Abstract: An improved read/write optical disk is disclosed which is capable of being rewritten more than 10.sup.6 times. The disk utilizes a storage medium in which data is stored by causing a localized region of the storage medium to assume one of two states. The two states can be converted from one to another by the application of electric fields to the localized region of the storage medium. The localized region in question is selected by illuminating an area on an addressing layer directly above the region in question with light. The preferred embodiment utilizes a lead lanthanum zirconate titanate material for the storage medium.

Abstract: A method for etching thin films of compostions from the PLZT family which have been deposited on substrates. The film is coated with a photosensitive material which is developed by photolithographic techniques to form a photoresist mask upon the film layer, the photoresist material having a predetermined pattern. The thin film coated substrate with the developed photoresist mask is immersed in a dilute etching solution containing hydrochloric acid and fluorine ion donor for a period of time sufficient to etch that portion of the thin film layer not covered with the developed photoresist, removing the thin film coated substrate after it has been etched, rinsing the substrate and then immersing the substrate in a second etching solution containing a dilute solution of a lead solubilizing medium such as nitric acid, or acetic for a period of time sufficient to remove lead residue remaining from the first etching step.