Engineering high Pockels coefficients in thin-film strontium titanate for cryogenic quantum electro-optic applications
Anja Ulrich, Kamal Brahim, Andries Boelen, Michiel Debaets, Ahmed E. Khalil, Conglin Sun, Yishu Huang, Sandeep Seema Saseendran, Marina Baryshnikova, Paola Favia, Thomas Nuytten, Stefanie Sergeant, Kasper Van Gasse, Bart Kuyken, Kristiaan De Greve, Clément Merckling, Christian Haffner
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 3 ) 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 3 as a promising material for cryogenic quantum photonics applications.