Net on-chip Brillouin gain based on suspended silicon nanowires

Abstract

The century-old study of photon-phonon coupling has seen a remarkable revival\nin the past decade. Driven by early observations of dynamical back-action, the\nfield progressed to ground-state cooling and the counting of individual\nphonons. A recent branch investigates the potential of traveling-wave,\noptically broadband photon-phonon interaction in silicon circuits. Here, we\nreport continuous-wave Brillouin gain exceeding the optical losses in a series\nof suspended silicon beams, a step towards selective on-chip amplifiers. We\nobtain efficiencies up to $10^{4} \\, \\text{W}^{-1}\\text{m}^{-1}$, the highest\nto date in the phononic gigahertz range. We also find indications that\ngeometric disorder poses a significant challenge towards nanoscale phonon-based\ntechnologies.\n