Xiangang Luo

Chinese Academy of Sciences, Peping, Beijing, China

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Publications (230)552.17 Total impact

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    ABSTRACT: Non-diffracting Bessel beams, including zero-order and high-order Bessel Beams which carry orbital angular momentum (OAM), enable a variety of important applications in optical micromanipulation, sub-diffraction imaging, high speed photonics/quantum communication, etc. The commonly used ways to create Bessel beams, including an axicon or a digital hologram written to a spatial light modulator (SLM), have great challenges to operate at the nanoscale. Here we theoretically design and experimentally demonstrate one kind of planar Bessel beam generators based on metasurfaces with analytical structures perforated in ultra-thin metallic screens. Continuous phase modulation between 0 to 2π is realized with a single element. In addition, due to the dispersionless phase shift stemming from spin-orbit interaction, the proposed device can work in a wide wavelength range. The results may find applications in future optical communication, nanofabrication and super-resolution imaging, etc.
    No preview · Article · Feb 2016 · Scientific Reports
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    ABSTRACT: With new degrees of freedom to achieve full control of the optical wavefront, metasurfaces could overcome the fabrication embarrassment faced by the metamaterials. In this paper, a broadband hologram using metasurface consisting of elongated nanoapertures array with different orientations has been experimentally demonstrated. Owing to broadband characteristic of the polarization-dependent scattering, the performance is verified at working wavelength ranging from 405 nm to 914 nm. Furthermore, the tolerance to the fabrication errors, which include the length and width of the elongated aperture, the shape deformation and the phase noise, has been theoretically investigated to be as large as 10% relative to the original hologram. We believe the method proposed here is promising in emerging applications such as holographic display, optical information processing and lithography technology etc.
    Full-text · Article · Jan 2016 · Scientific Reports
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    Yang Li · Xiong Li · Mingbo Pu · Zeyu Zhao · Xiaoliang Ma · Yanqin Wang · Xiangang Luo
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    ABSTRACT: Chromatism causes great quality degradation of the imaging system, especially for diffraction imaging. The most commonly method to overcome chromatism is refractive/diffractive hybrid optical system which, however, sacrifices the light weight and integration property of diffraction elements. A method through compensation between the structure dispersion and material dispersion is proposed to overcome the chromatism in flat integrated optical components. This method is demonstrated by making use of silver nano-slits waveguides to supply structure dispersion of surface plasmon polaritons (SPP) in metal-insulator-metal (MIM) waveguide to compensate the material dispersion of metal. A broadband deflector and lens are designed to prove the achromatic property of this method. The method demonstrated here may serve as a solution of broadband light manipulation in flat integrated optical systems.
    Full-text · Article · Jan 2016 · Scientific Reports
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    ABSTRACT: Terahertz (THz) absorber with dynamically tunable bandwidth possesses huge application value in the fields of switches, sensors, and THz detection. However, the perfect absorbers based on photonic crystals and metamaterials are not intelligent enough to capture the electromagnetic wave in a tunable way. In this paper, we utilized only patterned graphene to tune the absorption positions and the bandwidth in the terahertz regime. More distinguished than some dynamic absorbers proposed before, the performances with peak frequency relative tuning range of 68 % and nearly unity absorbance are obtained by a single cross-shaped graphene layer. Additionally, the working bandwidth can be broadened with stacked structured graphene. The almost perfect absorption shifted from 2.36∼3.2 to 3.26∼3.99 THz continuously via changing the chemical potential of graphene.
    No preview · Article · Jan 2016 · Plasmonics
  • Cheng Huang · Wenbo Pan · Xiaoliang Ma · Xiangang Luo

    No preview · Article · Jan 2016 · IEEE Transactions on Antennas and Propagation
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    ABSTRACT: Coherent control of the reflection and refraction in semicontinuous metasurfaces is realized. Both the reflection and refraction efficiency of a single-layered metasurface can be greatly improved with this method. By controlling the relative phase between the signal beam and the control beam, the Snell's law can be dynamically manipulated. This method may open possibilities to the practical application of metasurfaces.
    No preview · Article · Jan 2016 · Advanced Optical Materials
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    ABSTRACT: The past decade has witnessed a great deal of optical systems designed for exceeding the Abbe's diffraction limit. Unfortunately, a deep subwavelength spot is obtained at the price of extremely short focal length, which is indeed a near-field diffraction limit that could rarely go beyond in the nanofocusing device. One method to mitigate such a problem is to set up a rapid oscillatory electromagnetic field that converges at the prescribed focus. However, abrupt modulation of phase and amplitude within a small fraction of a wavelength seems to be the main obstacle in the visible regime, aggravated by loss and plasmonic features that come into function. In this paper, we propose a periodically repeated ring-disk complementary structure to break the near-field diffraction limit via plasmonic Fano resonance, originating from the interference between the complex hybrid plasmon resonance and the continuum of propagating waves through the silver film. This plasmonic Fano resonance introduces a π phase jump in the adjacent channels and amplitude modulation to achieve radiationless electromagnetic interference. As a result, deep subwavelength spots as small as 0.0045λ(2) at 36 nm above the silver film have been numerically demonstrated. This plate holds promise for nanolithography, subdiffraction imaging and microscopy.
    No preview · Article · Dec 2015 · Nanoscale
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    ABSTRACT: Two-dimensional metasurface has attracted growing interest in recent years, owing to its ability in manipulating the phase, amplitude and polarization state of electromagnetic wave within a single interface. However, most existing metasurfaces rely on the collective responses of a set of discrete meta-atoms to perform various functionalities. In this paper, we presented a quasi-continuous metasurface for high-efficiency and broadband beam steering in the microwave regime. It is demonstrated both in simulation and experiment that the incident beam deviates from the normal direction after transmitting through the ultrathin metasurface. The efficiency of the proposed metasurface approximates to the theoretical limit of the single-layer metasurface in a broad frequency range, owing to the elimination of the circuit resonance in traditional discrete structures. The proposed scheme promises potential applications in broadband electromagnetic modulation and communication systems, etc.
    Full-text · Article · Dec 2015 · Scientific Reports
  • Xianchao Liu · Xiong Li · Ling Li · Weidong Chen · Xiangang Luo

    No preview · Article · Nov 2015 · Optics Express
  • Cheng Huang · Wenbo Pan · Xiaoliang Ma · Bo Zhao · Jianhua Cui · Xiangang Luo
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    ABSTRACT: A reconfigurable transmitarray with beam steering and polarization manipulation capabilities is presented. The transmitarray element consists of an active side, a 360° reflective phase shifter, and a passive side. The active side is made of a polarization tunable patch structure, which can radiate electromagnetic wave at dual linear polarization. The passive side composed of a two-layer patch structure is unitized as a receiver cell. We adopt {8} × {8} unit cells to construct the whole transmitarray, and then place it above a horn antenna. The measured results show that the transmitarray-based horn antenna achieves beam steering with the scan range of \pm {60}° × \pm {60}° at 5.4 GHz, and this steering capability can be realized in two orthogonal linearly polarized modes. The polarization manipulation capability of this transmitarray is then studied, and it is found that four different output polarization modes, including two circular polarizations [right-handed circular polarization (RHCP) and left-handed circular polarization (LHCP)] and two linear polarizations, can be obtained over an 8.5% fractional bandwidth, with cross-polarization ratio larger than 15 dB.
    No preview · Article · Nov 2015 · IEEE Transactions on Antennas and Propagation
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    ABSTRACT: The independent control of electromagnetic waves with different oscillating frequencies is critical in the modern electromagnetic techniques, such as wireless communications and multispectral imaging. To obtain complete control of different light waves with optical materials, the chromatic dispersion should be carefully controlled, which is however extremely difficult. In this paper, we propose a method to control the behaviors of different light waves through a metasurface which is able to generate achromatic geometric phase. Using this approach, a doughnut-shaped and a solid light spot were achieved at the same focal plane using two light sources with different wavelengths as used in the stimulation emission depletion (STED) microscope system. In order to reveal the full capacity of such method, tight focusing at multiple wavelengths is also represented, where the focal spots of different wavelengths are located at the same position. The results provided here may open a new door to the design of subminiature optical components and integrated optical system operating at multiple wavelengths.
    Full-text · Article · Oct 2015 · Scientific Reports
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    ABSTRACT: For near-field imaging optics, minimum resolvable feature size is highly constrained by the near-field diffraction limit associated with the illumination light wavelength and the air distance between the imaging devices and objects. In this study, a plasmonic cavity lens composed of Ag-photoresist-Ag form incorporating high spatial frequency spectrum off-axis illumination (OAI) is proposed to realize deep subwavelength imaging far beyond the near-field diffraction limit. This approach benefits from the resonance effect of the plasmonic cavity lens and the wavevector shifting behavior via OAI, which remarkably enhances the object's subwavelength information and damps negative imaging contribution from the longitudinal electric field component in imaging region. Experimental images of well resolved 60-nm half-pitch patterns under 365-nm ultra-violet light are demonstrated at air distance of 80 nm between the mask patterns and plasmonic cavity lens, approximately four-fold longer than that in the conventional near-field lithography and superlens scheme. The ultimate air distance for the 60-nm half-pitch object could be theoretically extended to 120 nm. Moreover, two-dimensional L-shape patterns and deep subwavelength patterns are illustrated via simulations and experiments. This study promises the significant potential to make plasmonic lithography as a practical, cost-effective, simple and parallel nano-fabrication approach.
    Full-text · Article · Oct 2015 · Scientific Reports
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    ABSTRACT: The catenary is the curve that a free-hanging chain assumes under its own weight, and thought to be a " true mathematical and mechanical form " in architecture by Robert Hooke in the 1670s, with nevertheless no significant phenomena observed in optics. We show that the optical catenary can serve as a unique building block of meta-surfaces to produce continuous and linear phase shift covering [0, 2pi], a mission that is extremely difficult if not impossible for state-of-the-art technology. Via catenary arrays, planar optical devices are designed and experimentally characterized to generate various kinds of beams carrying orbital angular momentum (OAM). These devices can operate in an ultra-broadband spectrum because the anisotropic modes associated with the spin-orbit interaction are almost independent of the incident light frequency. By combining the optical and topological characteristics , our approach would allow the complete control of photons within a single nanometric layer.
    Full-text · Article · Oct 2015 · Science Advances
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    ABSTRACT: Nanofabrication technology with high-resolution, high-throughput and low-cost is essential for the development of nanoplasmonic and nanophotonic devices. At present, most metasurfaces are fabricated in a point by point writing manner with electron beam lithography or a focused ion beam, which imposes a serious cost barrier with respect to practical applications. Near field optical lithography, seemingly providing a high-resolution and low-cost way, however, suffers from the ultra shallow depth and poor fidelity of obtained photoresist patterns due to the exponential decay feature of evanescent waves. Here, we propose a method of surface plasmonic imaging lithography by introducing a reflective plasmonic lens to amplify and compensate evanescent waves, resulting in the production of nano resist patterns with high fidelity, contrast and enhanced depth beyond that usually obtained by near field optical lithography. As examples, a discrete and anisotropically arrayed nano-slots mask pattern with different orientations and a size of 40 nm × 120 nm could be imaged in photoresist and transferred successfully onto a metal layer through an etching process. Evidence for the pattern quality is given by virtue of the fabricated meta-surface lens devices showing good focusing performance in experiments. It is believed that this method provides a parallel, low-cost, high-throughput and large-area nanofabrication route for fabricating nano-structures of holograms, vortex phase plates, bio-sensors and solar cells etc.
    Full-text · Article · Oct 2015 · Nanoscale
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    ABSTRACT: A plasmonic resonant cavity-based hyperlens is theoretically proposed and demonstrated to achieve far-field phase contrast images of nano-transparent objects. The phase contrast super-resolution imaging is mainly contributed to the excited surface plasmons inside hyperlens and cavity structure surrounding nano-objects, which help to greatly enhance evanescent waves generated by nano-transparent objects and convert weak phase information to light intensity distribution with high contrast at the zoomed imaging plane of hyperlens. As examples, nano-dielectric object imaging is numerically demonstrated with half-pitch resolution about λ/10 and a minimum distinguishable refractive index difference down to 0.15.
    No preview · Article · Sep 2015 · Plasmonics
  • XianGang Luo
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    ABSTRACT: Metasurfaces are artificially structured thin films with unusual properties on demand. Different from metamaterials, the metasurfaces change the electromagnetic waves mainly by exploiting the boundary conditions, rather than the constitutive parameters in three dimensional (3D) spaces. Despite the intrinsic similarities in the operational principles of metasurfaces, there is not a universal theory available for the understanding and design of these devices. In this article, we propose the concept of metasurface waves (M-waves) and provide a general theory to describe the principles of such waves. Most importantly, it is shown that the M-waves share some fundamental properties such as extremely short wavelength, abrupt phase change and strong chromatic dispersion, which making them different from traditional bulk waves. We show that these properties can enable many important applications such as subwavelength imaging and lithography, planar optical devices, broadband anti-reflection, absorption and polarization conversion. Our results demonstrated unambiguously that traditional laws of diffraction, refraction, reflection and absorption can be overcome by using the novel properties of M-waves. The theory provided here may pave the way for the design of new electromagnetic devices and further improvement of metasurfaces. © 2015, Science China Press and Springer-Verlag Berlin Heidelberg.
    No preview · Article · Sep 2015 · Science China: Physics, Mechanics and Astronomy
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    ABSTRACT: Conventional optics is diffraction limited due to the cutoff of spatial frequency components, and evanescent waves allow subdiffraction optics at the cost of complex near-field manipulation. Recently, optical superoscillatory phenomena were employed to realize superresolution lenses in the far field, but suffering from very narrow working wavelength band due to the fragility of the superoscillatory light field. Here, an ultrabroadband superoscillatory lens (UBSOL) is proposed and realized by utilizing the metasurface-assisted law of refraction and reflection in arrayed nanorectangular apertures with variant orientations. The ultrabroadband feature mainly arises from the nearly dispersionless phase profile of transmitted light through the UBSOL for opposite circulation polarization with respect to the incident light. It is demonstrated in experiments that subdiffraction light focusing behavior holds well with nearly unchanged focal patterns for wavelengths spanning across visible and near-infrared light. This method is believed to find promising applications in superresolution microscopes or telescopes, high-density optical data storage, etc.
    Full-text · Article · Sep 2015 · Laser & Photonics Review
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    ABSTRACT: Metasurface provides extreme flexibility to manipulate the phase, polarization and amplitude of electromagnetic wave. By employing the abrupt phase shift in plasmonic nano-antenas, here we present an ultra-thin planar metalens for the azimuthally (or radially) polarized light illumination to obtain a focal spot (or doughnut-shaped focus). The designed metalens exhibits broadband frequency response at frequencies ranging from 300 to 400 THz. In addition, a tight spot size (0.47λ) is obtained when designed metalens with inner opaque annulus is illuminated by the azimuthally polarized light with wavelength 857 nm. It is expected that our scheme has potential applications in beam trapping, particle acceleration, integrated optics and super-resolution imaging.
    No preview · Article · Aug 2015 · Optics Communications
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    ABSTRACT: A new method is proposed to focus azimuthally polarized beam into an ultra-small or ultra-big dark spot under high numerical aperture lens system. Manipulated by proper designed binary 0-π phase plate, an ultra small dark spot regardless of side-lobe intensity is generated with main-lobe peak to peak distance shrunk to 0.24λ, which is 46% of the case without phase plate. For potential applications, shrinking the dark spot and suppressing the side-lobe intensity are analyzed, and several cases of squeezed dark spots with different levels of side-lobe intensities are presented. Additionally, using a two-zone phase plate to enlarge the dark spot is investigated in this paper, and an enlarged dark spot is readily acquired with the main-lobe peak to peak distance in a range of 100%–200%. The advantages of this method are its large scale manipulation of the dark spot size and its high performance in suppressing side-lobe intensity, which is of great worth in enhancing the performance of many systems such as optical tweezers and stimulated emission depletion (STED) microscope.
    No preview · Article · Aug 2015 · Optics Communications
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    Min Wang · Cheng Huang · Mingbo Pu · Xiangang Luo
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    ABSTRACT: A method of utilizing frequency selective surface (FSS) to reduce side lobe level (SLL) is proposed. The FSS composed of annular slot arrays loaded with resistors is divided into several regions along the electric field direction. Each region has difference transmission amplitude (TA) but the same transmission phase (TP). Through the appropriate distribution design for each region, the output wave with tapered TA and uniform TP is obtained when the FSS is illuminated by a plane wave. Thus the FSS could be utilized to reduce the antenna SLL. An H-plane sectorial horn array is adopted as an exciting source to validate its SLL reduction performance. Simulation results show that the proposed FSS superstrate makes the SLL of the horn array in the E-plane desirably suppressed from −12.4 to −25.9 dB at 10.3GHz with the gain reduced from 18.3 to 16.7 dBi. The measured results agree well with the simulated ones. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1971–1975, 2015
    Full-text · Article · Aug 2015 · Microwave and Optical Technology Letters

Publication Stats

3k Citations
552.17 Total Impact Points

Institutions

  • 2000-2015
    • Chinese Academy of Sciences
      • Institute of Optics And Electronics
      Peping, Beijing, China
  • 2013
    • Chongqing University
      • Key Laboratory of Optoelectronic Technology and System of the Education Ministry of China
      Ch’ung-ch’ing-shih, Chongqing Shi, China
  • 2011-2012
    • Southwest Jiaotong University
      • School of Information Science and Technology
      Hua-yang, Sichuan, China
  • 2006-2011
    • The institute of Optics and Electronics
      Hua-yang, Sichuan, China
  • 2010
    • University of Michigan
      • Department of Electrical Engineering and Computer Science (EECS)
      Ann Arbor, MI, United States
  • 2007
    • Nanyang Technological University
      Tumasik, Singapore
  • 1999
    • Academia Sinica
      T’ai-pei, Taipei, Taiwan