Angle-insensitive temporal multi-channel narrowband absorber using discrete photonic time crystals

The significant potential of time-varying media for manipulating electromagnetic (EM) waves has garnered extensive attention in recent years. By periodically modulating the EM properties of these time-varying media, photonic time crystals (PTCs) are created. A temporal multi-channel narrowband absorber (TMNA) based on discrete PTCs is introduced in this Letter. Three absorption channels (ACs) are formed through impedance matching and dielectric loss mechanisms. Leveraging the characteristics of PTCs, the proposed TMNA is capable of operating at any angle, exhibiting complete angle insensitivity. Unlike traditional multi-channel narrowband absorbers in non-time-varying systems, TMNAs offer controllable properties. By adjusting the duration of the temporal slab, additional ACs can be generated. Increasing the number of periods of the PTCs enhances the absorption peak. The proposed TMNA holds significant application potential in fields such as detection and optical switching.