EFFECTS OF SUBSTRATE BIREFRINGENCE AND TILT ON THE IRRADIANCE AND PHASE PATTERNS OF THE RETURN BEAM IN MAGNETOOPTICAL DISK DATA-STORAGE

Substrate birefringence in a magneto-optical disk system is shown to h ave a predictable effect on the return beam. The irradiance and phase patterns of the return beam at the exit pupil of the objective lens ar e calculated and experimentally verified for the cases of no substrate birefringence, birefringence aligned with the incident polarization, and birefringence aligned at 45 degrees to the incident polarization. The irradiance at the exit pupil is also calculated (and experimentall y verified) for a grooved substrate for various amounts of substrate t ilt.