Limits of validity of photon-in-cell simulation techniques

A comparison is made between two reduced models for studying laser propagation in underdense plasma; namely, photon kinetic theory and the slowly varying envelope approximation. Photon kinetic theory is a wave-kinetic description of the electromagnetic field where the motion of quasiparticles in photon coordinate-wave number phase space is described by the ray-tracing equations. Numerically, the photon kinetic theory is implemented with standard particle-in-cell techniques, which results in a so-called photon-in-cell code. For all the examples presented in this paper, the slowly varying envelope approximation is accurate and therefore discrepancies indicate the failure of photon kinetic approximation for these cases. Possible remedies for this failure are discussed at the end of the paper. (ABstract from: http://pop.aip.org/phpaen/v15/i2)