structures of silicon oxides or of silicon oxides and silicon nitride.

Abstract: A converter for enhancing power factor utilizes a line sense winding magnetically coupled to sense a voltage across a line inductor in the input of a high power factor power converter. This winding in the illustrative embodiment is typically a single turn. This winding provides a measurement of the derivative (with respect to time) of the line current, and a specially designed integrator connected to the winding provides the estimate of the line current. An integrator is operative to accurately estimate the current by using known properties of this current to prevent mismeasurement due to reconstructing the "constant of integration" and any small biases in the integrator which normally cause errors.

Abstract: A Si IC includes an Al-based layer which is deposited as a composite of sublayers of different composition Al-based materials. In one embodiment a first sublayer comprises an Al-Si-based alloy disposed so as to prevent substantial Si migration into the first sublayer, and a second sublayer, above the first, comprises an Al-based alloy with substantially no Si to alleviate precipitation-induced problems. The selection of the thickness of the second sublayer to be a major portion and the inclusion of barrier layers are also described.

Abstract: An optical isolator comprises a non-reciprocal rotator disposed between a pair of birefringent wedges, an input wedge and an output wedge. In order to reduce walk-off between the ordinary and extraordinary rays at the output of the isolator in one embodiment, the input signal is made incident on the input wedge at an angle above the normal to the wedge. At a particular angle related to various parameters of the isolator the relative walk-off can be reduced to essentially zero. In another embodiment, the input angle and various isolator parameters are mutually adapted so that the ordinary and extraordinary rays intersect within the isolator.

Abstract: The onset of haze on silicon wafers is controlled by treating the wafers with a chemical selected from the group consisting of hot water and isopropyl alcohol and then storing the treated wafers in an inert atmosphere such as nitrogen or argon.

Abstract: The loop gain of a phase locked loop is made to be controllably responsive to the transition density of an input data signal. In one embodiment a charge pump, positioned between the phase detector and the loop filter, supplies pulse-amplitude-modulated current pulses to the loop filter, the amplitude of pulses being related to the data transition density.

Abstract: A clock generator is described for generating an output clock frequency from an input clock frequency where the frequencies of the clocks are not integrally related. The division process is designed using the quotients of the Euclidean theorem for determining the greatest common divisor of two integers in such a way as to alleviate the adverse effects of jitter. Applications to oversampled sigma-delta codecs are described.