Study of the competition between forward and backward stimulated Raman scattering in methane |
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Authors: | J Leng G Sha X Hua H Yang C Zhang |
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Institution: | (1) State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, P.R. China |
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Abstract: | Simultaneous forward and backward stimulated Raman scattering (SRS) in methane pumped by a single longitudinal mode Nd:YAG
laser at 355 nm has been investigated both experimentally and numerically. For forward SRS, a maximum energy-conversion efficiency
of 55% was obtained under 24 atm, while for backward SRS the corresponding figure was 58% under 4.7 atm. Under low pressures
or at low pump energies, the conversion efficiency for backward SRS was found to be much higher than that for forward SRS,
while the situation is quite the contrary under high pressures and at high pump energies. A quasi-two-dimensional numerical
model is introduced to elucidate the competition between forward and backward SRS; we conclude that the high-pressure and
high-pump-energy experimental results should be caused by the thermal defocusing effect in the SRS process. This is confirmed
by the experimental fact that a decrease of the pulse-repetition rate increases the conversion efficiency for backward SRS
but decreases that for forward SRS under high pressures. Our calculated results are in good agreement with the experimental
results at a pulse-repetition rate of 2 Hz.
PACS 42.55.Ye; 42.65.Dr; 42.65.Es |
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Keywords: | |
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