Three-dimensional optical memory element and method of writing information therein

摘要

The invention relates to a three-dimensional optical memory element. This element is made of glass and includes: a glass matrix which has a first refractive index; and a plurality of spots which are three-dimensionally distributed in the glass matrix and each of which has a second refractive index different from the first refractive index. The element is prepared by condensing a pulsed laser beam to focal points in the element so as to prepare, at the focal points, the spots corresponding to the focal points. Each focal point has a diameter which is approximately equal to a wavelength of the pulsed laser beam. The element has a sufficient weatherability and a sufficient resistance to heat and light. It is possible to write information at each spot having a diameter equal to or shorter than the wavelength of the laser beam, with high density and good contrast.