Twin photonic hooks generated from two adjacent dielectric cylinders
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Twin photonic hooks generated from two adjacent dielectric cylinders Song Zhou1 Received: 20 January 2020 / Accepted: 13 August 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Photonic hooks (PHs) are a new class of curved light beams, they have been theoretically predicted and experimentally observed. The generation of photonic hook (PH) is related to the symmetry-broken of micro-particles under a plane wave illumination. Recently, twin photonic hooks (t-PHs) can be produced utilizing twin-ellipse micro-cylinder. In this paper, we investigate two adjacent parallel cylinders illuminated by a single TE-polarization plane wave for the t-PHs generation using the finite element method. We find that the full width at half-maximum (FWHM) of the t-PHs is less than the diffraction limit (λ/2), but larger than the FWHM of the photonic nanojet (PNJ) formed by a single cylinder. The shape profiles of the t-PHs can be modulated by changing the spacing length and the diameter of the two cylinders. As the spacing length increasing, the curvature degrees of center lines of the t-PHs become smaller. The curvature degree is fluctuant as the cylindrical diameter changing. This work will provide novel applications in optical trapping, nanolithography and integrated optics. Keywords Twin photonic hooks · Two adjacent cylinders · Hook modulation
1 Introduction Light traveling straight lines in a homogeneous medium is a well-known theory in geometric optics (Saleh et al. 1991). In 2007, Airy self-acceleration process was first predicated and experimentally observed in optics (Siviloglou et al. 2007; Siviloglou and Christodoulides 2007). This beam propagates along a curved parabolic trajectory in space. Its long curved traveling line makes itself defying diffraction effects. This makes Airy beam processing tremendous potential in super-resolution imaging (Zhang et al. 2017). Recently, another new class of curved light beam, the so-called “photonic hook” (PH), was first introduced by Minin and Minin (2015). They showed that an electromagnetic beam configuration can be bent after through an asymmetrically shaped dielectric particle (Ang et al. 2018; Yue et al. 2018; Minin et al. 2018, 2019). The nature of a PH is the dispersion of the * Song Zhou [email protected] 1
Faculty of Mechanical and Material Engineering, Huaiyin Institute of Technology, Huai’an 223003, China
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phase velocity of the waves inside a particle, resulting in an interference afterwards (Minin et al. 2019). Due to its sub-wavelength curvilinear trajectory, the PH has important application prospects in optical imaging, nanoparticle manipulation, and so on (Dholakia and Bruce 2019). Based on the idea of the dispersion of the phase velocity resulting PH generation, different approaches have been introduced to produce PHs, such as a dielectric trapezoid particle (Ang et al. 2018; Yue et al. 2018; Minin et al. 2018, 2019), Janus micro-cylinders (Gu et al. 2019), and twin-ellipse
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