Highly Nonlinear Excitons in 2D Semiconductors

Achieving strong nonlinear optical responses is of crucial fundamental and technological importance. In this talk, I will discuss the demonstration of giant optical nonlinearities in atomically thin semiconductors by exploiting the interaction between excitons and carriers in trilayer tungsten diselenide. By modulating the electric field and electrostatic doping, we observe the formation of Fermi polarons, which exhibit strong nonlinear optical behavior. The resonance of such optical excitations can shift as much as ~10 meV under moderate laser excitation. Additionally, an asymmetry in nonlinearity between electron and hole doping was observed, influenced by the applied electric field. I will discuss how these findings position atomically thin heterostructures as versatile platforms for nonlinear optical applications in both classical and quantum optoelectronics.