Elliott Brown

US Patent:

56636393, Sep 2, 1997

Filed:

Jan 18, 1994

Appl. No.:

8/183057

Inventors:

Elliott R. Brown - Billerica MA
Frank W. Smith - Liverpool NY

Assignee:

Massachusetts Institute of Technology - Cambridge MA

International Classification:

G01R 1900
H01J 4014
H04B 1006

US Classification:

324 96

Abstract:

An apparatus and method for optical heterodyne conversion and a radiation source and integrated diagnostics using the apparatus and method are disclosed. The radiation source can operate in a high-power narrow-band mode in which a constant-frequency output is provided or in a low-power broadband mode in which the frequency is tunable to allow the radiation source to act as a sweep oscillator. The apparatus or photomixer includes two sets of interdigitated conductive electrodes formed on top of a crystal lattice formed of column III-V compounds, particularly InAlGaAs compounds. Additional column V atoms are interspersed within the lattice structure to form defect energy states in the bandgap of the host material. The region of the material between the interdigitated electrodes is illuminated by optical radiation containing two different frequencies. Photon absorption in the material causes a current at the difference frequency to be generated and coupled to the interdigitated electrodes.

US Patent:

53814428, Jan 10, 1995

Filed:

Apr 1, 1993

Appl. No.:

8/041728

Inventors:

Elliott R. Brown - Billerica MA
Gregory G. Hogan - Stowe MA
Gerald M. Daniels - Norwood MA

Assignee:

Massachusetts Institute of Technology - Cambridge MA

International Classification:

G01N 2500
G01B 1106

US Classification:

374 7

Abstract:

A radiometer is described which coherently detects the thickness of oil films on water by converting continuous-frequency microwave or millimeter-wave brightness temperature versus frequency measurements from the frequency/wavenumber domain to the oil-film-thickness domain (received power versus film thickness) using Fourier-transform signal processing.

US Patent:

59006242, May 4, 1999

Filed:

May 29, 1996

Appl. No.:

8/654642

Inventors:

Simon Verghese - Boston MA
Elliott R. Brown - Billerica MA
Qing Hu - Boston MA

Assignee:

Massachusetts Institute of Technology - Cambridge MA

International Classification:

H01J 4014

US Classification:

250214LS

Abstract:

An optical correlator for correlating incident optical signals is described. The correlator comprises a transmission line in close juxtaposition to a photoconductor. The photoconductor may be positioned within the transmission line. The transmission line and the photoconductor may be monolithically integrated on a substrate. The optical correlator has an electrical non-linear response to the incident optical signals that results from a voltage divider formed from the combination of the transmission line and the photoconductor. The electrical non-linear response is proportional to a second-order intensity autocorrelation function g. sup. (2) (. tau. ). The response time of the electrical nonlinear response is less than the width of the narrowest pulse of the optical signals and may be less than twenty picoseconds.

US Patent:

56720076, Sep 30, 1997

Filed:

Jan 6, 1995

Appl. No.:

8/369621

Inventors:

Elliott R. Brown - Billerica MA
Gregory G. Hogan - Stowe MA
Gerald M. Daniels - Norwood MA

Assignee:

Massachusetts Institute of Technology - Cambridge MA

International Classification:

G01N 2500
G01B 1106

US Classification:

374 7

Abstract:

A radiometer is described which coherently detects the thickness of oil films on water by converting continuous-frequency microwave or millimeter-wave brightness temperature versus frequency measurements from the frequency/wavenumber domain to the oil-film-thickness domain (received power versus film thickness).

US Patent:

58252401, Oct 20, 1998

Filed:

Aug 22, 1997

Appl. No.:

8/916829

Inventors:

Michael W. Geis - Acton MA
Elliott R. Brown - Billerica MA
Stephen J. Eglash - Palo Alto CA
Christopher L. Dennis - Baker City OR

Assignee:

Massachusetts Institute of Technology - Cambridge MA

International Classification:

H03K 3315

US Classification:

327570

Abstract:

Resonant-tunneling transmission lines in the various architectures rely on discrete or continuous resonant-tunneling heterostructures to actively modify propagating logic signals. One embodiment utilizes amplification of logic signals to counteract ubiquitous losses and distortion associated with any transmission medium. Basically, the logic signal is incrementally reamplified and reshaped as it propagates along the transmission line. Another embodiment is directed to a clocking system that transmits a signal represented by a sinusoid. Then, in proximity to the logic gates or modules, the sinusoid is converted into a square wave that actually clocks the gates and other logic structures. The inventive active transmission line naturally performs this feature, thus enabling clock signal transmission over longer links coupled with sinusoid-to-square wave conversion in a limited area. Still other embodiments implement step or continuous variations in the physical width of the resonant-tunneling transmission line.

US Patent:

53862155, Jan 31, 1995

Filed:

Nov 20, 1992

Appl. No.:

7/979291

Inventors:

Elliott R. Brown - Billerica MA

Assignee:

Massachusetts Institute of Technology - Cambridge MA

International Classification:

H01Q 928

US Classification:

343795

Abstract:

Efficient transmission and reception of electromagnetic radiation are achieved by an antenna on a substrate. An antenna is fabricated on the top surface of a substrate which includes a periodic dielectric structure. The antenna operates at a frequency within the band gap of the periodic dielectric structure. Radiation emitted by the antenna cannot propagate through the structure and is therefore emitted only into space away from the substrate. When the antenna is receiving, radiation striking the device does not propagate through the substrate but is concentrated at the antenna. A phased array with isolated elements is achieved by fabricating the array elements on top of a substrate having a periodic dielectric structure and by surrounding the circuits associated with each antenna element with the periodic dielectric structure. Radiation from an element or associated circuitry at a frequency within the band gap of the structure cannot propagate into the substrate to interfere with other elements.

US Patent:

53048059, Apr 19, 1994

Filed:

Mar 26, 1993

Appl. No.:

8/037239

Inventors:

Elliott R. Brown - Billerica MA
K. Alexander McIntosh - Groton MA

Assignee:

Massachusetts Institute of Technology - Cambridge MA

International Classification:

G01J 502

US Classification:

2503381

Abstract:

A GaAs/AlGaAs multiple-quantum-well (MQW) is used as an optical mixer for environmental monitoring of atmospheric emission or absorption signals in the infrared (IR) region. The atmospheric signals are combined with coherent laser local oscillator emission lines to produce IF signals within the electrical bandwidth of the MQW mixer.