Waveplate-free electro-optic Q-switch enabled by a relaxor-PbTiO₃ crystal

The relaxor ferroelectric PbTiO3 crystals, such as 0.21PIN-0.47PMN-0.32PT (PIN-PMN-32PT), were recently reported in Science376, 371 (2022)10.1126/science.abn7711 as a new class of high-performance electro-optic (EO) materials, yet their potential in practical Q-switching systems remains largely unexplored. Here, we demonstrate for the first time (to the best of our knowledge) a waveplate-free EO Q-switched Nd:YAG laser based on a PIN-PMN-32PT crystal. By thermo-optically tuning the intrinsic birefringence, the crystal provides the required quarter-wave phase retardation without external compensation optics, enabling a simplified and compact cavity design. Benefiting from its ultrahigh EO coefficient (r33 ≈ 900 pm/V), the 1-mm-long device operates at a sub-kilovolt voltage. In a diode-pumped Nd:YAG laser, it delivers pulses with an energy of 790 μJ, a duration of 4.1 ns, and a repetition rate of 1 kHz. These results establish relaxor ferroelectric crystals as a promising platform for compact, low-voltage EO Q-switches.