Stabilization of reproducibility of frequencies of He-Ne lasers at 0.63 µ

We have investigated the frequency reproducibility of a He-Ne laser (0.63μ). We used the dependence of absorption on frequency in the strong-field standing-wave limit to provide stabilization. An absorption cell with a pure neon discharge at C could be placed both inside and outside the resonator. In the former case, a magnetic field was used to influence the gain profile of the line in the He-Ne mixture in such a way as to increase the accuracy with which the center of the absorption line corresponded to the frequency for maximum power output of the laser oscillation. In the latter case, we used a single-mode laser to obtain saturation of absorption in the cell. The long-term reproducibility obtained was . The short-term stability was much better. To obtain a very narrow dip in the center of the absorption line and consequently much higher stability (10^-13), we have investigated the vibration spectrum of absorption in the strong field of a standing wave in the CO2laser (10.6μ) and He-Ne-Ch4(3.39μ) systems.