Browse Prior Art Database

Optical Storage Head for Phase-Change Media

IP.com Disclosure Number: IPCOM000119941D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Related People

Bona, GL: AUTHOR [+2]

Abstract

A compact head for use in optical storage systems is proposed which uses a mircrolens for beam focussing and simple integrated beam splitters and mirrors realized by trenches etched in a planar waveguide. This storage head has the advantage over known structures that no diffraction gratings with small grating periods and associated tight manufacturing tolerances are required. Furthermore, microlenses have been shown to produce spot sizes close to the theoretical diffraction limit.

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Optical Storage Head for Phase-Change Media

      A compact head for use in optical storage systems is
proposed which uses a mircrolens for beam focussing and simple
integrated beam splitters and mirrors realized by trenches etched in
a planar waveguide.  This storage head has the advantage over known
structures that no diffraction gratings with small grating periods
and associated tight manufacturing tolerances are required.
Furthermore, microlenses have been shown to produce spot sizes close
to the theoretical diffraction limit.

      The principle of the proposed storage head is shown in the
figure.  All optical components with the exception of the external
microlens are integrated on the same substrate. The optical signal
emitted by a laser diode is coupled to a passive optical waveguide
layer (WG) where it is directed onto a double beam splitter (BS).  In
the forward pass of the optical beam, the deflected portion of the
beam is not used.  The remaining light is deflected via an etched
45-degree mirror (VM) to the external microlens for focussing onto
the disk surface.  With an elliptical lens the different beam
divergence angles can be corrected to form a circular spot.  The
light reflected from the disk surface is then coupled back to the
passive waveguide via the microlens and vertical mirror (VM).  The
returning light beam is then split in half by the beam splitter (BS)
and directed to the gaps between pairs of closely spaced photodiodes
(PD1,2 and...