Epitaxial Technologies

US Government as Represented by the Secretary of the Army

Harry Stephen Hier

Olaleye A Aina

Ayub Mohammed Fathimulla

Ivan C Lee

Patrick J Taylor

Zun Zhang

Priyalal S Wijewarnasuriya

Mark Dubinsky

Ayub M Fahimulla

Method and system for wavelength thermophotovoltaic (WTPV) power generation. In one embodiment, the system comprises a refractory waveguide that collects broadband infrared light generated by a heat source; a filter that filters the collected broadband infrared light to generate narrow-band infrared light; and a thermophotovoltaic (TPV) converter, thermally de-coupled from the heat source, that receives the narrow-band infrared light and converts the received narrow-band infrared light to electrical power.

Method and system for waveguide thermophotovoltaic power generation

An array of photon counting phototoreceivers is constructed as an imager with micro-digitized pixels. Each photoreciever comprises a vertical cavity optical amplifier (VCSOA) as an optical amplifier, an avalanche photodiode as detector and an analog-to-digital converter (ADC) in an integrated structure. The ADC serves as a 1-bit digitizer and uses a resonant tunneling bipolar transistor RTBT. While the preferred embodiment of the invention have been described, it will be apparent to those skilled in the art that various modifications may be made to the embodiments without departing from the spirit of the present invention. Such modifications are all within the scope of the present invention.

Photon counting optically preamplified photoreceivers with micro-digitized pixels

A vertical cavity semiconductor optical photoamplifer (VCSOA) is used as a modulating retro-reflector (MRR) as a pixel in an array. The boundary of the cavity in the VCSOA forms a mirror for reflecting an incident light as an amplified output.

Modulating retroreflector array using vertical cavity optical amplifiers

Alternate layers of wide band gap and narrow band gaps of different kinds of semiconductors are used to form multiple channels of a FET. The channels are doped or formed as 2-DEG/2-DHG in narrow band semiconductor by charge supply layer in the wide band gap semiconductor. The different kinds of semiconductors form heterojunctions to confine the electrons/holes in separate thin spikes layers. A number of spikes (3-10 nm thick) of different doped or 2-DEG/2-DHG concentrations in various channels can result in overall electron concentration gradient such as a 1/xelectron/hole concentrations profile. Such an electron/hole concentration gradient can result in a linear variation of drain current with voltage to obtain a wide dynamic range.

Ultra-linear multi-channel field effect transistor

Alternate layers of wide band gap and narrow band gaps of different kinds of semiconductors are used to form multiple channels of a FET. The channels are doped or formed as 2-DEG/2-DHG in narrow band semiconductor by charge supply layer in the wide band gap semiconductor. The different kinds of semiconductors form heterojunctions to confine the electrons/holes in separate thin spikes layers. A number of spikes (3&#x2013;10 nm thick) of different doped or 2-DEG/2-DHG concentrations in various channels can result in overall electron concentration gradient such as a 1/xelectron/hole concentrations profile. Such an electron/hole concentration gradient can result in a linear variation of drain current with voltage to obtain a wide dynamic range.

This invention describes an approach for monolithically integrating all the components of a photoreceiver&#x2014;optical amplifier, optical band-pass filter, and photodiode module&#x2014;on a single chip. The photoreceiver array employs unique optical amplifier and conversion technologies that provides the ultra-sensitivity required for free space optical communications networks. As an example, by monolithically integrating a vertical cavity surface emitting laser-diode (VCSEL) optical preamplifier with a photodiode receiver and related amplifiers and filters on the same chip, sensitivities as low as &#x2212;47 dBm (62 photons/bit at 2.5 Gb/s), along with an order of magnitude reduction in size, weight, and power consumption over comparable commercial-off-the-shelf (COTS) components can be demonstrated. In accordance with another aspect of the present invention, the concept of monolithic integration of optical amplifier with photodetector is extended to lasers, another amplifier and modulators covering ultra violet to very long wavelength infrared using the InP, GaAs, GaSb, InAs, InSb, SiGe, SiC and GaN etc based technologies.

Monolithic photoreceiver technology for free space optical networks

More than one photodetectors, each sensitive to different wavelengths, are integrated on a common semiconductor substrate. The different photodetectors can be stacked over one another or placed laterally on the common substrate. Gratings may be placed over each photodetector to sharpen the spectral response. Three such photodetectors can form a pixel of an active matrix array for an image sensor. The different photodetectors in each pixel can be multiplexed electronically. The electronic circuits for activating the different photodetectors can be integrated on the same substrate.

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Sykesville, MD, United States of America

Harry Stephen Hier