Answers are grounded in this paper and cite their sources.
In standing-wave laser oscillators the field energy density periodically varies along the resonator axis and creates a complex refractive-index grating in the gain medium. This grating couples the originally independent counterpropagating waves of the individual axial cavity modes. The coupling induces a mode frequency shift that is a nonlinear function of the unperturbed mode frequency. The uneven shifts can give rise to a substantial broadening of the beat-note linewidth of the multi-axial-mode free-running laser and to a corresponding increase in the threshold intracavity power for self-starting passive mode locking. The theoretical results are in good qualitative and quantitative agreement with previously reported experimental observations and measurements.
No takes yet. Share an insight, caveat, or question.
Krausz et al. (1993) studied this question.
Synapse has enriched 10 related papers. Consider them for comparative context: