We examined photochemical degradation of energetic molecules upon UV resonance Raman (UVRR)
excitation of the 229 nm UVRR spectra of solid HMX, TNT and RDX. Comparisons of the UVRR spectra of these
photodegraded samples to those of different carbon samples indicate some features similar to carbon compounds with
sp2 bonding, vaguely reminiscent of graphitic carbon as well as amorphous carbon. Spinning the energetic material
samples minimizes the per molecule photon flux which decreases the photochemistry. We very roughly estimated
photochemical degradation quantum yields of <10-6.
The need for routine, non-destructive chemical screening of agricultural products is increasing due to the health hazards
to animals and humans associated with intentional and unintentional contamination of foods. Melamine, an industrial
additive used to increase flame retardation in the resin industry, has recently been used to increase the apparent protein
content of animal feed, of infant formula, as well as powdered and liquid milk in the dairy industry. Such contaminants,
even at regulated levels, pose serious health risks. Chemical imaging technology provides the ability to evaluate large
volumes of agricultural products before reaching the consumer. In this presentation, recent advances in chemical
imaging technology that exploit Raman, fluorescence and near-infrared (NIR) are presented for the detection of
contaminants in agricultural products.
The fabrication of ion-exchanged waveguides with high-frequency doubling conversion efficiency requires high-quality crystalline substrates, an understanding of the effects of partial cation exchange on the optical properties of the waveguide, and control of the degree and effects of ion-exchange. To address these needs we have developed micro-Raman and luminescence spectroscopic techniques for the characterization and process control of Rb+ exchanged KTiOPO4 (R/KTP) waveguides. We report on the use of laser excited luminescence to screen device substrates for unacceptable levels of impurity transition metals, which contribute to photorefraction and optical losses due to absorption. Micro-Raman spectroscopy has been used to probe types of R/KTP channel waveguides for the degree and effects of Rb+ exchange. The high spatial resolution and nondestructive nature of micro-Raman spectroscopy make it suitable as a probe for in situ characterization of photonic devices. Specifically, micro-Raman spectroscopy can detect cation-exchange induced changes in the polarizability, reduction of crystal symmetry, and changes in the chemical bonding and orientation of TiO6 octahedra, the anionic groups primarily responsible for the nonlinear properties of the materia. Individual R/KTP waveguides from different devices have been studied by micro-Raman spectroscopy and structural differences have been detected. The uniformity of a channel waveguide is another quality that can be readily probed and quantified by micro-Raman spectroscopy.