Exxon Research and Engineering Company

At&t Bell Laboratories

At+t Corp.

Charles B Roxlo

Edward J Flynn

Harry William Deckman

Carl J McGrath

John William Osenbach

Won-Tien Tsang

Thomas Edward Darcie

Naresh Chand

George E Bodeep

J Thomas Tiedje

Robert B Comizzoli

Leonard J Ketelsen

Jan Lipson

Mark Steven Schaefer

Paul M Nitzsche

L C Upadhyayula

Peter D Persans

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

An advantageous method of fabricating lasers adapted for use in a multichannel analog optical fiber communication system, e.g., a CATV system, is disclosed. A laser generally can be used in such a communication system only if it meets, inter alia, very stringent intermodulation specifications. To identify such lasers typically requires extensive testing. It has now been discovered that certain readily determinable parameters can be used to predict the intermodulation behavior of a given device. This discovery makes possible a simpler, and therefore less costly, process of identifying suitable lasers, resulting in a more economical method of making lasers for the stated application. The method comprises measuring the light versus current (L versus I) characteristic of a given laser, determining therefrom the first, second, and possibly higher, order derivatives of L with respect to I, and determining thereform a parameter that is a predictor of the distortion behavior of the laser. Exemplarily, the quantity is the normalized second order distortion (2HD/C), defined as 20 log (mL'/4L'.sup.2), where m is the modulation index, and L' and L' are the first and second derivatives, respectively, of L. 2HD/C has a pronounced minimum at I=I.sub.op , the current at which L'=0. Advantageously, lasers are selected that have 2HD/C less than a predetermined value (e.g., -70 dbc, with m=0.04) over a relatively wide current range (e.g., at least 4 mA).

Method of producing a semiconductor laser adapted for use in an analog

An amplitude-modulated vestigial-sideband, television channel sub-carrier multiplexed optical fiber transmission system includes a laser diode operating linearly throughout the desired range of multiplex frequencies. Such linear laser diode operation is accomplished by limiting leakage current within the laser diode to a very low level. The composite second-order distortion in the optical output signal from the laser diode is down typically 50 db from the video carrier for each channel. For some laser diodes that exhibit slow turn-on in the L-I characteristic, there is a point of inflection in the L-I curve. Operation with the laser biased at or near this point results in extremely linear performance, even though the laser may have insufficient blocking of leakage current to otherwise produce acceptable linearity.

Optical sub-carrier multiplex television transmission system using a

Lasers for use in multichannel analog optical fiber communication systems (e.g., of the type contemplated for CATV) have to meet very stringent requirements, including high linearity. DFB lasers are advantageously used in such communication systems. Typically only a relatively small percentage of the nominally identical DFB lasers on a wafer meet the specifications. It has now been discovered that the likelihood that a given DFB laser will meet the requirements is substantially increased if the laser comprises means that are adapted for producing a non-uniform photon density in the laser cavity, with the density of photons being larger in the rear portion of the cavity than in the front portion, such that during operation of the laser the gain in the back portion is substantially independent of the laser current, whereas the gain in the front portion is a function of the laser current. Exemplarily, lasers according to the invention have power asymmetry less than about 5. Preferred embodiments are AR/HR lasers with KL in the range 1.6-2.5. Optionally lasers according to the invention have a phase shift located in the back portion of the grating, a split contact, and/or a non-constant mesa width.

Analog optical fiber communication system, and laser adapted for use in

A method for making a layered metal chalcogenide catalyst wherein the catalyst has a crystalline structure with increased edge sites produced by lithographic methods.

Method of making artifically textured layered catalyst

Electrooptic devices for the modulation and conversion of light which include semiconductor superlattices which have large electrooptic and non-linear optical coefficients due to their built-in electric fields. These materials can be deposited at low temperatures onto virtually any substrate.

Superlattice electrooptic devices

A high surface area substrate with controlled pore size and slot geometry is used in an adsorbing process. The material is made by depositing at least two materials in alternating layers. The film is then broken up and one of the materials is etched away to produce a slotted surface structure. These slots can add size and shape selectivity to separations and catalytic processes which because of the uniform and controllable dimensions (&gt;5A) would be superior to that obtainable from zeolites and clays.

Micro-porous superlattice separations

Piezoelectric transducers and oscillators made from amorphous superlattice structures are disclosed. These materials have large built-in fields necessary for piezoelectricity but they are materials which can be deposited at low temperatures onto virtually any substrate.

Growing community of inventors

Bridgewater, NJ, United States of America

Charles B Roxlo