Speaker
Description
Sum frequency generation (SFG) and difference frequency generation (DFG) are second order nonlinear processes where two lasers with frequencies ω_1 and ω_2 combine to produce a response at frequency ω = ω_1 ± ω_2 . Compared with other nonlinear responses, such as second harmonic generation, SFG and DFG allow for tunability over a larger range and by selecting the two laser frequencies, one can enhance the response through resonance with specific electron-hole transitions. We put forward a
first-principles framework based on the real-time solution of an effective Schrödinger equation to calculate the SFG and DFG in bulk materials. Within this framework, we can select from various levels of theory for the effective one-particle Hamiltonian to account for local-field effects and electron-hole interactions. To assess the approach, we calculate the SFG and DFG of two-dimensional crystals, h-BN and MoS2 monolayers, both within the independent-particle picture and including many-body effects.
Additionally, we demonstrate that our approach can also extract higher-order response functions, such as field-induced second harmonic generation. We provide an example using bilayer hBN.