title: Measuring the electric charge in cloud droplets by use of second-harmonic generation.
abstract: We report on the observation of second-harmonic generation (SHG) from electrically charged microdroplets while they are excited with femtosecond laser pulses. The intense SHG emission results from chi(3) coupling between two photons of the incident laser pulse and the electrostatic field induced by the surface charges. For Iinc= 2 x 10(12) W/cm2, we estimate the second-harmonic emission to be ISHG= 2.5 x 10(3) photons per droplet and per pulse. The possibility of using SHG to measure remotely the electric charge of water droplets in thunderclouds is discussed.
authors.affiliation: Laboratoire de Spectrométrie Ionique et Moléculaire, Unité Mixte de Recherche, Centre National de la Recherche Scientifique 5579, Université Claude Bernard Lyon 1, 69622, Villeurbanne Cédex, France. boutou@lasim.univ-lyon1.fr
authors.forename: Véronique
authors.initials: V
authors.lastname: Boutou
authors.forename: Catherine
authors.initials: C
authors.lastname: Favre
authors.forename: Ludger
authors.initials: L
authors.lastname: Woeste
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Wolf