Expérimental
About 30 years ago, it was recognized that photons can carry OAM, orbital angular momentum (𝐿=±ℓℏ), which corresponds to a beam with an integer number ℓ of intertwined helical phase-fronts. OAM beams, also known as vortex beams, exhibit unique topological properties and have recently found several applications. The physics of vortex beams is particularly fascinating in the nonlinear regime, where OAM can be transferred from the pump to the harmonic frequency and optical spin-orbit coupling can occur in exotic fashions, even in the generation of two-photon quantum states via SPDC. In this context, chi(2) optical metasurfaces are particularly interesting for their inherent capability to generate optical harmonics with on-demand spectral, spatial, polarization and phase properties, and we already showed that they are versatile SPDC-based sources of two-photon quantum states. This internship aims at demonstrating a nonlinear metasurface for the synthesis of OAM in SPDC, which has never been attempted to date. To achieve this breakthrough, we will design, fabricate and characterize an AlGaAs-on-insulator source for two-photon quantum states with controlled OAM. To this end, we can rely on solid grounds in both the technological platform and the theoretical domain (quasi-normal-mode modelling), while possessing state-of-the-art nonlinear and quantum optics experimental facilities, and an international leadership in this research field.