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Proceedings Paper

Laser excitation dynamics of argon metastables generated in atmospheric pressure flows by microwave frequency microplasma arrays
Author(s): W. T. Rawlins; K. L. Galbally-Kinney; S. J. Davis; A. R. Hoskinson; J. A. Hopwood
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Paper Abstract

The optically pumped rare-gas metastable laser is a chemically inert analogue to diode-pumped alkali (DPAL) and alkali-exciplex (XPAL) laser systems. Scaling of these devices requires efficient generation of electronically excited metastable atoms in a continuous-wave electric discharge in flowing gas mixtures at atmospheric pressure. This paper describes initial investigations of the use of linear microwave micro-discharge arrays to generate metastable rare-gas atoms at atmospheric pressure in optical pump-and-probe experiments for laser development. Power requirements to ignite and sustain the plasma at 1 atm are low, <30 W. We report on the laser excitation dynamics of argon metastables, Ar (4s, 1s5) (Paschen notation), generated in flowing mixtures of Ar and He at 1 atm. Tunable diode laser absorption measurements indicate Ar(1s5) concentrations near 3 × 1012 cm-3 at 1 atm. The metastables are optically pumped by absorption of a focused beam from a continuous-wave Ti:S laser, and spectrally selected fluorescence is observed with an InGaAs camera and an InGaAs array spectrometer. We observe the optical excitation of the 1s5→2p9 transition at 811.5 nm and the corresponding laser-induced fluorescence on the 2p10→1s5 transition at 912.3 nm; the 2p10 state is efficiently populated by collisional energy transfer from 2p9. Using tunable diode laser absorption/gain spectroscopy, we observe small-signal gains of ~1 cm-1 over a 1.9 cm path. We also observe stable, continuous-wave laser oscillation at 912.3 nm, with preliminary optical efficiency ~55%. These results are consistent with efficient collisional coupling within the Ar(4s) manifold.

Paper Details

Date Published: 3 March 2014
PDF: 18 pages
Proc. SPIE 8962, High Energy/Average Power Lasers and Intense Beam Applications VII, 896203 (3 March 2014); doi: 10.1117/12.2040083
Show Author Affiliations
W. T. Rawlins, Physical Sciences Inc. (United States)
K. L. Galbally-Kinney, Physical Sciences Inc. (United States)
S. J. Davis, Physical Sciences Inc. (United States)
A. R. Hoskinson, Tufts Univ. (United States)
J. A. Hopwood, Tufts Univ. (United States)


Published in SPIE Proceedings Vol. 8962:
High Energy/Average Power Lasers and Intense Beam Applications VII
Steven J. Davis; Michael C. Heaven; J. Thomas Schriempf, Editor(s)

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