Two-way interconversion of millimeter-wave and optical fields in Rydberg gases

TL;DR

This paper demonstrates a highly efficient method for converting millimeter-wave and optical fields using cold Rydberg gases, leveraging long Rydberg state lifetimes and quantum interference effects.

Contribution

It introduces a novel six-wave mixing process enabling bidirectional frequency conversion between millimeter waves and optical fields in Rydberg gases.

Findings

Conversion efficiency can exceed 90%.

Applicable to a broad spectrum of millimeter waves.

Two implementation schemes are discussed.

Abstract

We show that cold Rydberg gases enable an efficient six-wave mixing process where terahertz or microwave fields are coherently converted into optical fields and vice versa. This process is made possible by the long lifetime of Rydberg states, the strong coupling of millimeter waves to Rydberg transitions and by a quantum interference effect related to electromagnetically induced transparency (EIT). Our frequency conversion scheme applies to a broad spectrum of millimeter waves due to the abundance of transitions within the Rydberg manifold, and we discuss two possible implementations based on focussed terahertz beams and millimeter wave fields confined by a waveguide, respectively. We analyse a realistic example for the interconversion of terahertz and optical fields in rubidium atoms and find that the conversion efficiency can in principle exceed 90\%.