Frequency Pushing and Frequency Pulling in a He-Ne Gas Optical Maser

Measurements have been made of the variation of beat frequency between two simultaneously oscillating axial modes of a He-Ne gas optical maser as their disposition with respect to line center was continuously varied and as the discharge excitation level was increased above beat threshold for fixed mode positions. The results are compared with the theory of Lamb. The present calculations ignore mode interaction effects which are, however, included in Lamb's theory. The effects of frequency pushing, frequency pulling, and "hole repulsion" are apparent in the measurements as well as an excitation-dependent linewidth.