Yanan Hao

Multi-band terahertz metasurface absorber

A terahertz metasurface perfect absorber with multi-band performance is demonstrated. The absorber is composed of a ground plane and four split-ring resonators (SRRs) with different dimensions, separated by a dielectric spacer. The numerical simulation results illustrate that the proposed absorber has four distinct absorption peaks at resonance frequencies of 4.24, 5.66, 7.22, and 8.97 THz, with absorption rates of 96.8%, 99.3%, 97.3%, and 99.9%, respectively. Moreover, the corresponding full width at half-maximum (FWHM) values are about 0.27, 0.35, 0.32, and 0.42 THz, respectively, which are much broader than those of previously reported absorbers. Besides, the calculated magnetic field distributions allow us to understand the absorption mechanism in detail. The effects of incident angle and azimuthal angle on the absorber are also investigated. The results show that the proposed absorber is partially sensitive to the incident angle, which makes this design promising for practical applications in terahertz imagers and detectors.

Enhanced photoluminescence properties of SrTiO3:Pr3+ nanocrystals by the “TEG-sol” method

SrTiO3(STO):Pr3+ nanopowders are synthesized because of their excellent photoluminescence (PL) performance. The PL intensity is enhanced by morphological control and oxygen vacancy. The “TEG-sol” method is used to prepare STO:Pr3+ nanopowders with a size lower than 10 nm. Abundant oxygen vacancies are formed in the nanopowders without any further processing. The effect of annealing temperature on the PL properties is systematically studied. Bright green-white emission is achieved from pristine STO:Pr3+. Red emission is obtained after annealing at a temperature higher than 400 °C. A flexible and translucent STO:Pr3+/polyvinylidene fluoride nanocomposite film is fabricated, which shows outstanding PL and dielectric properties.SrTiO3(STO):Pr3+ nanopowders are synthesized because of their excellent photoluminescence (PL) performance. The PL intensity is enhanced by morphological control and oxygen vacancy. The “TEG-sol” method is used to prepare STO:Pr3+ nanopowders with a size lower than 10 nm. Abundant oxygen vacancies are formed in the nanopowders without any further processing. The effect of annealing temperature on the PL properties is systematically studied. Bright green-white emission is achieved from pristine STO:Pr3+. Red emission is obtained after annealing at a temperature higher than 400 °C. A flexible and translucent STO:Pr3+/polyvinylidene fluoride nanocomposite film is fabricated, which shows outstanding PL and dielectric properties.

High-efficiency polarization conversion phase gradient metasurface for wideband anomalous reflection

An ultra-wideband polarization conversion metasurface based on S-shaped metallic structure is designed and prepared. The simulation results show that the polarization conversion bandwidth is 14u2009GHz for linearly polarized normally incident electromagnetic waves and the cross-polarized reflectance is more than 99% in the range of 10.3u2009GHz–20.5u2009GHz. On the premise of high reflection efficiency, the reflective phase can be regulated by changing the geometrical parameter of the S-shaped metallic structure. A phase gradient metasurface composed of six periodically arrayed S-shaped unit cells is proposed and further demonstrated both numerically and experimentally. The specular cross-polarization reflection of the phase gradient metasurface is below −10u2009dB, which shows a good performance on manipulating the direction of the reflected electromagnetic waves.

Wideband terahertz absorber based on Mie resonance metasurface

Terahertz absorber has attracted much attention. However, most of them have complex structures and narrow bandwidth. Here, a wideband terahertz metasurface absorber based on Mie resonance is demonstrated. The metasurface absorber is prepared by combining four dielectric resonators with different permittivity values into a single unit cell. The absorption of the wideband metasurface absorber goes beyond 80% from 8.37 to 8.60 THz, showing wideband absorption performance. In addition, the center frequency of the wideband metasurface absorber can be tuned by the size and permittivity of the dielectric resonators, which makes the proposed absorber suitable for applications in wideband terahertz devices.

Bandwidth Enhancement of Microstrip Patch Antenna Using Complementary Rhombus Resonator

By using complementary rhombus resonator (CRR), a small-size and low-profile microstrip patch antenna (MPA) with broad bandwidth has been proposed. Parametric studies were conducted to illustrate the working principle of the proposed antenna. An additional resonance is introduced by the CRR to broaden the bandwidth. Compared with the MPA without the CRR, the bandwidth of the proposed antenna is increased by 200%. The measured results are in good agreements with the simulated ones, which demonstrate that this design provides a way to obtain the broadband antenna.

Outstanding Photoluminescence in Pr3+-Doped Perovskite Ceramics

Ba (Zr0.2Ti0.8) O3-50% (Ba0.7Ca0.3) TiO3 (BZT-0.5BCT) ceramics with different doping contents of Pr3+ were prepared by the conventional solid-state reaction. The phase structure and crystallinity of the fabricated ceramics were investigated by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. Photoluminescence (PL) emission spectra were measured to analyze the PL characteristics. The strong intensities of a green band at 489 nm and a red band at 610 nm were observed. The maximum emission intensity of the PL spectrum was achieved in the BZT-0.5BCT ceramic with 0.2% mol of Pr3+ ions. Furthermore, the PL spectra of BZT-0.5BCT ceramics were found to be sensitive to polarization of the ferroelectric ceramics. Compared with the unpoled ceramics, the green emission increased about 42% and a new emission peak at 430 nm appeared for the poled ceramics. With excellent intrinsic ferroelectricity and an enhanced PL property, such material has potential to realize multifunctionality in a wide application range.

Wideband metasurface filter based on complementary split-ring resonators

A wideband metasurface filter based on complementary split-ring resonators (CSRR) has been prepared. The frequency and transmission bandwidth of the metasurface filters with different split widths are discussed. After analyzing the mechanism of the metasurface, the proposed metasurface filters are fabricated. The electromagnetic properties of the metasurface are measured by a designed test system. The measured results are in good agreement with the simulated ones, which shows that the metasurface filter has a wideband property. As the split width of the CSRR increases, the frequency of the passband shifts to higher frequency regions and the transmission bandwidth decreases.