Time domain optical memories using rare earth ions

Rare earth doped crystals have many attractive characteristics for use in time-domain optical memories. However, the memories rely on the spectral holeburning process which is inefficient in the case of rare earth systems and results in weak signals. The situation can be improved by multiple writing of the data using a laser with good frequency and phase stability. In this work an ultra-stable laser has been developed and efficient and repeatable accumulated echoes are demonstrated with delays over 100 μs in a sample of Y₂SiO⁵:Eu³⁺.