Localized microwave plasma grid by laser-designation

The volumetric addition of energy into flowfields associated with high speed aircraft has the potential to provide drag reduction, flow control, and ignition speed improvements. Using a femtosecond laser system and a microwave cavity, we have shown the ability to deposit microwave energy at locations designated by the laser system. The temperature of the heated region has been measured as up to 3500-4000 K, with thermal energy deposition on the order of 10 mJ for centimeter scale laser designated lines. The microwave pulse may couple to the region excited by the laser pulse even after a 20 μs delay. We have also demonstrated an ability to write simple patterns with multiple laser beams, showing approximately equitable energy distribution across the formed grid. The ability to couple the microwave pulse to the designated region is shown to be not strongly dependent on the polarization and relative orientation of the microwave and laser systems.