Diffraction minima resolve point scatterers at tiny fractions (1/80) of the wavelength

Abstract

Discerning two or more identical and constantly scattering point sources using freely propagating waves is thought to be limited by diffraction. Here we show both theoretically and experimentally that by employing a diffraction minimum rather than a maximum for resolution, a given number of point scatterers can be discerned at tiny fractions of the employed wavelength. Specifically, we identify an 8 nm distance between two constantly emitting (non-blinking, non-switchable) fluorescent molecules, corresponding to 1/80 of the wavelength. Moreover, we show that contrary to naïve expectations, the measurement precision improves with decreasing distance between the scatterers and with increased scatterer density, thus opening up the prospect of resolving clusters of (optical) point scatterers at tiny fractions of the wavelength.