The opto-acoustic transducer (OAT), an essential element in a real-time acoustic imaging system, is a sandwich-type structure which consists of a planar transparent indium-tinoxide electrode, a sputter-deposited CdS photoconductive layer, a piezoelectric layer, and another planar electrode. In order to make the OAT operate in real-time, the photoconductive layer must have rise and decay times of less than 3.3 psec with a suitable switching ratio of dark to illuminated resistivities. A fast-reacting photoconductive layer of CdS has been fabricated by sputtering with a gas of 99% Ar and 1% H₂S. Rise and decay times of about 3 psec have been measured. By controlling the temperature of the substrate holder, the dark and illuminated resistivities can LI made to have switching ratios of 10² Ω-cm to 10 Ω-cm. This is the correct range of values needed for real-time operation.

Date Published: 1 November 1982
PDF: 7 pages
Proc. SPIE 0372, Physics and Engineering in Medical Imaging, (1 November 1982); doi: 10.1117/12.934525

Published in SPIE Proceedings Vol. 0372:
Physics and Engineering in Medical Imaging
Orhan Nalcioglu, Editor(s)