Bidirectional optical transportation and controllable positioning of nanoparticles using an optical nanofiber

Abstract

This work provides a technique allowing bidirectional optical transportation and controllable positioning of nanoparticles using two counter-propagating laser beams at a wavelength of 980 nm in an optical nanofiber. With the assistance of an evanescent wave at the fiber surface, particles suspended in water were trapped onto the fiber by a gradient force and then transported along the fiber by a scattering force. By changing the difference between the input laser powers coupled into two ends of the fiber with ΔP = -10 to 10 mW, the magnitude and direction of the scattering force that acted on the particles were changed, and thus the transportation direction and velocity of the particles were controlled. According to these properties, the bidirectional optical transportation of the particles along the fiber can be realized by coupling different laser powers into the two ends of the fiber (ΔP≠ 0 mW). At the same time, the transported particles can be controllably positioned on the fiber by coupling the same laser powers into the two ends of the fiber (ΔP = 0 mW). The relationship between the transportation velocity of the particles and the input optical power difference was investigated. Experiments were conducted with a 910 nm diameter fiber and 713 nm diameter polystyrene (PS) particle suspensions to demonstrate the effectiveness of this method. The experimental results were interpreted by numerical simulation and theoretical analysis.

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

Optical nanofiber integrated into an optical tweezers for particle manipulation and in-situ fiber probing

“…Finally, the nanofibre field may be tailored by changing the input wavelength, power, or light polarisation; this shows that the combined tweezers-nanofibre system has further potential for use in fluorescence and spectroscopy studies, using the nanofibre as a passive (collection) or active (excitation) probe. The evanescent field structures of non-uniform fibre elements [37], and complex evanescent fields under counter propagating light [20] and higher mode propagation [25,35,38] may also be investigated using this system.…”

“…These are then propelled along the direction of light propagation via radiation pressure. Since their establishment as optical propulsion tools [19], nanofibres have been used for bidirectional particle conveyance [20], wavelength selective particle sorting [21], and mass biological particle migration under photophoresis [22]. Such methods have exciting applications as particle 'conveyor belts' and sorting mechanisms in enclosed systems, particularly as their mm-scale lengths also facilitates continuous and long range trapping at any point in a sample, beyond limits achievable with conventional focussed-beam tweezers.…”

Optical Nanofiber Integrated into Optical Tweezers for In Situ Fiber Probing and Optical Binding Studies

“…The evanescent field structures of non-uniform fiber elements [36] and complex evanescent fields under counter propagating light [22] and higher mode propagation [27,34,37] may also be investigated using this system.…”

“…These are then propelled along the direction of light propagation via radiation pressure. Since their establishment as optical propulsion tools [21], nanofibers have been used for bidirectional particle conveyance [22], wavelength selective particle sorting [23] and mass biological particle migration under photopheresis [24]. Such methods have exciting applications as particle "conveyor belts" and sorting mechanisms in enclosed systems, particularly as their mm-scale lengths also facilitate continuous and long-range trapping at any point in a sample, beyond the limits achievable with conventional focused-beam tweezers.…”