Investigation of cascade generation in He-Cd laser with transverse high-frequency excitation

Abstract

It was reported in [i] that cascade generation was achieved on the 636and 537.8-nm lines of cadmium ions in a high-frequency transversedischarge in a helium--cadmium mixture. In the present work, we show the effect of lasing at each of these lines on the population inversion and the gain in the neighboring transition, the boundaries of combined lasing are 2 O determined, and the pumping rates at the levels of the 636-nm transition 6aG9/2--4 FT/~ are 2 O 2 measured. The level scheme for the cascade transition 62G9/2-4 F7/I-25 D~/a is presented in Fig. i. From the level 62G9/2, there is strong spontaneous emission only tothelevel4aF~ and from the level 42F~ only to the level 52D5/2 (lasing is possible on these transitions). The processes that lead to a decrease in the population of the levels indicated may be assumed to be collisional damping by electrons [2] and diffusion loss to the walls of the tube. The probabilities for step excitation of 42F ~ 52Ds/2--4=F ~ and 52Ds/262G9/2 are negligibly small compared to the total decay probabilities for the states examined. Solving the system of population balance equations for the three levels and assuming that the pumping rates RI, R2, and R~ do not depend on the presence of lasing, it is possible to obtain expressions that relate the inverted populations for the transitions 3--2 and 2--1 to the probabilities of stimulated emission: O0 NOOm I,,,7 N21~ N21 (Do -~ DIW3~) -~ 32~w32 (i) Do + DaW21+ D1W32 + D~W21Wa2 ' oo -JN21DsI~' 21 (2) N32_ N~2 (Do-iDsW21) oo , Do+ DsW21 aD1W3~ + D~W~IWs~ "