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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.
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.
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.
鄭敎龐,尹志秀 弘益大學校 科學技術硏究所 2001 科學技術硏究論文集 Vol.12 No.-
We design a 1-by-4 optical splitter made of photonic crystal waveguides and analyze the properties of the optical splitter using the finite-difference time-domain method with perfectly-matched-layer absorbing boundaries. The photonic crystal is constructed by cylindrical rods in air on a square lattice. Our simulation results show that there are different transmission properties for four bend geometries and different incident-wave frequencies, and the incident power splits in the four arms with almost the same ratio. Moreover, we perform numerical simulations of T-shaped waveguide branches to reduce the reflections at the T-branches in the splitter. The branching region is treated as a cavity that couples the input and output waveguides. The improvement of transmission is achieved by placing the defects of extra rods in the branching region.
鄭敎龐 弘益大學校 科學技術硏究所 1998 科學技術硏究論文集 Vol.9 No.2
In this paper, the algorithm of the finite- difference time-domain method with the total-field/scattered-field formulation and the Mur absorbing boundary condition for the two-dimensional TM case is established and programmed. The program is applied to the computation of the transmission characteristics of a two- dimensional photon bandgap structure composed of cylinders on a square lattice. Computed results confirm the existence of photonic bandgaps, and the variations of bandgaps with different parameters are observed.
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.