Frequency Stability of a He-Xe Laser with Nonresonant Feedback

The results of experimental investigation of frequency stability of a He-Xe laser (λ = 3.508μ) with nonresonant feedback are reported. It is experimentally proved that the mean frequency of oscillations does not depend on the distance between the mirror and the scatterer. It is shown that the spectral width depends on the number N of modes interacting due to scattering. The greater N is, the narrower is the linewidth. In a He-Xe laser with a relatively low number of interacting modes (N = 10) the linewidth is about 15 mHz. The lasers with a large number of interacting modes (N~104 to 106) are considered. The linewidth in such lasers is expected to be 104 to 105Hz. The short-term stability of the laser with nonresonant feedback is determined by the linewidth, but the long-term stability should be much better; it is determined only by the stability of the atomic resonance center.