Coupled Tamm phonon and plasmon polaritons for designer planar multi-resonance absorbers.

Wavelength-selective absorbers (WS-absorbers) are of interest for various applications, including chemical sensing and light sources. Lithography-free fabrication of WS-absorbers can be realized via Tamm plasmon polaritons (TPPs) supported by distributed Bragg reflectors (DBR) on plasmonic materials. While multi-frequency and nearly arbitrary spectra can be realized with TPPs via inverse design algorithms, demanding and thick DBRs are required for high quality-factors (Q-factors) and/or multi-band TPP-absorbers, increasing the cost and reducing fabrication error tolerance. Here, we experimentally demonstrate high Q-factor multi-band absorption with limited DBR layers (3 layers) by Tamm hybrid polaritons (THPs) formed by coupling TPPs and Tamm phonon polaritons (TPhPs) when modal frequencies are overlapped. Compared to the TPP component, the Q-factors of THPs are improved two-fold, and the angular broadening is also reduced two-fold, facilitating applications where narrow-band and non-dispersive WS-absorbers are needed. Moreover, we develop an open-source algorithm to inversely design THP-absorbers consisting of anisotropic media and exemplify that the modal frequencies can be assigned to desirable positions. Furthermore, we demonstrate that inversely designed THP-absorbers can realize same spectral resonances with fewer DBR layers than a TPP-absorber, thus reducing the fabrication complexity and enabling more cost-effective, lithography-free, wafer-scale WS-EMs for applications such as free-space communications and gas sensing. This article is protected by copyright. All rights reserved.