Method and system for maintaining and controlling the signal-to-noise ratio of hologams recorded in ferroelectric photorefractive materials

The hologram of claim 10, wherein said recording medium is at least one doped ferroelectric, said ferroelectric selected from the group consisting of SBN (Sr.sub.x Ba.sub.1-x Nb.sub.2 O.sub.6), BSKNN (Ba.sub.2-x Sr.sub.x K.sub.1-y Na.sub.y Nb.sub.5 O.sub.15, BSTN (Ba.sub.3-x Sr.sub.x TiNb.sub.4 O.sub.15), SCNN (Sr.sub.2-x Ca.sub.x NaNb.sub.5 O.sub.15), PBN (Pb.sub.x Ba.sub.1-x Nb.sub.2 O.sub.6), BaTiO.sub.3, LiNbO.sub.3, KNbO.sub.3, KTN (Kta.sub.1-x Nb.sub.x O.sub.3), PLZT, and other ferroelectrics having a tungsten bronze crystal structure.

A free-space optical interconnection switch, comprising:

• a plurality of holograms stored in a ferroelectric photorefractive medium, said medium being maintained at a temperature in the vicinity of or above the ferroelectric phase transition temperature during readout;
• and,
• an electric field selectively applied to said holograms during readout for selectively activating at least one of said holograms to diffract light from an input free-space optical channel to one or more output free-space channels.

A dynamic optical wavelength filter comprising:

• a plurality of holograms stored in a ferroelectric photorefractive material, each said hologram active to a state of increased diffraction efficiency by the application of an electric field during readout, and said material being maintained at a temperature in the vicinity of or above the ferroelectric phase transition temperature during readout,
• wherein predetermined wavelengths of light may be selectively diffracted by at least one of said selectively activated holograms.

A holographic data storage system comprising:

• a plurality of holograms stored in a ferroelectric photorefractive material, each said hologram is fixed in said material and activated to a state of increased diffraction efficiency by the application of an electric field to said material during readout, and said material being maintained at a temperature in the vicinity of or above the ferroelectric phase transition temperature during readout.

A recording and reconstruction cycle for a hologram stored in a ferroelectric photorefractive medium comprising:

• exposing said ferroelectric photorefractive medium to an optical interference pattern so as to record a hologram therein,
• fixing said hologram in said medium to substantially maintain the diffraction efficiency during readout, and,
• applying an electric field to said medium during readout to increase the diffraction efficiency of said hologram while maintaining said medium at a temperature in the vicinity of or above the ferroelectric phase transition temperature during readout.