Experimental demonstration of dyed water aerosol fluorescence stimulated by femtosecond laser postfilaments propagating in air

Abstract

We present the fluorescence spectra of single millimeter water droplets and micron-sized dyed water aerosol (rhodamine 6G) stimulated by a high-intensity femtosecond Ti:sapphire-laser pulse (carrier wavelength 792 nm) upon its nonlinear propagation in air. The distinctive feature of our experimental measurements is that the droplet fluorescence is obtained in the area of plasma-free pulse propagation after the pulse filamentation has already been terminated (postfilamentation region). Our results significantly expand the working area of femtosecond laser-induced fluorescence spectroscopy for remote diagnostics of atmospheric aerosols.

Postfilament-Induced Two-Photon Fluorescence of Dyed Liquid Aerosol Enhanced by Structured Femtosecond Laser Pulse

“…Femtosecond laser-induced fluorescence spectroscopy (FLIFS) and femtosecond laser-induced optical breakdown spectroscopy (FLIBS) are important tools for remote diagnostics of atmospheric aerosols using the LiDAR techniques. High intensity values inherent to the ultrashort optical radiation allow for overcoming the energy threshold for the realization of nonlinear-optical effects of multiphoton absorption and optical breakdown of matter inside the particles and provide for the receiving the emission signal from particles at long distances in the atmosphere via the lidars [1][2][3][4][5][6][7]. At sufficiently high laser intensity, a dyed liquid particle exposed to an optical radiation can be multiphoton-excited and exhibiting nonlinear emission in the spectral band of dye fluorescence.…”

“…Worthwhile noting, the method of light-induced fluorescence stimulated by the femtosecond laser radiation is not yet sufficiently developed for using on the long-range atmospheric links [7]. Primarily, this is due to the challenges of controlling the nonlinear propagation of a high-power laser pulse at long distances because of manifestation of the filamentation phenomenon [10].…”