低数值孔径聚焦系统俘获多个Rayleigh粒子

Low Numerical Aperture Focusing System Optical Trapping Multiple Rayleigh Particles

两束不同偏振态的光入射到由两个透镜组成的聚焦系统,利用Richard-Wolf矢量衍射理论计算系统的衍射场分布,分析了数值孔径(NA)较小时系统对Rayleigh粒子的俘获特性。金粒子的折射率大于周围介质(nm),空气泡的折射率小于周围介质。NA=0.58 nm时,光轴上产生明暗相间的光斑阵列,可以用来同时俘获多个亚波长大小的金粒子和空气泡。NA=0.35 nm时,沿着光轴产生波长大小的圆环阵列,可2D俘获多个空气泡。

Two beams of light with different polarizations are incident on a focusing system with two lenses. Based on Richard-Wolf vectorial diffraction theory, the diffraction field distribution is calculated. Properties of optical trapping using the focusing system are analyzed when numerical aperture （NA） of lenses is low. A gold particle＇s refractive index is higher than that of the medium （nm）, and an air bubble＇s is lower. When NA=0.58 nm, subwavelength bright and dark spot array is generated on the optical axis. These spots can be used to trap multiple gold particles and air bubbles. When NA=0.35 nm, wavelength cylindrical rings are formed around the optical axis, which can be used to two-dimensionally trap multiple air bubbles.