Programs in Physics & Physical Chemistry
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|Manuscript Title: PULSAMP: a program to predict the amplification of nano-second CO2 laser light pulses.|
|Authors: S.A. Roberts, K. Smith|
|Program title: PULSAMP|
|Catalogue identifier: ACXC_v1_0|
Distribution format: gz
|Journal reference: Comput. Phys. Commun. 12(1976)323|
|Programming language: Fortran.|
|Computer: ICL 1906A.|
|Operating system: GEORGE 4.|
|RAM: 65K words|
|Word size: 48|
|Keywords: Laser physics, Amplifier, Rotational coupling, Co2, Extracted energy.|
Nature of problem:
PULSAMP is a program which predicts the behaviour of a light pulse of duration - 1 ns., as it propagates through a gain medium. Singleline or multiline/multiband operation may be simulated. The laser medium consists of a pre-pumped CO2, N2, He mixture.
Initially the laser medium is described by the population number densities, N**10 degrees 0, N**00 degrees 1 and N**02 degrees 0, of the 10 degrees 0, 00 degrees 1 and 02 degrees 0 vibrational levels of CO2. These populations number densities are assumed initially to be constant within the laser cavity. Partial differential equations, which take into account the effects of stimulated transitions from the 00 degrees 1 vibrational level to the 10 degrees 0 and/or 02 degrees 0 vibrational level(s), as well as coupling among the rotational sublevels within each vibrational level, describe the propagation of a given input light pulse through the gain medium, and the time history of the population inversions. We follow Armandillo and Spalding in solving these equations by employing Simpson's rule swept over a two-dimensional (space-time) grid.
The model used neglects the effect of coherent propagation of the pulse and is therefore not valid for describing the propagation of pulses of duration less than the dipole dephasing time. Also neglected are the effects of all V-V and V-T transitions, so the pulse duration is further restricted to be less than the fastest V-V transition times. For the input pulse profile with respect to time, either an analytic shape is assumed, or experimental values may be read. The code is written to generate two analytic pulse shapes; rectangular or gaussian.
For the sample output given at the end of the paper the running time is 280 s on the ICL 1906A. Running time is dependent upon duration of the input pulse, number of transitions in the input pulse, and the laser cavity length.
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