Observation of Ultraslow and Stored Light Pulses in a Solid

We report ultraslow group velocities of light in an optically dense crystal of Pr doped ${\mathrm{Y}}_2{\mathrm{SiO}}_5$. Light speeds as slow as 45 m/s were observed, corresponding to a group delay of 66 μs. Deceleration and “stopping” or trapping of the light pulse was also observed. These reductions of the group velocity are accomplished by using a sharp spectral feature in absorption and dispersion that is produced by resonance Raman excitation of a ground-state spin coherence.