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Waveguide Frequency Doubler using Transverse Electric Modes

IP.com Disclosure Number: IPCOM000116119D
Original Publication Date: 1995-Aug-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 84K

Publishing Venue

IBM

Related People

Risk, WP: AUTHOR

Abstract

Waveguide frequency doublers based on the quasi-phasematching technique use periodic inversion of the ferroelectric domains of a nonlinear crystal to achieve phasematching for second-harmonic generation. This domain inversion is typically produced by applying some treatment to the crystal faces that are perpendicular to the polar axis of the crystal. For example, ion-exchange of certain species on the -z face is known to produce domain inversion in lithium niobate, lithium tantalate, and potassium titanyl phosphate is known to produce domain inversion in a shallow layer near the -z surface. Scanning of an electron beam across the -z faces has been demonstrated to produce deep inverted domains, as has application of an electric field across the thickness of a z-cut crystal.

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Waveguide Frequency Doubler using Transverse Electric Modes

      Waveguide frequency doublers based on the quasi-phasematching
technique use periodic inversion of the ferroelectric domains of a
nonlinear crystal to achieve phasematching for second-harmonic
generation.  This domain inversion is typically produced by applying
some treatment to the crystal faces that are perpendicular to the
polar axis of the crystal.  For example, ion-exchange of certain
species on the -z face is known to produce domain inversion in
lithium niobate, lithium tantalate, and potassium titanyl phosphate
is known to produce domain inversion in a shallow layer near the -z
surface.  Scanning of an electron beam across the -z faces has been
demonstrated to produce deep inverted domains, as has application of
an electric field across the thickness of a z-cut crystal.  This
periodic domain inversion provides quasi-phasematching for the d[33]
nonlinear coefficient, which is the largest component of the
nonlinear tensor for the three materials mentioned above.
Traditionally, waveguides are also fabricated on the z-face by an
ion-exchange process.  This results in a structure that converts
infrared light in a Transverse Magnetic (TM) mode of the waveguide to
blue light, also in a TM mode.

      This orientation presents a problem if the doubler is to be
monolithically integrated with a diode laser, as shown in Fig. 1.
The laser emission from a diode laser has the TE polarization, i.e.,
is polarized parallel to the diode laser junction, which is in turn
parallel to the common submount.  The waveguide doubler requires
light polarized perpendicular to the common submount.  Although the
diode laser can be forced to lase with a TM polarization in some
cases, the stability of the forced TM-mode oscillation is unclear.
Hence, it is hi...