Advanced double-pulse UV source for laser-induced fluorescence of bio-aerosols

摘要

To enhance discrimination of UV-laser-induced-fluorescence based bio-aerosol-detection-system, a UV-laser is described that allows multiple wavelength excitation of bio-aerosols and both fluorescence spectral and time-decay analysis. The latter requiring sub-ns pulse duration, a two-stage-amplifier boosts a 20-μJ-1064-nm-500-ps-actively-Q-Switch microchip-oscillator output energy up to 2.5 mJ. After frequency doubling and beam splitting, 20-μJ-293-and-337-nm pulses are generated by two different periodically-poled-KTP (parametric generation) and BBO (frequency doubling) crystal arrangements. In order to get distinct fluorescence signals for each wavelength, the beams are then time-delayed with two optical fibers of different lengths and launched into a chamber for bio-aerosol excitation connected to a fast detection system.