Abstract: In optical apparatus for reading, writing or erasing optical disks, the optical head is implemented in integrated form. Silicon optical bench technology, including integrated optical waveguides, Y-splitters and directional couplers, is used in the design of the tracking, lens focussing, and read/write/erase functions.

Abstract: An optoelectronic assembly is described which comprises an optoelectronic device (e.g. laser, photodiode or another fiber), an end portion of an optical fiber coupled to the device, and an integral lens formed on the end portion. The lens comprises a frustum of a first cone having a cone angle .theta..sub.1, and, on top of the frustum, a second cone having a cone angle .theta..sub.2 <.theta..sub.1, thus forming a double conical lens which requires no further operations (such as fire polishing) to provide coupling efficiencies of about 80% with a standard deviation of less than .+-.2%.

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

Abstract: A mixture of buffered hydrofluoric acid (e.g., HF and NH.sub.4 F) and a treating agent (e.g., acetic acid, phosphoric acid, hydrochloric acid, sulfuric acid or formic acid) is used to produce a matte finish on the pure silica cladding of an optical fiber, on a borosilicate glass tube and on a sodium lime glass plate. The matte finish may be used to increase the adhesion of other materials to the glass (e.g., of metal coatings to silica fibers) or to reduce glare.

Abstract: An InGaAs photodiode is described in which a double layer of silicon nitride on the front surface serves several functions; both layers passivate the surface; an opening in the lower layer provides a diffusion mask for forming the p-n junction; and a narrower opening in the upper silicon nitride layer provides a deposition mask for forming a restricted area contact. In order to reduce strain near the junction, and hence reduce leakage currents and enhance reliability, the contact geometry has a narrow pedestal portion which contacts the surface in a zone remote from the junction edges and has a wider cap portion which is formed on the pedestal portion to seal the surface from the introduction of contaminants. The photodiode may be back-illuminated or front-illuminated.

Abstract: Implantation of a Group V ion species (e.g., phosphorus or arsenic) into an In-based Group III-V compound semiconductor (e.g., InP, InGaAs) followed by implantation of Be ions produces a shallow p-type surface layer and avoids significant in-diffusion of the dopant species. High carrier concentrations and activation efficiences are attained. The technique has application in the fabrication of FETs, APDs and ohmic contacts.

Abstract: An m-input/n-output (e.g., 2.times.2) optical fiber switch is disclosed which alters the location of the fibers by the application of an external force. Illustratively, the switch uses a housing with a diamond-shaped opening extending therethrough, with pairs of optical fibers positioned in orthogonally located V-grooves. Upon the application of an external force, the fibers are moved into the remaining, vacant V-grooves formed by the diamond-shaped opening. In a preferred embodiment, a (2.times.2) switch is magnetically activated.

Abstract: A single frequency lightwave system employs semiconductor, optical amplifiers arranged in tandem with suitable nose filtering and isolation between amplifier stages. Feedback control maintains overlap between the signal frequency and one of the passbands of the amplifiers. Either direct detection or coherent detection can be used. Also described is a receiver front end which includes such an amplifier between the incoming signal and a photodetector. Both transmission systems and switching systems are described.

Abstract: A floating gate memory device comprises a channel for conducting carriers from source to drain, a semiconductor heterostructure forming a potential well (floating gate) for confining carriers sufficiently proximate the channel so as to at least partially deplete it, and a graded bandgap injector region between the control gate and the floating gate for controlling the injection of carriers into and out of the potential well. Also described is a three element memory cell, including the memory device and two FETs, which operates from a constant, non-switched supply voltage and two-level control voltages. Arrays of memory devices may also be used to detect light in a variety of applications such as imaging.

Abstract: A polarization independent semiconductor amplifier is used in a double-pass configuration; that is, the output of the amplifier is passed through a 45.degree. Faraday rotator to a mirror and then through the rotator and the amplifier again. Polarization independent gain is thus achieved.

Abstract: A liquid crystal device includes a liquid crystal material (30) in which the molecules (15) form a helix having its axis essentially parallel to the plates (13, 20) of the device. A suitable electric field (E), applied essentially perpendicular to the plates, causes planes of the directors (n) to rotate about the field direction to an acute angle .phi. with respect to the helix axis, thereby inducing alternating bands of splay and bend in the material. Such configurations, which have polar symmetry, give rise to the flexoelectric effect in which the polarization (P) of the molecules tends to be parallel to the applied field, and the magnitude of the field is linearly related to tan .phi.. The ability to rotate the directors means that the optical properties of the material can be changed.

Abstract: A floating gate memory device comprises a channel for conducting carriers from source to drain, a semiconductor heterostructure forming a potential well (floating gate) for confining carriers sufficiently proximate the channel so as to at least partially deplete it, and a graded bandgap injector region between the control gate and the floating gate for controlling the injection of carriers into and out of the potential well. Also described is a three element memory cell, including the memory device and two FETs, which operates from a constant, non-switched supply voltage and two-level control voltages. Arrays of memory devices may also be used to detect light in a variety of applications such as imaging.

Abstract: The integrity of surface structural features (e.g., distributed feedback gratings) in Group III-V compound semiconductors are preserved during heating (e.g., subsequent LPE regrowth) by a thin coating containing a transition metal (e.g., Os, Ru or Rh). DFP-DCPBH InP/InGaAsP single frequency lasers made in this way are also described.

Abstract: A back-illuminated InGaAs photodiode is described in which a double layer of silicon nitride on the front surface serves several functions; both layers passivate the surface; an opening in the lower layer provides a diffusion mask for forming the p-n junction; and a narrower opening in the upper silicon nitride layer provides a deposition mask for forming a restricted area contact. In order to reduce strain near the junction, and hence reduce leakage currents and enhance reliability, the contact geometry has a narrow pedestal portion which contacts the surface in a zone remote from the junction edges and has a wider cap portion which is formed on the pedestal portion to seal the surface from the introduction of contaminants.

Abstract: A vertical, enhancement mode InP MISFET includes a conducting n-type substrate, a semi-insulating Fe-doped InP blocking layer on the substrate, a conducting layer formed in the blocking layer, a groove which extends through both the conducting layer and the blocking layer, a borosilicate dielectric layer formed on the walls of the groove, a gate electrode formed on the dielectric layer, drain electrodes formed on each side of the gate electrode, and a source electrode formed on the bottom of the substrate. When a positive gate voltage relative to the source is applied, conduction channels are formed along the sidewalls of the groove, and current flows vertically from drain to source.

Abstract: Implantation of a Group V ion species (e.g., phosphorus or arsenic) into an In-based Group III-V compound semiconductor (e.g., InP, InGaAs) followed by implantation of Be ions produces a shallow p-type surface layer and avoids significant in-diffusion of the dopant species. High carrier concentrations and activation efficiencies are attained. The technique has application in the fabrication of FETs, APDs and ohmic contacts.

Abstract: The luminescent screen of a cathode ray tube includes an array of monocrystalline or amorphous phosphor rod-like elements which are covered with a reflective coating except for one end of each element which serves as an output face. The phenomenon of the light trapping is advantageously exploited to achieve enhanced brightness. The screen is illuminated with an electron beam which has an essentially oblong cross section and which is oriented along the elongated dimension of the elements. In one embodiment the elements comprise epitaxial Lu.sub.3 Al.sub.3 Ga.sub.2 O.sub.12 :Ce on the top of a YAG substrate, and a light absorbing layer of Lu.sub.3 Al.sub.3.5 Fe.sub.1.5 O.sub.12 is formed on the bottom of the substrate. A printer utilizing such a CRT is described. Also described is a configuration in which each of the rod-like elements functions as a laser.

Abstract: The integrity of surface structural features (e.g., distributed feedback gratings) in Group III-V compound semiconductors are preserved during heating (e.g., subsequent LPE regrowth) by a thin coating containing a transition metal (e.g., Os, Ru and Rh). DFB-DCPBH InP/InGaAsP single frequency lasers made in this way are also described.

Abstract: The congruently melting composition of gadolinium scandium gallium garnet comprisesGd.sub.2.96.+-.0.03 Sc.sub.1.90.+-.0.05 Ga.sub.3.14+0.05 O.sub.12.The composition may be used as the substrate for magnetic bubble domain devices or, when doped with a suitable activator (e.g., Cr.sup.+3 or Nd.sup.+3 or both), may serve as the active medium of a solid state laser.

Abstract: Devices having nonlinearities in their electrical/optical output characteristics are identified, and the location and magnitude of the nonlinearities are quantified, by a technique which includes generating an estimated first derivative of the device output response which would be obtained if the device had no nonlinearities, comparing the measured and estimated functions to generate a deviation function, and comparing the deviation function to a predetermined criterion in order to identify which devices have undesirable nonlinearities. The specific application of this technique to the identification and quantification of kinks and light jumps in semiconductor lasers is described.