Observations of self-induced ultraslow light in a persistent spectral hole burning medium.

We present observations of self induced ultraslow light in a persistent spectral hole-burning rare-earth doped crystal. The observed group delay (velocity) is as long as 40 micros (75 m/s), which is comparable to that obtained using electromagnetically induced transparency or coherent population oscillations. We analyze the observed ultraslow light as a function of frequency detuning, light intensity, and atom population (oscillator strength). The present observation of ultraslow light in a persistent spectral hole-burning medium gives potentials to all-optical information processing such as on-demand all-optical buffer memories.