Browse Prior Art Database

Grating-Coupled Light-Emitting Device

IP.com Disclosure Number: IPCOM000119904D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Gfeller, F: AUTHOR [+2]

Abstract

Disclosed is a structure for a grating-coupled surface-emitting light- emitting device which avoids the need for sub-micrometer gratings with critical tolerances in that the waveguided beam is coupled, at a shallow angle, into the transparent device substrate rather than directly into air, and then deflected out vertically.

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Grating-Coupled Light-Emitting Device

      Disclosed is a structure for a grating-coupled
surface-emitting light- emitting device which avoids the need for
sub-micrometer gratings with critical tolerances in that the
waveguided beam is coupled, at a shallow angle, into the transparent
device substrate rather than directly into air, and then deflected
out vertically.

      Integrated focussing gratings are useful for eliminating bulky
lenses.  However, the grating-period required to deflect a waveguided
beam directly into air from a GaAs substrate is about 0.3 micron.
This is at the limit of available patterning technologies and becomes
a serious problem since patterning errors cause severe abberations of
the focused spot.

      The proposed device is illustrated in Figs. 1A and 1B. It
comprises a laser 1, for example, an InGaAs/AlGaAs strained
quantum-well structure, emitting a light beam at a wavelength where
the GaAs substrate 2 is transparent.  The beam is guided by means of
a waveguide 3 to diffraction grating 4 which is used to focus and
couple the light, at a shallow angle, into the substrate.  The
phase-matching conditions to be satisfied allow a grating with a
period of about 6 to 14 microns.  The corresponding line widths are
about 3 to 7 microns.  These dimensions can be fabricated with high
precision using conventional lithography. Superior lens performance
is obtained.  The focused beam is then deflected out vertically using
an etched or pol...