Fig. 3. Imaging experiment with gold nanoparticles.

a False-colored SEM images of a PC surface with AuNPs of various sizes. Correspondingly, differential interferometric images are recorded using (b) NA = 0.95 and (c) NA = 1.46 objectives for the same AuNPs under PRISM modality. d Contrast histogram of AuNP signal distribution obtained using a NA = 1.46 objective. (n > 500 for each size of AuNP.) The broadening of the contrast distribution for the 40 nm-AuNPs is likely caused by the formation of multiple-particle aggregates. e Scatterplot of the signal contrast as a function of AuNP size. Each dot represents the average of 50 instances of AuNP events. Lower panel: hydrodynamic diameters of the same AuNPs obtained through dynamic light scattering measurement. A clear separation of the hydrodynamic diameter can be except for AuNPs below 10 nm in diameter, where the instability of the laser becomes overwhelming comparing with the weak NP scattering signal. The DLS measurement for each AuNP size was repeated separately five times. f Fourier plane image of the AuNP (d = 40 nm) scattered light obtained by averaging the 2D Fourier-transformed images over 6000 frames. The outer circle is equivalent to NA = 0.95 in air. Inset: a typical real-space signal pattern of a 40-nm AuNP. FOV: 4.5 μm.