Jingbo Sun

An extremely broad band metamaterial absorber based on destructive interference.

We propose a design of an extremely broad frequency band absorber based on destructive interference mechanism. Metamaterial of multilayered SRRs structure is used to realize a desirable refractive index dispersion spectrum, which can induce a successive anti-reflection in a wide frequency range. The corresponding high absorptance originates from the destructive interference of two reflection waves from the two surfaces of the metamaterial. A strongly absorptive bandwidth of almost 60 GHz is demonstrated in the range of 0 to 70 GHz numerically. This design provides an effective and feasible way to construct broad band absorber in stealth technology, as well as the enhanced transmittance devices.

Indefinite permittivity and negative refraction in natural material: Graphite

In this work, we report a nature indefinite permittivity in crystalline graphite that exhibits negative group refraction at ultraviolet region. A hyperbolic equifrequency contour was obtained from ellipsometry data at 254 nm and an all angle negative refraction was verified experimentally. The indefinite permittivity is attributed to extremely strong anisotropy in the crystal structure and the hybrid electronic transitions. This result not only explores a route toward natural negative-index materials, but also holds a promise for ultraviolet hyperlens, which may lead to a breakthrough in nanolithography for the next generation of electronics.

Voltage tunable short wire-pair type of metamaterial infiltrated by nematic liquid crystal

In this letter, we report an experimental demonstration on voltage tunable short wire-pair metamaterial with negative permeability at microwave frequencies. After infiltrated by nematic liquid crystal, magnetic resonance of short wire-pair can be effectively tuned via relatively low static electric field. The results show, by increasing bias voltage from 0 to 100 V, magnetic resonance is continuously and reversibly shifted from 9.91 down to 9.55 GHz. Moreover, the effective permeability of metamaterial, for operation frequency around magnetic resonance, varies from negative to positive values. Numerical analysis has a good agreement with experimental results.

Bidirectional pumped high power Raman fiber laser

This paper presents a 3.89 kW 1123 nm Raman all-fiber laser with an overall optical-to-optical efficiency of 70.9%. The system consists of a single-wavelength (1070nm) seed and one-stage bidirectional 976 nm non-wavelength-stabilized laser diodes (LDs) pumped Yb-doped fiber amplifier. The unique part of this system is the application of non-wavelength-stabilized LDs in high power bidirectional pumping configuration fiber amplifier via refractive index valley fiber combiners. This approach not only increases the pump power, but also shortens the length of fiber by avoiding the usage of multi-stage amplifier. Through both theoretical research and experiment, the bidirectional pumping configuration presented in this paper proves to be able to convert 976 nm pump laser to 1070 nm laser via Yb3+ transfer, which is then converted into 1123 nm Raman laser via the first-order Raman effect without the appearance of any higher-order Raman laser.

COUPLING EFFECT OF SPLIT RING RESONATOR AND ITS MIRROR IMAGE

We report on experimental and numerical studies on the coupling efiect of a single split ring resonator (SRR) and its mirror image inside an X-band hollow waveguide. It is shown that, for single SRR with gap bearing side perpendicular to E fleld, the magnetic resonance exhibits red/blue shift as SRR moves to the gap facing/backing waveguide edge, due to the capacitance and magnetic dipoles coupling efiect between original SRR and its mirror image, respectively. Furthermore, electric dipole interplay dominates the coupling efiect between SRR and its image when SRR has the gap bearing side parallel to the E fleld, although SRR is excited by E and H fleld simultaneously.

Artificial Magnetic Properties of Dielectric Metamaterials in Terms of Effective Circuit Model

An efiective series RLC model for the electromagnetic response of weakly absorbing dielectric sphere near the flrst magnetic dipole resonance was developed, and the efiective magnetic properties of Mie resonance-based dielectric metamaterials were obtained in terms of this model. In comparison with traditional efiective medium theory such as extended Maxwell-Garnett (EMG) theory based on Mie model, this approach is more intuitive and can give an analytical dependence of the magnetic properties of the composite on the electromagnetic and geometric parameters of the constituting dielectric particles.

Indefinite permittivity in uniaxial single crystal at infrared frequency

We propose a kind of indefinite media at infrared frequency without artificial structures. Natural existing indefinite media are realized based on strong anisotropy in polar lattice vibrations in different directions, parallel or perpendicular to the crystal axis. As an example, the dielectric dispersions of α -Al 2 O 3 single crystal with different polarizations of electric field are measured, the regions of indefinite permittivity are demonstrated and an all-angle negative refraction is also shown based on the simulated results. This mechanism to realize indefinite medium will supply a promising way to explore natural existing negative refractionmaterials.

Homogenous isotropic invisible cloak based on geometrical optics

Invisible cloak derived from the coordinate transformation requires its constitutive material to be anisotropic. In this work, we present a cloak of graded-index isotropic material based on the geometrical optics theory. The cloak is realized by concentric multilayered structure with designed refractive index to achieve the low-scattering and smooth power-flow. Full-wave simulations on such a design of a cylindrical cloak are performed to demonstrate the cloaking ability to incident wave of any polarization. Using normal nature material with isotropy and low absorption, the cloak shows light on a practical path to stealth technology, especially that in the optical range.

Low loss negative refraction metamaterial using a close arrangement of split-ring resonator arrays

In this work, we realize a low loss negative refraction using indefinite metamaterial of a close arrangement of split-ring resonator (SRR) arrays. A beam shift experiment has been performed to verify the negative refraction and demonstrate the low loss property. The enhanced magnetic resonance between two neighbouring SRRs broadens the resonance range and produces a frequency range with low loss. Transmission properties of the metamaterial are also analysed to characterize the negative refraction around the resonance frequency in detail.

LEFT-HANDED MATERIALS BASED ON CRYSTAL LATTICE VIBRATION

An all-dielectric composite route is proposed for the construction of a left-handed material at THz frequency. It is shown that the interaction between the crystal lattice vibration of the polaritonic dielectric and the electromagnetic wave could