An Experimental Study of CW HF Chemical Laser Amplifier Performance and Zero Power Gain

Sentman, L. H.; Theodoropoulos, P.; Waldo, R.; Nguyen, Thanh-Phuong; Snipes, Ray F.

doi:10.21236/ada185241

Cited by 12 publications

(15 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This is done by altering the dissociation fraction of the F atom precursor molecule (SF^, F^, etc.) xmtil the model agrees with the experimental data (Carroll et al 1993;Sentman et al 1987). …”

Section: Previous Investigationssupporting

confidence: 82%

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

et al. 2004

View full text Add to dashboard Cite

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.

show abstract

Section: Previous Investigationssupporting

confidence: 82%

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

et al. 2004

View full text Add to dashboard Cite

show abstract

“…The maximum suppression occurred between 2 and 6 mm downstream from the nozzle exit plane, near the center of the 9-mm overtone beam. There was minimal suppression of lines P 2 (8,9). The low J fundamental gains were suppressed more than the high J fundamental gains even though their upper or lower levels were not directly involved in overtone lasing.…”

Section: Introductionmentioning

confidence: 90%

“…C OMPARISON of residual fundamental amplification ratio (RF-AR) data obtained at relatively high medium saturation with two 99.7% reflective mirrors (a sal = 0.00010015 and L s = 30 cm) with the zero power amplification ratio (ZP-AR) data indicated that the gains of the low J lines P\ (4-6) and P 2 (4)(5)(6) were suppressed between 41 and 96% and the gains of the high J lines PI (7)(8)(9) and P 2 (7)(8)(9) were suppressed between 3 and 44%. u The 1 -> 0 lines were suppressed more than the 2-> 1 lines.…”

Section: Introductionmentioning

confidence: 99%

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

Theodoropoulos

Sentman

1996

AIAA Journal

Self Cite

View full text Add to dashboard Cite

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.

show abstract

“…L. H. Sentman, R.E. Waldo, etc. have done extensive experimental work on the MOPA configuration with only one amplifier [5][6][7] , and a simple model [8] was presented by R.E. Waldo, which based on the assumption, that the average gain in the amplifier is the same as the gain in the oscillator when the intensity in the oscillator is the same as the average intensity in the amplifier.…”

Section: Introductionmentioning

confidence: 99%

A simplified model for HF chemical laser amplifier

et al. 2012

View full text Add to dashboard Cite

HF chemical laser with MOPA configuration is a good solution to achieve high output power with high reliability. Kinetic models for HF amplifier are important for prediction and optimization of the performance of MOPA chemical lasers. In this paper, a simplified model for HF chemical laser amplifier is presented. The main processes which are included in the model are: (a) chemical pumping of HF (v=2) and HF (v=1), (b) stimulated transitions and spontaneous emission. (c) relaxation of vibration excited HF molecule by H 2 ,N 2 and HF. Some assumptions are taken in this model: (a) the density of H 2 , N 2 , HF, translational temperature and velocity of gas mixture are averaged across the laser cross section, (b) only two vibration-rotational transitions (2P6, 1P7) occurs in the amplifier, (c) gas temperature does not change during the lasing process in the amplifier. Based on these assumptions, a set of three-level rate equations is formulated and then solved by an iterative technique. Comparison is made with recent experimentally obtained data from a low power discharge-driven CW HF laser with MOPA configuration. It is shown that experimental results are consistent with the calculation from the simplified model.

show abstract

An Experimental Study of CW HF Chemical Laser Amplifier Performance and Zero Power Gain

Cited by 12 publications

References 0 publications

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

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

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

A simplified model for HF chemical laser amplifier

Contact Info

Product

Resources

About