Enhancement of electromagnetic pulse emission from ultrashort laser pulse irradiated solid targets

Ultrashort laser pulses (~100 fs duration) are known to generate charge separation in solid, liquid and gas targets through a variety of nonlinear mechanisms. This process results in the emission of a broadband electromagnetic pulse (EMP) in the microwave and terahertz (THz) regions of the electromagnetic spectrum. Possible applications of this phenomenon include remote RF and THz generation for material detection and diagnostics. We investigate the energy and spectrum of the EMP emitted from copper and glass targets irradiated by single 800 nm, 38 fs duration pulses with varying energy. The detector is two feet from the target and the detection bandwidth is 2-18 GHz. We also demonstrate our ability to enhance the emitted EMP energy from a copper target by more than an order of magnitude by irradiating the target with a 1064 nm, 14 ns duration pulse at a specific time delay relative to the ultrashort pulse. We attribute the increased optical to RF energy conversion to enhanced absorption of the ultrashort pulse by the nanosecond pulse-generated plasma at the surface of the target.