Optical data storage read out at 256 Gbits/in(2)

A new form of read out for high density read-only memory is presented whereby a data density of 400 bits/mu m(2), corresponding to 256 Gbits/in.(2), can be accessed at data rates in the tens of MHz range. The technique is based on detecting the modulation in light scattering from a sharp scattering object due to the dipole-dipole coupling between the probe and surface being scanned using a sensitive homodyne interferometer. Theoretical considerations indicate that data densities in the 100 Tbits/in.(2) range could be accessed at data rates of 100 MHz using this technology. (C) 1997 American Institute of Physics.