Yidong Hou

Design and Fabrication of Three-Dimensional Chiral Nanostructures Based on Stepwise Glancing Angle Deposition Technology

The chiral structures have displayed some inevitable and fascinating properties in many research fields, such as chemistry, biology, mathematics, and physics. In this Article, we report the use of stepwise glancing angle deposition technology to produce the 3D chiral nanostructures. Through the optimization of deposition parameters (such as the orientation angle of poly styrene spheres (PSs) array, the deposition angle, thickness, and number), a great number of chiral structures have been achieved, and their size depends on the diameter of PS spheres. These chiral structures all can be simulated and predesigned through the use of a 3D geometrical model, which greatly improves the efficiency of this method. In addition, the circular dichroism spectrum shows that these chiral structures own an obvious Cotton effect, indicating their potential application as 3D chiral metamaterials.

Synthesis and Photoluminescence Enhancement of Silver Nanoparticles Decorated Porous Anodic Alumina

Silver nanoparticles (Ag NPs) were successfully assembled in porous anodic alumina (AAO) templates via a green silver mirror reaction. The Ag NPs/AAO composite templates then were characterized by field emission scanning electron microscopy (FESEM), energy-dispersive X-ray microanalysis (EDX), and X-ray diffraction (XRD). Furthermore, the photoluminescence (PL) properties were also investigated. Compared with the blank AAO, the PL intensity of Ag NPs/AAO templates are enhanced and the maximum enhancement is 2.58 times. Based on the local electric field enhancement effect, the theoretical values were also deduced, which are basically coincident with the experimental.

Templated fabrication of hollow nanospheres with ‘windows’ of accurate size and tunable number

The ‘windows’ or ‘doors’ on the surface of a closed hollow structure can enable the exchange of material and information between the interior and exterior of one hollow sphere or between two hollow spheres, and this information or material exchange can also be controlled through altering the window’ size. Thus, it is very interesting and important to achieve the fabrication and adjustment of the ‘windows’ or ‘doors’ on the surface of a closed hollow structure. In this paper, we propose a new method based on the temple-assisted deposition method to achieve the fabrication of hollow spheres with windows of accurate size and number. Through precisely controlling of deposition parameters (i.e., deposition angle and number), hollow spheres with windows of total size from 0% to 50% and number from 1 to 6 have been successfully achieved. A geometrical model has been developed for the morphology simulation and size calculation of the windows, and the simulation results meet well with the experiment. This model will greatly improve the convenience and efficiency of this temple-assisted deposition method. In addition, these hollow spheres with desired windows also can be dispersed into liquid or arranged regularly on any desired substrate. These advantages will maximize their applications in many fields, such as drug transport and nano-research container.

Polarization conversion based on plasmonic phase control by an ultra-thin metallic nano-strips

Ultra-thin metallic nano-strips (thinner than skin depth) can lead to anomalous reflection for a transverse magnetic (TM) incidence of some wave-lengths, due to the phase modulation of localized surface plasmon resonance. Based on the principle above, we proposed a method of polarization modulation using ultra-thin metallic nano-strips. When irradiating nano-strips vertically by light with a given polarized angle, we can utilize the phase difference of the TM transmission and transverse electric (TE) transmission near anomalous reflection region to modulate transmission polarization. We have designed and fabricated the ultra-thin metallic nano-strips with the function of quarter-wave plate, the attained transmission Stokes parameter S3 is 0.95. The nano-strips is easy to design and fabricate, also compatible with other optics devices, hence has the potential applications in integrated optics field.

Broadband Asymmetric Light Transmission at Metal/Dielectric Composite Grating

Optical diode-like effect has sparked growing interest in recent years due to its potential applications in integrated photonic systems. In this paper, we propose and numerically demonstrate a new type of easy-processing metal/dielectric cylinder composite grating on semi-sphere substrate, which can achieve high-contrast asymmetric transmission of unpolarized light for the sum of all diffraction modes in the entire visible region, and effectively guide the diffraction light transmitting out the substrate. The asymmetric light transmission (ALT) ratio is larger than 2 dB in the waveband from 380 nm to 780 nm and the maximum ALT ratio can reach to 13 dB at specified wavelengths. The thorough theoretical research reveals that the proposed metal/dielectric pillar composite grating structure, together with the substrate, can effectively excite localized surface plasmonic resonance (LSPR) effect and waveguide mode (WGM), and enlarge the diffraction difference between forward and backward transmission spaces, including both number of diffraction orders and diffraction efficiency, thus resulting in high-contrast broadband ALT phenomenon. In particular, lowering the symmetry of the grating can achieve polarization-dependent ALT. Such a type of easy-processing ALT device with high performance for both polarized and unpolarized light can be regarded as suitable candidates in practical applications.

Theoretical Reveal of Intriguing Standing Wave Modes of Carrying Space Beat-Frequency Phenomenon in Nanopillar Arrays

In this work, we demonstrate a kind of new standing wave modes of carrying space beat-frequency effect in an optimized nanopillar array, which can greatly reshape the electric filed distribution and result in high-quality biosensors. The in-depth theoretical research reveals that the mismatch of SPP wave vector and the light wave vector of high-order modes in medium is the crucial factors. The coupling distance, the SPP propagation distance, and the structure parameters also have been systematically investigated. Our results enrich the standing wave modes in nanostructures and give new insights into the fundamental understanding of the standing wave modes.

Enhanced chiral response from the Fabry–Perot cavity coupled meta-surfaces*

The circular dichroism (CD) signal of a two-dimensional (2D) chiral meta-surface is usually weak, where the difference between the transmitted (or reflected) right and left circular polarization is barely small. We present a general method to enhance the reflective CD spectrum, by adding a layer of reflective film behind the meta-surface. The light passes through the chiral meta-surface and propagates towards the reflector, where it is reflected back and further interacts with the chiral meta-surface. The light is reflected back and forth between these two layers, forming a Fabry–Perot type resonance, which interacts with the localized surface plasmonic resonance (LSPR) mode and greatly enhances the CD signal of the light wave leaving the meta-surface. We numerically calculate the CD enhancing effect of an L-shaped chiral meta-surface on a gold film in the visible range. Compared with the single layer meta-surface, the L-shaped chiral meta-surface has a CD maximum that is dramatically increased to 1. The analysis of reflection efficiency reveals that our design can be used to realize a reflective circular polarizer. Corresponding mode analysis shows that the huge CD originates from the hybrid mode comprised of FP mode and LSPR. Our results provide a general approach to enhancing the CD signal of a chiral meta-surface and can be used in areas like biosensing, circular polarizer, integrated photonics, etc.

Fluorescence enhancement of the organic light-emitting material based on self-assembly technology

In this paper, a simple Tris (8-hydroxyquinolinato) aluminium (Alq3) /Ag particles/glass substrate trilayer structure was fabricated to investigate the metal-enhanced photoluminescence phenomena. The polystyrene sphere (PS) self-assembly technology was used to constitute nanoscale metallic particle array on the glass substrate. Based on the localized surface plasmons (LSPs) excited by these metallic particles, fluorescence enhancement of the organic light-emitting material has been actualized. The finite-difference time-domain (FDTD) simulations have been performed to analyze the experiment results. Subsequently, an optimized design which depended on the extinction cross-section of the metallic particles was proposed to improve the enhancement factor.