Photon Migration in Turbid Media with High Optical Gain

Thomas M. Drane, E. A. Shapiro, Valery Milner

Claes af Klinteberg

Antonio Pifferi, Paola Taroni, Giovanna Valenti +7 more

Yong Meng Sua, Shengyu Zhu, Patrick Rehain +5 more

High resolution three dimensional (3D) optical imaging in the turbid underwater scenarios over extended length remains an outstanding challenge, primarily impeded by the absorption and scattering in turbid water, which result in substantial signal attenuation over short propagation distances. Overcoming water absorption by using optimum illumination wavelengths (480- 600 nm) of the visible spectrum, however, still requires one to address the strong scattering effects. To address the above challenge, we introduce a novel 3D imaging modality based on quantum parametric mode sorting (QPMS). It is a nascent quantum measurement technique that utilizes mode-selective quantum frequency conversion (QFC) in a χ2 nonlinear waveguide to up convert signal photons in a single spatiotemporal mode efficiently. Undesirable photons in other modes, even if they spectrally and temporally overlap with the signal, are converted with much less efficiency. This unique feature, combining with picosecond time gated detection as defined by the pump pulse width, can isolate signal photon backscattered by the target from multiscattered photons by the obstacle. It thus enables imaging through a strongly scattering medium, where the background photons are orders of magnitude stronger. With QPMS, we demonstrate 3D imaging of a target occluded by strongly scattering turbid media with optical depth < 9 (<18 round trip), while needing only 10􀀀5 detected photons/pulse to achieve sub-millimeters resolution. This makes our single photon sensitive 3D imager suitable for imaging and remote sensing applications in photon-starved natural water environments where it's high sensitivity and excellent temporal resolution can be exploited to its full extent.

Bradley Worth

This thesis is divided into two parts.In Part 1 I describe the experimental setup used to investigate electromagnetically induced transparency (EIT).It is shown that impure polarization, stray magnetic fields and imperfect optical alignments cause broadening of the EIT signal and other spurious effects.A systematic approach to minimizing these undesired effects is described, which is shown to produce signals that are four to six times narrower than measurements taken prior to minimization.I conclude part 1 by outlining the progress made toward the production of "slow" light.In Part 2 I describe my earlier research, performed during the first year of my graduate studies, on optical sensing in turbid media.This research culminated in a first accurate measurement of the complex refractive index and in-situ particle sizing in highly scattering opaque media.

Давид Николаевич Клышко