Enhanced Light–Matter Interaction in <sup>10</sup>B Monoisotopic Boron Nitride Infrared Nanoresonators
Marta Autore, Irene Dolado, Peining Li, Rubén Esteban, Francisco Javier Alfaro‐Mozaz, Ainhoa Atxabal, Song Liu, James H. Edgar, Saül Vélez, Fèlix Casanova, Luis E. Hueso, Javier Aizpurua, Rainer Hillenbrand
Abstract
Abstract 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 10 B 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.