Dynamically switchable self-focused thermal emission.

The ability to manipulate thermal emission is paramount to the advancement of a wide variety of fields such as thermal management, sensing and thermophotovoltaics. In this work, we propose a microphotonic lens for achieving temperature-switchable self-focused thermal emission. By utilizing the coupling between isotropic localized resonators and the phase change properties of VO, we design a lens that selectively emits focused radiation at a wavelength of 4 µm when operated above the phase transition temperature of VO. Through direct calculation of thermal emission, we show that our lens produces a clear focal spot at the designed focal length above the phase transition of VO while emitting a maximum relative focal plane intensity that is 330 times lower below it. Such microphotonic devices capable of producing temperature-dependent focused thermal emission could benefit several applications such as thermal management and thermophotovoltaics while paving the way for next-generation contact-free sensing and on-chip infrared communication.