Magneto-optic readout method and apparatus using polarization switching of readout beam
US5235570A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 22, 1992 |
| Grant date | Aug 10, 1993 |
| Priority date | — |
| Expiry date | May 22, 2012 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B11/10545
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
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 th…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.