Kinetics of an optically pumped metastable Ar laser

Abstract

In recent studies, an optically pumped Ar*/He laser has been demonstrated using the Ar 4p[1/2] 1 →4s[3/2] 2 transition at 912.55 nm. Time-resolved data for this system, recorded using CW laser excitation and pulsed discharge production of Ar* 4p[3/2] 2 , yielded laser output pulses that were of unexpectedly short duration. It was speculated that radiative relaxation from the upper laser level to the 4s[3/2] 1 state (607 cm -1 above 4s[3/2] 2 ) caused termination of the laser pulse. In the present study this hypothesis has been tested by observing the energy transfer kinetics of the 4s[3/2] 2 and 4s[3/2] 1 states in Ar/He gas mixtures. Following pulsed laser excitation out of 4s[3/2] 2 , population recovery was observed on a μs time scale. Energy transfer from 4s[3/2] 1 to 4s[3/2] 2 , induced by collisions with He, was characterized. The rate constant was found to be (1.0±0.5)x10 -13 cm 3 s -1 . These observations confirmed that radiative transfer to 4s[3/2] 1 was responsible for the short duration laser pulses. Modeling of a fully CW optically pumped Ar* laser shows that radiative transfer to 4s[3/2] 1 reduces the number density of the Ar* atoms involved in lasing, but is otherwise benign.

Laser excitation dynamics of argon metastables generated in atmospheric pressure flows by microwave frequency microplasma arrays

“…[1][2][3] The inversion follows a basic three-level scheme, wherein the metastable 3 P J rare-gas atoms (e.g. Ar(4s)), generated in an electric discharge, are optically excited to an upper state, undergo collisional energy transfer to a state at slightly lower energy to produce the inversion, and lase back to the metastable state.…”

Optically pumped microplasma rare gas laser

“…The optically pumped rare-gas metastable laser (OPRGL) is an attractive means for efficient conversion of high-power diode laser output into gas laser output with high beam quality, at a variety of near-infrared wavelengths [1][2][3]. The mechanism for population inversion follows a basic three-level scheme, wherein the metastable 3 P J rare-gas atoms (e.g.…”

Modeling of diode pumped metastable rare gas lasers

“…First we study the influence of 21 k , the collisional relaxation rate from 4 1s to 5 1s . Jiande Han et al found that the relatively low value of 21 k may form a bottleneck in atomic cycling process, thus decrease the laser efficiency [14]. Our simulation results are shown in Fig.…”

“…The radiative decay to 4 1s , 3 1s and 2 1s accounts for 21.8%, 0.6% and 3.6% of the total decay rate of 10 2p . A relatively low collisional relaxation rate of 4 5 1 1 → s s may form a bottleneck in the population cycling process [14]. (2) The population in upper pump ( 9 2p ) and laser ( 10 2p ) levels could be further collisionally relaxed into higher levels by endothermic processes, especially to the 8 2p level, which subsequently radiates to the 5 1s , 4 1s and 2 1s states.…”

“…In the same year, Rawlins et al realized the first cw Ar* laser by using microwave frequency microplasma discharge [13]. Due to the observation of much shorter laser pulse duration than the discharge pulse duration, kinetics of OPRGLs that mainly focused on the influence of an intermediate 1s 4 state have been studied [14]. Demyanov et al have theoretically modeled the OPRGLs by considering the required discharge power [15].…”