Non-Hermitian Photonics in a Heterogenous Photonic Molecule

Nanophotonics offers an intriguing avenue to study non-Hermitian physics. Of particular interest is breaking the gain-loss balance in a photonic molecule consisting of coupled nanocavities to lower power thresholds for nanolasers. Previous work has focused on homogeneous photonic molecules consisting of coupled ring resonators integrated with gain material; however, the large mode-volumes of ring resonator cavities limits the light-matter coupling strength. In this work, we utilize heterogeneous photonic molecules wherein a low mode-volume nanobeam photonic crystal cavity is coupled to a ring resonator. We further utilize deterministic positioning of colloidal nanocrystal gain material to asymmetrically couple gain material only to the nanobeam cavity, thereby inducing gain solely in the nanobeam cavity. We explore non-Hermitian physics in the heterogeneous photonic molecule by modulating the system's gain-loss balance between the nanobeam cavity and the ring resonator.