Evanescent wave optical trapping and transport of micro- and nanoparticles on tapered optical fibers

Trapping and Propelling Microparticles at Long Range by Using an Entirely Stripped and Slightly Tapered No-Core Optical Fiber

“…Alternatively, we have also utilized the video-based particle-tracking software “Tracker” [15] to perform the quantitative particle video analysis [12]. Figure 4 shows the temporal trajectory of the trapped and propelled microparticle along the slightly tapered no-core optical fiber versus the recording time from 25.542 s to 35.958 s. Because the trapped microparticle was propelled at long range, the recorded images were taken at several different regions of the tapered fiber.…”

“…In the movie, we have found that the flow speed of an untrapped particle can reach as high as 154 μm·s −1 by using the particle video analysis. If the laser light source is replaced by a new one with an infrared wavelength [13], under which the optical absorption and heating effect of the silica glass fiber can be reduced, the observed propulsion speed will be at the same scale as the other reports [7,8,10,12,13]. The high propulsion speed of the trapped particle is also reported in Reference [11], where the wavelength of the used laser source is also 532 nm.…”

“…Nevertheless, the fabrication process of a submicrometer strip waveguide is tedious. Similarly, the evanescent wave optical trapping and propulsion of microspheres along subwavelength ultra-thin optical fibers has also been demonstrated [7–12]. In this approach, a short section of the single-mode optical fiber was tapered to submicrometer dimensions such that a significant fraction of the propagating mode coupled from the core to the cladding can penetrate an appreciable distance into the surrounding medium around the surface of the highly tapered optical fiber and thus can be exploited for the optical trapping and propelling of individual and clustered microparticles.…”

“…In this approach, a short section of the single-mode optical fiber was tapered to submicrometer dimensions such that a significant fraction of the propagating mode coupled from the core to the cladding can penetrate an appreciable distance into the surrounding medium around the surface of the highly tapered optical fiber and thus can be exploited for the optical trapping and propelling of individual and clustered microparticles. Microparticles around the tapered nanofiber surface can be trapped by the optical gradient force of the evanescent filed and propelled by the scattering force in the same direction as the laser light propagates [12]. The tapered fiber has the benefit of higher configuration flexibility and lower optical insertion loss compared with the planar integrated waveguide.…”

“…Further, since the glass rod that constitutes a no-core optical fiber is an optical waveguide that has an evanescent wave along its entire surface, using a slightly tapered no-core optical fiber for trapping and propelling microparticles results in longer delivery range. On the other hand, in comparison with a heavily tapered optical fiber (subwavelength optical wire) [7–12], because the diameter of the slightly tapered no-core optical fiber is much larger than the optical wavelength of the coherent laser light, the numerous high-order modes in the multimode no-core optical fiber will result in many tiny interfering optical speckles and provide a more uniform evanescent wave around the fiber surface, which may allow microparticles to be attracted and propelled with forces that have a smoother spatial distribution. As a result, the few-mode interference beating effect [14] can be avoided in performing the evanescent wave trapping and propelling of microparticles by a slightly tapered no-core optical fiber.…”