Systematic analysis of optical gradient force in photonic crystal nanobeam cavities

In this work, we provide systematic analysis of the optical force for a particle trapped in the waveguide/cavity/waveguide system. The theoretical analysis shows that the optical trapping force is proportional to QT1/2/V for the particle at a fixed position. We provide numerical proof for the proposed principles and systematically optimize the design recipe to investigate optical tapping force of photonic crystal (PhC) nanobeam cavities. The numerical results are in accordance with theoretical analysis and show that the maximum optical trapping force for a particle occurs at the transmission of cavity around 0.25 and the maxima are almost the same for different PhC cavities.