Internship & Doctoral Thesis :
Holographic Optical Coherence Tomography Combining Diffraction Grating and Wavelength-Scanning Source for Imaging in Scattering Tissues.
CNRS UMR 7587 - ESPCI - Institut Langevin, 75005 Paris. Hôpital des XV-XX, 75012 Paris. Institut de la vision, 75012 Paris. Hôpital Fondation Rothschild 75019 Paris. Fondation Digital Holography 75005 Paris. The University of Pittsburgh Medical Center (UPMC), Pennsylvania, United States. Contact : Michael Atlan. 
Background : The partner centers of this project have developed a uniquely innovative expertise in ultrafast digital holography, laser Doppler imaging, and optical coherence tomography, and their medical use in ocular pathologies.
Objective : To achieve deep optical coherence tomography in scattering tissues by combining a wavelength-scanning laser and a diffraction grating with holographic detection on a camera. A linear illumination and slit detection will ensure optimal spatial confocal filtering.
Approach : A linear pattern illumination generated by a scanning laser, in the wavelength range of 820 nm to 870 nm, will be formed to illuminate a tissue sample, similar to the approach proposed by Arnaud Dubois [1]. The backscattered light will be spatially filtered by a slit and diffracted by a diffraction grating, to create a diffraction pattern that will be angularly scanned according to the wavelength variation of the laser. This pattern will be recorded by an ultra-fast camera. The recording process will be done with an optical interferometer, by digital holography [2], to allow for high-sensitivity phase measurement under low-light conditions, thanks to the sampling of the beat at the frequency of the laser scanning cycle. The digital signal processing of the recorded optical field diffraction patterns will enable the selection of deep retro-scattered photons, and the filtering of coherent crosstalk that emerges from random optical path lengths in the scattering sample.
Mission and Profile : A prototype of a tomographic imaging device will be developed. Students will conduct experiments and perform data processing in Matlab. They will realize coherent image formation through wave propagation, fluctuation analysis, statistical filtering, and numerical correction of aberrations. Good skills in numerical analysis are desirable. Mobility to all the involved laboratories during the thesis is a recommended possibility (Paris, Clermont Ferrand, France + Pittsburgh, USA + Vienna, Austria + Melbourne, Australia).
References :
[1] Line-field confocal optical coherence tomography https://hal-iogs.archives-ouvertes.fr/hal-01913796
[2] Swept-source optical coherence tomography by digital holography in real-time https://arxiv.org/abs/2003.08960
