Water droplet characterization and broadband microwave emission from laser plasmas generated in water droplets

A high-power ultrashort laser pulse focused in air generates a plasma that radiates broadband electromagnetic waves. The transient current source responsible for the radiation remains an open area of study. The aim of this investigation is to understand the influence of water droplets on plasma formation and its effects on radio frequency (RF) radiation. More RF emission is seen as water droplet density increases, likely due to increased absorption of laser energy. Beyond a threshold droplet concentration, laser energy is depleted and RF signal decreases. An antenna is used to measure the radial pattern of RF from 2 to 13.6 GHz produced by the laser plasma. Our research demonstrates a method to control water droplet density, allowing study of the relationship between droplet concentration and the laser plasma radiation mechanism.

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