He-Cd lasers using re-circulation geometry

Performance studies of He-Ne, He-Cd, He-Zn, and He-Se lasers of same length and bore diameter will be described. They show that the He-Cd laser is most efficient of the metal vapor lasers and compares well with the He-Ne laser. Conventional He-Cd lasers suffer from problems with metal vapor confinement and high radiation noise. Both of these problems can be overcome by using the re-circulation geometry described in this paper. The most convenient re-circulation laser geometry uses a diffusion return path which coaxially surrounds the main laser bore and allows metal vapor transport in a direction opposite to the cataphoretic transport through the main discharge bore. Cataphoretic confinement sections are provided at each end making the coaxial vessel a "cataphoretic bottle" from which no metal vapor can escape. Continuous long-time operation has been demonstrated for such lasers having power outputs of 5, 10, 25, and 160 milliwatts.