Temperature Distribution and Cavity Length Properties of Internal-Mirror He-Ne Laser Tubes

The thermal properties of internal-mirror He-Ne (λ = 633 nm) laser tubes are reported. Inside and outside temperatures of the laser tube are measured with a PbS photodetector and thermo-couples, and also the thermal expansion properties of the laser tube are measured. The outside temperature at the fore part of the laser tube is higher than that at other parts of the laser tube. The heat that generated inside the fore part of the laser capillary tube is conducted in the radial direction and mainly elevates the temperature of other parts of the laser tube by heat conduction. The high temperature at the fore part would affect the laser thermal stability. The optimum laser tube structures are discussed.