Abstract
Based on the optical trapping force of an evanescent wave at a micro-ring resonator alongside a waveguide, we propose a tunable optofluidic sorting unit for micro-nanoparticles by localized thermal phase tuning. With the tuning of field build-up factor of resonator, the depth of trapping potential well and the size of trapped particle are adjustable. Furthermore, by considering the Brownian motion of trapped particles from a statistics perspective, we verify the critical trapping threshold of a potential well, which is usually assumed to be . The threshold depends not only on the optical power and particle size, but also on the length of the coupling region. Compared with a wavelength tuning mechanism, localized thermal tuning enables large-scale integration of many independent tunable resonators. As a demonstration, we propose a set of operations with three resonators for nanoparticle manipulation, including sorting, storing, and mixing. Our proposed function units are of great importance for on-chip large-scale integration of optofluidic systems.
© 2019 Optical Society of America
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