A theory of interaction among the longitudinal modes in a laser made of highly dispersive material is outlined and used to interpret a spontaneous pulsing of the laser intensity at a frequency two orders of magnitude lower than the mode separation, shown to occur in GaAs lasers. Power coupling among the modes in the presence of spontaneous or forced microwave modulation of the population inversion is also explained.

• Received 14 April 1969

DOI:https://doi.org/10.1103/PhysRevLett.22.1085