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Opto Thermal Phased Arrays for Focused and Directionally Selective Acoustic Beams

IP.com Disclosure Number: IPCOM000088172D
Original Publication Date: 1977-Apr-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Melcher, RL: AUTHOR [+2]

Abstract

The absorption of energetic pulses of light or other energy sources by thin metal films (which produces mechanical energy because of heating and thermal expansion) when the film is constrained at both surfaces is an efficient means of generating acoustic waves. The frequency of the waves is determined in part by the Fourier transform of the temporal energy pulse, as well as certain thermal and elastic parameters. This form of acoustic generation can be used together with special structures, easily fabricated with lithographic techniques, to produce acoustic beams which can be spatially directed and/or focused.

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Opto Thermal Phased Arrays for Focused and Directionally Selective Acoustic Beams

The absorption of energetic pulses of light or other energy sources by thin metal films (which produces mechanical energy because of heating and thermal expansion) when the film is constrained at both surfaces is an efficient means of generating acoustic waves. The frequency of the waves is determined in part by the Fourier transform of the temporal energy pulse, as well as certain thermal and elastic parameters. This form of acoustic generation can be used together with special structures, easily fabricated with lithographic techniques, to produce acoustic beams which can be spatially directed and/or focused.

Three separate, but related, techniques are discussed, consisting of thin films deposited on a substrate and constrained by an overlapping film or by mechanical clamping. The films are heated in a variety of ways among which are (1) an array of layers in such as GaAs (Fig. 1), (2) a single laser or electron beam 12 which is modulated and deflected to positions on the surface of the film (Fig. 2), and (3) electrical heating of small elements 26 of film (Figs. 3A and B). (In this last scheme an array of discrete film elements 26 is required, each separately accessed. Here the overlay need not be optically transparent.)

In Fig. 1, a substrate 18 has a film 16 deposited on it which is acoustically clamped on its top surface by a transparent overlay 20 which prevents film 16 from v...