Fabrication of Submicrometer High Refractive Index Tantalum Pentoxide Waveguides for Optical Propulsion of Microparticles

Design, fabrication, and optimization of tantalum pentoxide ($\hbox{Ta}_{2}\hbox{O}_{5}$ ) waveguides to obtain low-loss guidance at a wavelength of 1070 nm are reported. The high-refractive index contrast ( ${\mit\Delta}n\sim 0.65$, compared to silicon oxide) of $\hbox{Ta}_{2}\hbox{O}_{5}$ allows strong confinement of light in waveguides of submicrometer thickness (200 nm), with enhanced intensity in the evanescent field. We have employed the strong evanescent field from the waveguide to propel micro-particles with higher velocity than previously reported. An optical propelling velocity of 50 $\mu\hbox{m/s}$ was obtained for 8-$\mu\hbox{m}$ polystyrene particles with guided power of only 20 mW.