On the performance characteristics of multiple pass hydrogen fluoride chemical laser master oscillator/power amplifiers
Waldo, Robert Eugene
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https://hdl.handle.net/2142/22327
Description
Title
On the performance characteristics of multiple pass hydrogen fluoride chemical laser master oscillator/power amplifiers
Author(s)
Waldo, Robert Eugene
Issue Date
1991
Doctoral Committee Chair(s)
Sentman, Lee H.
Department of Study
Aerospace Engineering
Discipline
Aerospace Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Aerospace
Engineering, Electronics and Electrical
Language
eng
Abstract
The performance of a cw Hydrogen Fluoride (HF) chemical laser master oscillator with power amplifier was measured as a function of input power, the number of passes through the gain media, location of the optical axis of the input beam and oscillator/amplifier flow field match/mismatch. The amplification ratio is an inverse function of the input power (intensity) and, for maximum amplification, the peak of the intensity distribution must be matched to the peak of the zero power gain distribution in the amplifier. The measured single pass P$\sb{\rm out}$ versus P$\sb{\rm in}$ performance curve showed that, after a continuous increase, the difference P$\sb{\rm out} \cdot$ P$\sb{\rm in}$ remained almost constant over a wide range of input powers and that about one third of a device's oscillator output must be input to obtain single pass amplifier output equal to the device's oscillator performance. For two pass amplification, a substantial performance advantage was measured when the two passes overlapped at least sixty percent and filled less than eighty percent of the zero power gain zone of the amplifier. The measured two pass P$\sb{\rm out}$ versus P$\sb{\rm in}$ performance curve was significantly above the single pass data and showed that only one sixth of a device's oscillator output must be input to obtain two pass amplifier output equal to the device's oscillator performance.
When the input beam contained time-dependent oscillations, the amplitude modulation of the output beam was reduced by a factor that equaled the amplification ratio of the amplifier; the amplifier had no effect on the period (frequency) of the oscillations of the input beam.
An amplifier performance model that predicts a device's amplifier performance given the device's oscillator performance as a function of reflectivity was developed. The model was used to predict amplifier performance as a function of gain length and the number of passes through the gain media. When the amplifier performance is plotted in terms of non dimensional powers, $\zeta\sb{\rm out}$ versus $\zeta\sb{\rm in}$, gain length dependent, device independent curves result. The non dimensional amplifier performance curves showed that a one meter oscillator may be able to drive as many as twelve two pass amplifiers.
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