Layout of the instrument showing the laser sources (upper section), the optical chain (central section), and the detection and control electronics (lower section). The gray plugs represent connections to the personal computer dedicated to the acquisition. The analysis and the acquisition computers are linked through the Ethernet network.
Emission spectrum of the Ti:sapphire laser running in cw (black diamonds) and mode-locking (empty diamonds) regime with a pump power of . The FWHM of the instrumental response function (gray squares) is also shown on the right axis. The output power in mode locking is (horizontal marker) for almost all the wavelengths.
Plots of the fitted (a) and (b) for increasing values of the pulse width using, as IRF, either the system response recorded for the lowest width (empty diamonds) or the reference pulse (filled diamonds). In the latter case the effect of the pulse broadening can be compensated up to about .
Plots of the fitted (a) and (b) for increasing values of the temporal drift of the system using, as IRF, either the system response recorded for null drift (empty diamonds) or the reference pulse (filled diamonds). In the latter case the effect of the temporal shift is completely canceled out.
(a) Absorption and (b) reduced scattering spectra of a water solution of 0.53% Intralipid (solid fraction) with no added ink. The measured absorption [panel (a), empty diamonds] is compared to the absorption spectrum of pure water (panel a, solid line), while the measured scattering [panel (b), empty diamonds] is fitted with a power low derived from Mie theory [panel (b), solid line].
Linearity plots of the measured (top row) and (bottom row) as a function of the nominal absorption (left column) and reduced scattering coefficient (right column). The solid lines are the linear interpolations of measured values belonging either to the same scattering or to the same absorption series.
Plots of the CV on the fitted (a) and (b) as a function of the number of counts per curve. The solid line are linear interpolations in the log-log plot.
Time stability of the measured (a) and (b) over a period of . The whole spectral acquisition is repeated at intervals of . The plotted values are expressed as percentage variations with respect to the average parameters calculated over the entire experiment. Almost all the points fall within a range of variation, demonstrating the good stability of the system.
Example of application of the instrument to the characterization of the (a) absorption and (b) reduced scattering spectra of five different powders
Sample thickness and apparent density of the five powders characterized with the spectroscopy system.
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