Experimental study of the optical forces exerted by a Gaussian beam within the Rayleigh range

Numerical tools for the evaluation of optical forces exerted by non-focused Gaussian beams are becoming increasingly important for the design of integrated devices dedicated to cell manipulation without physical contact. Here we consider two methods for the evaluation of optical forces based on a ray-optics approach and we compare them with experimental results. We show that optical forces can be calculated with good accuracy also within the Rayleigh range of the Gaussian beam and for a wide range of particle sizes.