Electro-optic tuning of potassium tantalate-niobate whispering gallery resonators

摘要

Most centrosymmetric materials exhibit a neglectable electro-optic response; the Pockels coefficients are zero, while the DC-Kerr coefficients are typically small. For a standard material such as silica they are on the order of 10~(-22) m~2/V~2. Thus, refractive index tuning is achieved by thermal or mechanical means. Potassium tantalate-niobate (KTa_(1-x)Nb_xO_3 with 0 ＜ x ＜ 1, KTN) is a rare exception. It offers outstandingly high DC-Kerr coefficients in the 10~(-15) m~2/V~2 range. In this contribution, the first-ever KTX whispering gallery resonators (WGR) are demonstrated with quality factors Q ＞ 10~7 and electro-optic eigenfrequency tuning of more than 100 GHz at A = 1040 nm for moderate field strengths of 250 V/mm. These results potentially pave the way for applications such as electro-optically tunable Kerr frequency combs.