Expérimental et théorique
Saturation of the light-matter interaction is a general nonlinear feature of materials: atoms or semiconductors. In semiconductors, controlling saturation phenomena is important for fundamental physics and applications. A seminal example is the semiconductor saturable absorption mirror (SESAM), that revolutionized ultra-fast lasers in the vis/near-IR spectral range. In the mid-IR (lambda=3-30 um), the intensity required for saturation is high, about 1 MW/cm2. This high value explains why SESAM mirrors are missing from the toolbox of mid-IR opto-electronics. The host team proposed that absorption saturation can be engineered if the system operates in the strong light-matter coupling regime, and provided an experimental proof. The team designed SESAMs with low saturation intensities: the goal is generating mid-IR frequency combs with tabletop fiber or interband cascade lasers. The goal of the internship is to develop low-power SESAMs in the mid-IR, supported by recently obtained results, that suit the comb application with fiber and/or cascade lasers. Experiments will be performed by optical pumping with a tunable QC laser in an existing experimental setup. If time permits, time domain characterizations will be performed with a mid-IR pump/probe setup. This project evolves in the context of a running ANR grant and of an ERC Advanced grand. It opens up exciting perspectives in the realization of ultrafast, mode-locked mid-IR fiber and semiconductor lasers.