Enhancement of OH spectra in atmospheric pressure plasma jet by femtosecond laser

Abstract

A helium (He) atmospheric pressure plasma jet (APPJ) system with a single electrode was configured. A pulsed light of femtosecond (fs) laser was irradiated at the guided streamer of He APPJ through an objective lens to generate the laser induced plasma (LIP) inside the He APPJ. The optical emission spectra of LIP were measured as the light energy of the fs laser increased. The spectra of hydroxyl molecules and atomic oxygen were enhanced when the fs laser energy exceeded 114 μJ. The plasma parameters of LIP inside the APPJ were determined using He collisional-radiative model. Electron temperature and density increased to ∼7.2 eV and 1.7×1014 cm−3, respectively. The dominant processes underlying the enhancement were discussed in the interaction of fs laser and He APPJ.