Alexander Paarmann, Ilya Razdolski, Alexey Melnikov, Sandy Gewinner, Wieland Schöllkopf and Martin Wolf:
Appl. Phys. Lett. 107, 081101 (2015), pp 4;
The Reststrahl spectral region of silicon carbid e has recently attracted much attention owing to its potential for mid-infrared nanophotonic a pplications based on surface phonon polaritons (SPhPs). Studies of optical phonon resonances res ponsible for surface polariton formation, how- ever, have so far been limited to linear optics. In this Letter, we report the first nonlinear optical investigation of the Reststrahl region of SiC, empl oying an infrared free-electron laser to perform second harmonic generation (SHG) spectroscopy. We observe two distinc t resonance features in the SHG spectra, one attributed to resonant enhancement of the nonlinear susceptibility v (2) and the other due to a resonance in the Fresnel tra nsmission. Our work clearly demonstrates high sensitivity of mid-infrared SHG to phonon-driven phenomena and opens a route to studying non- linear effects in nanophotonic structures based on SPhPs..
The original publication is available by link DOI: 10.1063/1.4929358