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

Abstract

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.

Hydrogen fluoride overtone laser: 2D CFD modeling of the small signal gain

“…The overall temperature increase is presumably caused by heat release from the cold pumping reaction and heat transfer between the H 2 and primary flow streams. The temperature oscillations probably result from three-dimensional flow effects as discussed by Wisniewski [16]. Figure 9 shows measured and predicted average gain.…”

“…The V-V energy transfer rate adjustment has only a minor effect on the predicted magnitude and shape of the temperature profiles [16]. Although the location of peak gain moves toward the centerline as the flow progresses downstream, the model accurately predicts the location of peak gain so that measured and predicted temperatures occur at nearly the same vertical location at each downstream location.…”

“…In all cases, any change that improved agreement between the predicted and measured maximum gain (within the first 2 cm) caused poor agreement further downstream. Details are provided in Wisniewski [16].…”

Optically Pumped Carbon Monoxide Cascade Laser

“…The higher order terms are much smaller than lower order terms. This means that the bigger the Av transition the more unlikely it is to occur [13]. In CO a Av = ±2 is approximately 150 times more likely than a Av = ±3.…”

Comparison of HF and HCl Chemical Laser Parameters by using Mathematical Model

“…The above reaction (1) known as pumping reaction, of fluorine (oxidizer) and hydrogen (fuel) produces about 14.7 kJ/g of fluorine with approximately 60% of the energy going into excited vibrational states of HF molecule (Wisniewski, 2003). This energy distribution allows for the creation of population inversion required for lasing.…”