Electro-optic eigenfrequency tuning of potassium tantalate-niobate microresonators

Abstract

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 (${\mathrm{KTa}}_{1-x}{\mathrm{Nb}}_x{\mathrm{O}}_3$ with $0\le x\le 1$, 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 (WGRs) made of KTN with quality factors of $Q>10^7$ and electro-optic eigenfrequency tuning of more than 100 GHz at $\lambda =1040$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.

arXiv commentLetter, 4 figures, 6 pages

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