Ruisheng Liang

Active plasmonic band-stop filters based on graphene metamaterial at THz wavelengths.

Active plasmonic band-stop filters based on single- and double-layer doped graphene metamaterials at the THz wavelengths are proposed and investigated numerically by using the finite-difference time-domain (FDTD) method. The metamaterial unit cell structure is composed of two parallel graphene nanoscale ribbons. Simulated results exhibit that significant resonance wavelength shifts can be achieved with a slight variation of the doping concentration of the graphene ribbons. Besides, the asymmetry double-layer graphene metamaterial device has two apparent filter dips while the symmetry single-, double-layer and asymmetry single-layer graphene metamaterial devices just only one. The metamaterials with symmetry single-layer and asymmetry double-layer graphene can be used as a high-sensitivity refractive sensor with the sensitivity up to 5100 nm/RIU and a two-circuit switch, respectively. These prospects pave the way towards ultrafast active graphene-based plasmonic devices for THz applications.

The imaging property of photoacoustic Fourier imaging and tomography using an acoustic lens imaging system

The theory of photoacoustic tomography imaging using an acoustic lens imaging system has been investigated, and the photoacoustic (PA) Fourier imaging property of an acoustic lens is presented. The theoretical results show that an acoustic lens is able to realize two-dimensional PA Fourier imaging and the focal depth of the acoustic lens is 20mm. The PA signals with the advantage of time resolution can be resolved in time domain by time-resolved technique. Therefore, this long focal depth characteristic of the acoustic lens can be combined with time-resolved technique to realize PA tomography imaging. It is demonstrated by experiments that this method is able to provide PA tomography images of biological tissue. The images are clear and contrast sharply with their backgrounds. The depth resolution is 1.54mm.

Visible-wavelength metalenses for diffraction-limited focusing of double polarization and vortex beams

In recent years, two-dimensional functional optical devices utilizing metasurfaces to manipulate phases of light develop rapidly. In this paper, we demonstrated metalenses according to the geometric Pancharatnam–Berry phase concept based on zinc sulfide (ZnS) material. Metalenses at the visible wavelengths λ=405, 532 and 633 nm have the capacity to focus incident light down to diffraction-limited spots with corresponding transfer efficiencies of 72%, 65%, 67%, respectively. A full-hybrid metalens was developed to adapt for double-polarized light focusing, which altered the condition that metalenses designed by geometric phase concepts could not focus different polarized light into one spot. In addition, we realized the conversion of the circularly polarized plane light into a vortex beam and focusing the vortex beam simultaneously by one device.

Multifunctional Sensors and Switch in MDM Waveguide With Symmetric Dual Side-Coupled Nanodisks

A multirole waveguide with symmetric dual side-coupled nanodisk resonators, which can act as refractive index sensor, temperature sensor, and optical switch, is proposed and investigated numerically. By the finite-difference time-domain simulations, it is demonstrated that the value of the refractive index sensitivity of the nano-sensor can reach 1333 nm/RIU. And with ethanol fully filled in the resonators, it can act as a temperature sensor with temperature sensitivity of 0.52 nm/°C. Furthermore, by filling with liquid crystal material, the transmittance of the optical switch is up to 73.6% at the wavelength of 1310 nm. This letter may pave a way for multifunctional applications in the on-chip nano-sensing area.

Analogue of electromagnetically induced absorption with double absorption windows in a plasmonic system

We report the observation of an analog of double electromagnetically induced absorption (EIA) in a plasmonic system consisting of two disk resonators side-coupled to a discrete metal-insulator-metal (MIM) waveguide. The finite-difference time-domain (FDTD) simulation calculations show that two absorption windows are obtained and can be easily tuned by adjusting the parameters of the two resonance cavities. The consistence between the coupled-model theory and FDTD simulation results verify the feasibility of the proposed system. Since the scheme is easy to be fabricated, our proposed configuration may thus be applied to narrow-band filtering, absorptive switching, and absorber applications.