From Event: SPIE Commercial + Scientific Sensing and Imaging, 2018
The requirement for solid, rigid structures for the ability to precisely control and manipulate acoustic waves can be highly limiting in applications such as biomedical imaging where sound manipulation and control through such interfaces cannot easily be employed. In this work, we describe the ability to generate optically induced reflective sound barriers and waveguides. These barriers are generated by creating abrupt density barriers via photothermal depletion of the transport medium along the path of a laser beam, causing sharp differences in compressibility, resulting in significant acoustic reflection. Using this technique, acoustic reflection efficiencies of 30% have been demonstrated. Furthermore, employing multiple optically induced acoustic reflective barriers sequentially can result in complete suppression of incident acoustic sound wave transmission.
In addition to optically induced acoustic suppression, optical waveguiding can also be achieved using cylindrical, ring shaped laser beams. By containing the acoustic waves inside the cylindrical channel, dramatic improvements in acoustic transmission can be achieved. Optical waveguding of acoustic signals offers a new paradigm in the manipulation of sound over extended distances in various media, providing potentially significant improvements to photoacoustic sensing and imaging in many applications
Daniel S. Kazal, Ellen L. Holthoff, and Brian M. Cullum, "Optically induced acoustic waveguides and reflective barriers (Conference Presentation)," Proc. SPIE 10662, Smart Biomedical and Physiological Sensor Technology XV, 1066208 (Presented at SPIE Commercial + Scientific Sensing and Imaging: April 15, 2018; Published: 15 May 2018); https://doi.org/10.1117/12.2304437.5783315368001.
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Study of self-shadowing effect as a simple means to realize nanostructured thin films and layers with special attentions to birefringent obliquely deposited thin films and photo-luminescent porous silicon