Experimental Realization of a Handedness-Preserving Chiral Photonic Crystal Mirror

Selective reflection and transmission of the different spin states of light have been a long-explored area in nanophotonics and quantum optics [1]. Applications are diverse and encompass many areas such as quantum information processing, engineering of light-matter interactions and novel types of lasers. Particularly, cold atoms interact more strongly with circularly polarized lights. One can envision making cavities in which only one spin state of light is trapped-but such cavities cannot be implemented with conventional, metallic or dielectric-stack mirrors as such mirrors flip the photon spin and, e.g., left-hand circularly polarized (LHCP) light becomes right-hand circularly polarized (RHCP) upon reflection. Here, we report on the first experimental observation of intrinsic chira-optical response with near perfect extinction in an ultrathin planar structure. The selective reflection is achieved via guided mode resonance (GMR) in a SiN photonic crystal membrane with a chiral pattern of the perforating holes.