Massachusetts Institute of Technology

Joseph P Donnelly

K Alexander McIntosh

Erik K Duerr

Simon Verghese

James N Walpole

Richard D Younger

David C Chapman

Douglas C Oakley

Antonio Napoleone

Robin K Huang

Frederick J Leonberger

Mark Alexander Hollis

Stephen R Chinn

William D Goodhue

Paul William Juodawlkis

Gary E Betts

Christine A Wang

Reuel Bennett Swint

Hong K Choi

Patrick J Taylor

Robert J Bailey

Reuel P Swint

Lisa A Wright

Dominic Siriani

An avalanche photodiode detector is provided with a substrate including an array of avalanche photodiodes. An optical interface surface of the substrate is arranged for accepting external input radiation. There is provided at least one cross-talk blocking layer of material including apertures positioned to allow external input radiation to reach photodiodes and including material regions positioned for attenuating radiation in the substrate that is produced by photodiodes in the array. Alternatively at least one cross-talk blocking layer of material is disposed on the optical interface surface of the substrate to allow external input radiation to reach photodiodes and attenuate radiation in the substrate that is produced by photodiodes in the array. At least one cross-talk filter layer of material can be disposed in the substrate adjacent to the photodiode structures, including a material that absorbs radiation in the substrate that is produced by photodiodes in the array.

Cross-talk suppression in Geiger-mode avalanche photodiodes

There is provided an avalanche photodiode array that includes a plurality of avalanche photodiodes. Each avalanche photodiode in the array includes a stack of active photodiode materials. The stack of active photodiode materials includes a first electrical contact layer, a second electrical contact layer; an absorber material layer and an avalanche material layer each disposed between the first electrical contact layer and the second electrical contact layer; and an optical interface surface to the avalanche photodiode. The optical interface surface consists of an exposed surface of the first electrical contact layer, arranged for incident external radiation to directly enter the first electrical contact layer. Each avalanche photodiode stack of active photodiode materials is laterally isolated from the other avalanche photodiodes in the photodiode array.

Photodiode array structure for cross talk suppression

An electro-optic modulator imparts the information contained in an electrical signal traveling along a transmission line onto an optical carrier by using signal-related variations in the electrical signal's voltage to modulate the refractive index or absorption in an electro-optic material through which the optical carrier propagates. For optimal bandwidth and modulation efficiency, the microwave and optical waves should be matched in velocity. However, conventional microwave transmission lines have a microwave velocity that is somewhat higher than the optical group velocity in typical optical waveguides. Tuning a microwave transmission line's capacitance reduces the microwave velocity, but also reduces the impedance below the 50&#x3a9; impedance of most microwave components. Conversely, tuning the microwave transmission line's inductance makes it possible to match the microwave velocity to the optical group velocity over bandwidths of 100 GHz or greater while maintaining a microwave impedance of 50&#x3a9;.

Inductance-tuned electro-optic modulators

A slab-coupled optical waveguide laser (SCOWL) is provided that includes an upper and lower waveguide region for guiding a laser mode. The upper waveguide region is positioned in the interior regions of the SCOWL. The lower waveguide region also guides the laser mode. The lower waveguide region is positioned in an area underneath the upper waveguide region. An active region is positioned between the upper waveguide region and the lower waveguide region. The active region is arranged so etching into the SCOWL is permitted to define one or more ridge structures leaving the active region unetched.

High efficiency slab-coupled optical waveguide laser and amplifier

A very large mode (VLM) slab-coupled optical waveguide laser (SCOWL) is provided that includes an upper waveguide region as part of the waveguide for guiding the laser mode. The upper waveguide region is positioned in the interior regions of the VLM SCOWL. A lower waveguide region also is part of the waveguide that guides the laser mode. The lower waveguide region is positioned in an area underneath the upper waveguide region. An active region is positioned between the upper waveguide region and the lower waveguide region. The active region is arranged so etching into the VLM SCOWL is permitted to define one or more ridge structures leaving the active region unetched. One or more mode control barrier layers are positioned between said upper waveguide region and said lower waveguide region. The one or more mode control barrier layers control the fundamental mode profile and prevent mode collapse of the laser mode. The mode control barrier layers also block carrier leakage from the active region. These layers are essential to obtaining VLM SCOWLs.

Very large mode slab-coupled optical waveguide laser and amplifier

A laser and optical amplifier waveguide device with a plurality of layers that supports a single lowest-order optical mode with gain while higher order modes radiate and have a net loss. The supported lowest-order mode which has gain, has a mode cross section which is large compared to the operating optical wavelength in both the transverse and lateral directions. The contours of constant optical intensity of such lowest-order can be nearly circular, having an approximately elliptical shape with a small aspect ratio.

Stab-coupled optical waveguide laser and amplifier

An electro-optic push-pull modulator requiring reduced high switching voltages through combinations of device structure and operation, causing linear and quadratic electro-optic effects to add. Such combinations of device structure and operation include combinations of crystal axis orientation, waveguide structure, electrode structure, electric field biasing, operating wavelengths, and optical polarizations. By inducing linear and quadratic electro-optic effects to add, significant refractive index changes can be realized with lower switching voltages, V&pgr;. Furthermore, significant reduction in switching voltage for push-pull modulators can also be realized through combinations of device structure and operation effectively inducing solely the quadratic electro-optic effect.

Optical modulator using simultaneous push-pull drive of linear and quadratic electro-optic effects

A strained quantum-well diode laser with an AlInGaAs active layer and AlGaAs cladding and/or confining layers on a GaAs substrate is provided. AlInGaAs/AlGaAs lasers can be configured in laser geometries including ridge, waveguide, buried heterostructure, oxide-defined, proton-defined, narrow-stripe, broad-stripe, coupled-stripe and linear arrays using any epitaxial growth technique. Broad-stripe devices were fabricated in graded-index separate confinement heterostructures, grown by organometallic vapor phase epitaxy on GaAs substrates, containing a single Al.sub.y In.sub.x Ga.sub.l-x-y As quantum well with x between 0.14 and 0.12 and y between 0.05 and 0.17. With increasing Al content, emission wavelengths from 890 to 785 nm were obtained. Threshold current densities, J.sub.th 's, less than 200 A cm.sup.-2 and differential quantum efficiencies in the range 71 to 88 percent were observed.

Reliable AlInGaAs/AlGaAs strained-layer diode lasers

Two-dimensional surface-emitting diode laser arrays are described that take advantage of both the advanced state of development of linear laser arrays with conventional cleaved end faces and the rapid development of Si heat sink technology. A hybrid array consists of linear arrays of edge-emitting lasers that are mounted in grooves with flat bottoms and 45.degree. sidewalls etched in the top of a Si substrate containing microchannels for fluid flow on the backside. The 45.degree. sidewalls of the top Si grooves are coated with a highly reflecting metallic layer. These 45.degree. mirrors deflect the laser emission from the cleaved end faces of the linear laser arrays by 90.degree. so the emission is normal to the array surface. Use of the integral microchannel heat sink in the bottom of the Si substrate provides excellent heat removal capabilities for high power density operation.

Hybrid two-dimensional surface-emitting laser arrays

A planar semiconductor optical waveguide, modulator, variable coupler and switch are described. The waveguide has an epitaxial layer on a semiconductor substrate. Two spaced strips of opposite conductivity type are implanted in the layer to form an optical waveguide channel in the space. By closely spacing two waveguide channels so that they have a common strip and a strip outside each channel, coupling is obtained between the channels. For a switch, the coupling length is such that substantially all the optical energy in the input channel is coupled to and emerges from the other channel. Reverse biasing one of the outside strips causes the optical energy to divide between the input channel and the output channel to provide output power modulation or variable coupling, and substantially complete transfer of power (switching) for a particular value of reverse bias.

Growing community of inventors

Carlisle, MA, United States of America

Joseph P Donnelly