Lorentzian dispersive antireflection temporal coatings with multiple time durations.

Abstract

As the temporal counterparts of traditional antireflection coatings, antireflection temporal coatings (ATCs) provide a novel approach to eliminate reflections by employing two-step temporal modulations. The interval between these two temporal modulation steps is called the time duration of the ATC. In this Letter, we explore ATCs utilizing Lorentzian dispersive media through an extended temporal transfer matrix method, and we discover that they exhibit diverse time durations and offer the potential for enhanced transmission. On one hand, the Lorentzian dispersive ATC can function as a temporal quarter-wave impedance transformer, similar to nondispersive ATCs. In this scenario, the time durations are consistently shorter than those of nondispersive ATCs, gradually converging to a constant value as the dielectric constant of the output layer approaches infinity. On the other hand, by finely tuning the parameters of the Lorentzian dispersive temporal coating, reflections can also be accidentally eliminated, which is not achievable with nondispersive temporal coatings. Consequently, Lorentzian dispersive ATCs offer additional time durations compared with nondispersive ATCs. Furthermore, Lorentzian dispersive ATCs with different time durations lead to distinct transmission characteristics. In certain cases, they can even enhance transmissions, a feat unattainable for nondispersive ATCs. These Lorentzian dispersive ATCs are feasible in the gigahertz and even terahertz regimes.