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Functional Optical Filters Based on Two-Dimensional Photonic Crystals
기철식,고도경,이종민,임한조 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.48 No.5I
We propose three types of optical filters composed of point and line defects in two-dimensional photonic crystals, bent filters, directional filters, and multi-channel drop filters. The filtering is performed by using the coupling between the cavity modes of the point defects and the guiding modes of the line defects. The filtered frequency can be tuned to the desired frequency by designing the geometries of the point defects. The filtering position and direction are also controlled by choosing the positions of the point defects and the directions of line defects. The proposed filters could be useful in miniature photonic integrated circuits.
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Self-Collimated Beams in Two-Dimensional Photonic Crystals: Properties and Applications
기철식,고도경,박해용,이종민,이성구 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.II
The propagation properties of a self-collimated beam in two-dimensional photonic crystals have been investigated by using equifrequency contour calculations and finite-difference time-domain simulations. Total internal reflection of self-collimated beams can occur at the interfaces of photonic crystals and air. The Goos-H$\ddot{\rm a}$nchen shift of self-collimated beams totally reflected at the photonic crystal-air interface can be much smaller than the wavelength of the incident beam. We have also showed that a line defect can reflect self-collimated beams; thus, the power of self-collimated beam can be split by a line defect. The power ratio between two split self-collimated beams can be controlled by varying the radii of the rods in the line defect. The controllable splitting of self-collimated beams can be useful in steering the flow of light in photonic crystals.
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기철식(Chul-Sik Kee),최춘기(Choon-Gi Choi),윤근병(Keun Byoung Yoon),한상필(Sang-Pi Han),정명영(Myung Yung Jeong) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11
We present that two-dimensional periodic nano-patterns can be embossed on a polymer thin film using the nano-imprint process. The silicon masters with triangular arrays of rods such as square, hexagon, dodecagon and circle were successfully fabricated using the e-beam lithography and inductively coupled plasma etching. We also show that the polymer thin films with two-dimensional periodic patterns, polymer photonic crystals, can exhibit electromagnetic stop bands and the line defects introduced in the periodic patterns can serve as low loss waveguides from the photonic band calculations and the finite difference time domain simulations.
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김성일,기철식,박익모,임한조 한국전자파학회 2002 한국전자파학회논문지 Vol.13 No.10
In this paper, we have studied the dependence of insertion loss of a microstrip stepped impedance lowpass filter with coupled open stubs. Coupling mechanisms in the filter depend not only on the transmission line width of the filter but also the gap width of coupled open stubs and three attenuation poles are created with the proper conditions. Also edge capacitance between open stubs play an important role in having three attenuation Poles. We verify the results by obtaining [S] matrices.
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김성일,기철식,박익모,임한조 한국전자파학회 2002 한국전자파학회논문지 Vol.13 No.10
본 논문에서는 두 마이크로스트립 라인으로 이루어진 압축된 마이크로스트립 PBG 링 구조에서 두 마이크로스트립 라인간의 간격변화에 따른 삽입손실 특성을 연구하였다. 두 라인이 가까워짐에 따라 라인간의 커플링으로 인하여 두 개의 감쇄폴이 생겨 넓은 저지대역을 가지며 갭 간격이 매우 가까워지면 2개의 감쇄폴이 3개로 늘어나 저지대역은 매우 넓어지고 cutoff특성 또한 향상된다.
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스텁을 갖는 PBG 셀로 구현한 마이크로스트립 PBG 구조 및 듀플렉서
장미영,기철식,박익모,임한조,김태일,이정일,Jang, Mi-Young,Kee, Chul-Sik,Park, Ik-Mo,Lim, Han-Jo,Kim, Tae-Il,Lee, Jung-Il 대한전자공학회 2001 전자공학회논문지TC (Telecommunications) Vol.38 No.12
We have studied the design of the photonic bandgap (PBG) structure on the microstrip line that can effectively control the fractional bandwidth of the passband formed in the stopband by adding the stub in the cell of the microstrip PBG structure. As the length of the stub increases, the cutoff frequency and the center frequency of the stopband are decreased, while the bandwidth of the stopband is increased. We have also found that the fractional bandwidth of the passband formed in stopband by the introduction of defect decreases as the stub length is increased. These results mean that adding the stub in the normal PBG structure is an effective way to control the fractional bandwidth. As an application example, we have implemented a microwave duplexer using the proposed structure.
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