Nanoparticle characterization with off-axis holography

Particles with dimensions smaller than the wavelength of visible light are essential in many fields. As particle size and composition greatly influence particle function, fast and accurate characterisation of these properties is important. Traditional approaches use the Brownian motion of the particles to deduce their size, and therefore requires to observe the particles for many consecutive time-steps. In addition, such techniques can only be applied in environments with known viscosity, hindering characterization in complex environments. In this work, we demonstrate characterisation of subwavelength particle size and refractive index surpassing that of traditional methods using two orders of magnitude fewer observations of each particle, with no reference to particle motion. This opens up the possibility to characterise and temporally resolve the properties of subwavelength particles in complex environments where the relation between particle dynamics and size is unknown.