EP0107754A1
Expired / Lapsed
EP
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Apparatus for magneto-optical information storage
Assignee: Hitachi Ltd
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Filing: 1983-07-22
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Granted: —
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Expires: 2003-07-22
Abstract
Abstract An optical information storage apparatus wherein information is read from a magnetooptical storage medium (31) by exploiting the self-coupling effect of a semiconductor laser (10); characterized in that a Faraday rotator (9) is disposed in an optical path along which reflected light from the magnetooptical storage medium (31) returns to the semiconductor laser (10), the polarization rotating angle of the Faraday rotator (9) being selected so that the oscillating polarization plane of the semiconductor laser (10) may change depending upon the perpendicular magnetization direction of the magnetooptical storage medium (31), and that a linear polarizer (7) is interposed between the semiconductor laser (10) and a photodetector (4), to detect a polarization component parallel or vertical to the junction plane of the semiconductor laser (10) device by means of the photodetector (4).
Inventors
- 👤 Masahiro Ojima
- 👤 Toshio Niihara
- 👤 Hideo Fujiwara
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-03 09:17
CPC Classifications
G; G11; G11B; G11B11/00; G11B11/10; G11B11/105; G11B11/10532
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
186 words
In an optical information storage apparatus having a semiconductor laser (10) which irradiates a magnetically anisotropic storage medium (31) with a first laser beam (A), information being recorded in the storage medium (31) owing to a change in a magnetic direction, and which generates a second laser beam (B) self-coupled by reflected light from the storage medium, and photodetection means (4) to receive the second laser beam and to convert it into an electric signal; an optical information storage apparatus characterized by comprising a Faraday rotator (9) which is arranged in an optical path along which the reflected light from said storage medium (31) returns to said semiconductor laser, a polarization rotating angle of said Faraday rotator being selected so that a polarization plane of the second laser beam (B) may change depending upon the magnetized direction of said storage medium, and an analyzer (7) which is interposed between said semiconductor laser (10) and said photodetection means (4) and which takes out of the second laser beam (B) at least one of polarization components parallel and vertical to a junction plane of said semiconductor laser (10).
Claim 2
Dependent Claim
186 words
In an optical information storage apparatus having a semiconductor laser (10) which irradiates a magnetically anisotropic storage medium (31) with a first laser beam (A), information being recorded in the storage medium (31) owing to a change in a magnetic direction, and which generates a second laser beam (B) self-coupled by reflected light from the storage medium, and photodetection means (4) to receive the second laser beam and to convert it into an electric signal; an optical information storage apparatus characterized by comprising a Faraday rotator (9) which is arranged in an optical path along which the reflected light from said storage medium (31) returns to said semiconductor laser, a polarization rotating angle of said Faraday rotator being selected so that a polarization plane of the second laser beam (B) may change depending upon the magnetized direction of said storage medium, and an analyzer (7) which is interposed between said semiconductor laser (10) and said photodetection means (4) and which takes out of the second laser beam (B) at least one of polarization components parallel and vertical to a junction plane of said semiconductor laser (10).
Claim 3
Dependent Claim
21 words
An optical information storage apparatus according to claim 1, wherein said Faraday rotator (9) is made of an optically-transparent ferromagnetic material.
Claim 4
Dependent Claim
37 words
An optical information. storage apparatus according to claim 2, wherein said optically-transparent ferromagnetic material is a member selected from the group consisting of Y 3 Fe 5 O 12 and Gd 2 BiFe 5 O 12 .
Claim 5
Dependent Claim
36 words
An optical information storage apparatus according to claim 1, wherein said semiconductor laser (10) is a buried-heterostructure semiconductor laser in which a facet (10a) emitting the first laser beam is provided with an antireflection coating (12).
Claim 6
Dependent Claim
33 words
An optical information storage apparatus according to claim 1, wherein said analyzer (7) is a linear polarizer which has a polarization transmitting plane vertical to the junction plane of said semiconductor laser (10).
Claim 7
Dependent Claim
32 words
An optical information storage apparatus according to claim 1, wherein said analyzer (7) is a linear polarizer which has a polarization transmitting plane parallel to the junction plane of said semiconductor laser.
Claim 8
Dependent Claim
27 words
An optical information storage apparatus according to claim 1, wherein said analizer (7) is a polarization prism which takes out both the parallel and vertical polarization components.
Claim 9
Dependent Claim
55 words
An optical information storage apparatus according to claim 7, wherein said photodetection means is composed of first and second photodetectors (41, 42) which receive the parallel and vertical polarization components taken out by said polarization prism, respectively, and means (8) for obtaining a difference between outputs of both said photodetectors (41, 42) is further comprised.
Claim 10
Dependent Claim
81 words
An optical information storage apparatus according to claim 1, wherein said analyzer is composed of a beam splitter (51) which splits the second laser beam in two, a first linear polarizer (71) which takes out the polarization component parallel to the junction plane of said semiconductor laser from one of the split laser beams, and a second linear polarizer (72) which takes out the polarization component vertical to the junction plane of said semiconductor laser from the other split laser beam.
Claim 11
Dependent Claim
52 words
An optical information storage apparatus according to claim 9, wherein said photodetection means is composed of first and second photodetectors (41, 42) which receive transmitted lights through said first and second linear polarizers, respectively, and means (8) for obtaining a difference between outputs of both said photodetectors (41, 42) is further comprised.
References Cited (Backward Citations)
US4005259A
Cited
US4190775A
Cited
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