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    A computational investigation of third-harmonic generation in one-dimensional photonic band-gap materials with multiple-scale method
    (2014-09-02)
    Wicharn, Surawut
    ;
    Buranasiri, Prathan
    ;
    Ruttanapun, Chesta
    ;
    Jindajitawat, Phumin
    In this paper, we present a numerical investigation of third-harmonic (TH) generation in a one-dimensional photonic band-gap material that is doped with a nonlinear χ<sup>(3)</sup>medium. For modeling harmonic generation phenomena, a multiple-scale method has been introduced to perturb the nonlinear wave equation by a small factor with appropriate scale. So, we obtain coupled-mode equations (CMEs) with different from the conventional CMEs for this phenomenon. Then, we have solved these CMEs numerically to obtain the output amplitudes of TH waves in both forward- and backward-directions, and the conversion efficiencies. Finally, the solutions show that this photonic band-gap material can generate the TH waves whose amplitudes and the conversion efficiencies may be larger than the TH wave and the efficiency produced by an equivalent length of a phase-matched, bulk medium. © 2014 Taylor & Francis Group, LLC.
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    Third-harmonic pulse generation in one-dimensional photonic crystal structures
    (2014-01-01)
    Wicharn, Surawut
    ;
    Buranasiri, Prathan
    Enhanced third-harmonic generation in a one-dimensional photonic crystal doped with third-order nonlinear medium was numerically investigated using the multiple-scale method and the split-step Fourier transform. The optimal fundamental frequency for third-harmonic wave generation was determined from the transmission spectrum. The third-harmonic pulse intensities grow, depending on the structure thickness and the fundamental-frequency detuning parameter, which determines the band-edge phase matching condition. Furthermore, the total energy output of third-harmonic pulses, depending on the fundamental-frequency pulse width, may be more than 1000 times the energy produced by a phase-matched bulk medium. A narrow pulse with bandwidth less than the band-edge transmission peak enables high conversion efficiency. The maximum conversion efficiency of the forward component may be 12 to 13 orders of magnitude greater than that of the backward component. © Society of Photo-Optical Instrumentation Engineers.
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    Third-harmonic generation enhancement in polymer-dispersed liquid crystal grating
    (2014-01-01)
    Wicharn, S.
    ;
    Buranasiri, P.
    In this paper, the enhancement of third-harmonic generation in one-dimensional periodic grating structure with lowindex contrast, which is produced by holographic illuminated liquid crystal droplets and called polymer-dispersed liquid crystal grating, with near-infrared pumping has been demonstrated. The observed enhancement process is theoretically explained and modeled with a multi-scale perturbation analysis and split-step Fourier transform technique, respectively. We show that the third-harmonic generation has been enhanced by setting the fundamental frequency wavelength to the long-wavelength band-edge of the first photonic band-gap of this periodic structure and satisfying band-edge phasematched condition. The numerical results show that a dramatic enhancement of the third-harmonic field is observed near the long-wavelength band-edge of the second photonic band-gap. Furthermore, the conversion efficiency of thirdharmonic field of forward-propagating direction is more than of backward-propagating direction by a factor of 600.
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    Efficient third-harmonic generation in one-dimensional photonic crystals
    (2013-09-18)
    Wicharn, S.
    ;
    Buranasiri, P.
    ;
    Ruttanapun, C.
    ;
    Jindajitawat, P.
    In this paper, we have solved nonlinear coupled-mode equations valid for light propagation in a one-dimensional photonic crystal by using numerical expression. Moreover, the medium in this problem has been considered as a nonlinear x <sup>(3)</sup> material. The numerical results have been used to calculate the conversion efficiency in nondepleted-pump limit. The results have been shown us that the maximum conversion efficiency of third-harmonic generation could be occurred when the fundamental field has been tuned near the lower band-edge of photonic band-gap that band-edge phase matched condition has been satisfied. © 2013 SPIE.