Hyperlens consisted by period plasmonic metamaterials is an interesting technology for the optical imaging of arbitrary objects beyond the diffraction limit in the far field, which has great potential applications in nanophotonics. However, the functionality of previously presented hyperlens is limited to image two-dimensional (2D) objects and work at a certain wavelength due to the dispersion of metal, dramatically impose restrictions on its practical application. In this paper we proposed and theoretically demonstrated a multi-wavelength tunable hyperlens, with the ability of three dimensional (3D) imaging by focal plane tuning achieved by electro-optical modulation. The simulation results indicate that full-width half-maximum (FWHM) of minimum imaging spot can be reduced down to the level of less than half-wavelength of the incident in a wide wavelength range real-timely, down to the level of ~200 nm using visible light illumination. In addition, the focal position of the hyperlens can also be tuned in large spatial scope, which greatly facilitates the application of the hyperlens in optical signal acquisition and processing.

Metal nanoparticles have attracted great interest because of their unique near-field enhancement properties, and have important applications in many fields, such as surface-enhanced Raman scattering (SERS), fluorescence enhancement, solar cell efficiency enhancement and so on. In this paper, we use the finite element method to study the local field enhancement characteristics of the coupling system in which the gold ellipsoidal nanoparticles (GENP) on a mirror. In the coupling system, a hot spot will be formed at the gap between the GENP and the mirror under the appropriate incident light excitation. Based on the structural characteristics of GENP, we systematically study the local electric field produced by placing ellipsoids vertically and horizontally on the mirror. Under the excitation of the same polarized incident light, the maximum local electric field of the vertical GENP is 2200 (V/m), while that of the horizontal GENP is more than 9400 (V/m). Our proposed gap coupling system based on metal nanoparticles and thin films may open a new field of interest in the fields of plasmon, sensing, optical limitation and enhancement.

The characteristics of gap plasmon formed by nanoparticle-on-mirror (NPOM) structures composed of metal nanoparticles (MNPs) and metal thin films have aroused interest for use in various optoelectronic devices. The resonance enhancement characteristics in the gap region of an NPOM structure composed of gold nanoparticles and gold thin films are simulated theoretically by the finite element method (FEM). The resonant spectrum obtained by the internal coupling effect of the gap can be flexibly controlled by the polarization of incident light and the thickness of the dielectric layer between the MNPs and the metal thin films. We study the resonance spectra of polarization-dependent gold ellipsoidal nanoparticles (GENPs) and gold thin films in the gap region of an NPOM structure. The GENPs and gold thin films are separated by a dielectric layer with a refractive index of 1.36. We observe that the intensity of the resonance electric field in the gap region is inversely proportional to the polarization angle. Similarly, the intensity of the local electric field resonance peak in the gap region is inversely proportional to the thickness of the dielectric layer. When the thickness of the dielectric layer is 0.3 nm and the polarization angle is 0°, the best resonant electric field intensity of 2200 V/m is obtained in the gap region of the NPOM structure (the power of incident light is 1 mW). Finally, the resonant peak wavelength of the electric field in the gap region of the NPOM structure is also controlled by the polarization angle of the incident light and the thickness of the dielectric layer.

Three-dimensional plasma nanostructures with high light–thermal conversion efficiency show the prospect of industrialization in various fields and have become a research hotspot in areas of light–heat utilization, solar energy capture, and so on. In this paper, a simple chemical synthesis method is proposed to prepare gold nanoparticles, and the electrophoretic deposition method is used to assemble large-area three-dimensional gold nanostructures (3D-GNSs). The light–thermal water evaporation monitoring and surface-enhanced Raman scattering (SERS) measurements of 3D-GNSs were performed via theoretical simulation and experiments. We reveal the physical processes of local electric field optical enhancement and the light–thermal conversion of 3D-GNSs. The results show that with the help of the efficient optical trapping and super-hydrophilic surface properties of 3D-GNSs, they have a significant effect in accelerating water evaporation, which was increased by nearly eight times. At the same time, the three-dimensional SERS substrates based on gold nanosphere particles (GNSPs) and gold nanostar particles (GNSTs) had limited sensitivities of 10⁻¹⁰ M and 10⁻¹² M to R6G molecules, respectively. Therefore, 3D-GNSs show strong competitiveness in the fields of solar-energy-induced water purification and the Raman trace detection of organic molecules.

The growth of a low-temperature polycrystalline silicon (LTPS) thin film on a flexible polyethylene terephthalate (PET) substrate under the assistance of helium plasma has been examined in detail in this study. By utilizing the plasma enhanced chemical vapor deposition method, LTPS thin films are directly deposited on a PET substrate at a relatively low temperature (80 °C), and the variations in the morphology, structure, and electrical property of the samples with He flow are systematically characterized by performing a series of tests. The results show that the purely helium-diluted silane plasma has the function of inducing crystallization and fabricating the c-Si network. After optimizing the He flow rate to 600 SCCM, the LTPS thin film with the largest average grain size of ∼204.7 nm can be obtained, while the maximum dark conductivity (4.16 × 10−5 S/cm) is also achieved. Finally, a detailed discussion is presented to illustrate the growth mechanism of the LTPS thin film in He plasma.