Spatial self-locking of transverse modes in an He?Ne laser
Spatial self-locking of partially degenerate transverse TEMm0q modes was observed in an He–Ne laser (0.63 μ) 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 TEM00q modes, the radiation power was increased considerably and the spatial coherence of the output beam was fairly high.