Hollow laser beam induced photoacoustic trapping of micro-sized particles with various sizes

We report on the investigations on photoacoustic trapping with a ring-shaped ns-pulsed laser beam. Simulations indicate that magnitude of the photoacoustic force is closely dependent on laser energy, pulse duration and size of the particle. And position of the photoacoustic traps is decided by both the radius and width of the beam ring. Experimentally, we successfully achieved photoacoustic trapping of PS spheres of different radius. It is found that smaller samples are more likely to be trapped but larger particles are of higher trapping stability. The experimental results agree well with the simulations. This work is useful for understanding and describing photoacoustic trapping, and also provides references for choosing suitable experimental parameters in experiments.