We designed semiconductor metasurfaces comprised of rectangular arrays of all-Si antennas exhibiting sharp transmission dips. The sizes and periodicities of the antennas were shown to control the spectral positions and linewidths of the corresponding antenna resonances. The designed resonant metasurfaces were fabricated on a 600-nm-thick silicon-on-sapphire substrate using electron beam lithography, hard mask deposition, and inductively coupled HBr plasma etching. Multiple areas with different antenna sizes were defined on the same substrate. The samples were characterized with a FTIR system under normal incidence and paraxial beam configuration. The spectra revealed transmission dips in the spectral range of 3–4 μm, with the central wavelengths corresponding to the local simulated field enhancements of Eloc = 10–15. The metasurfaces were irradiated by a train of femtosecond laser pulses from a supercontinuum-based mid-IR optical parametric amplifier (OPA) pumped by a Ti:Sapphire amplifier. The incoming 200 fs mid-IR pulses, centered at 3.6 μm, had a maximum fluence of 60 mJ/cm2. The transmitted third harmonic radiation was refocused on and detected by an InGaAs detector based short wave-IR spectrometer. For pump–probe experiments, the residual near-IR 782 nm beam was split off from the output of the OPA, sent through a delay line, and focused at the sample collinearly to the mid-IR beam. Using a home-built calibrated mid-IR spectrometer based on a blazed diffraction grating and a mid-IR camera (Electrophysics PV320), we observed a pump-dependent blue-shifting and eventual disappearance of the resonant dips, accompanied by the reduction of the third harmonic generation.
Maxim R. Shcherbakov, Kevin Werner, Noah Talisa, Enam Chowdhury, and Gennady Shvets, "All-optical control of resonant semiconductor metasurfaces for nonlinear mid-IR nanophotonics (Conference Presentation)," Proc. SPIE 10541, Photonic and Phononic Properties of Engineered Nanostructures VIII, 105410A (Presented at SPIE OPTO: January 30, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2291268.5751529209001.
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