Influence of the ~3He isotope on the output parameters of the noble gas hollow cathode lasers

摘要

The influence of the ~3He isotope as a buffer gas on the operating characteristics of the He-Ne and He-Kr hollow cathode lasers is studied. A comparison of the laser output power on the Nel 1.15 mu m line (2s_2 - 2p_4 transition) and Rrll 469.4 nm line (6s ~4P_(5/2) - ~5p ~4D_(7/2) transition) in ~3He -noble gas and ~4He-noble gas mixtures is made. An increase of 4 times in the case of~3He-Ne gas mixture and of 33 percent in the case ~3He-Kr gas mixture is observed. The plasma kinetics is analyzed and it is shown that the observed increase of the laser parameters is due to the following changes in particle kinetics: 1) increased rate constant for the excitation transfer reaction; 2) increased density of the He (2 ~3S_1) metastable atoms; 3) decreased population rate of the Nel lower laser level ~2p_4; 4) decreased density of the Ne (1s_3,1s_5) metastable atoms and 5) increased density of the Kr ground state ions. The main reasons for that are the higher mean relative velocity of the colliding particles and the higher rate of electron cooling in ~3He -noble gas plasma. Peak powers of 10 W and 1.5 W and small signal gams of 85 percent /m and 64 percent/m are measured for the blue and violet Krll lines, respectively, from 21 cm active length.