Terahertz amplifiers based on gain reflectivity in cuprate superconductors

TL;DR

This paper demonstrates that parametric driving in cuprate superconductors can achieve reflectivity greater than one in the terahertz range, enabling laser-like amplification of terahertz radiation through collective mode excitation.

Contribution

It introduces a novel method to amplify terahertz radiation using parametric driving of collective modes in cuprates, supported by simulations of a driven-dissipative lattice gauge theory.

Findings

Reflectivity exceeds 1 in low terahertz frequencies.

Terahertz radiation can be amplified via driven Josephson plasma oscillations.

Amplification occurs at both zero and nonzero temperatures.

Abstract

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.