Abstract: A velocity match between a traveling optical wave and an interacting traveling electrical wave having a different velocity of propagation is simulated by shaping the electrical signal path so that interaction between the two waves occurs along selected regions of the electrical signal wavepath. In particular, the electrical wavepath bends away from the optical wavepath at uniformly spaced intervals to produce regions of no interaction along the electrical wavepath. This technique is employed to modulate optical waves via the electrooptic effect.

Abstract: In a heterostructure distributed Bragg reflector laser, at least one multilayer waveguide substantially comprised of a silicon dielectric compound is monolithically integrated with an active semiconductor heterostructure medium. Bragg reflectors are properly disposed within the waveguide.

Abstract: By introducing an asymmetry in the effective refractive index profile of a waveguide, wave energy can be extracted from the waveguide by radiation at wavelengths greater than a critical wavelength, where the latter is a function of the effective index distribution. This technique is employed to develop a variety of optical wavelength filters.

Abstract: The invention provides apparatus comprising at least two beams of coherent radiation directed so as to intersect and form a standing wave pattern having a period .LAMBDA. in an optically responsive medium. The optically responsive medium is a colloidal suspension of dielectric particles in a liquid medium, the dielectric particles and liquid having different indices of refraction, and the diameter of the particles being less than or approximately equal to the period .LAMBDA.. The dielectric particles are arranged into a grating by the electric fields carried by the beams of coherent radiation. In an embodiment of the invention, the dielectric particles are small dielectric spheres. The dielectric particles and the liquid may have approximately equal mass densities. A third beam of light may generate an output beam of light by degenerate four-wave mixing processes incorporating a dielectric grating made by the electric fields carried by the beams of coherent radiation.

Abstract: A simulated velocity match between a traveling optical wave and a traveling electrical modulating wave is obtained in traveling wave, velocity mismatched electrooptic devices by introducing, at longitudinally spaced intervals along the electrical signal wavepath, means for producing the equivalent of a 180 degree phase shift in the effect of the modulating signal upon the operative electrooptic parameter of said device. This technique is employed to minimize the effect of walk-off due to velocity mismatch in modulators, phase shifter and mode converters.

Abstract: A semiconductor laser is disclosed wherein a grid-like conductive current mask is fabricated between the active region of the laser and one of its electrodes. In one embodiment, the conductive current mask is fabricated in the bottom regions of a corrugated pattern that is created along the length of the semiconductor laser. In a second embodiment, the conductive current mask is totally embedded within a lightly doped buffer layer that is grown proximate to the active region.

Abstract: A method for determining crystallographic orientation of an InP substrate wafer includes the steps of immersing at least a portion of the substrate wafer in a chemical etchant for a predetermined amount of time to expose features having a predetermined shape and designating a particular crystallographic direction on the substrate wafer in accordance with relative positions of features on the portion of the substrate wafer.

Abstract: An AC-AC line current reversal technique is employed for generating a telephone ringing signal. Generation of the signal is accomplished by controllably activating one of two series full wave rectification circuits responsive to a transformer coupled AC signal during alternate periods at a rate substantially equal to a desired ringing signal frequency.

Abstract: A process for fabricating a high speed bipolar transistor is described wherein the collector, base and emitter layers are first grown using molecular beam epitaxy (MBE). A mesa etch is performed to isolate a base-emitter region, and a contact layer is grown using MBE over this isolated region to make contact with the thin base layer. The contact layer is selectively etched to expose the emitter layer, and metal is deposited to fabricate emitter, base and collector contacts.

Abstract: A waveform generator (FIG. 1) contains a static energy storage device circuit in which storage devices (C1 through C6) are interconnected in a fixed topological configuration. The storage device circuit has a plurality of input and output terminals (12 through 18). Charge storage is accomplished by controllably steering (20, 40) a supplied DC signal (10a,b) to a selected one, or selected ones, of the storage devices via the appropriate input terminals. AC waveforms are generated (11a,b) by controllably selecting (30, 40), in predetermined sequence, each output terminal of the storage device circuit.

Abstract: A display cell having at least two states of different opacity, comprises a first material having a first index of refraction, a second material dispersed within the first material and having a second index of refraction, the difference between the first and the second indices of refraction being variable over a range of values, and means for varying the difference in index of refraction over a portion of the range. When the indices of refraction of the first and second material are substantially the same, the display is substantially transparent. Otherwise it is opaque or substantially less transparent.

Abstract: In order to prevent drift between the two stable states in the bulk of the liquid crystal material, a specific cell isolation region formed from the same liquid crystal material is required. This cell isolation is provided in one embodiment by a uniformly tilted liquid crystal alignment. The surface of the substrates between which the liquid crystal material is disposed is treated to provide the uniform tilt in regions which surround the bistable volumes of liquid crystal material.

Abstract: Large current gains and high degrees of sensitivity to impinging primary photons are realized in photon feedback photodetectors embodying the invention. A photocurrent generated by an internal photodiode (10, 11) in response to the primary photons (6) causes secondary photons to be emitted by internal serially connected luminescence diodes (12, 13; 14, 15). Secondary photons traveling away from the photodiode are redirected by a reflector (16) to impinge on the photodiode and thereby sustain the photocurrent. Gains of the order of 100 are realized by these photodetectors.

Abstract: In a public key cryptographic system (FIG. 1) for communicating securely over an insecure communication channel (3), a sender (1, 2) enciphers a data message (D) using a public enciphering knapsack key (H) to generate an enciphered message (S.sub.H). An authorized receiver (4 6, 7, 20, 21, 22) with knowledge of a private deciphering key (E), a modulus (M) and an integer multiplier (W) generates a private enciphering key (A) which is employed in further enciphering the received enciphered message to form a doubly enciphered message (S.sub.E, S.sub.E). The doubly enciphered message is deciphered using the private deciphering key alone to recover the original data message.

Abstract: In a multifrequency receiver, a threshold level (VTH) supplied to a group of threshold comparators (105-1 through 105-N) is controllably adjustable by a variable threshold generation circuit (104) in response to received multifrequency signals. As the envelope of the received multifrequency signal experiences a positive amplitude transition, the threshold level is increased at a fast rate (fast attack). Also, as the envelope of the received multifrequency signal exhibits a negative amplitude transition, the threshold level is decreased at a much slower rate (slow release).

Abstract: Store group circuits (102a,b,c or 202a,b,c) in fixed priority bus allocation arrangements eliminate lockouts and reduce delays for devices (101a,b,c) requesting access to a shared resource such as a data bus. The store group circuit stores (111 or 205-1 through 205-3) all access requests (REQA, REQB, REQC) from the devices present at a time instant, inhibits (110 or 210 ) storage of subsequent requests until each device associated with a stored request is granted access (GRANTA, GRANTB, GRANTC), and removes from storage each request associated with a device which has been granted access. Arbitration is performed among the stored requests using existing arbiters (103) in the fixed priority bus allocation arrangement. Bus access is guaranteed for devices whose requests are stored in the store group circuit thereby eliminating lockouts.

Abstract: Accurate recovery of constituent data streams from a multiplexed serial data stream in which each symbol includes a nonintegral number of frames is accomplished by combining a coherently detected timing signal, which is a component of the received serial data stream, together with a bit clock signal and a symbol clock signal to locate a predetermined bit position within each frame. When the location of the predetermined bit position is determined, frame synchronization is complete and the constituent data streams are correctly demultiplexed from the multiplexed serial data stream. The timing signal has a pulse rate equal to the greatest common divisor of the frame and symbol rates.

Abstract: Combined amplitude and phase modulation of a multiplexed serial data stream is employed to generate a composite signal for transmission to a receiver. The composite signal includes a prescribed timing signal identifying a predetermined bit position in at least each n.sup.th symbol and group of n.multidot.M bits in the serial data stream. The timing signal forms the amplitude modulation component of the composite signal and is utilized by the receiver for properly resolving an n-fold ambiguity which arises when each symbol includes a nonintegral rational number of frames.

Abstract: Highly reproducible, optically flat mirror facets are created by contacting a predetermined area of the InGaAsP/InP heterostructure system with a chemical etchant for a time period sufficient to expose a substantially vertical crystallographic surface throughout the entire heterostructure system. Contact of the exposed surface with HCl causes a preferred crystallographic plane to be exposed as an optically flat mirror facet.