Xiangang Luo

Chinese Academy of Sciences, Peping, Beijing, China

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Publications (174)366.54 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We numerically demonstrated the sub-diffraction-limited magnified Talbot imaging in a metamaterial composed of cylindrical stacked metal/dielectric multilayer. It was found that the magnified Talbot imaging could occur without the requirement of the metal/dielectric permittivity matching condition as satisfied in the hyperlens. Specifically, in this work, a practical realization of the magnified Talbot imaging was performed by Ag/Al2O3 multilayer stack at the wavelength of 337 nm. Unlike the traditional Talbot effect, the Talbot length in this case is not a constant but a variable and the variable Talbot length can be predicted roughly by ray optics approach. The contrast of the magnified Talbot imaging is decided by both the imaginary part and the real part in permittivity of the metamaterial. In order to obtain a deep sub-wavelength magnified Talbot image at the outer surface of the cylindrical metamaterial, the outer cylindrical radius should be optimized and the imaginary part in the permittivity should be small enough.
    Applied Physics A 01/2015; · 1.69 Impact Factor
  • Advanced Optical Materials. 07/2014;
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    ABSTRACT: In this article, we present a low profile polarization reconfigurable dipole antenna using a tunable electromagnetic band-gap (EBG) structure as ground plane. The EBG structure can be dynamically modulated by tuning the loaded PIN diodes through bias voltage circuit. The EBG-based antenna is fabricated and measured. Experimental results show that the tunable EBG structure can make the dipole antenna work at four states. For the state 1 and state 2, the emitted waves with left-hand and right-hand circular polarization are produced at 4.6 GHz, and the axial ratio is 1.2 and 0.3 dB, respectively. For the state 3 and state 4, the dipole antenna radiates the linearly polarized waves with the gains of about 6 dB at 4.6 and 4.25 GHz, respectively. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1281–285, 2014
    Microwave and Optical Technology Letters 06/2014; 56(6). · 0.59 Impact Factor
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    ABSTRACT: Polarization state is of fundamental importance in electromagnetic scattering from periodic and random systems. Here we demonstrated that electromagnetic wave can be perfectly and achromatically transformed into its orthogonal polarization state by utilizing the huge anisotropy of meta-surface. More importantly, it is proved that the phase shift between two coherent inputs can be utilized to dynamically tune the polarization states of output waves. Depending on the phase difference, the outputs can be y-polarization, left handed polarization and right handed polarization for x-polarized inputs.
    Optics Communications 05/2014; 319:14–16. · 1.54 Impact Factor
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    ABSTRACT: A plasmonic bus waveguide with a side-coupled T-shaped (TS) or a reverse T-shaped (RTS) resonator consisting of a parallel and a perpendicular cavities is proposed. The compact configuration could serve as a wavelength demultiplexing device as a forbidden band is achieved based on the symmetric distribution of resonators. By shifting one cavity away from the center of the resonator, the system exhibits electromagnetically induced transparency (EIT) like transmission at the wavelength of the former forbidden band. The electromagnetic responses of the structure could be handled with certain flexibility by changing the asymmetric behavior of the TS or RTS resonator. Similar characteristics for two proposed structures could be obtained except for the center wavelength that is determined by the two cavities in the RTS resonator or by the cavity parallel to the bus waveguide in the TS resonator.
    Journal of Lightwave Technology 05/2014; 32(9):1701-1707. · 2.86 Impact Factor
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    ABSTRACT: Recently, the graphene-based absorber captures much attention due to its bright potential. In this paper, a modeling study of graphene-based absorber is made for variable magnetostatic bias, i.e., the magnetic circular dichroism (MCD). A strong MCD signal about ΔA = 0.94 is obtained in 7 T for a uniform graphene-based absorber. By periodically patterning subwavelength holes on the graphene, the structured absorber exhibits two obvious peaks induced by cavity resonance and localized resonance of meta-surface in 0 T, respectively. As the magnetic field increases, the absorption peaks show quite different electromagnetic response for the two kinds of circularly polarized lights. Two distinct MCDs signals of 0.711 at 2.02 THz and 0.91 at 2.49 THz in 7 T are observed. The results are well explained by a modified equivalent circuit model.
    Journal of Applied Physics 04/2014; 115(15):154312-154312-4. · 2.19 Impact Factor
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    ABSTRACT: wxAMPS, a custom-designed software package for solar cell simulation, is used to simulate the performance of dye sensitized solar cells (DSCs). A carrier transport process inside the semiconductor is illustrated based on the assistance of wxAMPS. It is assumed that a bent band with a build-in electrical field exists at the semiconductor-dye interface when the semiconductor particle size is large enough, while the flat-band potential exists when the semiconductor is nanocrystalline. Effects of the build-in electrical field on the performance of the unit cells are described on the basis of the simulation results. It is shown that the enhanced carrier transport and the low recombination velocity caused by the build-in electrical field lead to a better photovoltaic performance of the unit cells.
    Electrochimica Acta 04/2014; 125:218–224. · 4.09 Impact Factor
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    ABSTRACT: A dual circularly polarized horn antenna, which employs a chiral metamaterial composed of two-layered periodic metallic arc structure, is presented. The whole antenna composite has functions of polarization transformation and band-pass filter. The designed antenna produces left-handed circularly polarized wave in the band from 12.4 GHz to 12.5 GHz, and realizes right-handed circularly polarized wave in the range of 14.2 GHz-14.4 GHz. Due to low loss characteristic of the chiral metamaterial, the measured gains are only reduced by about 0.6 dB at the above two operation frequencies, compared with single horn antenna. The axial ratios are 1.05 dB at 12.45 GHz and 0.95 dB at14.35 GHz.
    IEEE Transactions on Antennas and Propagation 03/2014; 62(4). · 2.46 Impact Factor
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    ABSTRACT: Based on the theory of surface plasmon resonance and the special nano-optical effect of metal/dielectric multilayer composites, we obtained a high-resolution image of a sub-wavelength grating. We discussed multilayer parameters on equal thickness, and achieved sufficient contrast and high intensity through numerical simulation based on the finite element method. By chosen the best scheme, an experimental of multilayer planar lens lithography has been carried out. The main point is the use of metal–dielectric composites to realize high-resolution image under 365-nm polarization light incidence. By controlling the experimental parameters accurately, a fidelity image is recorded on the photoresist.
    Applied Physics A 03/2014; · 1.69 Impact Factor
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    ABSTRACT: Metamaterial composed of multistacked metal and dielectric films provides the access to ray tracing in subwavelength regions and to form a variety of transformation optical devices for manipulating light beyond the diffraction limit, such as hyperlens and cloak. In this paper, this method is employed to design planar hyperlens for demagnification imaging lithography. Variant ray route configurations are considered and compared for the sake of imaging quality as well as device structure complexity. It is found that specifically designed trajectory route from the object plane to the image plane help to yield imaging devices with uniform demagnification ratio and improved image quality. Then multiple similar imaging devices could be cascaded for further demagnification and reduce of structure complexity from the viewpoint of application. The imaging results with about 1/23 wavelength (16 nm) half-pitch resolution in the measure of electric field intensity are demonstrated with numerical simulations. Also presented are the imaging characteristic analyses including light intensity, demagnification ratio and resolution.
    Applied Physics B 02/2014; · 1.63 Impact Factor
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    ABSTRACT: We propose an efficient way to realize Fano-type resonances at optical frequencies based on a low-loss dielectric nanorod array. An ultrahigh Q factor (larger than 10000) is numerically demonstrated, which is attributed to the mode interference between the broadband Fabry–Perot (FP) resonance and the narrowband guided mode stemming from coupled quadrupoles. A wide gap region for field enhancement is formed between adjacent rods, making such a structure an ideal platform for related applications such as biological sensing and nonlinear devices.
    Applied Physics Express 02/2014; 7(3):032002. · 2.73 Impact Factor
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    ABSTRACT: In this paper, we propose a novel plasmonic lens design consisting of an annular slit and concentric grooves. The simulation results show that under radially polarized illumination, a super-resolution long depth of focus (DOF) spot can be achieved in optical meso-field due to the constructive interference of scattered light by the concentric grooves. We also analyze the influence of depth-tuned annular grooves on focusing performance, including focal length, DOF, and full-width half-maximum. Moreover, focusing efficiency can be enhanced (∼350 %) by introducing a circular metallic grating which surrounds the annular slit. This plasmonic lens has potential applications in nano-imaging and nano-photolithography.
    Plasmonics 01/2014; · 2.74 Impact Factor
  • Journal of Nanophotonics 01/2014; 8(1):083080. · 1.45 Impact Factor
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    ABSTRACT: We study on the negative and positive effect of surface roughness and loss coefficient on subwavelength imaging of the superlens structure. It has been found that even though surface roughness enables more transmission of high spatial frequency components, the random interferential noise between neighborhood images becomes more severe with increasing distortion. We show that additional loss is able to restrain the interferential noise caused by random roughness while preserving the imaging integrity. The results with practical parameters prove that the mean contrast and uniformity are improved by adding adequate loss on rough surface. Moreover, other two situations are further studied: (a) a single superlens with roughness on different interfaces and (b) a multilayered alternated metal–dielectric superlens with roughness on each surface. We found that the roughness on the imaging surface (metal–photoresist interface) plays a major role in determining the superlens imaging. The multilayer superlens is able to enhance the subwavelength imaging with fractionalized thinner films. But with the further fractionizing layers, the multilayer becomes more vulnerable to the roughness due to the multiple mixing and distorting. We still prove that additional loss is able to improve the performance in both situations.
    Plasmonics 01/2014; 9(1). · 2.74 Impact Factor
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    ABSTRACT: In this paper, an energy harvesting/re-radiating device is proposed to realize high efficiency energy conversion in the solar thermo-photovoltaic system. Such device consists of double-sided metamaterials which are assembled by a broadband absorber working in the major solar spectrum, and a back-by-back narrowband emitter working in the infrared band. It is theoretically proved that most of solar light (from 0.28 μm to 4 μm) can be collected, and then, converted to a sharp emission at the maximal response energy level (~0.4 eV) of photovoltaic cells in thermal equilibrium state. The impact of high temperature (as large as 966 K) and the parasitic radiation on the performance is discussed and compensated by geometric optimization.
    Optics Express 12/2013; 21(26):32207-16. · 3.53 Impact Factor
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    ABSTRACT: In this communication, a novel filtering antenna is proposed by utilizing active frequency selective surface (FSS), which can simultaneously achieve filtering and beam steering function. The FSS unit is composed of a metallic rectangular ring and a patch, with a pair of microwave varactor diodes inserted in between along incident electric field polarization direction. Transmission phase of the emitted wave can be tuned by changing the bias voltage applied to the varactor diodes. Through different configurations of the bias voltages, we can obtain the gradient phase distribution of the emitted wave along E- and H-plane. This active FSS is then fabricated and utilized as a radome above a conventional horn antenna to demonstrate its ability of steering the beam radiated from the horn. The experimental results agree well with the simulated ones, which show that the horn antenna with the active FSS can realize beam steering in both E- and H-plane in a range of ±30° at 5.3 GHz with a bandwidth of 180 MHz.
    IEEE Transactions on Antennas and Propagation 12/2013; 61(12):6218-6223. · 2.46 Impact Factor
  • Journal of Nanophotonics 10/2013; 7(1):073080. · 1.45 Impact Factor
  • Liang Fang, Li Pan, Changtao Wang, Xiangang Luo
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    ABSTRACT: Recently, superlens imaging lithography below the diffraction limit has been experimentally verified. However, the short exposure depth owing to the near-field attribute of this method restricts its practical application. A tri-layer resist process, which increases the pattern depth through two-step dry etching, can overcome this drawback. In this paper, we investigated the scheme of superlens imaging lithography employing a tri-layer resist process and analysed the effect of the air gap between the object and the photosensitive layer on the exposure depth by finite-difference time-domain analyses. Through optimising the three layer resist thicknesses and dry-etching parameters of the tri-layer resist process, we patterned a high aspect ratio structure with half pitch of 110 nm and depth of 400 nm in our experiment.
    Microelectronic Engineering 10/2013; 110:35–39. · 1.34 Impact Factor
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    ABSTRACT: By utilizing a reflective plasmonic slab, it is demonstrated numerically and experimentally in this paper deep sub-wavelength imaging lithography for nano characters with about 50nm line width and dense lines with 32nm half pitch resolution (about 1/12 wavelength). Compared with the control experiment without reflective plasmonic slab, resolution and fidelity of imaged resist patterns are remarkably improved especially for isolated nano features. Further numerical simulations show that near field optical proximity corrections help to improve imaging fidelity of two dimensional nano patterns.
    Optics Express 09/2013; 21(18):20683-20691. · 3.53 Impact Factor
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    ABSTRACT: A plasmonic device is proposed to produce a self-imaging surface plasmon void array (2D surface bottle beam array) by the interference of two nondiffracting surface beams, namely, cosine-Gauss beams. The self-imaging surface voids are shown by full-wave calculations and then verified experimentally with an aperture-type near-field scanning optical microscope. We also demonstrate that the void array can be adjusted with flexibility in terms of the pattern and the number of voids.
    Optics Letters 08/2013; 38(15):2783-5. · 3.39 Impact Factor

Publication Stats

1k Citations
366.54 Total Impact Points


  • 2003–2014
    • Chinese Academy of Sciences
      • Institute of Optics And Electronics
      Peping, Beijing, China
  • 2011
    • Chengdu University of Technology
      Hua-yang, Sichuan, China
    • Southwest Jiaotong University
      • School of Information Science and Technology
      Chengdu, Sichuan Sheng, China