Combined single/dual fiber optical trapping for flexible particle manipulation

a b s t r a c t Fiber-based optical tweezers have attracted increasing attention as a more flexible tool over conventional lensbased optical tweezers for particle manipulation.Stable trapping can be realized by single fiber gradient force, or dual fiber counter-propagating scattering forces.Both trapping modes and systems are often separately built and researched.In this paper, we demonstrate a combined single/dual fiber optical trapping (SD-FOT) system which allows dual trapping modes (i.e., single fiber gradient mode and dual fiber scattering mode) to be realized simultaneously in a single setup.Two tapered single fibers were used, with each fiber first captures a single microsphere near its tip by focus-induced gradient force; The two fibers (with trapped particles) were then aligned and adjusted to allow additional particles to be trapped and manipulated in the middle by the dual-fiber scattering trapping scheme.At least three particles will be trapped and manipulated by the combined trapping system, and each of particle can be used for in-situ experimental activity and analysis.Meanwhile, theoretical modeling of the optical force was established to quantify both trapping processes, and the process of the particle movement in the experiment is in accordance with the simulated force field.The developed system offers new possibilities in comparative research of single and dual fiber trapped objects and will find important applications in microspherebased super-resolution imaging and others.