Länk Nils Odebo, Johansson Peter, Käll Mikael
Opt Express. 2018 Oct 29;26(22):29074-29085. doi: 10.1364/OE.26.029074.
Nanoparticles made of high index dielectric materials have seen a surge of interest and have been proposed for various applications, such as metalenses, light harvesting and directional scattering. With the advent of fabrication techniques enabling colloidal suspensions, the prospects of optical manipulation of such nanoparticles becomes paramount. High index nanoparticles support electric and magnetic multipolar responses in the visible regime and interference between such modes can give rise to highly directional scattering, in particular a cancellation of back-scattered radiation at the first Kerker condition. Here we present a study of the optical forces on silicon nanoparticles in the visible and near infrared calculated using the transfer matrix method. The zero-backscattering Kerker condition is investigated as an avenue to reduce radiation pressure in an optical trap. We find that while asymmetric scattering does reduce the radiation pressure, the main determining factor of trap stability is the increased particle response near the geometric resonances. The trap stability for non-spherical silicon nanoparticles is also investigated and we find that ellipsoidal deformation of spheres enables trapping of slightly larger particles.
由高折射率介电材料制成的纳米颗粒引起了人们的极大兴趣，并已被应用于各种领域，如超颖透镜、光捕获和定向散射。随着能够制备胶体悬浮液的制造技术的出现，对这类纳米颗粒进行光学操控的前景变得至关重要。高折射率纳米颗粒在可见光范围内支持电和磁多极响应，这些模式之间的干涉会产生高度定向的散射，特别是在第一个克尔条件下反向散射辐射的抵消。在这里，我们展示了一项使用转移矩阵方法计算可见光和近红外光下硅纳米颗粒上光学力的研究。研究了零反向散射克尔条件作为降低光阱中辐射压力的途径。我们发现，虽然不对称散射确实会降低辐射压力，但阱稳定性的主要决定因素是几何共振附近颗粒响应的增加。还研究了非球形硅纳米颗粒的阱稳定性，我们发现球体的椭球变形能够捕获稍大一些的颗粒。
