Fig. 3: Pump wavelength and pump fluence dependence of THz generation.
From: Broadband terahertz wave generation from an epsilon-near-zero material
a Measured peak-to-peak THz amplitude as a function of the pump wavelength with pump fluences of 0.78 (red), 3.12 (blue), and 6.25 mJ/cm2 (yellow) in the transmission configuration. The dashed curve denotes the static ENZ wavelength of the bulk ITO film measured via spectroscopic ellipsometry. b Schematics of ultrafast electron dynamics in the ITO film, which consist of photoexcitation, hot-electron redistribution, and relaxation. The dashed line represents the parabolic conduction band approximation. c Measured peak-to-peak THz amplitude as a function of the pump fluence in the transmission configuration with a pump wavelength of 1350 nm for the ITO film (red) and 1 mm-thick ZnTe crystal (blue). The dashed lines are from the linear fitting. d Calculated λENZ of the ITO film (red) and THz amplitude (blue) as a function of the pump fluence in the transmission configuration
