22 February 2013 Modeling optical phase conjugation of ultrasonically encoded signal utilizing finite-difference time-domain simulations
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Abstract
Optical interrogation of tissue provides high biological specificity and excellent resolution, however strong scattering of light propagating through tissue limits the maximum focal depth of an optical wave, inhibiting the use of light in medical diagnostics and therapeutics. However, turbidity suppression has been demonstrated utilizing phase conjugation with an ultrasound (US) generated guide star. We analyze this technique utilizing a Finite-Difference Time-Domain (FDTD) simulation to propagate an optical wave in a synthetic skin model. The US beam is simulated as perturbing the indicies of refraction proportional to the acoustic pressure for four equally spaced phases. By the Nyquist criterion, this is sufficient to capture DC and the fundamental frequency of the US. The complex optical field at the detector is calculated utilizing the Hilbert transform, conjugated and played back" through the media. The resulting field travels along the same scattering paths and converges upon the US beams focus. The axial and transverse resolution of the system are analyzed and compared to the wavelengths of the optical and US beams.
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Joseph L. Hollmann, Charles A. DiMarzio, "Modeling optical phase conjugation of ultrasonically encoded signal utilizing finite-difference time-domain simulations", Proc. SPIE 8589, Three-Dimensional and Multidimensional Microscopy: Image Acquisition and Processing XX, 85890E (22 February 2013); doi: 10.1117/12.2004983; https://doi.org/10.1117/12.2004983
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