Postdoctoral position: Matrix approach for resonant multiple scattering of light (theory)

Langevin Institute, Paris

We propose a 2 years postdoctoral position in the Waves Theory and Mesoscopic Physics group of the Langevin Institute under the supervision of Arthur Goetschy. The goal of the project is to provide a theory for the scattering matrix of strongly scattering media made of resonant units for wavefront shaping applications. Applicants should have a Ph.D. in wave physics with a solid background on wave propagation in complex systems.
Contact: arthur.goetschy@espci.psl.eu

More information here:
 

Real-time shaping of entangled photons by classical control and feedback

[O. Lib, G. Hasson and Y. Bromberg, Sci. Adv. 6 (2020)]

Wavefront shaping offers the possibility to compensate for the effect of propagation through heterogeneous media. However, when using a single or a few photons, the feedback signal is typically too weak to allow real-time wavefront shaping applications, which limits applications for quantum communications using entangled photons. In this paper from the team of Yaron Bromberg at the Hebrew University of Jerusalem, the authors overcome this challenge by using as feedback the classical signal of the pump that follows the same path as the entangled photon. It allows adapting in real-time the pump wavefront to compensate for the aberrations/scattering introduced by a heterogeneous dynamic sample.

Controlling multimode laser modes using wavefront shaping inside the cavity

[X. Wei et al., Light Sci. Appl., 9 (2020)]

Multimode cavity lasers, such as multimode fiber lasers, are attractive for the opportunity they offer to generate high energy pulsed lasers, provided that one can achieve spatiotemporal mode-locking. However, it can be complicated to control the laser properties as 1) spatiotemporal dispersion, nonlinearity, gain and loss can nonlinearly interact, and 2) dispersion and mode coupling in such a system are difficult to predict or control. In a typical wavefront shaping experiment, one modulates the output of a laser beam, which can come at the cost of a significant energy loss, and only allows to control the spatial profile of the beam. In this paper, the authors use a spatial light modulator, but inside the laser cavity to modulate its boundary conditions. Using a genetic algorithm, they are able to efficiently control the laser properties, namely the output power, the output mode profile, the optical spectrum, and mode-locking.

Spatio-temporal shaping of light through a scattering medium

[A. Boniface et al., arxiv, 2007.09050 (2020)]

Controlling the spatial and temporal properties of a short pulse is already difficult in free space, and require a well-calibrated and specific setup. When the pulse propagates through a scattering medium, its temporal and spatial properties are randomized, leading to a spatio-temporal speckle. However, the effect of the medium can be described by means of the multi-spectral transmission matrix. In this paper, A. Boniface and his colleagues show that by measuring previously this matrix, and by only controlling the spatial input field using a spatial light modulator, they can modulate at will the spatio-temporal properties of the point spread function of a pulse traveling through a complex medium.