Fig. 4: Ultrastrong and anisotropic third-order nonlinear optical response in 1D vdW FRP.
From: Giant anisotropic photonics in the 1D van der Waals semiconductor fibrous red phosphorus
a THG intensities as a function of the excitation power with a fundamental pulse wavelength of ~ 1300 nm. The inset is the schematic diagram for the THG process. b Upper panel: THG spectra as a function of generated photon energies. Lower panel: the reflectance contrast spectrum \(\frac{\triangle {{{{{\rm{R}}}}}}}{{{{{{\rm{R}}}}}}}\) of 1D vdW FRP, \(\frac{\triangle R}{{{{{{\rm{R}}}}}}}=\frac{{{{{{{\rm{R}}}}}}}_{{{{{{\rm{sample}}}}}}}\,-\,{{{{{{\rm{R}}}}}}}_{{{{{{\rm{substrate}}}}}}}}{{{{{{{\rm{R}}}}}}}_{{{{{{\rm{substrate}}}}}}}}\), where Rsample and Rsubstrate are the reflected spectra measured from the sample and substrate, respectively. c Comparison between the THG intensity of 1D vdW FRP and other well-known materials (e.g., GaAs, Si, gold, and few-layer MoS2) with large third-order nonlinear optical responses under the same excitation conditions. The THG intensities of GaAs, Si, gold and few-layer MoS2 thin films are multiplied by a factor of 3, 30, 15, and 10, respectively, for comparison. d Polar plots of THG intensity versus the polarization angle θ for co-polarized (red) and cross-polarized (blue) configurations.
