Water pollution remote sensing by laser induced fluorescence based on microlaser and semiconductor photon counter

We are reporting on research and development of a water pollution remote sensing technique, based on laser induced fluorescence of organic pollutants floating on the water level or dissolved in water. We are relying on a diode pumped Nd:YAG microlaser, providing 1 microjoule 600 ps long pulses at 532 nanometers wavelength with repetition rate of 10 kHz within a compact, small and low power package. The fluorescence signal is detected by a silicon photon counting detector. A compact time to digital converter with 20 picoseconds timing resolution and a personal computer interface has been constructed for the device. The small receiving optics apertures together with advanced time filtering of the detected signal permits to operate in an outdoor environment in a daylight background conditions with acceptable signal to noise ratio. The indoor tests of the device indicate its capability of detection of sub-micrometer oil films on the water level even at high noon. The capability of detection of dissolved organic substances has been demonstrated as well.