Detection of sub-terahertz photoacoustic effect for non-contact material sensing

Abstract

We demonstrate the generation of photoacoustic signals in aqueous samples by continuous sub-terahertz irradiation detectable with a standard microphone. We confirm that the frequency response of the photoacoustic signals is dependent on the sound speed in the sample, demonstrating its potential for non-contact inspection. As a proof of concept, we demonstrate that water temperature can readily be discerned with the proposed method. The use of sub-terahertz waves for excitation and acoustic waves for detection allows us to inspect a sample inside a container through its wall in a non-contact manner.

Keywords

• Photoacoustic effect
• Sub-terahertz waves
• Sound speed
• Non-contact sensing