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ABSTRACT: We present a planar waveguide model and a mechanism based on standing wave resonances to interpret the unity absorptions of ultrathin planar metamaterial absorbers. The analytical model predicts that the available absorption peaks of the absorber are corresponding to the fundamental mode and only its odd harmonic modes of the standing wave. The model is in good agreement with numerical simulation and can explain the main features observed in typical ultrathin planar metamaterial absorbers. Based on this model, ultrathin planar metamaterial absorbers with multi-band absorptions at desired frequencies can be easily designed.
Optics Express 12/2012; 20(25):27756-65. · 3.59 Impact Factor
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ABSTRACT: Terahertz (THz) signals measured by means of the spectral-encoding technique with different temporal discrepancies between probe pulses and THz signals are investigated. It is found that imperfect synchronization between the chirped probe and THz pulses induce a distortion and this distortion affects significantly the retrieved THz spectrum if the temporal discrepancy is large. The distortion becomes more prominent if the probe pulse length is less than the optimal chirped probe pulse duration. A simple approach is proposed to realize the synchronization and minimize the distortion. THz signals from a high-voltage-biased air plasma filament are measured with this approach and distortion similar to the simulation results is observed.
Journal of the Optical Society of America A 10/2011; 28(10):2049-56. · 1.56 Impact Factor
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Yuan Hsing Fu,
Ai Qun Liu,
Wei Ming Zhu,
Xu Ming Zhang,
Din Ping Tsai,
Jing Bo Zhang,
Ting Mei,
Ji Fang Tao,
Hong Chen Guo,
Xin Hai Zhang, Jing Hua Teng,
Nikolay I. Zheludev,
Guo Qiang Lo,
Dim Lee Kwong
Advanced Functional Materials 07/2011; 21(18):3589 - 3594. · 10.18 Impact Factor
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ABSTRACT: The approach to realize the optimal chirped probe pulse length for an arbitrary pulsed terahertz (THz) signal measured with the spectral-encoding technique was investigated by simulation. It was found that either the maximum positive peak or the absolute value of the strongest negative peak of the normalized difference between the probe spectrum modulated by THz signal and the background probe spectrum tended to be maximized when the probe pulse duration approached to the optimal value. The probe pulse length can be adjusted continuously with a pair of triangular dispersive prisms. THz signals from high-voltage biased air plasmas induced by femtosecond laser pulse were measured with minimum distortion using our simple method.
Applied Physics Letters 07/2011; · 3.84 Impact Factor
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Wei Ming Zhu,
Ai Qun Liu,
Xu Ming Zhang,
Din Ping Tsai,
Tarik Bourouina, Jing Hua Teng,
Xin Hai Zhang,
Hong Chen Guo,
Hendrix Tanoto,
Ting Mei,
Guo Qiang Lo,
Dim Lee Kwong
Advanced Materials 04/2011; 23(15):1792-6. · 13.88 Impact Factor
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ABSTRACT: The principle of the spectral-encoding technique, one of the single-shot techniques for measurement of arbitrary pulsed terahertz (THz) signals, or T-rays, is demonstrated theoretically and through simulation. For single-cycle input THz pulse (bipolar wave form), THz signal could be retrieved faithfully under certain conditions, while for the multicycle input case, the THz signal cannot be retrieved without any distortion. However, there is an optimal length of the chirped-probe-pulse, corresponding to the characteristic time of the multicycle THz field, to minimize the distortion in the retrieved THz signal. Three main possible sources of distortions from both bipolar and multicycle THz signals are analyzed systematically. The first distortion originates from the mismatch of the optimal duration T<sub> co </sub> of the chirped-probe-pulse and the T-ray length T . The second one is relevant to the spectrum bandwidth of the probe pulse. The third one occurs when the modulation depth k≪1 is not satisfied. It comes from the neglect of the quadratic term of the modulation depth k , which reflects the strength of the THz signal in the retrieving process. Possible strategies are proposed to reduce these distortions.
Journal of Applied Physics 12/2010; · 2.17 Impact Factor
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Small 02/2009; 5(5):574-8. · 8.35 Impact Factor
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ABSTRACT: With planar photolithography and self-assembly techniques, multilayer colloidal crystals with a woodpile structure were fabricated. They represent a new kind of photonic crystals, that is, three-dimensional (3D) photonic crystals with a dual periodicity; one comes from the face-centered cubic (fcc) structure within the colloidal crystal strips and the other one results from the periodic arrangement of the colloidal crystal strips.
Langmuir 09/2006; 22(16):7001-6. · 4.19 Impact Factor
