Fig. 5: Fitting of measured DFG spectrum and comparison of second-order nonlinear susceptibility.
From: Giant enhancement of THz-frequency optical nonlinearity by phonon polariton in ionic crystals
a Spectrum of the THz waves at position x1 and Gaussian fittings of all the three frequency components. Blue and green curves fit v0 and v1, while the red curve fits the DFG signal vd. b Corresponding inverse Fourier transform showing time domain oscillations for v0, v1, and vd.
