Hard Materials Seminar - "Probing Cryogenic Thin-film Electro-Optic Response for Quantum Transduction"

Quantum interconnects require strongly responsive electro-optic (EO) materials at cryogenic temperatures for efficient quantum transduction. Here, we investigate two promising material systems. The first is a quantum paraelectric perovskite SrTiO₃ (STO), which shows a remarkably strong EO response in bulk form, but whose thin-film EO properties have not been studied. The second is the EO polymer JRD1, which combines a low dielectric constant with a high Pockels coefficient, and whose EO response appears to persist at cryogenic temperatures in device-level studies. However, the EO response of thin films depends strongly on their synthesis and processing. Therefore, direct measurement of the Pockels coefficient is essential to assess film quality. To probe these materials directly, we built an in-house Polarizer-Sample-Compensator-Analyzer (PSCA) setup to measure Pockels coefficients of thin films. We validated the setup on a bulk LiNbO₃ sample and are now extending the measurements to thin-film LiNbO₃. We will then apply the setup to thin-film STO and JRD1 at cryogenic temperatures. These measurements will help identify EO materials better suited to efficient cryogenic quantum transduction.