TY - GEN
T1 - Penetration depth of low-coherence enhanced backscattering photons in the sub-diffusion regime
AU - Subramanian, Hariharan
AU - Pradhan, Prabhakar
AU - Kim, Young L.
AU - Backman, Vadim
PY - 2007
Y1 - 2007
N2 - The mechanisms of photon propagation in random media in the diffusive multiple scattering regime have been previously studied using diffusion approximation. However, similar understanding in the low-order (sub-diffusion) scattering regime is not complete due to difficulties in tracking photons that undergo very few scatterings events. Recent developments in low-coherence enhanced backscattering (LEBS) overcome these difficulties and enable probing photons that travel very short distances and undergo only a few scattering events. In LEBS, enhanced backscattering is observed under illumination with spatial coherence length Lsc less than the scattering mean free path ls. In order to understand the mechanisms of photon propagation in LEBS in the sub-diffusion regime, it is imperative to develop analytical and numerical models that describe the statistical properties of photon trajectories. Here we derive the probability distribution of penetration depth of LEBS photons and report Monte Carlo numerical simulations to support our analytical results. Our results demonstrate that, surprisingly, the transport of photons that undergo low-order scattering events has only weak dependence on the optical properties of the medium ( ls and anisotropy factor g) and strong dependence on the spatial coherence length of illumination, L sc relative to those in the diffusion regime. More importantly, these low order scattering photons typically penetrate less than ls into the medium due to low spatial coherence length of illumination and their penetration depth is proportional to the one-third power of the coherence volume (i.e. [ls πLs2]1/3).
AB - The mechanisms of photon propagation in random media in the diffusive multiple scattering regime have been previously studied using diffusion approximation. However, similar understanding in the low-order (sub-diffusion) scattering regime is not complete due to difficulties in tracking photons that undergo very few scatterings events. Recent developments in low-coherence enhanced backscattering (LEBS) overcome these difficulties and enable probing photons that travel very short distances and undergo only a few scattering events. In LEBS, enhanced backscattering is observed under illumination with spatial coherence length Lsc less than the scattering mean free path ls. In order to understand the mechanisms of photon propagation in LEBS in the sub-diffusion regime, it is imperative to develop analytical and numerical models that describe the statistical properties of photon trajectories. Here we derive the probability distribution of penetration depth of LEBS photons and report Monte Carlo numerical simulations to support our analytical results. Our results demonstrate that, surprisingly, the transport of photons that undergo low-order scattering events has only weak dependence on the optical properties of the medium ( ls and anisotropy factor g) and strong dependence on the spatial coherence length of illumination, L sc relative to those in the diffusion regime. More importantly, these low order scattering photons typically penetrate less than ls into the medium due to low spatial coherence length of illumination and their penetration depth is proportional to the one-third power of the coherence volume (i.e. [ls πLs2]1/3).
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U2 - 10.1117/12.700974
DO - 10.1117/12.700974
M3 - Conference contribution
AN - SCOPUS:34548215140
SN - 0819465496
SN - 9780819465498
T3 - Progress in Biomedical Optics and Imaging - Proceedings of SPIE
BT - Complex Dynamics and Fluctuations in Biomedical Photonics IV
T2 - Complex Dynamics and Fluctuations in Biomedical Photonics IV
Y2 - 20 January 2007 through 23 January 2007
ER -