Chunya Luo

Dual-band tunable perfect metamaterial absorber in the THz range.

In this paper, a dual-band perfect absorber, composed of a periodically patterned elliptical nanodisk graphene structure and a metal ground plane spaced by a thin SiO(2) dielectric layer, is proposed and investigated. Numerical results reveal that the absorption spectrum of the graphene-based structure displays two perfect absorption peaks in the terahertz band, corresponding to the absorption value of 99% at 35μm and 97%at 59μm, respectively. And the resonance frequency of the absorber can be tunned by controlling the Fermi level of graphene layer. Further more, it is insensitive to the polarization and remains very high over a wide angular range of incidence around ±60(0). Compared with the previous graphene dual-band perfect absorption, our absorber only has one shape which can greatly simplify the manufacturing process.

Dynamically Electrically Tunable Broadband Absorber Based on Graphene Analog of Electromagnetically Induced Transparency

A broadband absorber, which is composed of graphene analog of electromagnetically induced transparency (EIT) and a metal ground plane spaced by a thin SiO 2 dielectric layer, is proposed and investigated. Numerical results reveal that the working bandwidth can be dynamically tuned between broadband absorption and narrowband absorption by varying the Fermi level of graphene through controlling of the electrostatic gating. Furthermore, absorption behaviors can be tuned to the state of off when the electric polarized is rotated to another axis. It is also found that the coupling strength between the radiative element and dark element is tuned by the distance between the disconnected vertical graphene strip and horizontal graphene strip. In addition, this type of graphene-based absorber is very sensitive to the incident angles.

Investigation of optical pump on dielectric tunability in PZT/PT thin film by THz spectroscopy.

The dielectric spectra of single-layer PbTiO3 (PT), single-layer PbZrxTi1-xO3 (PZT) and multilayer PZT/PT thin films under an external optical field were investigated at room temperature by time-domain terahertz (THz) spectroscopy. Results showed that the real part of permittivity increased upon application of an external optical field, which could be interpreted as hardening of the soft mode and increasing of the damping coefficient and oscillator strength. Furthermore, the central mode was observed in the three films. Among the dielectric property of the three thin films studied, the tunability of the PZT/PT superlattice was the largest.

Direct thermal tuning of the terahertz plasmonic response of semiconductor metasurface

In this study, the tunable depth of an array of semiconductor indium antimonide (InSb) subwavelength strips was studied by isothermally increasing the intrinsic carrier density, and then increasing the plasma frequency and the dielectric constant in the terahertz (THz) regime. It could be found that the tunable depth can attain 79.07% and the quality factor Q can be up to 7.1 in the window between 0 and 1.2 THz from 450 to 250 K. In order to improve the performance of the device, the strip array of semiconductor InSb on a ferroelectric strontium titanate film was also investigated. The results showed that when the temperature varied from 450 to 250 K, the modulation depth increased and attained 84.06%. These findings would facilitate the design of tunable components in the communication region of the THz regime.

Dynamically tunable terahertz cross polarization amplitude based on graphene metamaterial

We theoretically demonstrated broadband,highly efficient metamaterial-based terahertz polarization converters that the perpendicular polarization amplitude can be dynamically tuned by varying the Fermi energy without reoptimizing and refabricating the nanostructures.

Effect of optical pump on the dielectric properties of the Barium Strontium Titanate film

ABSTRACT We investigated the tunability of the dielectric characterization spectra of the Ferroelectric Barium Strontium Titanate (Ba0.5Sr0.5TiO3) thin films in an external optical field through the terahertz time-domain spectroscopy. The real part of the permittivity reached up to 22% when we applied the optical field up to 600mW/cm2 and the imaginary part is not really obvious. And the results are attributed to the soft mode harden caused by the excited optical field.

Investigation of Electric Field Induced Terahertz Modulation Effects in Graphene Nanoribbons

We describe very fast electron dynamics for a graphene nanoribbon (GNR) driven by a control electric field in the terahertz frequency regime.The electron mobility of the GNR can be calculated through the nonlinear Boltzmann transport equation by numerical simulation.The results indicate the terahertz modulation depth of graphene nanoribbon is 2.6%.

Study on Frequency Selective Surface Bandstop Filter in the terahertz frequency

Frequency Selective Surface Band stop Filter in THz frequency is presented. The center frequency of the filter is 0.103THz, its stopband transmission rate reaches to 99.37% and bandwidth of 3dB reaches to 105GHz.