Spatial pattern pulsations are observed at frequencies much less than the intermode beat frequencies in a He-Xe laser operating at 3.51 μm. Numerical studies indicate that such low-frequency pulsations can arise from secondary beat notes between the frequencies of unequally spaced modes. The decay rate of the active medium is an important parameter which sets the scale for mode pulling without locking, which leads to these pulsations.

• Received 29 September 1993

DOI:https://doi.org/10.1103/PhysRevA.49.2076