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Proceedings Paper

Q-factor enhancement of integrated lithium-niobate-on-insulator ridge waveguide whispering-gallery-mode resonators by surface polishing
Author(s): Richard Wolf; Ingo Breunig; Hans Zappe; Karsten Buse
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Paper Abstract

Whispering-gallery resonators (WGRs) are most promising for nonlinear-optical frequency-conversion due to their intensity enhancement by small mode volumes and high Q-factors. This has been shown frequently by millimeter-sized diamond-blade cut and polished bulk WGRs. For reproducible batch fabrication, however, the integration of WGRs into lithium-niobate-on-insulator (LNOI) substrates became of great interest. Here we report on integrated WGRs made by batch processes like lithography and reactive-ion etching. Since the Q-factor of integrated WGRs is limited by scattering losses, we focused on developing a polishing process for the waveguide sidewalls that allowed us to enhance the unloaded Q-factors already to more than 106 with room for further improvements. Furthermore we employ a coupling scheme with two waveguide chips, one comprising a linear coupling waveguide and one with the integrated WGR. By adjusting the distance between the coupling waveguide and the WGR, we can reproducibly and stably tune the coupling-efficiency between 0 and 95 %.

Paper Details

Date Published: 20 February 2017
PDF: 6 pages
Proc. SPIE 10090, Laser Resonators, Microresonators, and Beam Control XIX, 1009002 (20 February 2017); doi: 10.1117/12.2251516
Show Author Affiliations
Richard Wolf, Univ. of Freiburg (Germany)
Ingo Breunig, Univ. of Freiburg (Germany)
Hans Zappe, Univ. of Freiburg (Germany)
Karsten Buse, Univ. of Freiburg (Germany)
Fraunhofer Institute for Physical Measurement Techniques IPM (Germany)

Published in SPIE Proceedings Vol. 10090:
Laser Resonators, Microresonators, and Beam Control XIX
Alexis V. Kudryashov; Alan H. Paxton; Vladimir S. Ilchenko, Editor(s)

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