Li Wang

Liaocheng Teachers University, Tungchangfu, Shandong Sheng, China

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Publications (19)44.2 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We demonstrated that transmittance and field intensities of a thick metal sandwiched between two dielectric photonic crystals (PCs) can be enhanced by more than two orders of magnitude and by nearly 20 times, respectively, compared to a single metal layer with the same thickness. Under the tunneling mechanism, the light can enter the sandwiched structure without reflection and localizes at the two interfaces of the metal film and PCs. This configuration of fields facilitates the reduction of absorption in the metal. Experimental results are in good agreement with simulations.
    Journal of Applied Physics 11/2010; 108(10):103111-103111-4. · 2.21 Impact Factor
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    ABSTRACT: We investigate the propagation of electromagnetic wave through photonic quantum-well structures constructed by one-dimensional photonic crystals with defect layers. It is shown that non-destroyed high transmittance of each separated resonant mode can be found if photonic quantum-well structures are properly connected. Experimental fabrication of combined photonic quantum-well structures is carried out, and the results agree with the numerical calculations very well.
    Optics Communications 01/2010; 283(10):2155-2159. · 1.44 Impact Factor
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    ABSTRACT: There is an increasing necessity to use supersmooth surfaces, and quantitative Characterization of surpersmooth surface with roughness in the sub-nanometer range plays an important role in the controlling the super-polishing process and raising the final surface quality. So it is necessary to improve the methods of measuring and specifying the highly smooth optical surfaces. The estimating system based on the Power Spectral Density (PSD) function is introduced in this paper, including the basic theory and the physical meaning. Two kinds of supersmooth surface, isotropy and anisotropy, are measured by optical profiler and the topographies are gotten. Then PSD curves calculated from the discrete profile data and light scattering properties are discussed in detail. Furthermore, optical profiler and AFM are adopted to test the same sample with different measurement parameters to investigate the PSD analysis method. Eventually a polynomial is fitted to the data sets in an extanted spatial frequency domain, 10mum-1~12.8mum-1, including low frequency, mid-frequency, and high frequency band. Although the frequency response of the instruments and the scanning area can affect the test results, the results can still be compared with each other directly using the PSD. The research gives a powerful support to selecting appropriate measurement instrument and parameters in the interested frequency regime during the surface test, which is useful at controlling and giving feedback on the fabrication of supersmooth surface.
    Proc SPIE 05/2009;
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    ABSTRACT: Online low emissivity glass (Low-E glass) is a promising glass product. Simulation of the spectra and determination of the optical constants of online Low-E glass are of practical interest for many applications such as product design, adjustment of coating process and comparison of samples produced using different methods. The online Low-E glass investigated here has two layers of films on 6 mm thick float glass substrate, which include the functional layer (the upper layer) and the transition layer (the lower layer). In this paper, the relation between transmittance and the parameters used in the model in the visible and near-infrared region was derived, so was the relation between reflectance and the parameters used in the model in the infrared region. The parameters used in the model were obtained by fitting the measured and simulated spectra. From the obtained parameters, the optical constants of the functional layer of online Low-E glass in the visible region and the infrared region were obtained, respectively. The sheet resistance and the infrared reflectance of Low-E glass were also calculated from the obtained fitting parameters. The simulated results are well consistent with the experimental ones.
    Thin Solid Films 03/2009; 66. · 1.87 Impact Factor
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    ABSTRACT: By using the equivalent eigenvalue equation of a waveguide grating, the mirror effect (Deltalambda/lambda>15%) with very high reflectivity (R>99%) based on guided-mode resonance (GMR) effects in a poly-Si subwavelength periodic membrane is obtained, and the reflection performance of the poly-Si subwavelength periodic membrane is systematically studied. It is shown that the equivalent eigenvalue equation of a waveguide grating can provide a solid starting point for designing the broadband grating with very high reflectivity. The physical mechanisms of broadband reflection of the strongly modulated waveguide grating structures are investigated theoretically and the important role of multiple GMRs for a broad reflection band is discussed in detail. By using the overlap of a resonance pair in which leaky waveguide modes TE0 and TE1 are excited by the strong first diffraction order, enhanced reflection occurs and a flat reflection band with high reflectivity can be achieved by adding a poly-Si thin film under the grating. The grating period, the grating thickness, and the layer thickness do not change the mirror effect except for the incident angle and the filling factor. A flat band with high reflectivity centered near 1.55 microm is designed to demonstrate this concept.
    Journal of the Optical Society of America A 03/2009; 26(3):559-65. · 1.67 Impact Factor
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    ABSTRACT: The refractive index profiles in Fig. 2 were incorrect. The proper designs are presented here with additional comments.
    Optics Express 07/2008; 16(12):8902-8903. · 3.55 Impact Factor
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    ABSTRACT: We propose and demonstrate three approaches to achieve narrowband multichannel filters. These are multiple heterostructures with defects, guided-mode resonance (GMR) Brewster filters with multiple channels, and integrated narrow bandpass filter arrays. Transmission studies for multiple heterostructures with defects are presented. We show that the enlargement of the forbidden band and multiple-channel filtering can be reached simultaneously with these configurations. GMR Brewster filters with multiple channels can be obtained with a single-layer grating. The same properties can be obtained by use of double-layer structures that consist of a homogeneous layer and a grating with equal refractive index. We developed a combinatorial etching technique that has 32 elements on a single substrate with which to fabricate integrated narrow bandpass filters. Single- and double-chamber integrated optical filter arrays were fabricated by use of this etching technique. These narrowband multichannel filters and narrow bandpass filter arrays show good filtering features and can be utilized in many optical applications.
    Applied Optics 06/2008; 47(13):C1-8. · 1.69 Impact Factor
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    ABSTRACT: The Fourier transform thin film synthesis method often results in solutions that call for indices that lie outside the range of values of the available materials. To make the resulting refractive index profiles always realizable in our meta-mode sputtering machine, a modified Fourier transform synthesis method is proposed with which the reflectance spectra can be accurately synthesized with controllable and predictable refractive index profiles. In our procedure, an optimal phase function is explored to yield acceptable refractive index profiles. Then the overall thickness is estimated using the Parseval theorem. Finally, several errors inherent to the Fourier transform method, including the imprecision of the spectral function, the truncation of the film and the apodization of the refractive index profiles, are compensated by successive corrections to the magnitude of the spectral function. An explicit iterative formula based on the derivative of the magnitude function is proposed for the compensation of the spectral mismatches. We show with a number of examples that, with the proposed method, it is possible to synthesize gradient-index optical filters with almost any desired spectral performance using experimentally realizable refractive indices.
    Optics Express 03/2008; 16(4):2315-21. · 3.55 Impact Factor
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    ABSTRACT: Band structures of one-dimensional (1D) photonic crystals (PCs) containing dispersive left-handed metamaterials are studied theoretically. The results show that the structure possesses a type of photonic band gap originating from total internal reflection (TIR). In contrast to photonic band gaps corresponding to zero average refractive index and zero phase, the TIR gap exhibits sharp angular effect and has no polarization effect. It should also be noted that band structures of transverse electric (TE) and transverse magnetic (TM) mode waves are exactly the same in the PCs we studied.
    Chinese Optics Letters 02/2008; 6(3):198-200. · 1.07 Impact Factor
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    ABSTRACT: Transmission characteristics are studied for the hybrid structures combining defect and multiple heterostructures. It is shown that the non-transmission frequency range can be substantially enlarged and the phenomenon of narrow band-pass filter can be realized by adjusting the number, position and size of the defect. The theoretical and experimental results on heterostructures containing Ta2O5/SiO2 multilayer films are presented. With perfect non-transmission frequency range and high peak transmissivity, this structure opens a promising way to fabricate ultra-narrow band-pass filters with wide non-transmission frequency range.
    Chinese Physics Letters 01/2008; 25(6):2030-2032. · 0.92 Impact Factor
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    ABSTRACT: In this paper, double-layer surface-relief resonant Brewster filters consisting of a homogenous layer and a grating with equal refractive index are obtained by adjusting the grating filling factor, and linewidth properties of these types of filters are investigated. It is shown etch depth error does not change the filter linewidth, but the grating filling factor and the substrate refractive index can significantly change the filter linewidth. Moreover, the coupling strength can be appreciately affected by the homogeneous layer thickness, and one can obtain different linewidths at the same operating wavelength by selecting different homogeneous layer thickness with other physical parameters maintained.
    Optics Express 08/2007; 15(15):9659-65. · 3.55 Impact Factor
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    ABSTRACT: In this letter, the double-layer resonant Brewster filters and their properties were presented, which consist of a homogenous layer with a refractive index equal to that of the grating. By tuning the thickness of the homogeneous layer, a multichannel resonant Brewster filter with thin grating thickness can be obtained. For this type of filters, the variety of the grating thickness almost did not change the resonance location, but had a distinct effect on the filter linewidth. By changing grating period or tuning incident angle, different linewidths can be obtained at the same resonance wavelength without losing the low-reflection sideband feature.
    Applied Physics Letters 01/2007; · 3.79 Impact Factor
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    ABSTRACT: In this letter, a type of guided-mode resonance (GMR) reflection filter incorporating multimode resonance and the Brewster effect is presented. Long-range, low sidebands, and multiple channels are found to be obtainable for a single-layer GMR reflection filter with a TM-polarized plane wave incident at the Brewster angle. Detailed characteristics are calculated using rigorous coupled-wave analysis. In our calculation, for TM-polarized incident wave, we find it sufficiently accurate to calculate the effect index by using the zero-order permittivity ε<sub>0, TM </sub> of the effective media theory, and narrowband multichannel reflectance can be achieved at the Brewster angle by tuning the grating depth.
    Applied Physics Letters 07/2006; · 3.79 Impact Factor
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    ABSTRACT: A combinatorial etching technique is developed to fabricate integrated narrow bandpass filters on a single substrate. It is highly efficient for fabrication of integrated filter arrays in optical regions. A monolithic filter array has been fabricated by using the technique with a two-step deposition process. The filter contains 32 elements in the near-infrared region. The relative full width at half-maximum (FWHM) sigmalambda/lambda of the filter elements is less than 0.2%. Such a narrow bandpass filter array can be utilized in many optical applications.
    Optics Letters 03/2006; 31(3):332-4. · 3.39 Impact Factor
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    ABSTRACT: A weakly modulated dielectric grating is equivalent to a planar waveguide. As the high-order spatial sub-waves couple with the leaky mode of the grating, guided-mode resonance (GMR) occurs. In this paper, the resonance positions of a weakly modulated dielectric grating are studied based on the eigenvalue equation of a planar waveguide, and the results agree with the rigorous coupled-wave analysis (RCWA) very well. This shows that double reflection peaks at normal incidence can be realized and the reasons are given in detail. The reason that GMR is sensitive to the incident angle and the grating period is also discussed. GMR filters with good filtering features can be realized by using the thin film effect.
    Journal of Optics A Pure and Applied Optics 12/2005; 8(1):62. · 1.92 Impact Factor
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    ABSTRACT: One-dimensional metallodielectric heterostructural photonic band gap (PBG) material is designed to reach high transmittance band in short wavelength, broad and deep forbidden band in long wavelength, especially sharp cutoff edge between the transmission and forbidden bands. The designed PBG material is applied to modify the emission spectrum of a BaF2 scintillator and is proved to be adequate to suppress the slow component of the scintillation light. The suppression ratio of the slow to the fast component reaches 28 dB with a tolerable attenuation of the fast component.
    Applied Physics Letters 11/2004; 85(19):4337-4339. · 3.79 Impact Factor
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    ABSTRACT: Transmission studies for multiple heterostructures inserted with defects are presented. The results show that the enlargement of the forbidden band and the realization of multiple channeled filtering can be reached simultaneously with these configurations. The frequency, frequency interval, and number of channels can be tuned by adjusting geometric and physical parameters of the defects. Sidebands of the forbidden band can be substantially restricted as compared with that of periodic structures. Experimental fabrication of the designed configurations is carried out with the heterostructures containing TiO2/SiO2 multilayer defects, and the results agree with the calculation very well. © 2004 American Institute of Physics.
    Applied Physics Letters 03/2004; 84(10):1629-1631. · 3.79 Impact Factor
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    ABSTRACT: Transmission characteristics are studied for hybrid structures combining defects and multiple heterostructures. It is shown that the nontransmission frequency range can be substantially enlarged and the phenomenon of multiple-channeled filtering can be realized by adjusting the number, position, and size of the defects. One, two, and three channeled filters are considered in the structures. Examples are studied theoretically by transfer matrix methods. © 2004 American Institute of Physics.
    Journal of Applied Physics 01/2004; 95(2):424-426. · 2.21 Impact Factor

Publication Stats

94 Citations
44.20 Total Impact Points

Institutions

  • 2010
    • Liaocheng Teachers University
      Tungchangfu, Shandong Sheng, China
  • 2004–2010
    • Tongji University
      • Department of Physics
      Shanghai, Shanghai Shi, China
  • 2006
    • Northeast Institute of Geography and Agroecology
      • National Laboratory for Infrared Physics
      Beijing, Beijing Shi, China