Modeling CW HF fundamental and overtone lasers

Sentman, L. H.; Carroll, David L.; Gilmore, John

doi:10.2514/6.1989-1904

Cited by 6 publications

(6 citation statements)

References 3 publications

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“…1-6. These results indicate that RR populates the low J HF(0, 3-5), HF(1, [3][4][5], and HF (2,3,4) states at the expense of the high J HF(0, 6-10), HF(1, 6-10), and HF(2, 5-10) states, respectively. This effect was observed in the experiments by Polanyi and Woodall.…”

Section: Simulation Of Residual Fundamental Gain a Low J Line Gamentioning

confidence: 86%

“…1-3. Polanyi and Woodall 9 showed that the pumping reaction populates HF(1, 4-13), HF (2,(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14), and HF(3, 0-6) with the peaks at (1, 7, 8), (2,6,7), and (3,2) and that RR was the major collisional process responsible for the transfer of population from the high J states populated by the pumping reaction to the low J 0-4 states of v . = 1 and 2.…”

Section: Simulation Of Residual Fundamental Gain a Low J Line Gamentioning

confidence: 99%

“…Second, when there is no RR, overtone lasing results in a decrease in HF(0,3-5) populations below their zero power values. This is a consequence of the depletion of the HF(2, 6-11) states by overtone lasing, which results in decreased deactivation of these levels to the HF(0, [3][4][5] states. When RR is included, overtone lasing results in an increase in the populations of the HF(0, 3-5) states compared with their zero power values.…”

Section: Simulation Of Residual Fundamental Gain a Low J Line Gamentioning

confidence: 99%

“…1 and 4 shows two effects of overtone lasing on the populations of HF(0, 3-5). The first point to be noted is that RR is the major cause of population transfer from HF(0, 6-12) to HF(0, [3][4][5]. Second, when there is no RR, overtone lasing results in a decrease in HF(0,3-5) populations below their zero power values.…”

Section: Simulation Of Residual Fundamental Gain a Low J Line Gamentioning

confidence: 99%

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Fundamental gain suppression mechanisms in a continuous wave hydrogen fluoride overtone laser

Theodoropoulos

Sentman

1996

AIAA Journal

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When lasing occurs on the overtone, a rotational nonequilibrium computer model showed that the fundamental gains are determined by three independent mechanisms. First, overtone lasing decreases the gains of the P\ (7) and PiC/) lines whose upper or lower levels are directly involved in PioC/) overtone lasing. Second, overtone lasing reduces the rate at which the low/ v = 2 states are populated by rotational relaxation and increases the rate at which the low J v = 0 states are populated by rotational relaxation, resulting in suppression of the low J fundamental gains whose upper or lower levels are not directly involved in overtone lasing. Third, overtone lasing reduces the rate at which the HF(0, /) and HF(1, J) states are populated by the various collisional deactivation processes. The computer model gave reasonable agreement with the measured fundamental zero power gain profiles, Fabry-Perot power, and spectra. The model overpredicted the fundamental gain suppression (Aa) for the P\ (8,9) and P2(8,9) lines whose upper or lower levels were directly involved in overtone lasing and underpredicted the suppression for lines PI (4) and PI (4, 5). The model predicted the suppression for lines PI (5-7) and P2(6,7) reasonably well. When the rotational relaxation rate was increased by a factor of 10, the model was in reasonable agreement with the measured suppression, A a, of all P\ (4-9) and P2(4-9) lines. However, with the increased rotational relaxation rate, the model's prediction of the experimental zero power gain and residual fundamental gain profiles was not adequate.

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Section: Simulation Of Residual Fundamental Gain a Low J Line Gamentioning

confidence: 86%

Section: Simulation Of Residual Fundamental Gain a Low J Line Gamentioning

confidence: 99%

Section: Simulation Of Residual Fundamental Gain a Low J Line Gamentioning

confidence: 99%

Section: Simulation Of Residual Fundamental Gain a Low J Line Gamentioning

confidence: 99%

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Fundamental gain suppression mechanisms in a continuous wave hydrogen fluoride overtone laser

Theodoropoulos

Sentman

1996

AIAA Journal

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“…For example, it has been postulated that if the spatial optical modes of the laser do not fill the entire gain volume or if the HF laser medium is inhomogeneous (i.e., the laser has a non-uniform flow field), multi-line output could resuh. However, according to the HF laser modeling community, only models that include rotational nonequilibrium are able to reproduce multiline lasing (Cohen et al 1986;Sentman 1975;Sentman et al 1989a;Sentman et al 1984;Skifstad and Chao 1975). In addition, models that allow rotational nonequilibrium are more successful at predicting HF laser performance than those that assume rotational equilibrium (Cohen et al 1986;Sentman 1975).…”

Section: Saturated Gainmentioning

confidence: 99%

Spatially resolved sub-Doppler overtone gain measurements on a small-scale supersonic HF laser

et al. 2004

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Public reporting burden for this collection of information te Bstimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information. The overtone gain of a small-scale HF laser was measured using a sub-Doppler tunable diode laser system. Two-dimensional spatially resolved small signal gain and temperature maps were generated, which show a highly inhomogeneous gain medium indicating the dominant role that mixing of the fuel and oxidizer streams has in HF laser performance. The measured gain and temperature data were analyzed with the aid of a two-dimensional computational fluid dynamics code. To reduce uncertainty of important modeling input parameters, novel measurements of reactant concentration, flow velocity and gain length were made. Results show that reactant mixing mechanisms such as turbulence and large-scale vortex structures have a large effect on the gain averaged over a vertical profile while kinetic rate mechanisms such as reaction rate constants and reactant concentration have a greater effect on the maximum system gain. Overtone gain data measured while operating the laser saturated on the fundamental transitions are compared with fundamental lasing output spectra. In all cases, the data are consistent with an equilibrium rotational distribution.

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On the presence of rotational nonequilibrium in a supersonic hydrogen-fluoride laser

Manke

Hewett

Wisniewski

et al. 2003

IEEE J. Quantum Electron.

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Modeling CW HF fundamental and overtone lasers

Cited by 6 publications

References 3 publications

Fundamental gain suppression mechanisms in a continuous wave hydrogen fluoride overtone laser

Fundamental gain suppression mechanisms in a continuous wave hydrogen fluoride overtone laser

Spatially resolved sub-Doppler overtone gain measurements on a small-scale supersonic HF laser

On the presence of rotational nonequilibrium in a supersonic hydrogen-fluoride laser

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