Noncontact liquid crystalline broadband optoacoustic sensors [U.S. Patent US11366054B2]
U.S. Patent No. US11,366,054B2
Abstract
An optoacoustic sensor includes a liquid crystal (LC) cell formed between top and bottom plates of transparent material. A transverse grating formed across the LC cell that forms an optical transmission bandgap. A CL is aligned to form a spring-like, tunable Bragg grating that is naturally responsive to external agitations providing a spectral transition regime, or edge, in the optical transmission bandgap of the transverse grating that respond to broadband acoustic waves. The optoacoustic sensor includes a narrowband light source that is oriented to transmit light through the top plate, the LC cell, and the bottom plate. The optoacoustic sensor includes an optoacoustic spectrometer that is oriented below the bottom plate to receive the transmitted light and to record a time-domain modulation of transmission intensity at a selected one of a falling and rising edge of the transmission bandgap for detecting analog acoustic vibration.