University of Southern California

USA As Represented by Secretary of the Navy

Hughes Aircraft Company

Elsa M Garmire

Michael Bass

George C Valley

Marvin B Klein

Alan R Kost

Afshin Partovi

Katherine X Liu

Thomas R McMahon

Gary A Evans

Roger T Kuroda

Joseph W Niesen

Thomas C Hasenberg

Robert Russell

A laser system for the removal of graffiti from a retro-reflective highway sign or other surface includes a mobile crane adapted to support a laser scanner and an ablating laser under the control of a computer. An optical sensor and target indicator cooperate to function as a target acquisition device for identifying portions of a highway sign covered with graffiti. Responsive to the target acquisition device, the computer controls the laser scanner and laser to automatically ablate the graffiti covered portions of the highway sign to remove the graffiti. If needed, any remaining graffiti is manually brushed away and the highway sign is polished to restore the retro-reflective properties.

Laser system for removal of graffiti

An intersub-valence band quantum well detector (52), comprising alternating quantum wells (30') and barriers (32'), provided with differential strain permits obtaining hole mean free paths similar to the electron. Consequently, the gain and responsivity should dramatically increase. In addition, the absorption coefficient should increase, while the noise current should decrease; thus, the quantum efficiency and the detectivity (D*) should increase, compared to a detector without the added differential strain.

Light detector using intersub-valence band transitions with strained

Enhanced energy transfers are achieved between optical beams by operating at wavelengths in the near-bandgap region of a photorefractive material, and employing an electrorefractive effect previously proposed only for single beams. An electric field is applied across a photorefractive medium of sufficient intensity to induce an electrorefractive coupling and consequent energy transfer between the beams. Gain enhancements are possible by orienting the photorefractive medium to obtain an electro-optic as well as an electrorefractive effect, and by a moving grating technique. The direction of energy transfer between the beams is controlled by the electric field direction, and can be reversed by reversing the field. Operation in the infrared region is made possible with semi-insulating materials. Applications include optical switches, amplifiers and phase conjugators.

Method and apparatus for energy transfers between optical beams using

A semiconductor laser of the heterostructure type is grown on a p-type substrate and has a plurality of p-type active layers. In a preferred embodiment, the active layers are grown by liquid phase epitaxy from a single melt which is maintained just below its equilibrium temperature and is cooled very slowly during deposition. As a result, the active layers are substantially identical in composition and have a very low lattice mismatch. They emit light at characteristic wavelengths within 50 angstroms of each other, indicating that their modal gain envelopes coincide. This condition minimizes the threshold current.

Heterostructure laser

Disclosed is a GaA1As laser diode wherein an abrupt etch step in the waveguide layer forms a third mirror. The structure is a large optical cavity double heterostructure laser having a relatively long active cavity and a relatively short passive cavity. Output is temperature and current sensitive for single mode operation, widely-spaced dual mode operation, and narrow-band multimode operation.

Three-mirror active-passive semiconductor laser

A flexible hollow rectangular wave guide for transmission of radiation in the infrared portion of the spectrum, including infrared laser radiation. A wave guide which may be bent and twisted while providing low loss transmission of infrared radiation. An all metal wave guide with the width to heighth ratio at least 4 to 1. A wave guide with metal surfaces on the long dimension and dielectric surfaces on the short dimension and having a width to height ratio at least 2 to 1.

Growing community of inventors

Manhattan Beach, CA, United States of America

Elsa M Garmire