Various sources of noise in optical data storage systems

Noise in optical disk readout has been examined for different polarization of the incident beam. The disk studied is a bare grooved glass substrate. Measurements are done for E/sub /spl par// (parallel to track) and E/sub /spl perp// (tangential to track) polarization, using both differential magneto-optical (MO) readout and phase-change (PC) reflectivity readout. The incident beam of light is focused on the grooved-surface of the bare substrate either through substrate or directly from the air. Experiments reveal that the noise level is dependent on both the state of polarization and on the medium of incidence.