Raman excited spin coherences for high temperature spectral hole burning memories

The possibility of using Raman excited spin coherences to increase the operating temperature of spectral hole burning memories and processors is being explored experimentally. The approach is to store and/or process data using spin coherences excited by optical Raman transitions. This is motivated by the fact that spin coherence lifetimes are much less sensitive to temperature than optical coherence lifetimes. However, direct microwave excitation of spin coherences does not give a high storage density because of the large microwave wavelength. By using optical Raman fields to excite the spin coherences, full optical spatial resolution can be achieved. Initial experiments in Pr doped YSO demonstrated potential for higher temperature operation. Current experiments are concentrating on further increasing the operating temperature using this and other materials.