On-chip phase measurement for microparticles trapped on a waveguide

Polystyrene microparticles are trapped on a waveguide Young interferometer and the phase change caused by the trapped particles is measured. This is a novel, on-chip method that can be used to count and characterize trapped particles. The trapping of single particles is clearly identified. Simulations show that the phase change increases with the diameter up to 7 mu m, while for larger particles, morphologydependent resonances appear. For 7 mu m particles, a phase change of -0.13 rad is measured, while the simulated value is -0.28 rad. Extensive simulations are carried out regarding the phase change, waveguide transmission and the forces on the particles, and also regarding sources of the discrepancy between simulations and measurements.