INTENSITY CALIBRATION AND SENSITIVITY COMPARISONS FOR CCD RAMAN SPECTROMETERS

A calibrated tungsten source combined with a fiber optic was used to correct Raman spectra for instrumental response. With the placement of the fiber output at the Raman sample position, the product of throughput, collection efficiency, quantum efficiency, and sampled area could be assessed. This product is related to a spectrometer figure of merit, which provides a quantitative comparison of spectrometer sensitivity and signal-to-noise ratio. Four spectrometer configurations were compared to illustrate the approach. An additional feature of the white light calibration is correction of relative Raman peak intensities. This issue is particularly important due to the substantial differences between CCD quantum efficiency curves and those of photomultipliers or intensified photodiode arrays.