Fiber diameter influence on optical transport of dielectric particles along subwavelength optical fibers

We investigate a fiber diameter influence on optical transport of dielectric particles along subwavelength optical fibers using a near infrared laser of 1.55 μm wavelength. Theoretical analysis indicates that at 1.55 μm, the evanescent field at the fiber surface increases at first and then decreases with an increase of the fiber diameter from 600 nm to 1.6 μm, exhibiting a maximum at the fiber diameter of 950 nm. Based on three-dimensional finite-difference time-domain simulations, optical scattering forces acted on the dielectric particles and transport velocities of the particles were calculated for two fibers in the diameters of 930 nm and 1.5 μm. To support the theoretical analysis, experiments were performed using the two fibers to transport SiO2 particles (sizes of 530 nm and 1.5 μm) and TiO2 particles (size of 1.5 μm). The results show that with the same laser power launched into the two fibers, larger transport velocities can be obtained along the 930 nm diameter fiber.