Ultra broadband mirror using sub-wavelength grating

We demonstrate, for the first time, a very broadband (/spl Delta//spl lambda///spl lambda/>35%), high reflective (R>98.5%) grating structure. This structure is scalable to far infrared wavelengths and can be used to create low-voltage and widely tunable optical filters.

Broadband mirrors with high reflectivity (>99%) are essential for various applications such as sensors, surveillance, imaging and communications, ranging from wavelength. The conventional metal mirror and dielectric distributed Bragg reflectors (DBRs) are often limited by reflectivity, bandwidth, DBR thickness/index accuracy requirement (for high reflectivity), or overall DBR thickness. In addition, different materials need to be developed to fabricate mirrors for different wavelength regimes, which may not be compatible with Si or III-V processing technologies. In this paper, we demonstrate, for the first time, a single-layer sub-wavelength grating (SWG) using Si/SiO₂, with a very broad bandwidth, to , and high reflectivity. This structure is scalable to far infrared wavelengths and can be used to create low-voltage and widely tunable optical filters.