Software for computer modeling of laser-pulse propagation through an optical system with nonlinear optical elements

摘要

We developed a set of computer codes organized in a software package that allows us to model high-energy laser pulse propagation through bulk nonlinear optical media. Nonlinearities included in the model are two-photon absorption, the electronic Kerr effect, excited-state and free-carrier absorption along with the associated electrostrictive and photo-acoustic refractive index change. The propagation of CW beams, nsec/psec pulses and picosecond pulse trains is determined for various spatial distributions of the input beam. We used a cylindrically symmetric spatial geometry typical for laser outputs to reduce the CPU and memory requirements making modeling a real-time task on PC's, even for significant propagation paths (many Rayleigh ranges). The validity of the numerical outputs was tested against known results for a large range of parameters. In particular the codes are being used to investigate and design optical limiting devices with single or multi-element geometries, as well as limiters using stepped or graded density of nonlinear material. The linear propagation module integrated with the nonlinear beam propagation method (BPM) codes allow the simulation of typical experiments such as Z-scan (sample position changes in a focused beam) and limiting experiments (different input energy values).