We design two types of reflectors by using subwavelength high-index contrast gratings, which exhibit similar high focusing capabilities at normal incidence with a TE-polarized plane wave. One type has bars of different heights, whereas the other has bars of different depths. Both grating reflectors are designed to be approximately 22 \mu m in structural length and 10 \mu m in focal length, at an operating wavelength of 1.55 \mu m. Both achieve a full-width-half-maximum of 0.9 \mu m at the focal plane, which is fairly close to the diffraction limit. Their reflectance reach as high as 94% and 91%.
© 2014 Chinese Optics LettersPDF Article