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Electro-optic eigenfrequency tuning of potassium tantalate-niobate microresonators

: Szabados, Jan; Werner, Christoph; Herr, Simon J.; Breunig, Ingo; Buse, Karsten

Volltext ()

APL photonics 5 (2020), Nr.1, Art. 016106, 7 S.
ISSN: 2378-0967
Zeitschriftenaufsatz, Elektronische Publikation
Fraunhofer IPM ()
Frequency Combs; whispering gallery resonators; ferroelectric materials; electrooptical effects; Kerr Effects

Eigenfrequency tuning in microresonators is useful for a range of applications including frequency-agile optical filters and tunable optical frequency converters. In most of these applications, eigenfrequency tuning is achieved by thermal or mechanical means, while a few non-centrosymmetric crystals such as lithium niobate allow for such tuning using the linear electro-optic effect. Potassium tantalate-niobate (KTa1−xNbxO3 with 0 ≤ x ≤ 1, KTN) is a particularly attractive material for electro-optic tuning purposes. It has both non-centrosymmetric and centrosymmetric phases offering outstandingly large linear as well as quadratic electro-optic coefficients near the phase transition temperature. We demonstrate whispering-gallery resonators made of KTN with quality factors of Q > 107 and electro-optic eigenfrequency tuning of more than 100 GHz at λ = 1040 nm for moderate field strengths of E = 250 V/mm. The tuning behavior near the phase transition temperature is analyzed by introducing a simple theoretical model. These results pave the way for applications such as electro-optically tunable microresonator-based Kerr frequency combs.