Superradiance for Atoms Trapped along a Photonic Crystal Waveguide

We report observations of superradiance for atoms trapped in the near field of a photonic crystal waveguide (PCW). By fabricating the PCW with a band edge near the D-1 transition of atomic cesium, strong interaction is achieved between trapped atoms and guided-mode photons. Following short-pulse excitation, we record the decay of guided-mode emission and find a superradiant emission rate scaling as (Gamma) over bar (SR) proportional to (N) over bar Gamma(1D) for average atom number 0.19 less than or similar to(N) over bar less than or similar to 2.6 atoms, where Gamma(1D)/Gamma' = 1.0 +/- 0.1 is the peak single-atom radiative decay rate into the PCW guided mode, and Gamma' is the radiative decay rate into all the other channels. These advances provide new tools for investigations of photon-mediated atom-atom interactions in the many-body regime.