Yundong Ren, Rui Zhang, Chaoyang Ti, and Yuxiang Liu
Tapered optical fibers with special geometries are desired for probing monolithic in-plane nanophotonic devices, as well as for optical trapping and manipulation. In this work, we demonstrate two special geometries of tapered optical fibers, namely fiber loops and helices. The fiber loops in this work are distinct from previous ones in terms of their superior mechanical stability and high optical quality factors in air, thanks to a post-annealing process. We experimentally measured an intrinsic optical quality factor of 32,500 and a finesse of 137 for a fiber loop. A fiber helix was used to characterize a monolithic cavity optomechanical device. Moreover, a microfluidic “roller coaster” was demonstrated, where microscale particles in water were optically trapped and transported by a fiber helix. Tapered fiber loops and helices can find various applications ranging from on-the-fly characterization of integrated photonic devices to particle manipulation and sorting in microfluidics.