Interferometric Laser Diode Probing of Micrometer- and Nanometer-Scale Materials

We are developing a method for real-time detection, tracking, and categorization of micrometer- and nanometer-scale particles and materials using light scattered from a swept standing-wave probe. Synchronous, phase-sensitive detection of the weakly scattered optical field is exploited to provide interferometric sensitivity and improve the signal-to-noise ratio, allowing use of low-power laser diode sources and photodiode detectors. To demonstrate the technique, we probe a set of W, C, and Cu microfibers and determine diameters and refractive-index values from a detailed comparison of lightscattering data and a numerical model. We extrapolate these results and discuss the application of laser diode sources and photodiode receivers for the detection and study of nanoscale materials