Dual-Band Coupling of Phonon and Surface Plasmon Polaritons with Vibrational and Electronic Excitations in Molecules

Strong coupling (SC) between light and matter excitations bears intriguing potential for manipulating material properties. Typically, SC has been achieved between mid-infrared (mid-IR) light and molecular vibrations or between visible light and excitons. However, simultaneously achieving SC in both frequency bands remains unexplored. Here, we introduce polaritonic nanoresonators (formed by h-BN layers on Al ribbons) hosting surface plasmon polaritons (SPPs) at visible frequencies and phonon polaritons (PhPs) at mid-IR frequencies, which simultaneously couple to excitons and molecular vibrations in an adjacent layer of CoPc molecules, respectively. Employing near-field optical nanoscopy, we demonstrate the colocalization of near fields at both visible and mid-IR frequencies. Far-field transmission spectroscopy of the nanoresonator structure covered with a layer of CoPc molecules shows clear mode splittings in both frequency ranges, revealing simultaneous SPP-exciton and PhP-vibron coupling. Dual-band SC may offer potential for manipulating coupling between exciton and molecula r vibration in future optoelectronics, nanophotonics, and quantum information applications.

Automated summary

Strong coupling between light and matter excitations in both mid-IR and visible frequency bands is achieved by introducing polaritonic nanoresonators, which can manipulate material properties and have potential applications in optoelectronics, nanophotonics, and quantum information.