Feng Qun Zhou

Plasmonic analogue of electromagnetically induced transparency in a T-shaped metallic nanohole array and its sensing performance

In this paper, a plasmonic analogue of electromagnetically induced transparency (EIT) is demonstrated theoretically in a T-shaped silver nanohole array. A sharply narrow reflectance transparency window is clearly observed within the background spectrum of the broad dipole-like resonance at optical frequencies when structural asymmetry is introduced. Furthermore, the transparency peak exhibits highly sensitive response to the refractive index of surrounding medium and yield a sensitivity of 725 nm/refractive index unit (RIU), which ensures our proposed nanohole array as an excellent plasmonic sensor. In addition, the dependence of figure of merit (FOM) on structural asymmetry is investigated numerically to optimize the sensing performance of the EIT-based sensor.

Magnetic-coupling induced transparency in a planar terahertz metamaterial

In this paper, we demonstrate that an electromagnetically induced transparency (EIT)-like behavior is induced by the coupling of two magnetic resonances in a planar terahertz (THz) metamaterial structure, which consists of a U-shaped split ring (USR) as one bright resonator and a cut wire pair (CWP) as one dark resonator. It is found that the EIT-like spectral response is insensitive to the lateral distance between the two magnetic resonators, whereas an on-to-off modulation of the amplitude of the transparency window can be achieved by moving the USR vertically along the CWP. The underlying physical mechanism is mainly attributed to magneto-inductive excitation of the CWP. This investigation may provide an insight of the role of magnetic coupling in achieving EIT-like effect, inspiring interest in the developments of magnetically tunable transparency metamaterial for a wide range of optical devices with switching and modulation capabilities.

Unusual Blueshifting of Optical Band Gap of CdS Nanocrystals through a Chemical Bath Deposition Method

CdS nanocrystals are synthesized through a chemical bath deposition method. After annealing, these nanocrystals are enlarged according to Scherrer’s formula. Small nanocrystals display wide band gaps as a result of the quantum effect experienced by nanocrystals of a certain size. However, the absorption edge and green and red emissions of annealed CdS nanocrystals show obvious blueshift compared with the as-grown ones. After annealing, the intensity ratio of these green and red emissions increases, which indicated that the defect states are reduced. Therefore, the improvement in crystalline quality and the reduced strain contribute to the unusual blueshifting of the optical band gap and of the green and red emissions.

Influence of Buffer Agent Concentration on the Optical Properties from CdS Nanocrystals on Silicon Nanoporous Pillar Array

The chemical bath deposition (CBD) method is very crucial to the reaction rate. Generally, the rate can be controlled through tuning buffer agent concentration. CdS nanocrystals on the silicon nanoporous pillar array (CdS/Si-NPA) have been prepared through the CBD method. By varying the buffer agent concentration, the reaction rates can be tuned. The diffraction peaks of hexagonal CdS and Cd can be observed due to the reduction of Cd2