Amplitude Characteristics and Frequency Bias in a Zeeman Ring Laser under Three-Frequency Running Wave Excitation

The characteristics of the Zeeman ring laser (ZRL) have been investigated theoretically and experimentally under conditions of two- and three-frequency generation. The influence of the running wave, excited at the third frequency, on the frequency bias and the intensities of counterpropagating waves is examined. A comparison of experimentally measured characteristics with calculations based on vector theory has been conducted. It has been found that when a running wave is excited in a neighbouring longitudinal mode, kinks appear in the dependence of counterpropagating wave intensities on the detuning of the generation frequency from the gain-line center. It is shown that excitation at the third frequency results in a stronger dependence of the frequency bias on the detuning from the gain-line center compared to the two-frequency generation regime. Based on the comparison of theory with experiment, it is demonstrated that among the known values of the isotopic shift between Ne\({}^{20}\) and Ne\({}^{22}\) at a wavelength of 0.63 \(\mu\)m reported in the literature, the value \(\sigma=1050\) MHz leads to results that do not agree with the experiment, allowing for a refinement of the parameter \(\sigma\).