We demonstrate a novel technique to determine the size of Mie scatterers with high sensitivity. Our technique is based on spectral domain optical coherence tomography measurements of the dispersion that is induced by the scattering process. We use both Mie scattering predictions and dispersion measurements of phantoms to show that the scattering dispersion is very sensitive to small changes in the size and/or refractive index of the scatterer. We also show the light scattered from a single sphere is, in some cases, non-minimum phase, and therefore the phase of the scattered light is independent of the intensity. Phase dispersion measurements may have application to distinguishing the size and refractive index of scattering particles in biological tissue samples.

We present spectroscopic swept-source optical coherence tomography (OCT) measurements of the phase-dispersion of cell samples. We have previously demonstrated that the phase of the scattered field is, in general, independent of the intensity, and both must be measured for a complete characterization of the sample. In this paper, we show that, in addition to providing a measurement of the size of the cell nuclei, the phase spectrum provides a very sensitive indication of the separations between the cells. Epithelial cancers are characterized by many factors, including enlarged nuclei and a significant loss in the architectural orientation of the cells. Therefore, an in vivo diagnostic tool that analyzes multiple properties of the sample instead of focusing on cellular nuclei sizes alone could provide a better assessment of tissue health. We show that the phase spectrum of the scattered light appears to be more sensitive to cell spacing than the intensity spectrum. It is possible to determine simultaneously the cell nuclei sizes from the intensity spectrum and the nuclei spacing from the phase spectrum. We measure cell monolayer samples with high and low cell density and compare measured results with histograms of the cell separations calculated from microscope images of the samples. We show qualitative agreement between the predicted histograms and the interferometric results.

We demonstrate a novel technique to determine the size of Mie scatterers with high sensitivity. Our technique is based on spectral domain optical coherence tomography measurements of the dispersion that is induced by the scattering process. We use both Mie scattering theory and dispersion measurements of phantoms to show that the scattering dispersion is very sensitive to small changes in the size and/or refractive index of the scatterer.