Optical levitation of mie-resonant silicon particles in the field of bloch surface electromagnetic waves

Manipulating the motion of nanoparticles in liquid media using the near field of integrated optical elements is associated with enhanced viscous friction and an increased probability of adhesion. One of the ways to overcome these difficulties is the search for systems with a minimum of potential energy located at a distance from the structure surface. In this paper, we numerically study the forces acting on Mie-resonant silicon particles in water in the evanescent field of a Bloch surface wave and propose a method for localizing such particles at a controlled distance from the surface. For this purpose, we use surface waves at two optical frequencies, which provide different signs of interaction with the particle and different depths of field penetration into the medium. As an example, we consider a silicon sphere with a diameter of 130 nm in the field of laser radiation with wavelengths of 532 and 638 nm and a total power of 100 mW; taking into account the Brownian motion, we show that the proposed method provides stable particle localization at an equilibrium distance to the surface, adjustable in the range from 60 to 100 nm.