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디펙트를 보유한 2차원 광자 밴드 갭 구조의 파동 전달 특성
鄭敎龐 弘益大學校 科學技術硏究所 2000 科學技術硏究論文集 Vol.11 No.-
It has been observed that photonic bandgap crystals may work as functional photonic devices such as filters, waveguides, and microcavity lasers, if defects are inserted properly inside the structures. The work done to date has been concerned primarily with defects formed by removing rods in two-dimensional lattices. This paper presents the transmission characteristics of missing-rod defects and of circular, and square, and rectangular cross-section defects with different size and permittivity in a finite-size two-dimensional photonic bandgap crystal of square lattice. The transmission characteristics are computed numerically with the finite-difference time-domain method, along with the total-field/scattered-field formulation and the Mur absorbing boundafy condition.
2차원 광자 밴드 갭 구조의 유한 차분 시간 영역 모델링
鄭敎龐 弘益大學校 科學基術硏究所 1999 科學技術硏究論文集 Vol.10 No.2
In this paper, the transmission characteristics of a two-dimensional photonic bandgap crystal of finite size are computed with the finite-difference time-domain method, which is formulated with the total-field/scattered-field formulation and the Mur absorbing boundary condition for the two-dimensional TM case. The photonic crystal is composed of infinitely-long cylinders on a square lattice. Computed results confirm the existence of photonic bandgaps, and the variation of bandgaps with different parameters is observed. For the photonic crystals with missing cylinders, the transmission properties of one two defect modes are computed. The variation of defect-mode peaks inside the bandgap frequency is observed for various relative positions of defects.
제한된 수의 투사를 이용한 비 균일 경계 값을 가진 공간 분포의 재구성
鄭敎龐 弘益大學校 科學技術硏究所 1996 科學技術硏究論文集 Vol.7 No.2
A reconstruction method that makes use of smoothness of distributions and other apriori information, called the finite domain direct inversion (FDDI) method, was applied to the reconstruction of simulated distribution characteristic of a real experimental situation, e.g. measurements on a gas mixture within a duct. It was found that an abrupt discontinuity of a distribution at the periphery of its domain (and zero outside the domain) poses difficulty in the FDDI reconstruction because the basis functions used in the method cannot accommodate the discontinuity well. The inversion method was extended to include shifting functions which dealt specifically with the nonzero peripheral values of the distribution. We developed a systematic way of finding suitable shifting functions that improve the reconstructions substantially.
광자 크리스탈 채널드롭 터널링을 이용한 파장분할 소자에 대한 연구
鄭敎龐,吳世澤 弘益大學校 科學技術硏究所 2003 科學技術硏究論文集 Vol.14 No.-
We design a 1 X 4 wavelength demultiplexer based on channel drop tunneling in photonic crystals. We show the results of simulation of the demultiplexer device for tunneling properties of electromagnetic waves in a two-dimensional photonic crystal, with an application of the finite-difference time-domain method with perfectly-matched-layer absorbing boundary condition. We find four frequencies at which the channel drop tunneling occurs, and design a 1 X 4 wavelength demultiplexer based on the frequencies. To improve the channel drop transmission, we separate spurious reflections in photonic crystal waveguide simulations using a large computational domain, and obtain the results of highly efficient transmission.
Properties of Surface Modes Used for Directional Emission from Photonic Crystal Waveguides
정교방 한국광학회 2008 Current Optics and Photonics Vol.12 No.1
Directional emission of light exiting a photonic crystal waveguide by a coherent action of radiative surface modes was recently demonstrated, and subsequently the substantial enhancement of the directional emission was achieved by engineering the surface and adjusting relevant parameters. Here we present the analysis of surface modes causing the enhanced emission by the plane wave expansion method and the finite-difference time-domain method. In particular, surface band structures are calculated for nonradiative and radiative surface modes, respectively, and intensity profiles of some representative modes for nonradiative and radiative cases are given.
Effects of Surface Termination on Directional Emission from Photonic Crystal Waveguides
정교방 한국광학회 2008 Current Optics and Photonics Vol.12 No.1
We numerically investigate by the finite-difference time-domain method the effects of surface termination on directional emission exiting a photonic crystal waveguide. The directed power and far-field beam profile for the original proposal [E. Moreno et al., Phys. Rev. B 69, 121402 (2004)] and its enhancement [S. K. Morrison et al., Appl. Phys. Lett. 86, 081110 (2005)] are computed for different values of some important parameters. We find another surface termination condition with a positive surface displacement in the structure of the original proposal which has a negative surface displacement. Our surface termination is more effective than the original structure, and nearly as effective as the termination for the enhancement, for directional emission. Besides, our termination is simpler than that for the enhancement. We confirm the effectiveness of directional emission from our termination in its far-field beam profile, radiation intensity distribution, and additionally the wave-vector space representation by the Fourier analysis.