Full polarization control of photons with supermodes in photonic molecules

Polarization of photon plays key roles in quantum optics and light-matter interactions, but however, is difficult to control in nanosystems since the eigenstate of nanophotonic cavity is usually fixed and linearly polarized. Here we reveal a full polarization control of photons using photonic molecules (PMs) that host supermodes of two coupled nanobeam cavities. The nanobeam cavity couples to the other through the evanescent field in surrounding environment forming a non-Hermitian system. When the coupling strength between the two cavities increases, non-trivial features arise, e.g., the energy shift of antisymmetric supermode is suppressed. Furthermore, we observe that both the polarization degree and polarization angle of the antisymmetric mode strongly depend on the shift and gap, exhibiting polarization states from linear to circular. The full polarization control along with the stable resonant energy indicate great potential of the PM in quantum optical devices and spin-resolved cavity quantum electrodynamics.