Magneto-optic readout method and apparatus using polarization sw

Details Magneto-optic readout method and apparatus using polarization sw Magneto-optic readout method and apparatus using polarization sw

1992-05-22

1993-08-10

Heinz, A. J.

Dynamic information storage or retrieval

Storage or retrieval by simultaneous application of diverse...

Magnetic field and light beam

369110, 365122, 2502015, 360 59, G11B 1304, G11B 700

Patent

active

052355705

ABSTRACT:
A method and apparatus for recovering information prerecorded in a vertically magnetized magneto-optic recording element wherein a laser is operated in a state of polarization instability (i.e., its TE and TM losses are equal). The linearly polarized (TE and TM) output of the laser is converted to circularly polarized (left-handed and right-handed) polarized radiation, and the latter is used to scan irradiate the recording element. Upon being reflected by the recording element, the circularly polarized radiation is reconverted to linear polarization and fed back to the laser cavity. Depending on which polarization mode (TE or TM) experiences the lesser loss as a result of the MCD effect, the laser operates in either its TE or TM mode. Means are provided for detecting the instantaneous polarization mode of the laser which, in turn, is indicative of the orientation (up/down) of the magnetic domains scanned by the laser radiation. Being dependent on a media-produced differential absorption of left-handed and right-handed circularly polarized radiation, the polarization switching scheme of the invention is advantageous vis-a-vis similar schemes which rely on small angular changes in the plane of polarization of the reflected beam.

REFERENCES:
patent: 4410277 (1983-10-01), Yamamoto et al.
patent: 4571650 (1986-02-01), Ojima et al.
patent: 4955006 (1990-09-01), Fukushima et al.
patent: 4959821 (1990-09-01), Morimoto et al.
patent: 5153860 (1992-10-01), Sunagawa et al.

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