16/03 – Pascal BERTO : Unconventional optical wavefront shaping and imaging

SPPIN’s webinar winter-spring 2021, 16 Mar. at 10h30, online – Ask link to a SPPIN member.

Pascal BERTO, Institut de la Vision, Paris

In recent decades, the advent of spatially-resolved techniques to control and image the phase of light waves has profoundly transformed photonics, enabling major advances in several fields, including microscopy. In this talk, I will first present a wavefront shaping concept in which the phase of the transmitted light is shaped at the micro-scale by using the thermo-optical effect. By engineering the temperature landscape in a thermo-optical material, one forms a distribution of refractive index associated to a desired micro-optical element (lens, axicon, etc.), with an electrically-tunable amplitude. I will explain how this simple and compact concept could complement the existing optical shaping toolbox by offering low-chromatic-aberration, polarization-insensitive and transmission-mode micro-components. 

In the second part of this talk, dedicated to phase imaging, I will describe how a broadband and cost-effective wavefront sensor (WFS) can be simply implemented by placing a thin diffuser in the close vicinity of a camera. For such a diffuser, a local wavefront gradient yields a local translation of the speckle pattern, a property ensured by the so-called “memory effect”. After describing the WFS itself, I will discuss the potential of the technique for quantitative phase imaging of biological samples and for 3D nanoparticle super-localization and tracking. Finally, we will see that the unique signature of the speckle patterns allows to multiplex several wavefronts incoming at various angles.