Modeling of amplitude and exit location variations of light propagation under ultrasonic modulation
While phase variation due to ultrasonic modulation of coherent light has been extensively studied in acousto-optical imaging, fewer groups have studied non-phase mechanisms of ultrasonic modulation, which may be important in exploring ultrasonic modulation of incoherent light for imaging. We have developed a versatile Monte Carlo based method that can model not only phase variation due to refractive index changes and scatterer displacement, but also amplitude and exit location variations due to the changes in optical properties and refractive index under ultrasonic modulation, in which the exit location variation has not been modeled previously to our knowledge. Our results show that the modulation depth due to the exit location variation is one to two orders of magnitude higher than that due to amplitude variation, but two to three orders of magnitude lower than that due to phase variation for monochromatic light. Furthermore, it is found that the modulation depth in reflectance due to the exit location variation is larger than that in transmittance for small source-detector separations.
