Broadband Generation of Terahertz Waves via Infrared Frequency Nondegenerate Parametric Down-Conversion by Nonlinear Graphene Arrays
To analyze the THz wave generation by the mid-IR frequency nondegenerate parametric down-conversion (NPDC) process in the nonlinear graphene arrays the nonlinear simulations using the perturbation method for solving the nonlinear diffraction problems were performed. First we find the resonant frequencies of surface plasmon polaritons (SPP) modes in graphene nanoribbon arrays using calculated multimode linear absorption spectra of incident waves with s-, p-polarization. Then we select the graphene ribbon sizes to satisfy the excitation condition of the SPP modes in the mid-IR frequency range. We choice the frequencies of pump and signal waves equal to resonant frequencies of the fundamental and high order SPP modes of the graphene arrays, respectively. It is shown that the efficiency of THz wave generation via frequency NPDC of mid-IR to THz by nonlinear graphene arrays increases by several orders of magnitude when the frequency of signal and pump waves are close to the resonant SPP mode frequencies. An optimal value of the chemical potential at which the maximum NPDC efficiency of mid-IR to THz was determined. Using this method to generate THz waves the wide frequency tunability from 1.5 to 8.5 THz can be realized by tuning the pump frequency and the corresponding chemical potential from 0.25 to 1 eV.
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Southern Federal University
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