Extraction of Quasi-Straightforward-Propagating Photons Through a Scattering Medium by Up-Conversion Method as a Coherent Light Detection Technique

Abstract

Aiming at the realization of optical CT (computed tomography), the extraction of quasi-straightforward-propagating photons from optical pulses transmitting through a standard scattering medium of Intralipid-10% aqueous solution has been demonstrated by an up-conversion method (second harmonic generation). We have found that this operates as a coherent light detection method rather than a time-gate one and extends the dynamic range where the Lambert-Beer's law holds to ~86 dB. We have also proposed improvements to obtain the largest possible dynamic range by such an up-conversion technique.