Probing colloidal physics on the nanometer length scale

The sharp spectral features associated with ultra-high Q microresonator modes are sensitive to changes in the local environment and surface of the resonator [1]. Microresonator cavities have been used to detect the binding of single molecules [2] and viruses in an aqueous medium. We report on recent experiments that use microresonators to access colloidal physics on the nanometer length scale. We examine shifts in the resonator as a function of bulk ionic strengths and surface adsorption in a colloid. \\[3pt] [1] S. Arnold et al., Nature Methods {\bf 5}, 591 - 596 (2008)\\[0pt] [2] A. M. Armani, et al. Science {\bf 317}, 783-787 (2007).