Using dual-plane leakage radiation microscopy, we investigate plasmon propagation in individual penta-twinned crystalline silver nanowires. By measuring the wavevector content of the light emitted in the substrate, we unambiguously determine the effective index and the losses of the mode propagating in these structures. The experimental results, in particular, the unexpectedly low effective index, reveal the direct influence of the nanowire crystallinity and pentagonal structure on the observed plasmon modes. By analogy with molecular orbitals of similar symmetry, the plasmon modes are also determined numerically in good agreement with the observed values. We further investigate the effect of wire geometry (length, diameter) on the effective index and propagation loss. Our results show that, beyond dissipation concerns, the morphological and structural control obtained in crystalline colloidal plasmonic nanostructures can be exploited to finely tune their optical properties.

Superchiral light, generated by the interference of two counter-propagating circularly polarized light (CPL) with same frequency, opposite handedness and different intensity, exhibits enhanced dissymmetry in its interaction with chiral molecules, and has the potential for ultrasensitive detection and characterization of chiral molecules. It is anticipated that the enhanced optical dissymmetry in superchiral light (SCL) field may be utilized to promote asymmetric photochemical reactions efficiency. Herein we reported SCL impart greater chiral bias to trigger asymmetric photo-polymerization reaction from initially achiral diacetylene (DA) monomer, and the enhanced optical dissymmetry for whole polydiacetylene (PDA) films could be achieved. An explanation based on the chiral transfer and amplification of chiral bias from SCL during the polymerization process has been proposed. Moreover, thus formed chiral PDA films polymerized by SCL exhibited enhanced enantioselective recognition ability, and can serve as a direct visual probe for the discrimination of some specific enantiomers.

We demonstrate the realization of a coherent random fiber laser (RFL) in the extremely weakly scattering regime, which contains a dispersive solution of polyhedral oligomeric silsesquioxanes nanoparticles (NPs) and laser dye pyrromethene 597 in carbon disulfide that was injected into a hollow optical fiber. Multiple scattering of polyhedral oligomeric silsesquioxanes NPs greatly enhanced by the waveguide confinement effect was experimentally verified to account for coherent lasing observed in our RFL system. This Letter extends the NPs-based RFLs from the incoherent regime to the coherent regime.

Surface plasmon resonance microscopy (SPRM) with single-direction illumination is a powerful platform for biomedical imaging because of its wide-field, label-free, and high-surface-sensitivity imaging capabilities. However, two disadvantages prevent wider use of SPRM. The first is its poor spatial resolution that can be as large as several micrometers. The second is that SPRM requires use of metal films as sample substrates; this introduces working wavelength limitations. In addition, cell culture growth on metal films is not as universally available as growth on dielectric substrates. Here we show that use of azimuthal rotation illumination allows SPRM spatial resolution to be enhanced by up to an order of magnitude. The metal film can also be replaced by a dielectric multilayer and then a different label-free surface-sensitive photonic microscopy is developed, which has more choices in terms of the working wavelength, polarization, and imaging section, and will bring opportunities for applications in biology.

Polymeric fibres with small radii (such as ≤125 nm) are delicate to handle and should be laid down on a solid substrate to obtain practical devices. However, placing these nanofibres on commonly used glass substrates prevents them from guiding light. In this study, we numerically and experimentally demonstrate that when the nanofibre is placed on a suitable dielectric multilayer, it supports a guided mode, a Bloch surface wave (BSW) confined in one dimension. The physical origin of this new mode is discussed in comparison with the typical two-dimensional BSW mode. Polymeric nanofibres are easily fabricated to contain fluorophores, which make the dielectric nanofibre and multilayer configuration suitable for developing a large range of new nanometric scale devices, such as processor–memory interconnections, devices with sensitivity to target analytes, incident polarization and multi-colour BSW modes.

Bloch surface waves (BSWs) on one-dimensional photonic crystals (1DPC) have been used to beam the fluorescence emission from the dye molecules. All dielectric 1DPC displays its low propagating loss, narrow resonance and the absence of absorption or quenching. In this letter, back focal plane imaging reveals that in addition to the BSW mode, a guided mode and cavity mode also exist in the 1DPC which all couple with the excited dye molecules. The appearance of these modes is sensitive to the wavelength of the fluorescence and alters the beaming effect by the 1DPC. Numerical simulations verify the existence of these modes which are consistent with the experimental results. Comparisons between the Bloch surface wave-coupled emission (BWCE) and surface plasmon-coupled emission (SPCE) are also presented for a more clear understanding of the multilayered film-enabled directional emission.

An optical waveguide based on a PDA microtube has been prepared through a novel hierarchical assembly method. The waveguide performance of the PDA microtube can be easily modulated upon external stimuli. The polarization of the out-coupled emission light seems independent of the propagation distance, which should be ascribed to the ordered alignment of PDA chains in the microtube.

Plasmonic nanolasers have ultrahigh lasing thresholds, especially those devices for which all three dimensions are truly subwavelength. Because of a momentum mismatch between the propagating light and localized optical field of the subwavelength nanocavity, poor optical pumping efficiency is another important reason for the ultrahigh threshold but is normally always ignored. Based on a cavity-embedded nanoantenna array design, we demonstrate a room-temperature low-threshold plasmonic nanolaser that is robust, reproducible, and easy-to-fabricate using chemical-template lithography. The mode volume of the device is~0.22(/2n) 3 (here,  is resonant wavelength and n is the refractive index), and the experimental lasing threshold produced is ~2.70MW/mm 2 . The lasing polarization and the function of nanoantenna array are investigated in detail. Our work provides a new strategy to achieve room-temperature low-threshold plasmonic nanolasers of interest in applications to biological sensoring and information technology. Regarding conventional lasers, the experimental lasing threshold is known to be determined by not only the intrinsic loss of the cavity but also the pumping efficiency, which has drawn little attention in previous reports on spasers. Although electric pumping is considered to offer better prospects for spasers 22,23 Here, we report a low-threshold, room-temperature plasmonic laser and demonstrate that an optical antenna array can efficiently lower the lasing threshold of a spaser. The new device is constructed by embedding a fluorescence polystyrene sphere into a silver nanoparticle (nanoantenna) array, which combines the nanocavity and optical antennas together to promote pumping efficiency. The lasing threshold is 2.70 MW/mm 2 , more than 20 times lower than that of a room-temperature arrayed nanocavity spaser 18 . Unlike earlier struggles to decrease lasing thresholds by eliminating spaser intrinsic metal loss, we propose to increase the pumping efficiency with the optical antenna array. This array will resonantly absorb light from the pump beam and concentrate the energy into the cavity of the embedded fluorescence polystyrene sphere. Moreover, the cavity mode, which is mainly localized within the 4 polystyrene sphere, will also reduce the intrinsic metal loss. The lasing threshold and other properties of the spaser are reported and their dependences on geometric parameters of the devices are described. KEYWORDSThe lasing system, sketched in Fig.1a, is constructed by embedding a fluorescence polystyrene ball into a two-dimensional silver nanoantenna array. The 150-nm-diameter ball functions not only as a gain medium but also as a nanocavity together with the surrounding silver nanoantennas. A scanning electron microscopy (SEM) micrograph (Fig.1b), shows a periodicity of about 65 nm for the silver nanoantenna array and a diameter of about 100 nm for the cavity. The height of the nanoantenna is around 15 nm as indicated in the AFM image (Fig.1c). All these parameters are optimized to match ...