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/μm2, 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.