Energy deposition into a collisional gas from optical lattices formed in an optical cavity

The DSMC method was used to investigate the interaction between a test gas and ten successive, pulsed, optical lattices. The one-dimensional lattices were formed by two 100 ps, 393 mJ, 532 nm, simulated laser pulses and assumed to be far from resonance. The maximum centerline temperature was simulated as a function of the intervening time between pulses. An optimum intervening time was found and related to the mean collision time and available energy modes. Subsequent pulses can act to cool the gas for intervening times near zero. For long intervening times, thermal diffusion carries energy away from the centerline, reducing the maximum temperature. At one atmosphere the optimal intervening time was found to be 0.7, 1.0 and 0.25 ns for argon, nitrogen, and methane respectively. The highest temperature simulated for nitrogen was 2480 K after 50 pulses with an optimal intervening time. The combination of small intervening time and high intensity requires the use of an optical cavity for successive laser pulses as commercially available high repetition rate lasers have neither the repetition rate nor the energy per pulse.