Fig. 1
From: An all-dielectric metasurface as a broadband optical frequency mixer
Generation of new frequencies with the GaAs metasurface mixer. a Schematic of an optical metamixer consisting of a square array of subwavelength GaAs dielectric resonators. Two femtosecond near-IR pulses pump the metamixer and a variety of new frequencies are simultaneously generated. Inset: a 60° side-view scanning electron microscope image of the GaAs metamixer. The scale bar corresponds to 3 μm. Bottom inset: schematic energy diagrams of the seven nonlinear optical processes that occur simultaneously in our metamixer: second-hamonic generation (SHG), third-harmonic generation (THG), fourth-harmonic generation (FHG), sum-frequency generation (SFG), two-photon absorption-induced photoluminescence (TPA PL), four-wave mixing (FWM) and six-wave mixing (SWM). b Measured (solid line) and numerically simulated (dashed line) reflectance spectra of the metasurface with two cross-section local electric field distributions at the wavelengths of 1.246 μm and 1.535 μm, which correspond to the maximal electromagnetic field enhancements inside the GaAs nanodisk. c Spectra of second-, third- and fourth-harmonics when pump pulses of λ1 ~ 1.57 μm are used to excite the GaAs metamixer. Inset is the zoom-in of the fourth harmonic generation
