On the stabilization of a high-power single-frequency laser

A single-mode 6328Å He-Ne laser is described which has a single-frequency power output of 50 mW. Amethodof stabilizing the output of this laser is described, and experimental results are quoted to show that the output can be stabilized to the resonance frequency of a stable reference cavity to within ± 1 Mc/s. This stabilization scheme has two advantages over an earlier scheme used with such a single-mode laser: 1) the output is neither amplitude nor frequency modulated by the feedback system; and 2), the output coupling may be continuously varied so that optimum output may be obtained without experimenting with mirrors of various transmissivities.