A Simple Method for Single-Frequency Operation and Amplitude- and Frequency-Stabilization of an Internal-Mirror He–Ne Laser

This paper describes a new and simple method for obtaining the amplitude- and frequency-stabilized single mode output of an internal-mirror He–Ne laser (λ=633 nm). The laser tube is cooled with a constant-speed fan and the electric current signal which is proportional to the total back beam intensity is detected with a silicon photodiode and is applied to an electric heater which controls the laser tube length change due to thermal contraction. Consequently, the laser amplitude and frequency are stabilized at the same time. A relative amplitude stability of ±0.16% and relative frequency stability of ±9×10 -9 are obtained over a period of 10 minutes or longer.