• Current Optics and Photonics
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• 제5권4호
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• pp.466-476
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• 2021

Frequency-multiplication technology based on microwave photonic principles can be used to generate microwave and millimeter wave signals with a wide frequency tuning range. However, the existing cascaded external modulation frequency-tupling scheme needs to ensure the phase coherence of the modulated Radio Frequency (RF) signal, while the phase modulation directly limits the frequency tuning range of the external modulation frequency multiplication. In this paper, a novel approach for generating an incoherent frequency 12-tupling signal with cascade modulation is proposed. The structure of cascaded dual-parallel Mach-Zehnder modulators can generate a frequency 12-tupling signal. The proposed structure uses no filter or phase control of the RF driving signal. Microwave photonic frequency-tupling was realized under incoherent conditions. Software simulations and experiments validated the proposed structure and proved that it can generate frequency 12-tupling microwave signals under incoherent conditions. Both the frequency range and reliability of the frequency-tupling system has been improved by the proposed structure.

• 한국광학회지
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• 제16권3호
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• pp.261-265
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• 2005

광자결정의 밴드갭이 크면서도 모든 편광방향에 대해 동일하게 설계될 수 있다면, 이러한 광밴드갭은 다양한 소자의 응용에 있어 보다 유용해 질 수 있다. 현재까지는 원형의 공기구멍으로 이루어진 삼각격자 구조가 가장 큰 광밴드갭을 갖는 것으로 알려져 왔으나, 본 논문에서는 각종 구조적 변화에 의한 밴드갭의 변화경향을 분석하고 체계화함에 따라, 모든 편광방향에 대해 광밴드갭이 동일하면서 가장 크게 되는 새로운 격자구조를 제안하였다. 이 구조의 광밴드갭 비율$(\Delta\omega/\omega)$은 기존의 삼각격자에 비해 약 $30\%$ 정도 증대된 것임을 확인하였다.

• 한국전자파학회논문지
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• 제12권7호
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• pp.1182-1190
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• 2001

본 논문에서는 마이크로스트립 선로상의 금속부분을 일부 제거한 형태의 Photonic bandgap (PBG) 구조의 특성을 분석하고 형태를 최적화 한 후 전력 증폭기에 적용하여 고조파 동조를 수행하였다. 이 구조는 제작 및 접지에서 타 구조에 비해 유리하다. PCB 제작 과정의 오차를 줄이기 위해 단위 격자의 크기를 수직방향으로 증가시키고, 테이퍼 선로를 이용하여 입출력을 50 $\Omega$으로 유지시켰다. EM 시뮬레이션으로 PBG 구조의 특성을 분석하고 설계하였으며, 최종적으로 통과대역 손실 0.3~0.4dB, 저지대역폭 6~7GHz의 특성을 얻었다. 전력 증폭기에 PBG구조를 적용한 후 출력 전력은 0.72~0.99dB, PAE는 1.14~7.8 %, 3차 IMD는 1 dBc 증가하는 결과를 얻을 수 있었다.

• 한국전기전자재료학회논문지
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• 제28권3호
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• pp.175-179
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• 2015

In this study, we propose Ti hole pattern structure on the transparent conductive oxide (TCO) less dye-sensitized solar cells (DSSCs) using the lift-off process to improve the low light transmittance and low efficiency caused by opaque Ti electrode. The formation of Ti hole patterns make it possible to move the dye adsorption and electrolyte. The DSSCs with Ti hole patterns showed a higher photoelectric conversion efficiency (PCE) than those with general structure by 11.1%. As a result, The Ti hole pattern structure can be improved to increase the light absorption of the dyes and PCE of the TCO-less DSSCs is also increased.

• 대한전자공학회논문지TC
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• 제41권2호
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• pp.53-58
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• 2004

본 논문에서는 부성저항을 갖는 발진부의 귀환 경로에 PIN 다이오드를 이용한 스위칭 회로를 추가하여 저 위상잡음 듀얼밴드 전압제어 발진기를 구현하였다. PIN 다이오드에 전원이 인가되지 않았을 때는 5㎓ 대역에서 발진이 일어나고, 인가되었을 때는 1.8㎓ 대역에서 발진이 일어난다. VCO의 위상잡음을 향상시키기 위하여 공진기에 PBG(Photonic Bandgap)구조를 접지 면에 적용하였다. 5.25㎓에서 출력 전력은 -9.17㏈m, 위상잡음은 -102㏈c/㎐이고, 1.8㎓에서 출력 전력은 -5.17㏈m, 위상잡음은 -101㏈c/㎐이다.

• Transactions on Electrical and Electronic Materials
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• 제16권3호
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• pp.117-123
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• 2015

Cholesteric liquid crystals are one dimensional photonic band-gap materials due to their birefringence and periodic structure. Dye doped cholesteric liquid crystals are self-assembling, mirror-less, low threshold laser structures that exhibit distributed feedback. In this review paper, we have presented the development in the field of lasing characteristics of dye doped cholesteric liquid crystals.

• Bulletin of the Korean Chemical Society
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• 제31권7호
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• pp.1891-1896
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• 2010

Submicron-sized polymeric colloidal particles can self assemble into 3-dimensional (3D) opal structure which is a useful template for photonic crystal. Narrowly dispersed polymer microspheres can be synthesized by emulsion polymerization in water using water-soluble radical initiator. In this report, we demonstrate a facile and reproducible emulsion polymerization method to prepare various polymeric microspheres within 200 - 400 nm size ranges which can be utilized as colloidal photonic crystal template. By controlling the amount of monomer and surfactant, monodisperse polymer colloids of polystyrene (PS) and acrylates with various sizes were successfully prepared without complicated synthetic procedures. Such polymer colloids self-assembled into 3D opal structure exhibiting bright colors by reflection of visible light. The colloidal particles and the resulting opal structures were rigorously characterized, and the wavelength of the structural color from the colloidal crystal was confirmed to have quantitative relationship with the size of constituting colloidal particles as predicted by Bragg equation. The tunability of the structural color was achieved not only by varying the particle size but also by infiltration of the colloidal crystal with liquids having different refractive indices.

• 한국재료학회지
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• 제27권12호
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• pp.695-698
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• 2017

ZnMgBeGaO/Ag/ZnMgBeGaO multilayer structures were sputter grown and characterized in detail. Results indicated that the electrical properties of the ZnMgBeGaO films were significantly improved by inserting an Ag layer with proper thickness (~ 10 nm). Structures with thicker Ag films showed much lower optical transmission, although the electrical conductivity was further improved. It was also observed that the electrical properties of the multilayer structure were sizably improved by annealing in vacuum (~35 % at $300^{\circ}C$). The optimum ZnMgBeGaO(20nm)/Ag(10nm)/ZnMgBeGaO(20nm) structure exhibited an electrical resistivity of ${\sim}2.6{\times}10^{-5}{\Omega}cm$ (after annealing), energy bandgap of ~3.75 eV, and optical transmittance of 65 % ~ 95 % over the visible wavelength range, representing a significant improvement in characteristics versus previously reported transparent conductive materials.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 춘계학술대회 논문집
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• pp.49-51
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• 2009

Photonic crystal is a dielectric materials or a set of different dielectric materials with periodic structure of refractive index. Line defect obtained by leaving out a row of rod along the $\Gamma$-X direction. We showed the change of group velocity in waveguide mode and found a small group velocity. Characteristic of the small group velocity described by electric field distribution. As the phase variation, small group velocity confirmed from positive to negative.

• 한국광학회:학술대회논문집
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• 한국광학회 2003년도 제14회 정기총회 및 03년 동계학술발표회
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• pp.184-185
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• 2003

Unlike the conventional waveguide such as optical fiber using total internal reflection, photonic crystal waveguide(PCW), a waveguide made of a line defect in a photonic crystal(PC) structure, does not admit an analytic approach due to its complexity but requires a direct numerical approach. Here, we present numerical results of computer simulation for PCW by using the three-dimensional(3D) Finite-Difference Time -Domain(FDTD) algorithm. (omitted)