Optically gated two-photon recording and nonvolatile readout in volume holographic data storage uses a pair of mutually incoherent light sources during recording and only one for readout. Substantial (up to two orders of magnitude) improvement in two-photon recording sensitivity can be achieved in stoichiometric partially reduced lithium niobate. By adding certain deep donor dopants (Fe and Mn) to near- stoichiometric LiNbO3 we can increase dark storage time and gating efficiency compared with undoped material. The recording mechanism involves small polarons as metastable shallow species and bipolarons (in undoped material) or extrinsic donors (in Fe- or Mndoped material) as deep levels.
© 1999 Optical Society of AmericaPDF Article