Nonequilibrium Manybody Theory for GHz-THz Nonlinearities in Superlattices

Abstract: This talk introduces a concept to study nonlinear optics in the GHz-THz ranges through controllable nonlinearities in semiconductor superlattices. A fully predictive microscopic Nonequilibrium Green's Functions approach is used to deliver input to a relaxation-rate approximation approach leading to fully analytical expressions for the nonlinear polarization at arbitrary orders. These results open the possibility of extending the whole field of nonlinear optics to the GHZ-THz range and the possibility of designing materials and devices for a large number of applications, including spectroscopy of biomolecules, which typically have strong GHz-THz resonances. After an outline of the approach that led to the first publication [M.F. Pereira et al, PRB 96, 045306 (2017)] a few ideas for deeper theoretical investigations will be discussed that could lead to long term cooperations between theory and experimental efforts.