Excess spontaneous-emission factor in unstable-resonator lasers

Spontaneous emission of an atom in a cavity with nonorthogonal eigenmodes

The spontaneous emission of an excited atom in a lossy cavity with nonorthogonal eigenmodes is analyzed. The quantum Langevin formalism is used to describe the dynamics of the spontaneous decay. The analysis shows that the spontaneous decay is modified by the Q value and the effective mode volume factor of each cavity eigenmode. The effective mode volume is generalized for cavities with nonorthogonal modes, which can be a very significant modification in the microcavity regime. It is shown that the spontaneous decay is not enhanced by the excess noise factor as claimed by other analyses.

High-power monolithic unstable-resonator solid-state laser

We report the operation of a diode-pumped monolithic Q-switched unstable-resonator solid-state laser that generates 2.15-mJ, 2-ns pulses in a single transverse mode and a single longitudinal mode. We show that the unstable resonator is effective in suppressing the spatial and the temporal instability of the laser beam in a disk-shaped laser whose transverse dimension is comparable with or larger than its longitudinal dimension.