We report on a compact laser system for detection of hazardous biological agents by standoff coherent anti-Stokes Raman spectroscopy (CARS). The system is based on ytterbium-laser technology featuring broad spectral coverage and high sensitivity. High-quality CARS spectra have been obtained for NaDPA powder, a substitute for CaDPA, which is the Raman marker of bacterial spores. In addition, endospores of B. atrophaeus deposited over a glass substrate have been detected by their CARS signature at a standoff distance of 1 m and an integration time of 1 s. The system will be further developed for imaging of bacterial spores deposited over wide surface areas at standoff distances.
We report on a fiber-format laser system for Fourier-transform coherent anti-Stokes Raman spectroscopy (FT-CARS) of toxic chemical hazards, such as chemical warfare agents (CWAs). The system is based on ytterbium-fiber technology featuring ultra-broad spectral coverage and high-sensitivity. High-quality CARS spectra with maximum Raman shifts of 3000 cm-1 and signal-to-noise ratio >200 for observation times of 160 μs are measured; a detection limit of one part per thousand is demonstrated with a cyanide/water solution. The system was developed as the basis for a highly accurate, sensitive, reliable and portable device for the real time detection of water contaminants and deposited CWAs at trace levels.
In this paper Tm-doped tellurite glasses (75TeO2-20ZnO-5 Na2O, mol%) were prepared and characterized, and codoping
with Yb was investigated in order to improve pump efficiency and wavelength emission range. Emission spectra and
lifetime measurements were obtained by pumping Tm-doped tellurite glasses at 800 nm and Yb-Tm co-doped tellurite
glasses at 980 nm, thus exploiting the Yb-Tm energy transfer mechanism. Highly Yb-doped Tm-tellurite glasses were
investigated (Yb2O3 concentrations up to 5 wt%) and an increase in 3F4 lifetime with Yb2O3 concentrations higher than
3% was observed. This showed that high amounts of Yb do not affect lifetime of the metastable state, thus allowing
investigation of lasers in this range of doping concentrations.
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