Enhanced Light-Matter Interaction In B-10 Monoisotopic Boron Nitride Infrared Nanoresonators

Phonon-polaritons, mixed excitations of light coupled to lattice vibrations (phonons), are emerging as a powerful platform for nanophotonic applications. This is because of their ability to concentrate light into extreme sub-wavelength scales and because of their longer phonon lifetimes compared to their plasmonic counterparts. In this work, the infrared properties of phonon-polaritonic nanoresonators made of monoisotopic B-10 hexagonal boron nitride (h-BN) are explored, a material with increased phonon-polariton lifetimes compared to naturally abundant h-BN due to reduced photon scattering from randomly distributed isotopes. An average relative improvement of 50% of the quality factor of monoisotopic h-BN nanoresonators is obtained with respect to nanoresonators made of naturally abundant h-BN, allowing for the sensing of nanometric-thick films of molecules through both surface-enhanced absorption spectroscopy and refractive index sensing. Further, even strong coupling between molecular vibrations and the phonon-polariton resonance in monoisotopic h-BN ribbons can be achieved.