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Browse Prior Art Database

Method for Increasing Optical Contrast of Ridge-Wageguide Lasers

IP.com Disclosure Number: IPCOM000105756D
Original Publication Date: 1993-Sep-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 2 page(s) / 62K

Publishing Venue

IBM

Related People

Cohan, MS: AUTHOR [+2]

Abstract

It is sometimes advantageous to increase the optical contrast of features which are delineated on ridge-waveguide lasers; made, for example, by the processes described in [1]. One application where high optical contrast is needed is in passive alignment of laser-fiber modules by the "index alignment" method [2]. Here fiducial marks which are patterned on the laser chip are registered to a glass-alignment plate carrying corresponding fiducial marks; alignment of a fiber-carrier to the alignment plate using the same fiducial-mark registration technique then assures correct laser-fiber alignment.

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Method for Increasing Optical Contrast of Ridge-Wageguide Lasers

      It is sometimes advantageous to increase the optical contrast
of features which are delineated on ridge-waveguide lasers; made, for
example, by the processes described in [1].  One application where
high optical contrast is needed is in passive alignment of
laser-fiber modules by the "index alignment" method [2].  Here
fiducial marks which are patterned on the laser chip are registered
to a glass-alignment plate carrying corresponding fiducial marks;
alignment of a fiber-carrier to the alignment plate using the same
fiducial-mark registration technique then assures correct laser-fiber
alignment.

      A preferred method of fabricating the laser fiducial marks is
to make them out of laser ridge material, using the same masking step
to delineate both the laser ridge and the fiducial marks.  This
"self-alignment" technique ensures that there is no misregistration
error between the laser ridge and the fiducial marks.  In the
original experiments using this method, optical contrast was obtained
simply by depositing gold over both the ridge (for electrical
contact) and the fiducial marks.  However, it was found that a
significant improvement in contrast could be attained by an
alternative method.

      In laser processing, the top ridge surface is protected by
deposition of a  "embedding insulation", which surrounds but does not
overcoat the ridge.  This embedding insulation (which is typically Si
N sub x or SiO&sub2.)  also surrounds and is contiguous to the
fiducial marks which are also made...