Ben Eshel and Glen P. Perram, "Five-level argon–helium discharge model for characterization of a diode-pumped rare-gas laser," J. Opt. Soc. Am. B 35, 164-173 (2018)
A five-level discharge kinetics model is developed to characterize the
scaling potential of the diode-pumped rare-gas laser. The predicted
excited state populations are examined as functions of the gas
pressure, gas temperature, electron density, and electron temperature.
The density of the metastable level is a sensitive function of
electron temperature, increasing from at 1 eV to
at 1.2 eV, for a total
pressure of 400 Torr and a gas temperature of 440 K.
This is in contrast to the distribution among excited states, which
are most sensitive to the electron density and result from the
interplay of the electron-impact and neutral-impact spin-orbit mixing
rates. The model is benchmarked using absorption, emission, and gain
data from recent laser demonstrations. A metastable
number-density/path-length product of is required for optimal lasing
performance at a strong pump intensity of . This system requires an aperture of
in order to sustain 100 kW
performance in the total volume of . The primary difficulty in the
development of such a discharge system is due to the combined
requirements of a large-volume, homogeneous, atmospheric pressure
discharge with sufficient electron temperature to sustain significant
production of the metastable state.
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They are defined for a gas temperature,
, in units of kelvin. The
rate coefficients in brackets correspond to the Arrhenius
law modification made to several of the rates.
Table 4.
Einstein A Coefficients Are Provided for the States Considered
in the Modela
The rate in parenthesis is the radiatively trapped rate
used in the model.
Table 5.
Threshold Gain and Inversion Are Defined for the Output Coupler
Reflectivity, Gain Lengths, and Window Transmissions Applied
to the Various Examples of This Work
Case
Pressure [Torr]
Temperature [K]
Gain Length
[cm]
Output Coupler
Transmission
Gain
[]
Inversion
[]
PSI model
769
600
1.9
0.85
0.9
0.15
4.6
AFRL model
400
440
7.62
0.2
0.9
0.13
2.3
Optimized model
100–1000
750
10
0.2
0.98
0.085
0.29–2.9
Table 6.
Electron Density, , Electron Temperature,
, and Gas Temperature,
, for the Simulations
Presented in Fig. 4 Are Provided
Tables (6)
Table 1.
Mechanisms and Rates for the Electron Impact Excitation and
Spin-Orbit Mixing of Ar s and p Statesa
They are defined for a gas temperature,
, in units of kelvin. The
rate coefficients in brackets correspond to the Arrhenius
law modification made to several of the rates.
Table 4.
Einstein A Coefficients Are Provided for the States Considered
in the Modela
The rate in parenthesis is the radiatively trapped rate
used in the model.
Table 5.
Threshold Gain and Inversion Are Defined for the Output Coupler
Reflectivity, Gain Lengths, and Window Transmissions Applied
to the Various Examples of This Work
Case
Pressure [Torr]
Temperature [K]
Gain Length
[cm]
Output Coupler
Transmission
Gain
[]
Inversion
[]
PSI model
769
600
1.9
0.85
0.9
0.15
4.6
AFRL model
400
440
7.62
0.2
0.9
0.13
2.3
Optimized model
100–1000
750
10
0.2
0.98
0.085
0.29–2.9
Table 6.
Electron Density, , Electron Temperature,
, and Gas Temperature,
, for the Simulations
Presented in Fig. 4 Are Provided