Showing papers by "Minghui Hong published in 2013"
TL;DR: Recently, a large number of experimental and theoretical works have revealed a variety of plasmonic nanostructures with the capabilities of Fano resonance (FR) generation as mentioned in this paper, and more attention is given to the optical properties of PLASmonic oligomers due to the high potential of such structures in optical spectra engineering.
Abstract: Recently, a large number of experimental and theoretical works have revealed a variety of plasmonic nanostructures with the capabilities of Fano resonance (FR) generation. Among these structures, plasmonic oligomers consisting of packed metallic nanoelements with certain configurations have been of significant interest. Oligomers can exhibit FR independently of the polarization direction based on dipole–dipole antiparallel modes without the need to excite challenging high-order modes. The purpose of this review article is to provide an overview of recent achievements on FR of plasmonic nanostructures in recent years. Meanwhile, more attention is given to the optical properties of plasmonic oligomers due to the high potential of such structures in optical spectra engineering.
273 citations
174 citations
TL;DR: This work demonstrates the efficacy and ease of resonance tuning via GST in the near infrared, suggesting the possibility to design broadband non-volatile tunable devices for optical modulation, switching, sensing and nonlinear optical devices.
Abstract: Tunable lattice resonances are demonstrated in a hybrid plasmonic crystal incorporating the phase-change material Ge2Sb2Te5 (GST) as a 20-nm-thick layer sandwiched between a gold nanodisk array and a quartz substrate. Non-volatile tuning of lattice resonances over a range Δλ of about 500 nm (1.89 µm to 2.27 µm) is achieved experimentally via intermediate phase states of the GST layer. This work demonstrates the efficacy and ease of resonance tuning via GST in the near infrared, suggesting the possibility to design broadband non-volatile tunable devices for optical modulation, switching, sensing and nonlinear optical devices.
162 citations
TL;DR: It is demonstrated that surface-enhanced infrared absorption gains in the order of 10(5) can be easily obtained in a spectral window of 3 μm with attomolar concentrations of molecules, providing new opportunities for ultrasensitive broadband detection of molecular species via vibrational spectroscopy techniques.
Abstract: Optical antennas represent an enabling technology for enhancing the detection of molecular vibrational signatures at low concentrations and probing the chemical composition of a sample in order to identify target molecules. However, efficiently detecting different vibrational modes to determine the presence (or the absence) of a molecular species requires a multispectral interrogation in a window of several micrometers, as many molecules present informative fingerprint spectra in the mid-infrared between 2.5 and 10 μm. As most nanoantennas exhibit a narrow-band response because of their dipolar nature, they are not suitable for such applications. Here, we propose the use of multifrequency optical antennas designed for operating with a bandwidth of several octaves. We demonstrate that surface-enhanced infrared absorption gains in the order of 105 can be easily obtained in a spectral window of 3 μm with attomolar concentrations of molecules, providing new opportunities for ultrasensitive broadband detection...
125 citations
TL;DR: The vesicular membrane design may provide new insights into the design and fabrication of Aqp-embedded biomimetic membranes.
87 citations
TL;DR: In this article, a broadband log-periodic nano-antenna was proposed to generate significant electromagnetic intensity enhancements from the visible to the mid-IR wavelength regions for multispectral probing of random chemical species.
Abstract: Plasmonic nanoantennas provide new routes for efficiently detecting, analyzing, and monitoring single biomolecules via fluorescence, Raman, and infrared absorption spectroscopies. The development of efficient biosensors for multispectral spectroscopy remains nevertheless limited by the narrowband responses of plasmonic devices, as they are generally designed to operate in a specific bandwidth, matching with the absorption, scattering, or emission frequency of target biomolecules under investigation. Therefore, performing biosensing from visible to infrared frequencies systematically requires designing and fabricating multiple plasmonic nanoantenna configurations and prevents the development of nanoscale integrated sensors for multispectral probing of random chemical species. Here, we propose to overcome these limitations by using broadband log-periodic nanoantennas designed to generate significant electromagnetic intensity enhancements from the visible to the mid-IR wavelength regions. We demonstrate simu...
77 citations
TL;DR: It is proved analytically that the far-field optical properties of pentamers have to be polarization-independent due to their rotational symmetry, and the coupled dipole approximation method is employed to define a qualitative model revealing the relationship between the near and far field in such structures.
Abstract: Flexible control over the near- and far-field properties of plasmonic nanostructures is important for many potential applications, such as surface-enhanced Raman scattering and biosensing. Generally, any change in the polarization of the incident light leads to a change in the nanoparticle’s near-field distribution and, consequently, in its far-field properties as well. Therefore, producing polarization-invariant optical responses in the far field from a changing near field remains a challenging issue. In this paper, we probe experimentally the optical properties of cruciform pentamer structures—as an example of plasmonic oligomers—and demonstrate that they exhibit such behavior due to their symmetric geometrical arrangement. We demonstrate direct control over hot spot positions in sub-20 nm gaps, between disks of 145 nm diameter at a wavelength of 850 nm, by means of scattering scanning near-field optical microscopy. In addition, we employ the coupled dipole approximation method to define a qualitative m...
56 citations
TL;DR: It is concluded that uniaxial stretching has potential in patterning film topography with anisotropic structures and could be used as "basic units" to create tissue constructs with microscale control of cellular alignment and elongation for tissue engineering applications.
Abstract: Anisotropic geometries are critical for eliciting cell alignment to dictate tissue microarchitectures and biological functions. Current fabrication techniques are complex and utilize toxic solvents, hampering their applications for translational research. Here, we present a novel simple, solvent-free, and reproducible method via uniaxial stretching for incorporating anisotropic topographies on bioresorbable films with ambitions to realize stem cell alignment control. Uniaxial stretching of poly(ɛ-caprolactone) (PCL) films resulted in a three-dimensional micro-ridge/groove topography (inter-ridge-distance: ∼6 μm; ridge-length: ∼90 μm; ridge-depth: 200–900 nm) with uniform distribution and controllable orientation by the direction of stretch on the whole film surface. When stretch temperature (Ts) and draw ratio (DR) were increased, the inter-ridge-distance was reduced and ridge-length increased. Through modification of hydrolysis, increased surface hydrophilicity was achieved, while maintaining the morphol...
49 citations
TL;DR: In this paper, the authors examined the carbonaceous deposits on the surface of piston crown part before and after laser cleaning by FTIR, XPS and SEM/EDX, and they found that the deposits were distributed non-uniformly on surface and they could be distinguished as a thicker layer of contaminants, located mainly in the plug region, while a thinner layer can be found in the remaining area.
44 citations
TL;DR: In this article, a chiral meta-foil consisting of a self-supported square array of interconnected conjugated rosettes is demonstrated at terahertz frequencies.
Abstract: A chiral meta-foil consisting of a self-supported square array of interconnected conjugated rosettes is demonstrated at terahertz frequencies. It exhibits strong optical activity and circular dichroism. Negative refractive index with a figure-of-merit as high as 4.2 is achieved, attributed to its free-standing nature. Experimental results are in good agreement with numerical simulation. Free-standing chiral meta-foils provide a unique approach to create a completely all-metal chiral metamaterial, which can be flexibly integrated into optical setups while eliminating dielectric insertion losses.
32 citations
TL;DR: An increase of the photoluminescence enhancement by a factor larger than three is observed compared to antennas without the reflecting-layer and the possibility of influencing the polarization of the light emitted by utilizing asymmetry of dimer antennas is studied.
Abstract: We report on a straightforward way to increase the photoluminescence enhancement of nanoemitters induced by optical nanotantennas. The nanoantennas are placed above a gold film-silica bilayer, which produces a drastic increase of the scattered radiation power and near field enhancement. We demonstrate this increase via photoluminescence enhancement using an organic emitter of low quantum efficiency, Tetraphenylporphyrin (TPP). An increase of the photoluminescence enhancement by a factor larger than three is observed compared to antennas without the reflecting-layer. In addition, we study the possibility of influencing the polarization of the light emitted by utilizing asymmetry of dimer antennas.
TL;DR: The singular surface plasmon beam that presents a dark channel generated by a point dislocation and a long diffraction-free propagation distance up to 70λ(sp) is proposed and experimentally demonstrated.
Abstract: We propose and experimentally demonstrate the singular surface plasmon beam that presents a dark channel generated by a point dislocation and a long diffraction-free propagation distance up to 70λsp. The singular surface beam is the result of the interference of two surface plasmon polariton (SPP) plane waves, which are launched by two coupling gratings with lateral displacement. An aperture-type near-field scanning optical microscope is used to map the intensity distribution of the singular SPP waves. The propagating point dislocation embedded in the beam is shown by full-wave calculations and is later verified by near-field interference in the experiment.
TL;DR: The self-imaging surface voids are shown by full-wave calculations and then verified experimentally with an aperture-type near-field scanning optical microscope and it is demonstrated that the void array can be adjusted with flexibility in terms of the pattern and the number of voids.
Abstract: A plasmonic device is proposed to produce a self-imaging surface plasmon void array (2D surface bottle beam array) by the interference of two nondiffracting surface beams, namely, cosine-Gauss beams. The self-imaging surface voids are shown by full-wave calculations and then verified experimentally with an aperture-type near-field scanning optical microscope. We also demonstrate that the void array can be adjusted with flexibility in terms of the pattern and the number of voids.
TL;DR: By using finite element modelling to best reproduce experimental results the dielectric response of the graphene film can be determined and the potential of such structures for chemical sensing applications is discussed.
Abstract: In this article, we use optical transmission spectroscopy to measure the changes in the resonance features of a Au plasmonic nanoresonator array consisting of concentric ring/disc cavity elements, when graphene is introduced as an encapsulating medium. We show that by using finite element modelling to best reproduce our experimental results the dielectric response of the graphene film can be determined. We discuss the potential of such structures for chemical sensing applications.
TL;DR: In this article, the design and fabrication of hybrid plasmonic structures by laser means are investigated to extend flexible tuning of optical properties of metallic micro/nano-structures for high-sensitivity detection and enhancement of solar cell antireflection performance for high energy-conversion efficiency.
Abstract: Design and fabrication of hybrid plasmonic structures by laser means are investigated to extend flexible tuning of optical properties of metallic micro/nano-structures for high-sensitivity detection and enhancement of solar cell antireflection performance for high energy-conversion efficiency. It is shown that the identical micro/nano-structures in well-defined arrays fabricated by laser interference lithography can be used as a versatile platform to enhance fluorescence intensity of the molecules. Meanwhile, postprocessing of such structures via thermal annealing can result in ordered clusters of nanodots 50 nm in average size, which enhances Raman scattering intensity. A dramatic reduction in silicon surface reflectance is achieved via pulsed fiber laser texturing. The suppression of reflectance can be further improved by decorating the laser-textured Si surface with metallic nanoparticles by thermal annealing of metallic thin films deposited on the Si surfaces. This hybrid plasmonic structure scheme can achieve broadband (300-1000 nm) antireflection with a surface reflection as low as 5.5%. The improved broadband antireflection of the surfaces could have applications in solar energy, renewable energy, and electrooptical devices.
TL;DR: It is shown that nanoscale light localizations in the immediate proximity of plasmonic nano-antennas can be spatially positioned and isolated energy hot-spots at a subwavelength scale can be created and adjusted across the landscape of the plAsmonic system at a step resolution of λ/20.
Abstract: By utilizing the strongly induced plasmon coupling between discrete nano-antennas and quantitatively controlling the crystalline proportions of an underlying Ge2Sb2Te5 (GST) phase-change thin layer, we show that nanoscale light localizations in the immediate proximity of plasmonic nano-antennas can be spatially positioned. Isolated energy hot-spots at a subwavelength scale can be created and adjusted across the landscape of the plasmonic system at a step resolution of λ/20. These findings introduce a new approach for nano-circuitry, bio-assay addressing and imaging applications.
TL;DR: In this article, the effect of target temperature (TG) on electrical and optical properties was investigated, and the origin of electrical conduction was verified as the result of high TG, which enhances crystal quality that provides higher mobility of electrons as well as more effective activation for the Al dopants.
Abstract: Al-doped ZnO (AZO) films with high transmittance and low resistivity were achieved on low temperature substrates by radio frequency magnetron sputtering using a high temperature target. By investigating the effect of target temperature (TG) on electrical and optical properties, the origin of electrical conduction is verified as the effect of the high TG, which enhances crystal quality that provides higher mobility of electrons as well as more effective activation for the Al dopants. The optical bandgap increases from 3.30 eV for insulating ZnO to 3.77 eV for conducting AZO grown at high TG, and is associated with conduction-band filling up to 1.13 eV due to the Burstein–Moss effect.
TL;DR: In this paper, a 3D optical micro/nanostructures are designed and fabricated by laser means to enhance broadband optical antireflection by coating metallic nanoparticles into the structures can reduce the average reflectance down to 1.8%.
Abstract: 3D optical micro/nanostructures are designed and fabricated by laser means to enhance broadband optical antireflection. Coating metallic nanoparticles into the structures can reduce the average reflectance down to 1.8%.