Transition Correlation Studies In A Water Vapour Laser

The interaction between several pairs of coupled water vapour lines was investigated with a compound mirror-grating-grating (MGG) laser, which allows the simultaneous and coaxial lasing of two linearly polarized wavelengths parallel or perpendicular to each other.;The interaction experiments were done with four pairs of competitive water vapour lines; the 26.6 and 47.70, 26.6 and 47.47, 27.97 and 47.70, and 27.97 and 47.47 micrometer lines. The coupled lines share an upper or lower energy level.;From the experimental results of 26.6 and 47.70 micrometer lines, the parallel polarized line coupling constant was 0.18 {dollar}\pm{dollar} 0.04, and the perpendicular constant was 0.54 {dollar}\pm{dollar} 0.06. The ratio of the two coupling constants, which is a ratio of the competition between the two lines for magnetic sub-level population of the shared level, was equal to 0.40 {dollar}\pm{dollar} 0.14 which compares well with the theoretical value of 0.35.;Although the experimental results of the three other pairs of lines did not allow coupling constants to be calculated, the power suppression of the longer wavelengths demonstrated that the lines were coupled, and that the coupling depended on the relative polarization of the lines: the 47.70 micrometer line was completely suppressed whenever the 27.97 micrometer line lased.;The single line two perpendicular polarization mode control features of a compound mirror-grating-mirror (MGM) laser were also investigated: the output can be in one or the other or both modes. The resonator\u27s polarization properties are due in part to the different effective phase change upon reflection from the resonator\u27s grating for radiation parallel and perpendicular to the grating lines. This can be expressed as a difference in the effective optical plane positions for the two polarizations. From the simultaneous measurement of the modes with the displacement of the resonator mirrors, the optical plane difference was measured to be 17 {dollar}\pm{dollar} 1 micrometers for the 30 micrometer blazed grating used. The ratio of the optical plane difference to the groove depth of the grating was 0.32 {dollar}\pm{dollar} 0.02, in fair agreement with the theoretical calculated value of 0.21