These guided SPPs, which are referred to as SPPs with 1D materials (SPP-1D), are attracting great interest for use in high-density photonic nanocircuits. Recently, many 1D configurations have been proposed to function as SPP waveguides, such as metal nano-stripes, V-shaped grooves milled in a metal film and chemically synthesized crystalline-silver nanowires 19, 20, 21, 22, 23. Similar applications have also been demonstrated with SPP-based platform. The surface confinement of BSWs allows their propagation to be controlled by planar two-dimensional (2D) optical components, such as the controlled propagation of BSWs with simple 2D lenses 18. For example, studies have proposed and demonstrated that BSWs have some specific sensing properties, which include chemical and biosensing, gas sensing, fluorescence emission enhancement and sorting, and surface-enhanced Raman scattering 12, 13, 14, 15, 16, 17. Because of these similarities and differences with SPPs, and the extensive use of surface-bound biomolecules in research and medical diagnostics, in recent years BSWs have received much attention from the research community in recent years. BSWs can be either transverse electric (TE) or transverse magnetic polarized electromagnetic waves. They do not suffer from losses caused by metal absorption that allow for BSW resonances with high-quality factors and enhanced field intensities ( E 2) 9, 10, 11. BSWs also possess specific properties that differentiate them from SPPs. Similar to surface plasmon polaritons (SPPs), BSWs are also confined close to the interface between a dielectric multilayer and the surrounding medium, but with somewhat weaker localization the resonant angle or wavelength (referred to the position of the dip in the reflection spectrum) is very sensitive to the environment 7, 8. The multilayer substrates can be adopted to support the fragile nanofibres 5, 6. For example, a nanofibre with a radius of 125 nm will not support signals at 632.8 nm wavelength.ĭifferent from the bare glass substrates, periodic dielectric-multilayer substrates contain the well-known photonic band gap (PBG) and, in some cases, support the Bloch surface waves (BSWs). However, nanofibres on glass substrates cannot transport optical signals if the fibre radius is too small. Polymeric nanofibres are fragile, delicate to handle and must be laid down on a solid substrate (such as the commonly used glass substrate), to lead to practical devices. Electrospun fibres also display excellent biocompatibility, can be doped, are low cost and are relatively simple to align, assemble and process for a variety of applications 4. In the past years, electrospinning has been developed to the point where it is now a rapid and efficient process to fabricate continuous ultra-long one-dimensional (1D) nanomaterials composed of polymers, oxides, carbon and, more recently, metals 3. These applications demonstrate the advantages of dielectric nanofibres (or nanowires) for a wide range of technologies. Functionalized polymer nanofibres provide a versatile platform for manipulating light on the nanoscale 2. For example, semiconductor alloy nanowires with spatially graded compositions (and bandgaps) provide a new material platform for many new multifunctional optoelectronic devices, such as broadly tunable lasers, multispectral photo-detectors, broad-band light-emitting diodes and high-efficiency solar cells 1. In recent years, nanowires or nanofibres made of polymeric, semiconducting or their hybrid materials have attracted a great deal of attention.
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