Hybridized phonon polaritons assisted broad range SEIRA-based multi-molecular Sensing

In this work, we propose and theoretically investigate a van der Waals heterostructure for detection of multiple analytes in the mid-infrared range (10.5 - 15 μm). The proposed hybrid structure consists of a two dimensional (2D) silver grating and a thin slab of biaxial Molybdenum Trioxide (MoO 3 ) on top. Hybrid Phonon Polaritons (HPhPs) are formed by the strong coupling between magnetic polaritons of silver grating and phonon polaritons of MoO 3 . Our structure is angle insensitive upto an incidence angle of 30 degrees for both polarization directions. Tuning of HPhPs inside their respective reststrahlen bands is achieved by incorporating a monolayer of graphene. A wide-wavelength range from 10.5 μm to 15 μm, can be actively accessed by varying Fermi potential of graphene and incidence polarization. Moreover, by overlapping structural response with vibrational fingerprints of analytes, enhanced light-matter interaction (SEIRA-based sensing) is achieved, allowing detection of minute amount of analytes (30 nm thick). We have numerically detected five different analytes (30 nm thick) namely Styrene, Dimethyl Methylphosphonate, Polyethylene Terephthalate, Polystyrene and Ethanol, thereby proving the efficacy of our proposed vdWs heterostructure as highly sensitive multi-analyte sensor.