Long-term stability and reproducibility of the emission frequency of an He–Ne laser with internal mirrors

A study was made of the long-term stability and reproducibility of the emission frequency of a laser with internal mirrors stabilized by the method of thermal control of the resonator length using a fixed ratio of the orthogonally polarized components of the radiation. The spectral characteristics and the thermal regime of the gas-discharge tube were investigated. A theoretical estimate was made of the long-term stability allowing for the drift of the reference point and instability of the parameters of an automatic frequency control system. Experimental values of 2×10^–9 for the instability and 2×10^–8 for the irreproducibility of the frequency of the investigated laser were obtained.