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

A three-dimensional optical memory element which is made of glass, said element comprising:

• a glass matrix which has a first refractive index;
• and
• a three-dimensional structure having a plurality of layers, each of said layers including a plurality of spots two-dimensionally distributed in said glass matrix, each of said spots having a second refractive index different from said first refractive index.

A method of writing information in a three-dimensional optical memory element having a glass matrix, said method comprising the steps of:

• (a) condensing a pulsed laser beam in said glass matrix having a first refractive index;
• (b) during the step (a), three-dimensionally scanning said glass matrix with said pulsed laser beam, such that a plurality of spots which are three-dimensionally distributed in said glass matrix and each of which has a second refractive index different from said first refractive index are prepared.

A method of writing information in a three-dimensional optical memory element having a glass matrix, said method comprising the steps of:

• (a) condensing a pulsed laser beam in said glass matrix havinq a first refractive index;
• (b) during the step (a), three-dimensionally scanning said glass matrix with said pulsed laser beam, such that a plurality of spots which are three-dimensionally distributed in said glass matrix and each of which has a second refractive index different from said first refractive index are prepared,
• wherein, during the step (a), said pulsed laser beam is condensed to focal points in said element so as to prepare, at said focal points, said spots corresponding to said focal points, each focal point having a diameter which is substantially equal to a wavelength of said pulsed laser beam, each spot having a diameter which is equal to or shorter than said wavelength of said pulsed laser beam.