Phonon-Polaritons in Nanoscale Waveguides

We investigate the phenomena of Brillouin induced opacity in nanoscale linear waveguides and Brillouin induced transparency in nanoscale ring waveguides. The concept of phonon-polariton is required in order to get a deep understanding of such phenomena. Phonon-polaritons are coherent superposition of photons and phonons obtained in the strong coupling regime induced through stimulated Brillouin scattering in the presence of a pump field. The formation of phonon-polaritons can be observed via linear optical spectra that are calculated here using the input-output formalism. For a linear waveguide the signature of phonon-polaritons appears as two peaks in the transmission spectrum with an opacity gap, and for a ring waveguide as two dips in the transmission spectrum with a transparency gap.