Description:
Phonon polaritons (PhPs) have a long lifetime and high confinement of light fields compared with their plasmonic counterparts in the mid-infrared range. Thus, PhPs are promising candidates for realizing vibrational strong coupling (VSC) with molecules. However, VSCs of PhPs in nanoresonators and thin films require the near-field technique and are limited to the transverse magnetic mode. Here we propose a new configuration based on the Tamm structure, which supports PhPs excited by the free-space incident light in both transverse-electric and transverse-magnetic modes. The VSC of a 300 nm thick molecular layer can be achieved with 21 c m − 1 Rabi splitting, according to the numerically obtained angle resolved reflectivity spectra with the transfer matrix method. Our findings provide a promising platform for applications in free-space sensing of vibrational modes and control of chemical reactions in compact devices.