Szabados, JanJanSzabadosWerner, Christoph S.Christoph S.WernerHerr, Simon J.Simon J.HerrBreunig, IngoIngoBreunigBuse, KarstenKarstenBuse2022-03-062022-03-062020https://publica.fraunhofer.de/handle/publica/26081010.1063/1.5133029Eigenfrequency 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&#8722;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 l = 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.enFrequency Combswhispering gallery resonatorsferroelectric materialselectrooptical effectsKerr Effects621journal article