Abstract
A mid-infrared thermal emitter with high emissivity property is proposed and fabri-cated. The thermal emitter is based on all-dielectric architecture where the intrinsic losses of dielectric materials are low. Therefore, we achieve a highly efficient thermal emitter relative to common thermal emitter through a novel approach- the array of low loss die-lectric particles. We characterize the thermal emitter based on all-dielectric architecture via the finite difference time domain method (lumerical). Kirchhoff's law states: For an arbitrary body emitting and absorbing thermal radiation in thermodynamic equilibrium, the emissivity is equal to the absorptivity for the same frequency, same direction, and same polarization. The law holds only when the condition of thermodynamic equilibrium is satisfied. In general, a good absorber is a good emitter. In the design stage, emissivity is regarded as absorptivity, which could be calculated and analyzed in simulation software. In lumerical simulation, absorptance of 97.6% is calculated at the wavelength of 9μm in all-dielectric-based thermal emitter. It is expected that all-dielectric-based thermal emitter possesses some high extent of emissivity. Besides, in numerical simulation result, power absorbed spatial distribution indicates that electromagnetic energy is dissipated within the array of all-dielectric cavities. In the fabrication stage, UV lithography is used to define the pattern of mid-infrared thermal emitter device. It is followed by the deposition of die-lectrics via E-gun evaporation technique. The pattern is formed after the lift-off process. In the measurement setup, the amount of radiant power of all-dielectric-based thermal emitter is measured by the Fourier transform infrared spectroscopy. Then, around 90% emissivity and quality factor of 2.5 are evaluated and calculated in the emission spectrum. Spatial coherence of thermal radiation field is also estimated through the response of emission field over a wide range of incident angles in the simulation.