In this work, quantum cascade laser (QCL) mid-infrared (MIR) reflectance spectroscopy is used to discriminate silicate and carbonate minerals in a standoff measurement setting. The tunable external cavity QCL source that was used allows measurements from 5.2 μm to 13.4 μm wavelength, where the fundamental vibrational bands of silicates and carbonates are observed. Spectra measured from a half-core sample were analyzed using multivariate analysis to extract and identify the end-member spectra from the mixtures. The end-member spectra were compared and validated using the ASTER database spectra and the spectra measured on reference samples with the same QCL MIR reflectance spectroscopy setup. Spectra of minerals commonly found in the mining industry were compared: quartz, microcline, albite, chlorite, muscovite, biotite, calcite and dolomite. MIR reflectance spectroscopy using compact QCL sources allow rapid spectral measurements at standoff distances and high spatial resolution. All these advantages show the potential of QCL MIR reflectance spectroscopy for in-the-field mining applications.
Cavity ring down measurement approach is a promising technique for biosensing as it is insensitive to intensity
uctuations of a laser source. This technique in conjunction with ultra high Q microcavities have a great
potential for ultra sensitive biosensing. Until now, most work on microcavity biosensors has been based on
measurement of the resonant frequency shift induced by binding event on surface of the microcavity. Such
measurements suer from the noise due to intensity
uctuations of the laser source. However, the binding event
will also introduce shift in quality factor of the microcavity, which can be tracked by using cavity ring down
spectroscopy. In this work, we report on experimental demonstration of application of ring down measurement
approach to microcavities for biosensing by tracking disassociation phase of a biotin-streptavidin reaction. These
measurements were performed by using a bioconjugated ultra high Q microtoroidal cavity immersed in a liquid
microacquarium. We found that disassociation curves agree with previously reported results on the protein
kinetics measurements.
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