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Advanced Techniques in Optical Diffraction Tomography

Ahmed Bassam Sayed Ayoub Mohamed Emam

In this thesis, we study the 3 challenges described above. First, we study different reconstruction techniques and assess the fidelity of each reconstruction results by means of structured illumination and phase conjugation. By reconstructing the 3D refractive index of the sample using different algorithms (i.e. Born, Rytov, and Radon) and then perform a numerical back-propagation of experimentally measured structured illumination pattern we are able to assess the fidelity of each reconstruction algorithms without prior information about the 3D RI distribution of the sample.The second part of the thesis is concerned with the 3D reconstruction of samples using intensity-only measurements which the need to holographically acquire them. We show that using intensity-only measurements, we could still be able to reconstruct the 3D volume of the sample with edge-enhanced effects which was proven useful for drug delivery applications in which nano-particles were identified on the cell membrane of immune T-cells in a drug delivery studies. Such reconstruction technique would result in more robust imaging system where the commercial imaging microscope systems can be incorporated with LEDs for high-quality speckle noise-free imaging systems. In addition, we show that under certain conditions, we can be able to reconstruct the 3D refractive index distribution of different samples.The third part of the thesis is contributing to high-speed complex wave-front shaping using DMDs. In that part, new modulation technique is demonstrated that can boost the speed of the current time-multiplexing techniques by a factor of 32. The modulation technique is based on amplitude modulation where an amplitude modulator is synchronized withvthe DMD to modulate the intensity of each bit-plane of an 8-bit image and then all the modulated bit-planes are linearly added on the detector. Such modulation technique can be used not only for structured illumination microscopy but also for high-speed 3D printing applications as well as projectors.The last part is concerned with using deep learning approaches to solve the missing cone problem usually accompanied with optical imaging due to the limited numerical aperture of the imaging system. Two techniques are discussed; the first is based on using a physical model to enhance the quality of the 3D RI reconstruction and the second is based on using deep neural network to solve the missing cone problem.

EPFL2022

Optical computing and reconfiguring with spatiotemporal nonlinearities in waveguides

Christophe Moser, Demetri Psaltis, Ugur Tegin

A device for optical computing comprises at least one modulator (210, 710, 810, 910, 1010, 1110, 1210, 1310, 1410, 1520, 1610, 1710, 1810, 1910, 2010, 2110, 2210) and at least one waveguide (220, 720, 820, 920, 1020, 1120, 1220, 1320, 1420, 1530, 1620, 1720, 1820, 1920, 2020, 2120, 2220). The at least one modulator (210, 710, 810, 910, 1010, 1110, 1210, 1310, 1410, 1520, 1610, 1710, 1810, 1910, 2010, 2110, 2210) is configured to modulate incident radiation, whereby input radiation is generated. The at least one waveguide (220, 720, 820, 920, 1020, 1120, 1220, 1320, 1420, 1530, 1620, 1720, 1820, 1920, 2020, 2120, 2220) is configured to guide the input radiation along a propagation direction. The at least one waveguide (220, 720, 820, 920, 1020, 1120, 1220, 1320, 1420, 1530, 1620, 1720, 1820, 1920, 2020, 2120, 2220) is configured to nonlinearly optically transform the input radiation propagating in the at least one waveguide, whereby output radiation that is outputted from the waveguide (220, 720, 820, 920, 1020, 1120, 1220, 1320, 1420, 1530, 1620, 1720, 1820, 1920, 2020, 2120, 2220) is optically computed.

2022

Controlling Light in Scattering Materials for Volumetric Additive Manufacturing

Antoine Vincent Boniface, Paul Delrot, Damien Claude-Marie Loterie, Jorge Andres Madrid Wolff, Christophe Moser

3D printing has revolutionized the manufacturing of volumetric components and structures in many areas. Several fully volumetric light-based techniques have been recently developed thanks to the advent of photocurable resins, promising to reach unprecedented short print time (down to a few tens of seconds) while keeping a good resolution (around 100 mu m). However, these new approaches only work with homogeneous and relatively transparent resins so that the light patterns used for photo-polymerization are not scrambled along their propagation. Herein, a method that takes into account light scattering in the resin prior to computing projection patterns is proposed. Using a tomographic volumetric printer, it is experimentally demonstrated that implementation of this correction is critical when printing objects whose size exceeds the scattering mean free path. To show the broad applicability of the technique, functional objects of high print fidelity are fabricated in hard organic scattering acrylates and soft cell-laden hydrogels (at 4 million cells mL(-1)). This opens up promising perspectives in printing inside turbid materials with particular interesting applications for bioprinting cell-laden constructs.

WILEY2022

Advanced Techniques in Optical Diffraction Tomography

Ahmed Bassam Sayed Ayoub Mohamed Emam

EPFL2022