Photon-gated holeburning materials: Directions in high density memory storage

Spectral holeburning based optical memories offered a promise for high density storage and other applications in communication technology more than two decades ago. However, only recently demonstrations of photo-spectral holeburning (PSHB) applications such as fast page oriented image storage with random frame access and several gigabits per square inch memory storage have established the superiority of PSHB technology over the existing ones. At present there are definite barriers to the use of PSHB technology. Although the nature of these barriers and their significance differs from one application to another, problems associated with PSHB materials are the most pressing ones. Developing materials where the temperature of operation, presently at or below liquid helium temperatures, can be raised to room temperature or even liquid nitrogen temperature, without sacrificing the high density of storage, will completely change the outlook for PSHB based technology. So far, rare earth based materials have topped the list for almost all applications of PSHB materials. This paper reviews the progress in developing the rare earth based photon-gated holeburning materials so far and projects future directions for high density spectral holeburning materials.