Laser induced plasma column heated by Tesla coil discharges as a radio-frequency antenna

Summary form only given. Even if the concept of a plasma antenna, where plasma replaces metallic radiating elements, is not new¹, most designs use a low-pressure plasma confined inside a solid dielectric vessel. We demonstrate a functional emitting antenna in air based on a plasma column created by an ultrashort (700 fs) terawatt laser pulse undergoing filamentation. This low-density plasma (n_e = 10¹⁶ cm^-3) has a short lifetime (a few ns). We consequently use the column to guide a high-voltage electric discharge of meter scale from a compact Tesla coil (output voltage: 360 kV), resulting in the increase of the plasma lifetime to at least 100 ns². We then couple radio-frequency (RF) power in the plasma by means of an inductive coupler placed around the column, fed from a 35 W solid-state RF amplification chain. RF signal is detected by a remote slot antenna with a 100 MHz-11 GHz bandwidth. Two types of coupler have successfully been tested: a solenoid coil, resonating between 100 and 200 MHz, and a hollow metallic cylindrical cavity, resonating around 1 GHz. We observed a significant emission peak at the seeded frequency in presence of a plasma column, while we could not detect anything outside the noise without plasma³. This plasma antenna is able to emit RF waves over a bandwidth spanning at least between 100 MHz and 1 GHz.