Browse Prior Art Database

Magneto-optic Head with Fiber Pick Up and Frequency Modulated Signal Detection

IP.com Disclosure Number: IPCOM000107836D
Original Publication Date: 1992-Mar-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 1 page(s) / 41K

Publishing Venue

IBM

Related People

Lean, EG: AUTHOR [+2]

Abstract

Disclosed is a fiber/magneto-optic recording head with frequency-modulated signal detection using the magneto-optic disk as one side of a laser cavity.

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This is the abbreviated version, containing approximately 83% of the total text.

Magneto-optic Head with Fiber Pick Up and Frequency Modulated Signal Detection

       Disclosed is a fiber/magneto-optic recording head with
frequency-modulated signal detection using the magneto-optic disk as
one side of a laser cavity.

      Current magneto-optic recording heads require a large moving
mass of optical and detection components.  Recently a novel detection
scheme has been demonstrated, using the magneto-optic disk as one
side of an external cavity laser diode.  The Kerr effect induces a
phase difference between incident left- and right-hand circular
polarized light that results in two different lasing frequencies
coexisting in the cavity.  Interference in the two modes yields a
beat frequency corresponding to the presence of a magnetic domain,
thereby allowing a single detector to do the job of the quadrant
detector and beam splitters found in conventional heads.

      The disclosed head concept incorporates this novel detection
scheme in a flyable, low-profile magneto-optic head with very low
moving mass.  Since the beat frequency depends only on the path
difference between the two polarizations, an optical fiber can serve
as a link between a fixed laser diode and a flyable head containing
only a lens and a small quarter-wave plate.  Flying the head
eliminates the focussing servo mechanism, and is only possible if the
head is very light.  A phase-locked loop slewing with the best
frequency would detect magnetic transitions as abrupt cha...