COMPETITION BETWEEN SELECTED AND NON-SELECTED MODES IN A MULTIMODE LASER

Utilizing a simple previously introduced model for a laser emitting a broad homogeneous line, which takes account of mechanisms giving rise to mode coexistence, mode competition is studied for the case of one mode (or a small group of modes) being selected, by means of a wavelength selective element, out of the whole spectrum of a cw laser. It is shown that a critical value for the loss of the privileged mode ĝh1 exists, in the sense that for ĝh1 ≥ η1 the privileged mode completely quenches the remaining modes, while for ĝh1 < η1 the latter grow up and, hence, influence the privileged mode by mode competition. As a consequence, the slope in the intensity of the selected mode, as a function of its loss η1, exhibits a distinct jump at the critical point. As will be shown in detail, from a measurement of this jump the effective strength of mechanisms responsible for mode coexistence, can be determined directly. © 1978.