Engineering high Pockels coefficients in thin-film strontium titanate for cryogenic quantum electro-optic applications.

Ulrich, Anja; Brahim, Kamal; Boelen, Andries; Debaets, Michiel; Khalil, Ahmed; Sun, Conglin; Huang, Yishu; Saseendran, Sandeep Seema et al. · Science · 2025

basic_science · Level V

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Abstract

Pockels materials are notable for their strong electro-optic interaction and rapid response times and are therefore used extensively in optical communications. However, at cryogenic temperatures, Pockels coefficients are reduced in many materials optimized for room-temperature operation, which is a major hurdle for emerging quantum technologies. Here, we show that strontium titanate (SrTiO<sub>3</sub>) can be engineered to exhibit a Pockels coefficient of 345 picometers per volt at 20 hertz at cryogenic temperatures, a value twice as high as any other thin-film electro-optic material. By adjusting the stoichiometry, we were able to increase the Curie temperature and realize a ferroelectric phase yielding a high Pockels coefficient, so far with limited optical losses of decibels per centimeter. Our findings position SrTiO<sub>3</sub> as a promising material for cryogenic quantum photonics applications.