Optical memory based on the ellipsometric principle

Abstract

An optical three-dimensional multilayer memory device based on the principle is presented. The possibilty to utilize the flexibility of organic layers e. g. conducting polymers will be discussed. PRINCIPLES A concept of an optical three-dimensional memory device based on the ellipsometric principle1 is presented. This effipsometric memory is a thin film multilayez device with an optical read-out. The information is contained in the optical properties of thin films and is read by analyzing the state of polarization ofa polarized light beam reflted at oblique incidence from a memory cell. The device is here examplified with the case of two layers on a substrate which is equivalent to a memory cell capable of storing one 2-bit word. If the optical properties of the two layers can be controlled independently we can generate 4 different of polarization in the reflected beam corresponding to the logical states (0 (0 (1 and (1 ofthe memory cell. In a generalization to n layers it is possible to have 2fl different states. In other words an n-bit word can be stored at one location. Fig. 1. An optical memory device having 2-bit memory cells. With an ellipsometric read-out the state of polarization in the reflected beam is described by the two ellipsometric angles and These angles can be determined with a precision better than 0. 01''. The lateral resolution limiting the memory