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Dielectric Overlayer for TE-Mode Suppression in Potassium Titanyl Phosphate Waveguide Frequency Doublers

IP.com Disclosure Number: IPCOM000113067D
Original Publication Date: 1994-Jul-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 74K

Publishing Venue

IBM

Related People

Kurdi, B: AUTHOR [+3]

Abstract

Waveguides fabricated by rubidium-potassium ion exchange in potassium titanyl phosphate (KTP) guide both TE and TM modes. For integration of a frequency doubling waveguide with a semiconductor diode laser in an external cavity configuration, it is desirable for the waveguide to support only the TM modes. The waveguide can then act as an intracavity polarizer to force the laser diode to oscillate in a TM mode, permitting integration of the waveguide "chip" and semiconductor laser "chip" on a common submount.

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Dielectric Overlayer for TE-Mode Suppression in Potassium Titanyl
Phosphate Waveguide Frequency Doublers

      Waveguides fabricated by rubidium-potassium ion exchange in
potassium titanyl phosphate (KTP) guide both TE and TM modes.  For
integration of a frequency doubling waveguide with a semiconductor
diode laser in an external cavity configuration, it is desirable for
the waveguide to support only the TM modes.  The waveguide can then
act as an intracavity polarizer to force the laser diode to oscillate
in a TM mode, permitting integration of the waveguide "chip" and
semiconductor laser "chip" on a common submount.

      Due to the birefringence of KTP, the TM modes have effective
indices that are approximately 0.1 greater than those of the TE
modes.  Hence, deposition of a dielectric film having a refractive
index greater than the effective indices of the TE modes but lower
than the effective indices of the TM modes can create a composite
waveguide structure in which the TE modes are guided in the
dielectric film and the TM modes are guided in the ion-exchanged
channel.  This spatial separation of the TE and TM modes makes it
possible for the waveguide to produce polarization discrimination
(Fig. 1).

      This composite waveguide structure has several properties that
reduce the amount of TE-polarized light fed back to the laser diode.
When the input light is mode matched for the excitation of the
TM&sub0.&sub0.  mode, the excitation of the TE modes is inefficient
because of the spatial separation of the TE and TM modes in the
direction perpendicular to the interface between the film and
substrate.   Furthermore, light that i...