We have conducted studies of deep UV laser-induced fluorescence (LIF) for the reagentless detection of trace species and Dissolved Organic Compounds (DOC's) in water. Our LIF detection system had two interchangeable UV lasers, 266 nm and 355 nm, illuminating a flow cell containing a water sample. The fluorescence emitted at 90 degrees to the laser beam was collected by focusing optics, passed through cut-off and interference filters with 21 optical bandpass channels (240–680 nm ), and detected by a photomultiplier tube (PMT). The samples analyzed by the system included bottled, tap and river water; we have also worked with biological and chemical species (Bacillus Globigii, malathion). In terms of the excitation wavelength, it was observed that the deep UV excitation resulted in spectra that contained more features, and had better separation of the LIF from the Raman peak, thus enhancing the detection of unique spectral features.
Capturing a reflective cross-sectional image of an optical fiber with partially coherent laser light to measure the refractive index profile of a multimode optical fiber