A New Magneto-Optic Readout Technique with High Speed and High Sensitivity

A new magneto-optic readout technique is proposed, giving high-speed, highly-sensitive readout of magnetic information stored in a recording medium with a relatively small magneto-optic rotation power. This technique is essentially a polarization modulation technique (which gives highly-sensitive readout) combined with the differential method (which gives high-speed readout). The new technique enables us to detect a magneto-optic rotation angle as small as 9' at a signal-to-noise ratio (SNR) of 45 dB in a 100 kHz bandwidth at 3 mW laser power (λ =632.8 nm). This value of the SNR is 15 dB larger than that obtained by the conventional differential method.