Two-photon optically pumped molecular gas visible laser. [Ammonia] Page: 5 of 11
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At NH3 pressures greater than -200 torr, in addition to the right-angle
emission, strong directional radiation is observed collinear with the excita-
tion laser. This radiation is detected both in the forward and the backward
direction, and occurs without external mirrors to provide feedback. An exci-
tation profile of the forward radiation for the C'-2 state is shown in Fig. 4,
and when the emission is dispersed, it has a bandwidth of about 1.0-nm FWHM
centered about the C'-2 to A-2 transition (-570 nm). The lasing has been
observed from numerous C'-vibronic le-els in NH3 and ND The output energy
scales linearly with pressure up to 1100 torr where it levels off, finally
decreasing when the NH3 pressure approaches -2000 torr. C'-+A lasing fluctuates
strongly from shot to shot, with occasional pulses reaching conversion effi-
ciencies (NH3 output pulse energy/input pulse energy) as high as 2%. Emission
in the forward direction is significantly stronger than in the backward
direction (7 to 1 for a 20-cm focal-length lens). The forward to backward
ratio is strongly dependent on input laser intensity and increases as the
focal length of the focusing lens is increased.
Examination of the time behavior of tbe right angle fluorescence of both
C' and B states using a fast detector/digitizer arrangement (~1-ns resolution)
revealed that the fluorescence at low pressure essentially tracked the input
pulse, as expected for predissociated states with a short lifetime. The
C'+I stimulated emission pulse exhibits complicated behavior and is not
completely understood at this time. The salient features observed so far
are as follows. First, emission is restricted to the first half of the pump
pulse (~4-ns FWHM). Second, the emission consists of subnanosecond spikes
(usually one, but occasionally two or three are observed, with varying
intensities) which occur within the first half of the pump pulse, changing
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Quick, C.R. Jr.; Glownia, J.H.; Tiee, J.J. & Archuleta, F.L. Two-photon optically pumped molecular gas visible laser. [Ammonia], article, January 1, 1983; New Mexico. (digital.library.unt.edu/ark:/67531/metadc1110570/m1/5/: accessed February 18, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.