10 February 2012 Modeling optical phase conjugation of ultrasonically encoded signal utilizing finite-difference time-domain simulations
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Abstract
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 signal 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 sucient 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 wavelength of the optical and US beams. The source geometries are varied and the effect of afinite etendue is modeled and studied to aid in system design.
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Joseph L. Hollmann, Joseph L. Hollmann, Charles A. DiMarzio, Charles A. DiMarzio, } "Modeling optical phase conjugation of ultrasonically encoded signal utilizing finite-difference time-domain simulations", Proc. SPIE 8227, Three-Dimensional and Multidimensional Microscopy: Image Acquisition and Processing XIX, 82270I (10 February 2012); doi: 10.1117/12.907084; https://doi.org/10.1117/12.907084
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