Two-dimensional space-time terahertz memory in bulk SrTiO3

Polarizable materials with ultrafast responses are of great interest for the development of new sensors and memories under the influence of an electromagnetic field. Recent research efforts have demonstrated the role of optical excitation and intense terahertz (THz) pulses in inducing an ultrafast polar order and revealing a hidden phase transition in SrTiO3 (STO), respectively. Here we show that the surfaces of STO crystals at room temperature act as ultrafast sensors that enable sub-picosecond switching through the Kerr effect and recording of polar THz intensity with spatial resolution below the diffraction limit through THz-field-induced dipole alignment followed by multi-picosecond relaxation time recovery. The contrast sensitivity and spatial resolution achieved by the STO sensor are significantly superior to those of present-day near-field THz sensors based on the linear Pockels effect, and more importantly, its ability to remain polarized for several picoseconds opens the door to a new strategy for building an ultrafast space-time THz memory. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement