10.6-µm amplification in metallic waveguide by external discharge pumping

Amplification of 10.6-μm radiation in a metallic waveguide and waveguide CO
2
-laser action was achieved by excitation of the CO
2
(00
⁰
1) mode by vibrational energy transfer from metastable
N\min{2}\max{\ast}(\upsilon = 1)
molecules. Excitation of N
2
was accomplished in a separate dc discharge tube. The N
2
-He mixture, after flowing through the discharge region, was pumped into the waveguide and there CO
2
was added. Maximum small-signal gain values of 25.6 and 15.3 dB/m were obtained at amplifying waveguide sections of 2 and 6-cm length, respectively. A theoretical analysis, based on rate equations for the (00
⁰
1) and the (10
⁰
0) states of CO
2
and the concentration of
N\min{2}\max{\ast}(\upsilon = 1)
molecules, is presented, which leads to predictions for the small-signal gain and the saturation intensity. In the pressure range covered by experiments the calculated gain values were found to be consistent with measurements.