HOLOGRAPHIC RECORDING, USING LIQUID-CRYSTALLINE SIDE-CHAIN POLYMERS

The review describes the principles of a holographic storage process b ased on the liquid crystalline state of organic polymeric materials. S uch materials are capable of forming anisotropic glasses, which can be obtained as thin films. By suitable means one is able to align the op tical axis of the uniaxial system within the film along a given direct ion or parallel to the film normal. A storage process is made possible by incorporating into the polymer a suitable dye-such as azobenzene-c haracterized by the fact that it is able to undergo a light-induced is omerization process even in the solid glassy state. This in turn leads to a reorientation of the optical axis within the film and thus to st rong modifications of the optical properties. The information written- in in this way can be erased either by heating to temperatures above t he glass transition temperature or by light. The paper describes the p hysical processes involved in the storage process and the capability o f such materials to store holograms. Of particular interest is that th e novel type of storage material is not only able to store information on amplitude and phase (scalar properties) of the light but also on t he state of polarization. It may thus be used for polarization hologra phy.