Broadband Nonlinear Optical Absorption Induced by Bandgap Renormalization in CVD-Grown Monolayer MoSe 2 .

Optical modulation on ultrashort time scales is both of central importance and an essential operation for applications in photonics and optoelectronics. Here, with a giant bandgap renormalization due to a high density of carrier injected by a femtosecond pulse, we realize an expected broadband saturable absorption in chemical vapor deposition grown monolayer transition-metal dichalcogenide MoSe 2 . Our findings reveal the band edge shift from ∼1.53 to ∼0.52 eV under the pump excitation of 0.80 eV, which is induced by the nonequilibrium occupation of electron-hole states after a Mott transition as well as the increase of carrier temperature.