An optical data storage system that utilizes the frequency dimension to increase the storage capacity. The storage system has a storage material which contains a guest material such as cinnoline, which is dissolved in a host material such as naphthalene. This storage material system exhibits an inhomogeneous absorption line broadening and undergoes a photochemical reaction upon exposure to light.

Information is stored by a process involving the steps of (1) sensitizing a recording medium comprising a two-photon, four-level material by exposing said medium to flood illumination with ultra-violet or visible light, and then (2) exposing the sensitized medium simultaneously to two beams of coplanar laser irradiation intersecting within said recording medium to create a microscopic interference pattern.

A process and recording medium for four-level, two-photon holography are provided. These media are particularly useful for recording holograms using continuous wave lasers. The recording medium is formed by a transport resin containing a tetrazine compound.

A gated self-developing, non-bleachable holographic material is disclosed which is useful in the infrared region. The holographic material comprises a polymeric matrix with an .alpha.-diketone compound uniformly dispersed therein.

The present invention relates to an improved process for producing photorefractive net gain two beam coupling utilizing polymeric materials.