Spin dissymmetry in optical cavities
We introduce the spin dissymmetry factor, a measure of the spin-selectivity in the optical transition rate of quantum particles. This spin dissymmetry factor is valid locally, including at material interfaces and within optical cavities. We design and numerically demonstrate a metasurface optical cavity with three-fold rotational symmetry that maximizes spin dissymmetry, thereby maximizing the spin-selective radiative coupling of a cavity-coupled emitter. We also show the near-field and far-field response of spin and chiral dipoles to these cavities that preferentially enhance either spin or chirality. Our approach emphasizes the difference between spin and chirality in the near-field and reveals a compact parameter for designing more efficient quantum optical devices.