Micromaser line broadening without photon exchange

TL;DR

This paper analyzes the linewidth of a micromaser using master equations, identifying a dephasing contribution from photon-number conserving pumping, and evaluates the convergence of an approximation method.

Contribution

It introduces a new dephasing term in micromaser linewidth calculations and assesses the convergence of a recent Lindblad approximation.

Findings

Dephasing contribution affects micromaser linewidth.

Uniform Lindblad approximation converges slowly.

Examples include single-atom and broad-distribution interaction cases.

Abstract

We perform a calculation of the linewidth of a micromaser, using the master equation and the quantum regression approach. A `dephasing' contribution is identified from pumping processes that conserve the photon number and do not appear in the photon statistics. We work out examples for a single-atom maser with a precisely controlled coupling and for a laser where the interaction time is broadly distributed. In the latter case, we also assess the convergence of a recently developed uniform Lindblad approximation to the master equation; it is relatively slow.