Experimental Comparison of Fiber Receivers and a Pinhole Receiver for Dynamic and Static Light Scattering

Abstract

We have done a study to compare the performance of different optical receivers in both static light scattering and photon correlation spectroscopy experiments. We have compared the results of a commercially available pinhole receiver and three different self-constructed fiber receivers using respectively single-mode, few-mode, and multimode optical fibers. Collection efficiency and spatial coherence factor were experimentally determined and linked to the fiber parameters. Four different monomodal and three different bimodal colloidal suspensions were prepared and measured by photon correlation spectroscopy using different optical receivers. Five different analysis algorithms were used to retrieve particle parameters and size distribution functions: the cumulant method, the non-negatively least-squares method, the exponential sampling method, CONTIN, and the double-exponential method. All programs were part of the Brookhaven ISDA software analysis packet. Special attention was focused on the reproducibility and experimental resolution of the different optical receivers. One monodisperse sample was used to study the noise characteristics of the different optical receivers and to interpret them in terms of Schätzel's noise model for photon correlation spectroscopy (Schätzel, K. Quantum Opt. 1990, 2, 287). For their performance in static light scattering experiments, special attention was given to ease of alignments of the different optical receivers to get a stable symmetrical optical configuration. Each optical receiver was used to perform a static light scattering experiment on the biological macromolecule bovine lens α-crystallin. The experimental results were compared for their reliability and experimental errors on the macromolecular parameters. The single-mode and pinhole receiver performed very well for photon correlation spectroscopy while for static light scattering the best results were obtained for the pinhole and the few-mode receiver. The multimode receiver performed much worse than the other receivers in both photon correlation spectroscopy and static light scattering.