Cheng-ping Huang

Optical switching of a metamaterial by temperature controlling

We have fabricated a metamaterial of metal/semiconductor/metal sandwich nanostrips structure comprising a pair of gold strips and a vanadium dioxide (VO2) strip. The optical response of the metamaterial has been studied. The results indicate the nanostructure with VO2 strips can be used as a temperature-controlling optical switch and the mechanism of this switch can be explained by the magnetic resonance.

Enhanced optical transmission through metal films with rotation-symmetrical hole arrays

The transmission of light through metal surface with subwavelength holes are influenced by many factors, and the rotational symmetry of hole arrays can be one of them. In this paper, we fabricated the hole lattices in metal films with different symmetry and measured the transmission spectra from the visible to near-infrared region. It is found that both the spectrum shape and the transmission efficiency are strongly dependent on the rotational symmetry. The spectrum shape is governed by the reciprocal vectors. And the higher is the symmetry order, the larger the peak efficiency. The results provide us with new insight into the unusual effect.

Dual effect of surface plasmons in light transmission through perforated metal films

The light transmission through square and rectangular holes in a metal film has been studied. By taking account of plasma response of real metal on hole walls as well as metal surface, an analytical result for the transmission has been deduced, which agrees well with the experiments. We show that the light transmission involves both the diffraction modes and the surface plasmons. Strong coupling of diffraction modes to surface-plasmon polariton results in the transmission minima, whereas the coupling to cavity surface plasmon leads to the transmission maxima. The results suggest a dual effect of the surface plasmons.

Study of plasmon resonance in a gold nanorod with an LC circuit model

Gold nanorod has generated great research interest due to its tunable longitudinal plasmon resonance. However, little progress has been made in the understanding of the effect. A major reason is that, except for the metallic spheres and ellipsoids, the interaction between light and nanoparticles is generally insoluble. In this paper, a new scheme has been proposed to study the plasmon resonance of gold nanorod, in which the nanorod is modeled as an LC circuit with an inductance and a capacitance. The obtained resonance wavelength is dependent on not only aspect ratio but also rod radius, suggesting the importance of self-inductance and the breakdown of linear scaling. Moreover, the cross sections for light scattering and absorption have been deduced analytically, giving rise to a Lorentzian line-shape for the extinction spectrum. The result provides us with new insight into the phenomenon.

Long-Wavelength Optical Properties of a Plasmonic Crystal

The optical properties of a plasmonic crystal composed of gold nanorod particles have been studied. Because of the strong coupling between the incident light and vibrations of free electrons, the long-wavelength optical properties such as the dielectric abnormality and polariton excitation etc., which were suggested originally in ionic crystals, can also be present in the plasmonic crystal. The results show that the plasmonic and ionic lattices may share a common physics.

Second-harmonic generation in a periodically poled congruent LiTaO3 sample with phase-tuned nonlinear Cherenkov radiation

Second harmonic generation (SHG) in a two-dimensional periodically poled congruent LiTaO3 crystal was investigated experimentally. Multiple conical and dotted SHG have been observed, which features phase-tuned Cherenkov radiation, elastic scattering quasi-phase matching process, and random phase matching process. These results are closely connecting with the domain structure and can be utilized as characterization methods for practical purposes.

Transmission resonance in a composite plasmonic structure

The design, fabrication, and optical properties of a composite plasmonic structure, a two-dimensional array of split-ring resonators inserted into periodic square holes of a metal film, have been reported. A type of transmission resonance, which makes a significant difference from the conventional peaks, has been suggested both theoretically and experimentally. To understand this effect, a mechanism of ring-resonance-induced dipole emission is proposed.

Splitting of transmission peak due to the hole symmetry breaking

We studied experimentally and theoretically the optical transmission through asymmetrical holes of a metal film, which is constructed by introducing small protuberances to the sides of individual square holes. Due to the symmetry breaking of the hole shape, an interesting transmission feature appears: both the Ag-glass (1, 0) and Ag-glass (1, 1) peaks split distinctly. Detailed studies indicate that the peak splitting is actually associated with the two asymmetrical waveguide surface-plasmon (WSP) modes confined on the surface of opposite hole walls. The finding demonstrates the crucial role of WSP modes and enriches our understanding of the phenomenon.

Suppression of transmission minima and maxima with structured metal surface

Extraordinary optical transmission through perforated metal films has received much attention recently. In this letter, the authors propose a method for studying the transmission properties, in which the Fourier coefficient of reciprocal lattice vectors is manipulated. Especially, due to a zero Fourier coefficient, the suppression of transmission minima and maxima has been experimentally observed. The results open a way to tailor the transmission properties of light.

Optical transmission through gold film with Archimedean-like subwavelength hole arrays

In this paper, two kinds of Archimedean-like hole arrays [Archimedean 4 (A4) and Archimedean 7 (A7)] that have been fabricated in gold films and the optical transmission spectra from the visible to near-infrared region have been measured. With A4 and A7 hole arrays, the Fourier coefficients of reciprocal lattice vectors are manipulated, with which the transmission suppression and enhancement have been experimentally observed. The results provide the possibility to manipulate the light transmission through the design of both reciprocal vectors and Fourier coefficients by engineering the metal surface.