High power He–Cd+ white light laser

A new hollow cathode He–Cd+ laser—an improvement of the flute type—was investigated experimentally. Using wideband mirrors, the 194-mW simultaneous oscillation power output was obtained within the visible light range; red lines (635.5,636.0 nm), green lines (533.7,537.8 nm), and a blue line (441.6 nm), at 2-A anode current. Conversion efficiency of 0.032% was obtained. The laser tube is provided with 20 anodes on the upper side at 3-cm intervals and a cathode having an effective activated length of 61 cm. The diameter of the bore is 4 mm. Cadmium reservoirs are provided in the middle of each anode on the lower opposite side. The cathode is made of pure iron. By virtue of close contact between the cathode and the Pyrex glass envelope, the glow is condensed within the cathode bore, resulting in high efficiency. With this construction, sputtered material in the bore may quickly be exhausted out of the bore, keeping the inside of the bore clean; moreover the uniform arrangement of cadmium reservoirs over the whole length of the cathode contributes to high efficiency and stability.