Abstract

The backward stimulated echo has been considered as a novel high-speed high-density optical data storage method. But its potential application has been confined to transient dynamic memory because of relatively short lifetime of optical coherence inside low-temperature solids. Here we report the longest observed storage time of at least six hours in the 581.8 nm⁷F₀-⁵D₀ transition of eu³⁺ -doped YAlO₃ crystal at 2°K. The experiments are performed using YAG-pumped pulsed dye lasers, beamsplitters and optical delay lines to produce five DATA pulses, at 20 nsec intervals, and WRITE and READ pulses. The measured echo intensity as a function of storage time has exponential decay time of 3.8 hours. This very long storage time is due to the very small effective nuclear magnetic moments of Eu³⁺ ions, and is consistent with the long lifetime of spectral hole in this system. We also observed that the signal fidelity is not noticeably affected by the number of DATA pulses and the long storage time.

© 1988 Optical Society of America