1987 年 15 巻 2 号 p. 98-105
An internal-mirror He-Ne (λ=633 nm) laser tube is mounted in a duralumin box which is thermally connected to other box attached thermo-elements, via heat pipes. The output power and the frequency of the laser are stabilized by two simple method. First, the total back beam intensity detected with a silicon photodiode is fed to a heater wound around the laser tube. The output stability of±0.15% and the frequency stability of ±1.3×10-8 are obtained over a period of 10 min or longer. Second, the laser tube temperature detected with a thermistor is fed to a heater. The output stability of ×0.3% and the frequency stability of ±4.5×10-8 are obtained over a period of 10 min or longer. This method does not use the laser beam intensity, thus the optical-feedback effect does not affect the laser stabilization.