Position detection using differential signals of the coupling light in a tapered-lensed dual-beam optical fiber trap

A technique for position detection in a tapered-lensed dual-beam optical fiber trap based on differential measurements is proposed. The difference in the coupling power of two tapered fibers is used to sense the position of the trapped particle. The detecting resolution can reach 45 nm. The fiber coupling theory is used to analyze the coupling efficiency of the fibers. Results show that tapered fibers are more beneficial than cleaved fibers in the differential measurements system. The influences of the radius of the taper end and the fiber separations are discussed in detail. © 2019 The Japan Society of Applied Physics