Photonic-chip-based tunable slow and fast light via stimulated Brillouin scattering

The ability to control the speed of light on an optical chip is fundamental to the development of nanophotonic components for alloptical signal processing and sensing [1-7]. However this is a significant challenge, because chip-scale waveguides require very large changes in group index (Δng) to achieve appreciable pulse delays. Here, we use Stimulated Brillouin Scattering (SBS) to report the demonstration of on-chip slow, fast and negative group velocities with Δng ranging from -44 to +130, and delays of up to 23ns at a pump power of ∼300mW and propagation length of 7cm. These results are obtained using a highly-nonlinear chalocogenide (As2S3) rib waveguide, in which the confinement of both photons and phonons results in strong interaction. SBS can be used to achieve controllable pulse delays at room temperature over a large wavelength and signal-bandwidth [5]. These results open up a new set of photonic applications ranging from microwave photonics [8] to spectrometry [4]