Abstract
Due to rotational hole burning Q-switched laser pulses sometimes saturate a molecular absorber more effectively than CW laser radiation. The absorption by SF6 of frequencies near the P(28) line in the 10.6 μm CO2 laser band provides an interesting example. In this case it has been reported elsewhere that for peak intensities [Formula: see text] an increase in pulse intensity produces a monotonic increase in transmission whereas the CW transmission decreases monotonically with intensity. We report new measurements made over a wider range of laser power levels and at several SF6 pressures, which show that the global behavior of the transmission as a function of average beam power is quite similar for both CW and pulsed radiation. The pulse transmission is somewhat greater at all power levels, but when the average power is sufficiently high the growth of hot-band absorption and possibly other intensity dependent changes in the ground and excited-state absorption cross sections cause the transmission to fall well below its low-intensity value for CW radiation and pulses alike. The experimental transmission curves for both cases display as many as three extrema and cannot be explained, even qualitatively, by the five-level model used in the earlier work. The extended results are consistent with the modified five-level model presented in Part I of this pair of papers.
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