Spatial self-locking of transverse modes in an $He-Ne$ laser

Spatial self-locking of partially degenerate transverse $TEM_{\operatorname{moq}}$ modes was observed in an He–Ne laser $(0,63\mu m)$ with a confocal resonator. Self-locking was achieved as a result of an increase in the diffraction coupling between the modes found when a perturbing element was incorporated in the resonator. Compared with emission of longitudinal $TEM_{\operatorname{ooq}}$ modes, the radiation power was increased considerably and the spatial coherence of the output beam was fairly high.