Numerical analysis of a superradiance-sideband-assisted laser with a zero frequency pulling and a narrow linewidth

TL;DR

This paper presents a numerical study of a superradiant laser with a zero frequency pulling effect and narrow linewidth, demonstrating potential for ultra-stable optical clocks.

Contribution

It introduces a novel laser configuration showing simultaneous superradiant peaks and zero frequency pulling, with linewidths surpassing traditional gain narrowing limits.

Findings

Achieved linewidths as narrow as a millionth of atomic linewidth

Observed superradiant peaks at ±Δpa with a central zero frequency pulling peak

Proposed use of side peak asymmetry for laser locking and frequency stabilization

Abstract

Numerical simulations based on the quantum Langevin equations have been performed for a large number of two-level atoms in a beam interacting with a low-Q cavity with the atomic initial superposition states close to the north pole of the Bloch sphere. When the pump Rabi frequency was modulated at $\Delta_{pa}$ with zero pump-atom detuning for various cavity-atom detunings, we obtained a lasing peak at the atomic resonance and superradiant lasing peaks at $\pm\Delta_{pa}$ simultaneously while the central peak exhibiting a zero frequency pulling coefficient. The linewidth of the central peak was reduced beyond the gain narrowing as the mean number of atoms was increased, resulting in a minimum linewidth as small as a millionth of the atomic or cavity linewdith. A pump carrier detuning caused asymmetric heights for the side superradiant peaks, the height difference of which can be used to lock the pump laser to the atom within the linewidth of the central lasing peak. Our results may lead to development of a new type of ultra-stable active optical clocks for future frequency standards when applied to proper atomic systems.