Investigation of output-power instability in a helium–neon laser with a planospherical resonator

A study was made of output-power fluctuations in a 0.63 μ helium–neon laser with a planospherical resonator. When the substrate of the plane exit mirror was heated, fluctuations occurred in the power transmitted by the exit mirror. These fluctuations were in phase, antiphase, or twice the frequency of those in the power transmitted by the other (rear) mirror. An interpretation is given of the effect observed, based on the well-known expressions for the power emitted through the exit and rear mirrors. A simple method is proposed for determining the optical reflection coefficient of the exit mirror which is based on this effect.