A Chiral Microcavity based on Apparent Circular Dichroism

Breaking the symmetry between left-handed and right-handed chiral optical modes in planar Fabry–Pérot (FP) microcavities would enable a variety of chiral light-matter phenomena, with applications in spintronics, polaritonics, and chiral lasing. Such symmetry breaking, however, has remained underexplored and has been purported to require Faraday mirrors. We present a simple solution to chiral symmetry breaking in FP microcavities, preserving low mode volumes by embedding organic thin films exhibiting "apparent circular dichroism" (ACD); an optical phenomenon based on interfering linear birefringence and linear dichroism with offset optical axes. ACD interactions are opposite for counter-propagating light and increase with path length. Consequently, we demonstrated chiral asymmetry of the cavity modes over an order of magnitude larger than that of the isolated thin film. Through both circular dichroism spectroscopy and simulation using theoretical scattering matrix methods, we characterize the spatial, spectral, and angular chiroptical responses of this new type of chiral microcavity.