Non-Hermitian Thermal Emitters using Metal-Semiconductor Hybrid Resonators

Thermal emitters always have absorption losses and hence are open systems. Open systems are non-Hermitian and are best described by non-Hermitian physics. Here, we develop a non-Hermitian description of resonant thermal emitters and thereby take advantage of absorption loss in the system. Further, the non-Hermitian description provides new design tools such as symmetry, phase, and topology to control the properties of the thermal emission. We demonstrate such a thermal emitter using coupled plasmonic and photonic resonators. A lossless silicon photonic resonator is coupled to a lossy tungsten plasmonic resonator via a spacer. As the spacer thickness is increased, the thermal emission from the device held at 1000 K exhibits a transition from PT-symmetric to symmetry-broken phase through an exceptional point. The thermal emission from the device breaks the trade-off between emission brightness and spectral selectivity and simultaneously achieves both. Further, we show that the internal phase of resonators is a powerful tool to control the thermal emission from this device. Overall, this work is an unorthodox approach towards designing not only thermal but also other nanophotonic light sources.