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Variable Width Aperture Ion Etching Process

IP.com Disclosure Number: IPCOM000117952D
Original Publication Date: 1996-Jul-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Bates, K: AUTHOR [+2]

Abstract

Disclosed is a method to produce variable groove depth grating waveguide couplers on planar waveguides using ion beam etching and a specially shaped aperture.

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Variable Width Aperture Ion Etching Process

      Disclosed is a method to produce variable groove depth grating
waveguide couplers on planar waveguides using ion beam etching and a
specially shaped aperture.

      Grating couplers can be used to couple light into or out of
planar waveguides.  The intensity profile of the light beam coupled
out of the waveguide can be controlled by varying the grating groove
depth along the waveguide propagation direction.

      An example of a variable groove depth grating profile that will
produce an out-coupled beam with a Gaussian profile is shown in Fig.
1.  The dashed line shows the output beam irradiance profile and the
solid line shows the required variable groove depth grating profile.
A specially shaped aperture is used to control the cross sectional
area of the ion beam impinging upon the planar waveguide (target)
during the ion beam etching process.  The target to be etched moves
along the y axis at a constant velocity, Vt, underneath the specially
shaped aperture.  The specially shaped aperture width, W(x), varies
along the x axis in a precise manner related to the desired grating
groove profile.  The etched grating groove depth, dg(x), is equal to
(W(x)*R)/Vt, where R is the ion beam etching rate.  The desired
grating groove depth profile shown in Fig. 1 can be fabricated by
using a variable width aperture with a width, W(x), equal to dg(x)
*(Vt/R).  This last equation shows that the specially shaped apert...