We demonstrate that parametric driving of suitable collective modes in cuprate superconductors results in a reflectivity R>1 for frequencies in the low terahertz regime. We propose to exploit this effect for the amplification of coherent terahertz radiation in a laser-like fashion. As an example, we consider the optical driving of Josephson plasma oscillations in a monolayer cuprate at a frequency that is blue-detuned from the Higgs frequency. Analogously, terahertz radiation can be amplified in a bilayer cuprate by driving a phonon resonance at a frequency slightly higher than the upper Josephson plasma frequency. We show this by simulating a driven-dissipative U(1) lattice gauge theory on a three-dimensional lattice, encoding a bilayer structure in the model parameters. We find a parametric amplification of terahertz radiation at zero and nonzero temperature.
@article{arxiv.2109.02612,
title = {Terahertz amplifiers based on gain reflectivity in cuprate superconductors},
author = {Guido Homann and Jayson G. Cosme and Ludwig Mathey},
journal= {arXiv preprint arXiv:2109.02612},
year = {2022}
}