Superradiance from spectrally tailored absorption lines in a cavity

Superradiance is a coherent emission phenomenon from an ensemble of emitters that share a collective excitation, and has potential applications in quantum metrology, quantum communication, and quantum computing. We demonstrate superradiant emission in a thulium-doped yttrium aluminium garnet (Tm:YAG) crystal, whose input and output faces are reflection coated to form a cavity that satisfies the impedance matching condition for light on resonance with the Tm transition line. This implementation allows us to observe superradiant emission in the low optical depth regime (OD approx. 1). We engineer the characteristic decay of the superradiant emission by tailoring the inhomogeneously broadened spectrum of Tm:YAG into absorption lines with different shapes, depths, and widths, and perform simulations over a wide range of parameters. We extend this investigation and discuss the possibility of a broadband quantum memory based on superradiance for long-distance quantum networks.