Unidirectional and highly dispersive grating emitters for silicon photonic beam steerers.

Grating emitters are the key component used in silicon photonic beam steerers to create light emission and allow dispersion-based steering. Conventional grating emitters are inefficient due to bidirectional emission, and their angular dispersion is only on the order of 0.1°/nm. In this paper, we develop unidirectional grating emitters by choosing a top cladding material with a refraction index higher than that of the bottom cladding. The refractive index difference allows the phase-matching condition to be satisfied only for the upward diffraction. We demonstrate experimentally grating emitters with a directionality of 83% and an angular dispersion of 0.79°/nm. These grating emitters have a simple device structure compatible with the standard silicon photonic platform.