Atomically thin gallium telluride nanosheets: A new 2D material for efficient broadband nonlinear optical devices

Abstract

Here, we experimentally demonstrate the nonlinear optical properties of atomically thin two-dimensional layered gallium telluride (GaTe). We performed open aperture and close aperture Z-scan measurements in the femtosecond regime for the spectral range of 520–700 nm to study the broadband nonlinear absorption and nonlinear refraction. Interestingly, exfoliated GaTe displays strong saturable absorption and high negative Kerr nonlinearity in this spectral range. We observed a high nonlinear refraction coefficient, n2I, of −(7.61±0.07)×10−1 cm2/GW with near band edge excitation at 700 nm. Additionally, it shows a significant nonlinear absorption coefficient, β, of −(18.02±0.20)×104 cm/GW at an intensity of 40 GW/cm2 with high modulation depth and low saturation intensity. Transient absorption spectroscopy measurement is also performed to investigate the carrier dynamics of exfoliated GaTe and to identify the physical mechanisms responsible for the optical nonlinearity, such as Pauli blocking. The measured nonlinear optical data of the exfoliated GaTe presented in this Letter will pave the way for potential application in ultrafast photonic devices like optical switching, passive Q-switching, and mode-locking, due to high Kerr nonlinearity and saturable absorption in the femtosecond regime.