Target-oriented spectral emissivity design: Mechanism and prediction of magnetic polaritons based on transmission line theory

Micro-nano spectral emitters are crucial in applications such as radiative cooling, gas detection, and infrared stealth. However, current designs depend heavily on optimization algorithms that require extensive calculations. Therefore, achieving the rapid design of target-oriented spectral emitters remains a fundamental challenge. A comprehensive investigation into the mechanisms of microscale radiation regulation ensures the rapid design of spectral emitters. Among these mechanisms, magetic polaritons (MPs) have become a significant resonance mode in the field of micro nano scale thermal radiation due to its Perfect absorption. Equivalent inductor-capacitor circuit (LC) model is an important theoretical model for calculating the resonance frequency of MP, but it requires a constant for fitting, which seriously restricts the Fast design of micro-nano emitters. In this paper, transmission line (TL) theory is proposed to directly determine the frequency of MP excitation for grating and slit arrays without fitting. Numerical simulation results indicate that the MP excitation frequency calculated by TL theory are accurate. Moreover, TL model directly gives the fitting constants in the LC model. Compared with previous studies, TL theory has achieved the calculation of the excitation frequency of MP without fitting. Finally, as a practical application, TL model is employed to illustrate the Fast design of heat emitter. Our research seeks to facilitate the expedited design of target-oriented spectral emitters and to advance the application of LC model and TL model in spectral emitters.