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Ultrasound modulation of coherent light in a multiple-scattering medium: experimental verification of nonzero average phase carried by light

Singh, Mayanglambam Suheshkumar and Kanhirodan, Rajan and Vasu, Ram Mohan and Roy, Debasish (2012) Ultrasound modulation of coherent light in a multiple-scattering medium: experimental verification of nonzero average phase carried by light. In: BIOMEDICAL OPTICS EXPRESS, 3 (9). pp. 2100-2110.

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Official URL: http://dx.doi.org/10.1364/BOE.3.002100

Abstract

We demonstrate the phase fluctuation introduced by oscillation of scattering centers in the focal volume of an ultrasound transducer in an optical tomography experiment has a nonzero mean. The conditions to be met for the above are: (i) the frequency of the ultrasound should be in the vicinity of the most dominant natural frequency of vibration of the ultrasound focal volume, (ii) the corresponding acoustic wavelength should be much larger than l(n)*, a modified transport mean-free-path applicable for phase decorrelation and (iii) the focal volume of the ultrasound transducer should not be larger than 4 - 5 times (l(n)*)(3). We demonstrate through simulations that as the ratio of the ultrasound focal volume to (l(n)*)(3) increases, the average of the phase fluctuation decreases and becomes zero when the focal volume becomes greater than around 4(l(n)*)(3); and through simulations and experiments that as the acoustic frequency increases from 100 Hz to 1 MHz, the average phase decreases to zero. Through experiments done in chicken breast we show that the average phase increases from around 110 degrees to 130 degrees when the background medium is changed from water to glycerol, indicating that the average of the phase fluctuation can be used to sense changes in refractive index deep within tissue.

Item Type: Journal Article
Additional Information: Copyright for this article belongs to The Optical Society
Department/Centre: Division of Mechanical Sciences > Civil Engineering
Division of Physical & Mathematical Sciences > Instrumentation and Applied Physics (Formally ISU)
Division of Physical & Mathematical Sciences > Physics
Date Deposited: 10 Dec 2012 09:43
Last Modified: 10 Dec 2012 09:44
URI: http://eprints.iisc.ernet.in/id/eprint/45229

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