Lucent Technologies Inc.

At+t Corp.

At&t Bell Laboratories

Agere Systems Guardian Corp.

Naresh Chand

John William Osenbach

Won-Tien Tsang

Sung-Nee George Chu

Robert Alan Hamm

Yong-Kwan Park

Charles B Roxlo

Venkataraman Swaminathan

Thomas H Daugherty

Robert B Comizzoli

Wouterus Muys

Alexei V Syrbu

Laurens Bakker

Doutje Tjitske Van Veen

This invention is a new communication system in which multichannel broadcast digital services are distributed to each user with the broadcast services signal riding in the passband above a digital baseband signal. The system can deliver more than 1 Gbps additional bandwidth to each subscriber. The passband bandwidth will accommodate growth in downstream services including video on demand, higher speed web downloads including improved streaming audio and video, HDTV, interactive video, and personalized video. The invention requires only a single fiber path and a single optical receiver for each user or group of users. A single fiber, single optical receiver system is much less expensive than two systems, one transmitting baseband and the other passband. A single receiver is greatly cost beneficial to achieving economical fiber to the home.

Optical communication system optically combining both baseband and passband signals

An optical transmitter for digitally modulated RF sub-carriers comprising an electroabsorption modulator integrated distributed feedback laser for transmitting the digitally modulated RF sub-carriers in the sub-octave frequency range. The negative bias is optimized for maximum carrier signal to noise ratio (CNR) which occurs when the composite triple beat (CTB) non-linear distortion is minimum that allows higher modulation index without causing any in-band distortion. A higher CNR increases the receiver sensitivity and thus more users can be served from a single transmitter or the transmitting signal can be modulated with higher order of digital modulation.

Electroabsorption modulator integrated distributed feedback laser transmitter

The specification describes techniques for cleaving crystal bodies, e.g. semiconductor laser bars, using thermostatic cleaving tools. Use of such tools allows the cleaving process to occur in an ultra high vacuum chamber without the use of mechanical devices activated from the exterior of the chamber. Cleaving occurs automatically and controllably by locally heating the cleaving tools, thereby deflecting the thermostatic element against the laser bar and causing fracture.

In-situ technique for cleaving crystals

Provision of a novel passivation layer can result in improved reliability of semiconductor lasers having a laser cavity defined by 2 laser facets. In a preferred embodiment, the passivation layer is a zinc selenide layer (e.g., 5 nm), formed on an essentially contamination-free laser facet. More generally, the passivation layer comprises at least one of Mg, Zn, Cd and Hg, and at least one of S, Se and Te. Typically, the facets are formed by cleaving in vacuum, immediately followed by in-situ deposition of the novel passivation layer material on the facets.

Passivated faceted article comprising a semiconductor laser

The disclosed novel method of making III/V semiconductor lasers involves cleaving of the wafer along predetermined cleavage planes. A cleavage plane is defined by means of aligned non-continuous depressions. The depressions are spaced from the laser contact regions, and typically are V-grooves produced by photolithography and anisotropic etching. A further surface feature, typically a precisely positioned scribe mark, facilitates cleavage initiation. When carried out in vacuum the novel method can provide high quality, accurately positioned cleavage surfaces, and consequently can facilitate increased yield of high power lasers.

Method of making III/V semiconductor lasers

Disclosed are high reliability semiconductor lasers that need not be maintained inside a hermetic enclosure. Such lasers can advantageously be used in a variety of applications, e.g., in optical fiber telecommunications, and in compact disc players. Such 'non-hermetic' lasers comprise facet coatings that comprise a dielectric layer that has very low water saturation value. In preferred embodiments this dielectric layer is SiO.sub.x (1.ltoreq.x&lt;2), deposited by a molecular beam method. Deposition conditions are selected to result in a dense material that is largely free of particulates and blisters, and is substantially impermeable to moisture. Among the deposition conditions is substantially normal beam incidence, and a relatively low deposition rate. Deposition is advantageously carried out under relatively high vacuum conditions. A quantitative method of determining the water level in a SiO.sub.x film is disclosed.

Article comprising a semiconductor laser with stble facet coating

A long wavelength (6 to 20 .mu.m) phototransistor is described which has n-doped silicon as emitter and collector regions bracketing a base region having a quantum well structure made up of alternating layers of p-doped silicon germanium and undoped silicon, The silicon germanium layer adjacent to the emitter region is thicker and has a higher percentage of germanium in order to provide a quantum well that is wider and deeper than the other quantum wells in the base region thereby resulting in a larger current and optical gain. The silicon barrier layer of the quantum well closest to the collector region is p-doped in order to reduce the leakage current of the base-collector junction.

Phototransistor with quantum well base structure

The presence of oval defects on MBE-grown compound semiconductor (e.g., GaAs, InP, or InGaAs) epitaxial layers has proven to be a serious obstacle to the use of such material for the manufacture of integrated circuits (ICs), even though the use of such material potentially could result in ICs having superior performance. One particularly prevalent type of oval defect is generally referred to as .alpha.-type. It has now been discovered that compound semiconductor epitaxial layers that are essentially free of .alpha.-type oval defects can be grown by MBE if first at least a portion of the Ga and/or In metal crucible is coated with an appropriate second metal. The second metal is chosen from the group of metals that are wetted by the first metal and that are less electronegative than the first metal. Aluminum is a currently preferred second metal. Advantageously the interior of the (typically pBN) crucible is Al-coated at least at and near the orifice of the crucible, whereby formation of drops of first metal is prevented.

Growing community of inventors

Berkeley Heights, NJ, United States of America

Naresh Chand