Illustration of a quantum paraelectric lens (cross-section) that focuses light pulses with frequencies from 5-15 terahertz. Incoming terahertz light pulses (red, top left) are converted into surface phonon-polaritons (yellow triangles) by ring-shaped polymer gratings and disk resonators (grey) atop a substrate of strontium titanate (blue). The width of the yellow triangles represents the increasing electric field of the phonon-polaritons as they propagate through each grating interval prior to reaching the disk resonator that focuses and enhances outgoing light (red, top right). A model of the atomic structure of a strontium titanate molecule at bottom left depicts the movement of titanium (blue), oxygen (red) and strontium (green) atoms in the phonon-polariton oscillation mode.