Integrated multiphysics design of high-power short-pulse lasers

The design of next-generation petawatt-scale femtosecond laser systems will require parallel multiphysics simulations with realistic errors and nonlinear optimization. End-to-end 4D modeling (3D with explicit time dependence) is essential to accurately capture and mitigate problems such as pre-pulses and post- pulses arising from optical imperfections. Existing commercial software does not address these requirements. Modeling of bulk media lasers will be addressed by developing 3 computational modules. The gain module will capture 3D pump energy distribution and associated thermal lensing in the crystal amplifier, as well as amplified spontaneous emission (ASE). Slice-by-slice pumping and depletion of stretched pulses will be included to capture wavelength-dependent gain and spectral evolution. The optics module will provide wavefront propagation with full physical optics, including all apertures and lenses. Realistic input parameters for the seed and pump beams will be taken from experimental measurements. Use of the gain and optics modules together will capture essential aspects of pulse stretching and compression. Multi-pass and multi-pump geometries will be considered. The thermal module will capture all relevant aspects of thermal transport in the crystal. The 3 modules together will capture the evolution of hot spots. The 3 modules will be prototyped, including inter-module interactions. The thermal module will be built on commercial computer-aided engineering software. A prototype browser-based GUI will be developed, leveraging the company’s open source technology for scientific cloud computing. A novel treatment of wavefront propagation through the crystal amplifier will work with arbitrary meshed wavefronts. This, together with inclusion of nonidealized thermal effects on the 3D gain profile, will enable initial modeling of localized thermal maxima (i.e. hot spots) in the crystal. The software developed for this project will be open source, and novel aspects of the software design will be published in the scientific literature. The cloud computing approach is uniquely powerful. New users can be up and running in minutes, and can share their simulations with collaborators instantaneously. The open source business model enables low-cost delivery of free access to basic capabilities for many users. Use of a commercial computer-aided engineering package for the fully detailed simulations will enable upselling of the complete software capabilities to paying customers.