Taming parasitic thermal emission by Tamm plasmon polaritons for the mid-infrared

Abstract

We investigated the concept of a 1D layered structure for resonant selective thermal emission by excitation Tamm plasmon polaritons (TPPs). The modeled and simulated TPP structures for the mid-IR spectral region yield a promising approach for integrated sensing applications. In particular, the TPP structure is composed of an aperiodic multilayer stack of dielectric layers (silicon and silica) on a planar metallic surface acting as a heater and thus emitter for thermal radiation. By varying the layer depths, this design is highly optimizable for individual specifications, such as for enhancing the thermal emittance near to unity around a target wavelength and achieving a resonance with high Q-factor. Here, for demonstration purposes we chose λ=4.26 μm as the target emission wavelength (corresponding to a major CO2 absorption line). However, considering a larger spectral range within the mid-IR region, parasitic resonances emerge in a more or less unpredictable manner and lead to multiband emission. A transfer matrix approach and genetic algorithm (GA) optimization were used to identify feasible stack configurations and characterize the behavior of parasitic resonances. In order to analyze and control the emergence of parasitic emission, different parameters characterizing the stack–metal composition were set. In particular, we found that keeping constraints on the number of dielectric layers and their individual thicknesses allows effective control of parasitic emission while also facilitating modern microlayer fabrication processes. Even though those constraints can hamper the enhancement of the Q-factor at the target resonance, highly performant configurations and parameters for the TPP structures could be identified. Each configuration corresponds to a particular choice of substrate metals (Ag or W), number of layers, and individual layer thicknesses. The behavior of the target and the parasitic resonances was discussed by using concepts of topological photonics and lumped parameter models.