Abstract

A unidirectional ring laser operated on the 3.51-μm transition in xenon has been studied for its behavior under injection of a constant intensity signal from a separate single-mode laser. The combined output variously shows simple beating (heterodyne mixing of the two lasers in the infrared detector) and more complicated nonlinear interactions that lead to pulsations and locking. Nonlinear interaction is indicated by the appearance of harmonics of the free-running laser beat frequency which result in nonsinusoidal intensity pulsations. A stronger indicator of the nonlinear interaction is found in the heterodyne spectrum where we see clear evidence that the injected signal is joined by a new optical frequency component symmetrically located with respect to the ring laser frequency. The degree of nonlinear interaction depends principally on the frequency difference between the two initial frequencies of the free-running lasers. The strength of the injected field also helps to determine the exact nature of the interaction. As the degree of homogeneous broadening of the xenon transition can be varied with the buffer gas (helium) pressure, various parameter-dependent details of the system have been determined for comparison with recent theoretical and numerical results.

© 1985 Optical Society of America