Extremely wide band Rayleigh resonant reflector with sharp angular spectra in near infrared wavelength band

Abstract

In this paper, we propose an extremely broadband Rayleigh resonant reflector with sharp angular spectra operating in near infrared wavelength band, this device consisting of a single germanium resonant grating layer is designed and analyzed by using with the rigorous vector diffraction theory. At the Rayleigh angle, the first diffracted order can be appear from evanescent to a propagating one, thus, a very sharp angular spectrum characteristics can be presented in the device. Based on the guided mode resonant effect, high index material such as silicon and germanium can be designed as wide band reflector, beam splitter and polarizer in near infrared wavelength region. Through connecting Rayleigh phenomena and guided mode resonant effect, we can design a new kind of optical devices with versatile characteristics such as sharp angular spectra and extremely wide reflection band. In this paper, we present a Rayleigh resonant reflector with extremely high reflection (R>99.5%) for TE polarization light over ∼600nm wavelength range and sharp angular spectral distribution. In addition, it is shown from our calculations that the high-index nano-layer located adjacent to the substrate is seen to critically affect the resulting spectra of Rayleigh resonant reflector.