Efficient Bragg diffraction in thin semiconductor two-dimensional gratings

Abstract

Highly improved diffraction properties are demonstrated in a two-dimensional [2D] grating consisting of a transmission grating optically recorded in a semiconductor one-dimensional photonic crystal (1D-PC). Near unity internal diffraction efficiency, high wavelength selectivity, and Bragg diffraction regime operation are demonstrated when the read beam is set at Bragg incidence on the transmission grating while its wavelength corresponds to the band edge of the 3 microm thick 1D-PC. When the 2D grating is grown on a Bragg mirror, a single diffracted beam is obtained, which makes the device promising for optical signal processing.

Bragg diffraction in thin 2D refractive index modulated semiconductor samples

“…The thickness is also an issue as it must not be too large if an integrated device is wanted, although the diffraction regime associated with thin crystals is a Raman-Nath regime involving multiple diffracted beams. Besides the already wellknown simple [2][3][4] and double resonance [5][6][7][8][9] in a Fabry-Perot cavity, a new approach using slow light at the band edge of a one-dimensional photonic crystal (1D-PC) was recently demonstrated to overcome these difficulties, first in photopolymers [10] and then in semiconductor Bragg reflectors [11]. Results are especially attractive in the latter case due to the high index contrast of Bragg reflectors.…”