光纤探针型近场光镊光强分布特性的数值模拟

光纤探针型近场光镊是近场光学领域中的新型技术,因其可对纳米尺度微粒直接进行捕获和操纵而受到广泛关注,其光纤探针尖端的近场分布特性影响着纳米粒子捕获及操纵的成败探针金属膜外侧电磁场由光波在针尖小孔处衍射而成,根据夫朗和费衍射公式分析了圆形纳米小孔的光波衍射图样,运用时域有限差分法（FDTD）研究了均匀平面波垂直入射于镀膜光纤探针的近场分布,比较了不同锥角、不同出射孔径、不同金属膜厚度及不同入射波长的近场分布情况,并对不同情况下的通光效率进行了分析。通过对各参数的计算与比较,结果表明,当锥角越大、孔径越大、镀合适膜厚并且入射波长越小时,探针尖端的出射光强越大并具有较大的通光效率

Numerical Simulation of the Near-field Properties of Near-field Optical Tweezers Probe

Near-field optical tweezers is a new technique in the near-field optics that attracts much attention for trapping and manipulating nano—scale particles,and needs to obtain the near-field distribution of tapered metal-coated optical fiber probe.The study on the diffraction properties after passing through nano-aperture can forward understand the diffraction phenomenon of probe in near-field electromagnetic distribution.The near—field distribution of tapered metal-coated optical fiber probe is then characterized based on the 3D finite difference time domain（FDTD）.The relationships between the near-field magnitude and the taper angle,aperture size,metallic cover thickness and the incident wavelength are analyzed,keeping other parameters unalterable.The calculation result reveals that large light intensity and good limiting efficiency of optical fiber probe can be obtained with bigger taper angle,larger aperture size,proper cover thickness and shorter wavelength.