Optical chromatography of ultrasmall particles by Brownian motion in a tilted optical potential induced by bound states in the continuum

We investigate sorting Rayleigh optical particles up to several nanometers in size during Brownian motion in a tilted periodic potential with multiple deep wells. The wells are induced by optical bound states in the continuum within a system of parallel photonic crystal slabs immersed in a liquid. The Brownian dynamics of the particles is significantly altered by resonant optical forces, leading to the complete spatial separation of particles with a size difference of approximately 1% during the diffusion process. In addition, the possibility of creating an integrated platform for continuous optical sorting is discussed. (c) 2025 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI)training, and similar technologies, are reserved.