Locking of the longitudinal modes of an He–Ne laser using a Fabry–Perot etalon

The example of an He–Ne laser is used to consider the influence of the dispersion of the active mediiun on mode locking. The calculations and experimental data show that an inclined Fabry–Perot etalon, placed inside the laser resonator, may increase considerably the maximum permissible – for self-modelocking – excess over the threshold.