Aluminum: A qualified material for Tamm plasmon polariton in visible band

Tamm plasmon polariton (TPP) is a cavity mode confined in a multilayer structure consisting of a distributed Bragg reflector and a metallic layer. It can be excited with varied polarizations and any angle of incidence, attracting significantly growing attention recently. To date, the majority of TPP structures are constructed with gold or silver. The qualification of aluminum as an alternative material for TPP mode is pending. Here, we show that it is possible to realize comparable characteristics with aluminum (Al)-based TPP structures, in terms of spectral behavior, quality factor (Q-factor), and electric field enhancement. Experimentally, we demonstrate that Al is qualified for the TPP mode with an exceptionally narrow linewidth (∼17 nm), high Q-factor (∼35.8), and moderate field enhancement (2.38-fold) in the visible band. Moreover, we found that Al-based TPP structures are more tolerant to polarization divergences (with a polarization splitting of only 11 nm at the incidence angle of 50°) compared to noble metal counterparts. This work paves the way toward the usage of Al as a viable and low-cost material for TPP devices beyond noble metals.