Subnarrow linewidth, hole, and split in micromaser spectrum

Abstract

By calculating the two-time correlation function of a one-photon micromaser, we study the line shapes and linewidth of the micromaser spectrum. We find that the half-width at half maximum of the spectrum can be less than the smallest decay rate of the off-diagonal density-matrix elements ${\mathrm{\rho }}_{\mathit{n},}$ ${\mathit{n}}_{+1\mathrm{}}$, that a hole can appear in the spectrum, and that the spectrum can be split by shifted spectral components.