Paper published in Optics Communications

Our work on the focal volume structure of spatially inhomogeneous polarization beams focused by a novel 'fractal' axicon has been published as Zhirong Liu, Kelin Huang, Xun Wang & P. H. Jones 'Tight focusing of radially polarized beams modulated by a fractal conical lens' Opt. Commun. 402 231-237 (2017).

From the abstract: A novel high numerical aperture (NA) focusing system with a fractal conical lens (FCL) is proposed, and tight focusing of radially polarized beams through the proposed optical system is investigated theoretically and numerically. The influence of several relevant factors, including the FCL’s stage $S$, objective lens’ NA, and truncation parameter ${\beta }_0$, on the targeted beam’s focusing characteristics in the focal region is discussed in detail. It is found that, when a FCL with S≥0$\mathrm{}$ is employed, position of the major focal point would shift from the geometric focal point, and the focused intensity distributions cannot maintain symmetrical about the focus any more, although they present different profiles for various truncation parameters ${\beta }_0$. When $S\ge 2$, multiple focal points can be generated, i.e., a single major focus and a series of subsidiary foci surrounding it along the optical axis, which form a focal region. These unique focusing characteristics with a FCL are remarkably different from that of without a FCL. The fascinating findings here may be taken advantage of when using radially polarized beams in exploiting new-type optical tweezers and making use of a FCL.

Paper published in Nano Letters

Our theoretical study of optical binding effects between nonspherical particles has been published as S. H. Simpson, P. Zemánek, O. M. Maragò, P. H. Jones & S. Hanna.  'Optical binding of nanowires', Nano Letters 17 3485-3492 (2017).

 From the abstract:  Multiple scattering of light induces structured interactions, or optical binding forces, between collections of small particles. This has been extensively studied in the case of microspheres. However, binding forces are strongly shape dependent: here, we turn our attention to dielectric nanowires.  Using a novel numerical model we uncover rich behavior. The extreme geometry of the nanowires produces a sequence of stationary and dynamic states. In linearly polarized light, thermally stable ladder-like structures emerge. Lower symmetry, sagittate arrangements can also arise, whose configurational asymmetry unbalances the optical forces leading to nonconservative, translational motion. Finally, the addition of circular polarization drives a variety of coordinated rotational states whose dynamics expose fundamental properties of optical spin. These results suggest that optical binding can provide an increased level of control over the positions and motions of nanoparticles, opening new possibilities for driven self-organization and heralding a new field of self-assembling optically driven micromachines.