Phase-coupling between modes of two 6328-Å He-Ne lasers through nonlinear gain characteristics of the inverted population Å

Mode coupling can occur if the gain of a laser is modulated by a frequency near the axial-mode spacing. This modulation is produced by a second laser acting partially upon the same active medium. Mode coupling and intensity pulsations close to the frequency
c/2 [(1/L_{1}) - (1/L_{2})]
were observed, in a good agreement with the theoretically calculated waveshapes.