Decade Spanning Radiofrequency Emission from Ultrashort Laser Generated Plasma

The unique electron distribution, timescales and geometry of ultrashort pulse laser generated plasmas are a novel source of radio-frequency electromagnetic emission, with a bandwidth larger than 70 GHz. To identify the emission mechanism, we characterize the RF signal for a wide variety of experimental conditions and compared to theoretical predictions. The field time evolution and magnitude is controlled by the electron mobility, dictated by electron temperature and electron-atom collisions. The time dependent electric field drives a longitudinal surface current which emits RF. The entire process is therefore dictated by the plasma density gradient at the edge of the column, the electron energy distribution, and the collision rate.