Femtosecond filamentation induced fluorescence technique for atmospheric sensing*
Yuan Shuaia),b),c), Chin See Leangc), Zeng He-Pinga),b),†
Fig.#cod#x00A0;2. a Typical spectrum in the range of 303#cod#x2013;322#cod#x00A0;nm for filament-induced fluorescence of water vapor in air over a surface of water. The fluorescence spectrum was taken from the side at a water temperature of 80#cod#x00A0;#cod#x00B0;C and filament-to-water surface of 5#cod#x00A0;mm. b Partial pressure of water vapor in air as a function of the OH fluorescence signal at 308.9#cod#x00A0;nm at a water temperature of 21#cod#x00A0;#cod#x00B0;C. The filament was generated by focusing a pulse at 800#cod#x00A0;nm50#cod#x00A0;fs2#cod#x00A0;mJ with a lens of 50-cm focal length. The fluorescence was measured from the side.