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High contrast circular grating reflector on silicon-on-insulator platform.

A compact circular high contrast grating (HCG) reflector with a footprint of only 4.03  μm×4.32  μm on 220 nm silicon-on-insulator (SOI) platform is proposed and experimentally demonstrated. The proposed device breaks the high wavelength selectivity limitation for the conventional grating reflectors on a thin SOI platform by using the circular structure in a compact region. In addition, the device provides a high polarization selectivity over a wide wavelength range which is useful for applications such as tunable laser cavities and resonators to provide wide tuning range and high polarization stability. The circular structure based HCG reflector has an ultra-wide operational bandwidth (Δλ) of over 385 nm with the center wavelength (λ) set at 1550 nm, providing a Δλ/λ=24.83%. An average reflectance high of 94.15% is observed from 1525 to 1610 nm in the experimental measurement. The polarization extinction ratio is greater than 13 dB over the entire measured wavelength range.