Optical frequency mixers generally rely on bulk nonlinear crystals and weak nonlinear optical processes. Sheng Liu and colleagues from Sandia National Laboratories, USA have now demonstrated an ultra-compact all-dielectric metamixer that enables many simultaneous nonlinear optical processes across a broad spectral range. The device is a gallium arsenide-based metasurface consisting of an 840-nm periodic square array of nanocylinders with a diameter of ~400 nm. Each nanocylinder is composed of an ~300-nm-thick SiOx etch mask, an ~450-nm-thick GaAs nanodisk and an ~400-nm-thick (AlxGa1–x)O3 layer. On pumping the metamixer with two femtosecond pulses at ~1.24 μm and ~1.57 μm, near the magnetic and electric dipole resonances of the metasurface, the team observed the generation of 11 new frequencies spanning from ~380 nm to ~1,000 nm, generated by 7 different concurrent nonlinear processes (second-harmonic, third-harmonic and fourth-harmonic generations, sum-frequency generation, two-photon-absorption-induced photoluminescence, four-wave mixing and six-wave mixing). Applications in communications, quantum optics, sensing and biology are expected.
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Won, R. Metasurface mixer. Nature Photon 12, 443 (2018). https://doi.org/10.1038/s41566-018-0230-4