E Wu

East China Normal University, Shanghai, Shanghai Shi, China

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Publications (94)259.38 Total impact

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    ABSTRACT: Saturation excitation of individual nanocrystals represents a powerful strategy to explore unique optical characteristics of luminescent activators. Here we report the intense multiphoton upconversion ofb-NaYF4: Yb3+-Tm3+ individual nanocrystals benefiting from the perfect ladder-type electrom configuration of Tm3+ under saturation illumination excitation. This leads to a luminescent switching between the emissions from 2-photon upconversion and 4-photon upconversion, which exhibits significantly enhanced luminescence intensity by up to a factor of 70. Such intense multiphoton upconversion may have potential application in super-resolution imaging.
    J. Mater. Chem. C. 11/2014;
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    ABSTRACT: Direct interference between the orthogonal electric and magnetic modes in a hybrid silicon-gold nanocavity is demonstrated to induce a pronounced asymmetric magnetic-based Fano resonance in the total scattering spectrum at near-infrared frequencies. Differing from the previously reported magnetic-based Fano resonances in metal nanoparticle clusters, the narrow discrete mode provided by the silicon magnetic dipole resonance can be directly excited by external illumination, and greatly enhanced electric and magnetic fields are simultaneously obtained at the Fano dip.
    Optics Express 10/2014; 22(20). · 3.55 Impact Factor
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    ABSTRACT: We experimentally studied photon-counting laser ranging at 1550 nm using InGaAs/InP avalanche photodiode based single-photon detectors (SPDs). The SPDs operated in the passive quenching and 1-GHz sinusoidal gating Geiger modes, corresponding to continuous and quasi-continuous photon-counting ranging, respectively. Despite that the passively quenched SPD provided relatively high effective detection efficiency, quasi-continuous photon-counting ranging excelled the continuous one with fast acquisition speed and improved depth resolution due to the short deadtime and low timing jitter of the SPD in 1-GHz sinusoidally gated mode.
    Optik - International Journal for Light and Electron Optics 07/2014; · 0.77 Impact Factor
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    ABSTRACT: Sensitive laser ranging was demonstrated at few-photon level using photon-number-resolving (PNR) detectors. The reflected photon pulses from a non-cooperation remote target were distinguished in a sunlight environment of 2.5×103 lx by setting the discrimination threshold at 5-photon level. By comparing the detected photon numbers, two remote targets with different reflection coefficients were well recognized. PNR detection facilitated remote laser ranging of few-photon sensitivity with similar capabilities of linear optical detectors. This technique avoids photon-counting saturation and is important for ultra-long distance LIDAR and 3D imaging at a few photon level.
    Applied Optics 06/2014; 53(18):3908-3912. · 1.69 Impact Factor
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    ABSTRACT: Optical properties of quantum dots can be drastically changed by surface plasmons excited in neighboring metallic nanostructures. Here we investigated the photoluminescence enhancement dependence of single quantum dots on the separation distance with Au microplates by a single particle spectroscopy. The quantum dot–Au microplate hybrid structures provided a photoluminescence enhancement of up to 16-fold when the separation distance between the surface of Au microplate and the center of QD was 18 ± 1.9 nm. Accordingly, the lifetime of those quantum dots was shortened compared with the ones on glass plates directly. Theoretical simulation revealed that the variation of photoluminescence enhancement was closely dependent on the separation distance between the QD and the Au microplate, in good agreement with the experimental results.
    The Journal of Physical Chemistry C 04/2014; 118(16):8514–8520. · 4.84 Impact Factor
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    ABSTRACT: We demonstrated a time-of-flight (TOF) ranging system employing laser pulses at 1550 nm with multiple repetition rates to decrease the range ambiguity, which was usually found in high-repetition TOF systems. The time-correlated single-photon counting technique with an InGaAs/InP avalanche photodiode based single-photon detector, was applied to record different arrival time of the scattered return photons from the non-cooperative target at different repetition rates to determine the measured distance, providing an effective and convenient method to increase the absolute range capacity of the whole system. We attained hundreds of meters range with millimeter accuracy by using laser pulses of approximately 10-MHz repetition rates.
    Optics Express 02/2014; 22(4):4662-70. · 3.55 Impact Factor
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    ABSTRACT: We theoretically investigate the plasmonic coupling in heterogenous Al-Ag nanorod dimer. A pronounced Fano dip is found in the extinction spectrum produced by the destructive interference between the bright dipole mode from a short Al nanorod and the dark quadrupole mode from a long Ag nanorod nearby. This Fano resonance can be widely tuned in both wavelength and amplitude by varying the rod dimensions, the separation distance and the local dielectric environment. The Al-Ag heterogeneous nanorod dimer shows a high sensitivity to the surrounding environment with a local surface plasmon resonance figure of merit of 7.0, which enables its promising applications in plasmonic sensing and detection.
    Applied Physics A 12/2013; 117(2). · 1.69 Impact Factor
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    ABSTRACT: We demonstrated few-photon-level mid-infrared imaging at 3.39 μm by efficient frequency up-conversion. The quantum frequency up-conversion efficiency of mid-infrared photons was high to 32.9%, while mid-infrared images were up-converted with the quantum efficiency of 12.5%. The mid-infrared imaging sensitivity was improved by counting the frequency up-conversion photons temporally confined within the time-window of the pump pulse. The frequency up-conversion system induced a background noise of 1.1 × 103 counts per second.
    Applied Physics Letters 06/2013; 102(24). · 3.52 Impact Factor
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    ABSTRACT: We demonstrated few-photon-level mid-infrared imaging at 3.39 μm by frequency up-conversion with conversion efficiency of 78.5%. The mid-infrared image was spectrally up-converted into the near-infrared regime captured by a silicon electron multiplying charged coupled device.
    CLEO: Science and Innovations; 06/2013
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    ABSTRACT: We report on a novel method to fabricate single, multiple and large-area high-density ensembles of nitrogen vacancy (NV) color centers in synthetic type Ib bulk diamond by femtosecond laser illumination. Electron beams generated in propagation of intense infrared laser pulses in air sputtered on a diamond sample under high temperature aroused by the laser illumination, creating NV color centers. Typical photoluminescence (PL) spectra of NV centers could be observed on the illuminated spots. Photon streams from individual photoluminescent points exhibited anti-bunching effect by the second-order correlation measurement, evidencing single and multiple photon-emitters around the laser illuminated spots.
    Optics Express 05/2013; 21(10):12843-8. · 3.55 Impact Factor
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    ABSTRACT: We studied the orientations of single Nitrogen-Vacancy (NV) color centers in nanodiamonds on a gold film by defocused imaging with a scanning confocal microscopy system and an electron-multiplying charge-coupled device. It was demonstrated that the perpendicular oriented dipole of single NV color center showed shorter fluorescence lifetime and higher fluorescence intensity than any other oriented ones on account of higher coupling efficiency of local electronic field induced by the surface plasmon resonance on the gold film for a vertical transition dipole.
    IEEE Journal of Selected Topics in Quantum Electronics 05/2013; 19(3):4602404-4602404. · 4.08 Impact Factor
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    ABSTRACT: Up-conversion luminescence in rare earth ions (REs) doped nanoparticles has attracted considerable research attention for the promising applications in solid-state lasers, three-dimensional displays, solar cells, and biological imaging etc. However, there have been no reports on REs doped nanoparticles to investigate their polarized energy transfer up-conversion, especially for single particle. Herein, the polarized energy transfer up-conversion from REs doped fluoride nanorods is demonstrated in a single particle spectroscopy mode for the first time.Unique luminescent phenomena, e.g., sharp energy level split and singlet to triplet transitions at room temperature, multiple discrete luminescence intensity periodic variation with polarization direction, are observed upon excitation with 980 nm linearly polarized laser. Furthermore, nanorods with the controllable aspect ratio and symmetry are fabricated for analysis of the mechanism of polarization anisotropy. The comparative experiments suggest that intra-ions transition properties and crystal local symmetry dominate the polarization anisotropy, which is also confirmed by density functional theory (DFT) calculations. Taking advantages of the REs based up-conversion, potential application in polarized microscopic multi-information transportation is suggested for the polarization anisotropy from REs doped fluoride single nanorod or nanorod array.
    Nano Letters 04/2013; · 13.03 Impact Factor
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    ABSTRACT: With recent development of nanotechnology, novel devices with nanostructures arise to improve the performance of photodetectors. Here, we demonstrated that by surface decoration with gold nanoparticles on the active area, the quantum detection efficiency of a multi-pixel photon counter was increased due to surface plasmon resonance enhancement. The deposited gold nano-particles actually brought about almost the same enhancement factor for any photon-number fields. As a result, the photon-number-resolving capability of the multi-pixel photon counter was well reserved with the gold nano-particle deposition induced efficiency augment. This result provides guidance to the development of the high-efficiency photon-number-resolving detectors.
    Optics Express 03/2013; 21(5):6442-6447. · 3.55 Impact Factor
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    ABSTRACT: We demonstrate an efficient mid-infrared single-photon detection system with ultra-low background counts based on the frequency upconversion detection technique. The signal photons of 3.39 μm came from a He–Ne laser and the pump beam was provided by a mode-locked ytterbium-doped fiber laser. Taking into account the pulsed pumping and continuous-wave signaling scheme, the peak conversion efficiency of 64% was achieved at an average pump power of 28.3 mW. The corresponding detection efficiency was inferred to be 6.1% with ultra-low background counts of 400 s−1.
    Laser Physics Letters 03/2013; 10(5):055401. · 2.96 Impact Factor
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    ABSTRACT: We experimentally demonstrate a pulsed mid-infrared photon source at 3.16 μm with a bandwidth of 3.7 nm by coincidence frequency downconversion with a conversion efficiency of 65%. The mid-infrared photons were generated by frequency downconversion in the saturation regime where the signal photons at 1.04 μm were synchronously pumped by intense laser pulses at 1.55 μm. In principle, the mid-infrared photon source could not only inherit the complete quantum characteristics of the input photon state, but could also be coherently manipulated in the spectral and temporal domains by engineering the classical pump field.
    Laser Physics 03/2013; 23(4):045401. · 1.03 Impact Factor
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    ABSTRACT: Transparent strontium titanium silicate glass–ceramics (GCs) containing Ni2+-doped SrTiO3 nanocrystals were synthesized by heat treatment method. Absorption spectra confirmed that the coordination environment of Ni2+ ions was changed from the trigonal bipyramid fivefold sites in as-cast glasses to the octahedral sites in the GCs. Upon 980 nm laser excitation, the GCs exhibited broadband near-infrared emissions covering 1.1–1.7 μm wavelength region with the full width at half maximum (FWHM) of more than 290 nm and fluorescent lifetime of up to 735 μs, which originated from the 3T2g (3F) → 3A2g (3F) transition of octahedral Ni2+ ions in the SrTiO3 nanocrystals. This kind of Ni2+-doped transparent GCs have potential applications in super-broadband optical amplifiers and tunable lasers.
    Optical Materials 03/2013; 35(5):983–987. · 2.08 Impact Factor
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    ABSTRACT: We demonstrate a high-speed photon-number-resolving detector based on a sinusoidally gated multipixel photon counter (MPPC) at a repetition rate of 200 MHz. Two steps of low-pass filters are used to minimize the MPPC's capacitive response noise in sinusoidally gated Geiger mode, resulting in the efficient detection of weak photon-induced avalanche currents. Compared with passive quenching schemes, the sinusoidal gating scheme is conducive to shortening the recovery time for each pixel of the MPPC to detect the next coming photons, thus improving the detector's photon-number-resolving capability at a high repetition rate. The gated MPPC can identify the photon numbers of the incident pulses with a repetition frequency of 50 MHz clearly at as high as an average of 7.22 photons/pulse detected before saturation at room temperature.
    IEEE Photonics Technology Letters 10/2012; 24(20):1852-1855. · 2.04 Impact Factor
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    ABSTRACT: Metallic nanowires are of great research interest due to their applications in surface plasmon polariton coupling of light. The efficiency is much dependent on the polarization of the light due to the phase matching requirement in the light-surface plasmon polariton coupling. By scanning confocal microscope, the photoluminescence from a single Ag nanowire was demonstrated strongly dependent on the excitation laser polarization, showing good consistency with the theoretical simulation. Meanwhile strong avalanche photoluminescence from a single Ag nanowire was observed when the excitation laser was polarized along the long axis of the Ag nanowire. The photoluminescence emission exhibited a polarization-sensitive spatial distribution. This may stimulate promising applications in designing polarization-controllable nanoscale plasmonic devices.
    Optics Express 09/2012; 20(20):22290-7. · 3.55 Impact Factor
  • K. Huang, X. Gu, H. Pan, E. Wu
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    ABSTRACT: We experimentally demonstrate a compact synchronized fiber laser system that enables fast and efficient coincidence single-photon frequency upconversion detection. Robust synchronization between the pump and signal pulses was achieved with a long-term stability. Moreover, the synchronized pulses were wellmatching in both of the time and spectrum domains. As a result, a coincidence single-photon frequency upconversion was realized with a conversion efficiency of 91.8% and low background counts around 2.8 × 10 $^3$ s $^{-1}$ .
    IEEE Journal of Selected Topics in Quantum Electronics 05/2012; · 4.08 Impact Factor
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    ABSTRACT: We demonstrate few-photon-level infrared imaging at 1040 nm by coincidence frequency upconversion with a high conversion efficiency of 33.5%. By synchronous pulse pumping at 1549 nm, the infrared object image was spectrally upconverted into the visible regime. The upconverted image was captured by a silicon electron multiplying charged coupled device without any scanning devices, thus gaining in simplicity and speed. The imaging sensitivity was improved by reducing the background noise with coincidence pulsed pumping at long wavelength.
    Applied Physics Letters 04/2012; 100(15). · 3.52 Impact Factor

Publication Stats

654 Citations
259.38 Total Impact Points

Institutions

  • 2003–2014
    • East China Normal University
      • • State Key Laboratory of Precision Spectroscopy
      • • Department of Physics
      • • Key Laboratory of Optical and Magnetic Resonance Spectroscopy
      Shanghai, Shanghai Shi, China
  • 2008–2009
    • Northeast Institute of Geography and Agroecology
      • • State Key Laboratory of High Field Laser Physics
      • • National Laboratory for Infrared Physics
      Beijing, Beijing Shi, China
  • 2006–2008
    • Ecole normale supérieure de Cachan
      • Laboratoire de photonique quantique et moléculaire (LPQM)
      Cachan, Ile-de-France, France