Metamaterials invoke the image of subwavelength metallic resonators, but there is absolutely no reason why it should be made of metals. So we designed and tested Silicon-process compatible metasurface in the infrared wavelength range. These metasurfaces show very high Q (>100), extreme chirality, and polarization conversion along with very low-loss operation. The high- Fano-resonant dielectric metasurfaces described here represent a novel and promising platform for a variety of applications that depend on high optical energy enhancement and precise spectral matching between molecular/atomic and electromagnetic resonances. Those include infrared spectroscopy of biological and chemical substances and nonlinear infrared optics. Chiral properties of such metasurfaces might be exploited for developing novel ultra-thin infrared detectors sensitive to light’s chirality, as well as spectrally-selective CP thermal emitters. Even higher quality factors (∼1000 ) Fano resonant metasurfaces can be developed by judicious engineering of near-field coupling between resonant modes if inhomogeneous broadening due to fabrication imperfections can be overcome. Combining the large field enhancements achieved in such high-Q silicon metasurfaces with coherent radiation sources such as quantum cascade lasers capable of delivering high-power low-divergence beams would open new exciting opportunities in nonlinear infrared optics such as harmonics generation and four-wave mixing using free-space excitation. They show promise for sensing applications as well as spectrally selective CP thermal emitters.
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