Versatile and high-quality manipulation of asymmetric modes in bent metal nanowires

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As a symmetry-breaking system, bent metal nanowires (MNWs) are able to guide asymmetric plasmon modes, but are also subject to deteriorated waveguiding performance. Previous studies mainly focused on bending losses or longitudinal modes, while the inherent asymmetric nature of the transverse mode was often overlooked and its potential in high-performance manipulation has remained unlocked. Meanwhile, they also showed contradictory conclusions regarding the effect of the bend that need further study. Here, we investigate the previously neglected field-deformation effects to demonstrate their significance on mode behaviors, and propose manipulation strategies of asymmetric modes with excellent qualities that are even higher than their symmetric counterparts in straight MNWs. We show that the field distributions can be translationally, rotationally, and longitudinally reformed, allowing not only extra degrees of freedom in manipulations, but also possibilities to convert the bending into a favorable factor for mode quality. Even for sharply bent MNWs with a sub-wavelength bending radius, the quality of the asymmetric mode can be greatly enhanced, even enabling a figure of merit almost twice its symmetric counterpart in straight MNWs without bending. Our findings may greatly extend the capabilities of bent MNWs, offering new opportunities in high-performance plasmonic components and flexible devices.