Nonlinear Coherent Perfect Absorption Based on Second Harmonic Generation in a Spoof Plasmonic Waveguide

We propose a nonlinear method to achieve coherent perfect absorption (CPA), for which a specialized nonlinear spoof surface plasmon polariton (SSPP) waveguide is designed for experimental verification. The dispersion relation of the designed SSPP structure satisfies the phase-matching condition, and the second harmonic wave generated by the pump wave is a pair of coherent waves with the signal wave, so the absorption rate of the signal wave can be adjusted by changing the phase of the pump wave. In addition, the perfect absorption of the signal waves with different powers is realized by controlling the powers of the pump waves.