Tamm plasmonic-based elliptical anisotropic photonic crystals with multifunctional optical features.

In recent years, multifunctional photonic structures have attracted increasing interest due to their ability to perform diverse optical functions within a single platform. In this work, we design and investigate a one-dimensional anisotropic photonic crystal that simultaneously exhibits high-performance optical sensing, filtering, direction-dependent reflection and absorption, as well as an electromagnetically induced transparency (EIT)-like phenomenon. The structure consists of periodic layers of SiO₂ and a layer with a variable refractive index ranging from 1.36 to 1.44, along with a thin gold film that supports the excitation of a Tamm plasmon mode (TPM). To enhance and diversify the optical functionalities, an elliptically anisotropic metamaterial layer is incorporated into the periodic structure. Numerical simulations reveal that the structure not only exhibits a sharp TPM-related resonance shift in response to refractive index variations but also acts as a perfect absorber. Furthermore, the presence of anisotropy introduces polarization and propagation-direction-dependent reflection characteristics and enables the emergence of a Tamm-EIT-like transparency window in the reflection spectrum. These findings highlight the potential of the proposed anisotropic photonic crystal as a compact multifunctional platform for advanced photonic applications.