Multiplexed long-range electrohydrodynamic transport and nano-optical trapping with cascaded bowtie photonic crystal nanobeams

Photonic crystal cavities with bowtie defects that combine ultra-high Q and ultra-low mode volume are theoretically studied for low-power nanoscale optical trapping. By harnessing the localized heating of the water layer near the bowtie region, combined with an applied alternating current electric field, this system provides long-range electrohydrodynamic transport of particles with average velocities of 30 $\mathrm{\mu m/s}$ towards the bowtie region on demand by switching the input wavelength. Once transported to a given bowtie region, synergistic interaction of optical gradient and attractive negative thermophoretic forces stably trap a 10 nm quantum dot in a potential well with a depth of 10 $k_\mathrm{B}T$ using a mW input power.