Expand this Topic clickable element to expand a topic
Skip to content
Optica Publishing Group
  • Applied Spectroscopy
  • Vol. 76,
  • Issue 11,
  • pp. 1346-1355
  • (2022)

Thermally Induced Optical Reflection of Sound (THORS) in Ambient Air: Characterization and Temporal Dynamics

Not Accessible

Your library or personal account may give you access

Abstract

Thermally induced optical reflection of sound (THORS) provides a means to manipulate sound waves without the need for traditional acoustically engineered structures. By photothermally exciting a medium, with infrared light, a barrier can be formed due to abrupt changes in compressibility of the excited medium. Discovery and initial characterization of the THORS phenomenon utilized air saturated with ethanol vapor as the absorbing medium and a CO2 laser, operating at 9.6 µm, as the excitation source to achieve acoustic reflection efficiencies of 25–30% of the incident wave. In this work, we demonstrate for the first time, the ability to generate THORS barriers in ambient air (i.e., without the need for ethanol vapor). Employing atmospheric water vapor as the absorbing medium and a modulated, multiline carbon monoxide laser, operating at 5.5 ± 0.25 µm, THORS barriers capable of acoustic and ultrasonic reflection–suppression efficiencies greater than 70% are readily generated. To achieve these significant reflection–suppression efficiencies, the temporal dynamics of THORS barriers in ambient air were characterized using 300 kHz ultrasonic pulses incident on the barriers, revealing three different operational regimes. In the first regime, a single laser pulse generates a transient THORS barrier that lasts tens of milliseconds and exhibits minimal acoustic reflectivity. In the second regime, multiple laser pulses interact with the water vapor prior to complete relaxation of the THORS barrier from the previous excitation pulse, resulting in an additive response and reflectivity/suppression efficiencies as great as 72%. Finally, in the third regime, non-modulated continuous wave (CW) excitation of the water vapor occurs resulting in no measurable acoustic reflectivity/suppression from the THORS barrier. This work characterizes these different regimes and the optimal modulation timing to generate efficient continuous acoustic barriers using THORS.

© 2022 The Author(s)

PDF Article
More Like This
Optical reflection and waveguiding of sound by photo-thermally induced barriers

Brian M. Cullum, Ellen L. Holthoff, and Paul M. Pellegrino
Opt. Express 25(19) 22738-22749 (2017)

High precision photoacoustic interferometer for the determination of the speed of sound in liquid media

George J. Tserevelakis and Giannis Zacharakis
Opt. Express 30(16) 28559-28568 (2022)

Internal reflection ellipsometry in air and water ambient

Soichi Otsuki and Mitsuru Ishikawa
Opt. Lett. 35(24) 4226-4228 (2010)

Cited By

You do not have subscription access to this journal. Cited by links are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access Optica Member Subscription

Select as filters


Select Topics Cancel
© Copyright 2024 | Optica Publishing Group. All Rights Reserved