Investigation of a strontium vapor laser

An experimental investigation was made of the time dependence of the intensity of spontaneous lines of strontium atoms and ions in an He?Sr plasma formed in 5- and 10-cm diameter discharge tubes. The intensity of the intercombination atomic line (? = 689.3 nm) fell on reaching the maximum current. An absorption method was employed to measure the time dependence of the population of the 4d2D5/2Sr+ metastable level which is the lower active level for the ? = 1033 nm self-terminating transition. Three decay time constants were discovered, depending on the helium pressure pHe. It was found that the decay of the population of the metastable level mainly resulted from collisions with electrons, the most rapid decay of the population with ?1 = 1 ? 10 ?sec being due to relaxation of the electron temperature and the slowest decay (with ?2 = 10?80 ?sec) due to plasma recombination. At low values of pHe < 1.5 kPa, ambipolar diffusion made the principal contribution to the process of decay of the population of the 4d2D5/2Sr+ level. The minimum time delay after which ? = 1033 nm lasing appeared following the second excitation pulse was equal to the time needed for the completion of the decay of the 4d2D5/2Sr+ level population, while the influence of the first excitation pulse on the second vanished after a time ?2.