A Superradiant Maser with Nitrogen-Vacancy Center Spins

TL;DR

This paper proposes a superradiant maser using nitrogen-vacancy center spins in microwave resonators, predicting ultra-narrow linewidths below millihertz through moderate incoherent pumping of a large spin ensemble at low temperatures.

Contribution

It introduces the concept of a superradiant maser with NV center spins, demonstrating theoretical feasibility and robustness against inhomogeneous broadening.

Findings

Linewidth below millihertz achievable with moderate pumping

Superradiant masing persists despite inhomogeneous broadening

Numerical and analytical models elucidate parameter dependence

Abstract

Recent experiments have demonstrated Rabi-oscillations, superradiant pulses and stimulated emission from negatively-charged nitrogen-vacancy ($\mathrm{NV}^{-}$) center spins in microwave resonators. These phenomena witness the kind of collective and strong coupling which has been prerequisite for observation of superradiant lasing in the optical frequency regime. In this article, we investigate the possibility to employ coherence, present in both the collective $\mathrm{NV}^{-}$ spin ensemble and the microwave field, to achieve a superradiant maser. Our calculations show that a superradiant maser with a linewidth below millihertz can be achieved with moderate kilohertz incoherent pumping of over $10^{14}$ spins kept at low temperature. We show that the superradiant masing prevails in the presence of inhomogeneous broadening, and we present numerical and analytical studies of the dependence of the phenomenon on the various physical parameters.