Bismuth Titanate-Photoconductor Optical Storage Medium.
Final rept. 8 Aug 68-31 Dec 69,
RCA LABS PRINCETON NJ
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The basic feasibility of a bismuth titanate-photoconductor sandwich as a high-resolution read-write optical storage medium has been demonstrated. Pattern and holographic storage has been achieved in a Bi4Ti3O12-ZnSe sandwich. Read-out has been accomplished in both transmission and reflection. The memory sandwich has been built with a-axis poled and also with naturally grown unpoled Bi4Ti3O12 crystals. For the covering electrodes both rf-sputtered tin oxide and thin evaporated metal have been used. Gratings with a period of 1.26 mu have been stored and read out. The best methods of fabrication and the relevant electrical and optical properties of the component parts of the memory sandwich were investigated. The most important electro-optic property discovered was that c-axis reversals cause in depoling of an a-axis poled crystal. The best photoconductive layer was obtained by co-evaporation of ZnSe and ZnCl2 onto Bi4Ti3O12 held at a temperature of 400C. Such layers typically have a peak response at 4900A, a gain of about 0.005 and a response time of less than 5 usec. Author
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