双层介质球体所受光作用力的分析与计算

Analysis and Calculation of the Optical Force on a Double-Layer Dielectric Sphere

计算了双层介质球体的光作用力。结果表明 ,双层结构内外层相对折射率和相对厚度的变化都将影响光作用力的大小。特别是当内层折射率大于外层折射率时 ,减小内层半径可得到一较小区域 ,在此区域光镊系统刚度将得到有效提高 ,可实现对双层介质球体的稳定束缚 ;而当内层折射率小于外层折射率时 ,随内层半径的减小 ,介质小球可能有两个稳定平衡点出现。

Optical force was calculated for a double- layer dielectric sphere. Results indicate that the optical force was determined by the relative refractive index and thickness of the two layers.Especially,when the refractive index of the innerlayeris higherthan thatof the outerlayer,a smallerregion,where the trapping stiffness is improved effectively,can be achieved with the reducing of the radius of the inner layer,and the double- layer dielectric sphere can be confined stably in this region.In comparison,if the index of refraction of the inner layeris lowerthan thatof the outerlayer,two stable equilibrium positions may be found when the inner radius decreases.