INTERFEROMETRIC SYSTEM FOR PRECISE SUBMICROMETER PARTICLE SIZING

Following a recently exploited line of thought, we present an interfer ometric system for particle sizing in the submicrometer region. The ph ase of the field that results from the interference between the incide nt and the scattered waves is measured through a heterodyne detection scheme in a Mach-Zehnder-type interferometer. We explored the possibil ity of extending previous work on this subject to the case of larger p articles, i.e., particles larger than 0.5 mu m. Experimental results o btained with polystyrene spheres in the range of diameters 0.16-0.71 m u m are reported and compared with theoretical predictions. We show th at in this range univocal detection of the particle size is not succes sful because the phase versus particle-size plot exhibits a maximum in correspondence to diameters close to 0.5 mu m. (C) 1997 Optical Socie ty of America.