Nearly perfect transmission of unpolarized infrared radiation through a one-dimensional metal grating embedded in a monolithic high-contrast grating

We demonstrate a conceptually simple polarization-independent mechanism for nearly perfect infrared light transmission through a subwavelength one-dimensional metal grating implemented in the grooves of a deep-subwavelength monolithic high-contrast grating (metalMHCG). We provide theoretical background explaining the transmission mechanism, which eliminates Fresnel reflection as well as significantly reduces metal absorption and the reflection of transverse electric and transverse magnetic light polarizations. Careful design of a metalMHCG implemented at the interface between the regions of high refractive index contrast enables the coincidence of high transmission conditions for both light polarizations, enabling up to 97% transmission of polarization-independent infrared radiation. Our analysis shows excellent electrical properties of the metalMHCG as evidenced by sheet resistance of 2 Omega Sq(-1) facilitating straightforward horizontal electron transport and vertical injection of the current into the semiconductor substrate on which the electrode is implemented. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement