Optical Characterization of Transmitted Visible Photoluminescence of Bragg-resonanced Porous Silicon

박미애,김진수,조수경,손홍래 대한화학회 2018 Bulletin of the Korean Chemical Society Vol.39 No.2

The investigation and optical characterization of Bragg resonance luminescence porous silicon (BRL PS) exhibiting both optical reflectivity and sharp photoluminescence (PL) at the Bragg resonance wavelength were reported. Two types of Bragg reflector porous silicon (BR PS) samples which exhibit strong reflection in visible or near infrared region and broad red PL were fabricated. When the Bragg reflection wavelength places in the range of emission wavelength, BR PS starts to exhibit narrowing of PL behavior. The optimization of Bragg resonance phenomenon of PL to generate sharp Bragg-resonated PL by changing the number of repeats of Bragg-stack layers. BR PS showing the reflection wavelength of 640 nm with 50 repeats exhibited sharp PL at the Bragg resonance wavelength with broad weak PL. BRL PS having 70% porosity with 1.45 refractive index displayed the second-order reflectivity peak at 640 nm, thus sharp PL peak at 640 nm was the second-order transmitted and amplified PL peak at the Bragg resonance wavelength. The optical properties of free-standing BR PS film were investigated. The front side surface of BR PS shows both reflectivity and PL, however the back side surface of free-standing BR PS shows only reflectivity without PL.

비스듬히 입사하는 파랑의 Bragg반사

조용식,안영창 한국수자원학회 2002 한국수자원학회논문집 Vol.35 No.1

본 연구에서는 경계요소법을 이용하여 비스듬히 입사하는 파랑의 반사에 대하여 다루었으며, 비스듬히 입사하는 파랑이 정현파형 지형을 통과하는 경우 그 때의 반사율과 Bragg반사에 대하여 조사하였다. 특히, 비스듬히 입사하는 파랑의 Bragg반사를 발생시키는 파수를 계산하여 이론적인 결과와 비교하였다. 해석결과의 검증을 위하여 고유 함수전개법에 의한 정현파형 지형의 반사율과 본 모형의 결과를 비교하였으며, 전체적으로 본 연구의 결과는 기존의 연구결과들과 비 The present research describes the Bragg reflection of obliquely incident waves propagating over sinusoidally varying topographies. A numerical model based on the boundary element method is employed. Wave numbers providing Bragg reflection are calculated

경사지형에서의 Bragg반사

이종인,조용식,이정규 한국수자원학회 1999 한국수자원학회논문집 Vol.32 No.4

본 연구에서는 Boussinesq방정식으로부터 유도한 지배방정식을 수치 적분하여 정현파형 지형이 일정한 경사에 놓여 있는 해저지형을 통과하는 크노이드파인 Bragg반사를 해석하였다. 지배방식에 포함된 급변항의 효과와 비선형성의 크기에 따른 Bragg반사를 해석하였다. 또한, 다양한 경사에 따른 반사율의 변화를 계산하여 반사율은 경사에 따라 크게 변화하지 않음을 밝혀냈다. In this study, the Bragg resonant of cnoidal waves propagating over a sinusoidally varying topography lying on a uniformly sloping beach is investigated. The governing equations derived from the Boussinesq equations are numerically integrated. The effects

Polymer-waveguide Bragg-grating Devices Fabricated Using Phase-mask Lithography

박태현,김성문,오민철 한국광학회 2019 Current Optics and Photonics Vol.3 No.5

Polymeric optical waveguide devices with Bragg gratings have been investigated, for implementing tunable lasers and wavelength filters used in wavelength-division-multiplexed optical communication systems. Owing to the excellent thermo-optic effect of these polymers, wavelength tuning is possible over a wide range, which is difficult to achieve using other optical materials. In this study the phase-mask technology, which has advantages over the conventional interferometeric method, was introduced to facilitate the fabrication of Bragg gratings in polymeric optical waveguide devices. An optical setup capable of fabricating multiple Bragg gratings simultaneously on a 4-inch silicon wafer was constructed, using a 442-nm laser and phase mask. During fabrication, some of the diffracted light in the phase mask was totally reflected inside the mask, which affected the quality of the Bragg grating adversely, so experiments were conducted to solve this issue. To verify grating uniformity, two types of wavelengthfiltering devices were fabricated using the phase-mask lithography, and their reflection and transmission spectra were measured. From the results, we confirmed that the phase-mask method provides good uniformity, and may be applied for mass production of polymer Bragg-grating waveguide devices.

사다리꼴형상 투과성 수중방파제에 의한 정현파의 Bragg 반사

전찬후,조용식,이종인 한국수자원학회 2003 한국수자원학회논문집 Vol.36 No.5

본 연구에서는 사다리꼴형상 투과성 수중방파제에 의한 정현파의 Bragg반사에 대해 수리모형실험과 수치모형실험을 수행하였으며, 두 실험결과를 비교하였다. 수치해석에 적용된 모형에서는 공간 평균된 Wavier-Stokes 방정식을 투과체 내에서의 지배방정식으로 사용하였고, 자유수면변위를 추적하기 위해 VOF기법을 적용하였다. 수리실험결과와 수치해석결과는 비교적 잘 일치하였으며, 투과성 수중방파제에 의한 반사계수는 불투과성에 비해 낮게 나타나고, 방파제의 배 This study presents a combined experimental and numerical effort to investigate experimentally and numerically the Bragg reflection of sinusoidal waves due to trapezoidal submerged porous breakwaters. Numerical predictions of the study are verified by com

CsI:Tl 섬광 단결정 내에서 양성자 Bragg 피크 측정값과 몬테카를로 시뮬레이션 결과 비교

강상준 한국물리학회 2012 새물리 Vol.62 No.5

우리는 잘 정의된 환경 내에서 CsI:Tl 섬광 단결정에 양성자를 조사하고,전하결합소자 (CCD, Charge-Coupled Device)가 장착된 케논 디지털카메라로 촬영하여 양성자의 투과 깊이를 측정하였다. 같은 환경 내에서같은 재질의 섬광체를 몬테카를로 시뮬레이션 툴킷인 Geant4와 SRIM 코드를 사용하여 시뮬레이션을 수행 하였다. 실험 데이터와 시뮬레이션결과를 비교하여 실제 실험을 몬테카를로 시뮬레이션이 얼마나 유사하게구현하는지 살펴보았다. 또한 이 결과를 Bragg-Kleeman 법칙으로 알려져있는 실험법칙과 비교하였다. We investigated the proton penetration depth in a CsI:Tl scintillation crystal in a well-defined environment. We irradiated the CsI:Tl scintillation crystal with proton beams and measured the proton penetration depth by using a Canon digital camera on which a charge-coupled device (CCD) had been mounted. We simulated the same situation by using the Monte Carlo simulation tool kit, SRIM and Geant4. We compared the experimental data with the simulation results. We also compared the experimental data with the results obtained by using the empirical rule known as the Bragg-Kleeman rule.

Evaluation of dose distribution from 12C ion in radiation therapy by FLUKA code

Jamshid Soltani-Nabipour,Abdollah Khorshidi,Faezeh Shojai,Khazar Khorami 한국원자력학회 2020 Nuclear Engineering and Technology Vol.52 No.10

Heavy ions have a high potential for destroying deep tumors that carry the highest dose at the peak of Bragg. The peak caused by a single-energy carbon beam is too narrow, which requires special measures for improvement. Here, carbon-12 (12C) ion with different energies has been used as a source for calculating the dose distribution in the water phantom, soft tissue and bone by the code of Monte Carlo-based FLUKA code. By increasing the energy of the initial beam, the amount of absorbed dose at Bragg peak in all three targets decreased, but the trend for this reduction was less severe in bone. While the maximum absorbed dose per bone-mass unit in energy of 200 MeV/u was about 30% less than the maximum absorbed dose per unit mass of water or soft tissue, it was merely 2.4% less than soft tissue in 400 MeV/u. The simulation result showed a good agreement with experimental data at GSI Darmstadt facility of biophysics group by 0.15 cm average accuracy in Bragg peak positioning. From 200 to 400 MeV/u incident energy, the Bragg peak location increased about 18 cm in soft tissue. Correspondingly, the bone and soft tissue revealed a reduction dose ratio by 2.9 and 1.9. Induced neutrons did not contribute more than 1.8% to the total energy deposited in the water phantom. Also during 12C ion bombardment, secondary fragments showed 76% and 24% of primary 200 and 400 MeV/u, respectively, were present at the Bragg-peak position. The combined treatment of carbon ions with neutron or electron beams may be more effective in local dose delivery and also treating malignant tumors.

A New Planar Spiral Inductor with Multi-layered Bragg Reflector for Si-Based RFIC's

Mai Linh,Lee Jae-Young,Le Minh-Tuan,Pham Van-Su,Yoon Gi-Wan The Korea Institute of Information and Commucation 2006 Journal of information and communication convergen Vol.4 No.2

In this paper, a novel physical structure for planar spiral inductors is proposed. The spiral inductors were designed and fabricated on multi-layered substrate Bragg-reflector/silicon (BR/Si) wafer. The impacts of multi-layered structure substrate and pattern on characteristics of inductor were studied. Experimental results show that the inductor embedded on Bragg reflector/silicon substrate can achieve the best improvement. At 0.4-1.6 GHz, the Bragg reflector seems to significantly increase the S11-parameter of the inductor.

2차원 경계요소법을 이용한 Bragg반사 해석

김영택,조용식,이정규 한국수자원학회 2000 한국수자원학회논문집 Vol.33 No.6

본 연구에서는 경계요소법을 이용하여 수심이 변하는 지형을 통과할 때 발생하는 파랑의 회절을 수치해석하였다. 먼저, 트렌치지형을 통과하는 파랑의 반사율과 통과율을 계산하였으며 고유함수전개법에 의한 결과와 비교하여 본 모형을 검증하였다. 아울러, 경계요소법을 정현파형 지형에 적용하여 반사율 및 Bragg 반사를 연구하였다. 수치해석에 의한 반사율은 수리모형실험에 의한 관측결과 및 고유함수전개법에 의한 결과와 비교하였다. 전체적으로 본 연구의 결과는 기존의 A numerical model based on the boundary element method is employed to describe diffraction of monochromatic water waves due to varying topographies. The model is firstly verified by comparing obtained reflection and transmission coefficients of waves over

반복 주름을 갖는 이차원 덕트의 음파차단 해석

김현실,김재승,김봉기,김상렬,이성현,Kim, Hyun-Sil,Kim, Jae-Seung,Kim, Bong-Ki,Kim, Sang-Ryul,Lee, Seong-Hyun 한국음향학회 2012 韓國音響學會誌 Vol.31 No.1

본 논문은 경계가 주기적으로 변하는 주름관에 음파가 전파할 때 발생하는 차단주파수밴드 (stopband)를 이론 및 BEM으로 해석한 내용을 다루었다. 2-D 덕트를 고려하였으며 경계가 길이방향의 사인함수로 변하는 주름관에서 주름의 크기가 덕트 높이에 비해 충분히 작은 경우 다중 스케일 섭동법 (Multiple Scaling Perturbation Method)을 이용하여 해를 구하였다. 주파수가 복소수가 되는 조건에서 Bragg 공진과 Non-Bragg 공진에서 발생하는 차단주파수밴드의 형성조건을 구하였다. 2-D BEM 해석을 수행하여 주름관의 삽입손실 (Insertion Loss)을 계산하였으며 이론적으로 예측한 차단주파수밴드의 존재를 확인하였다. In this paper, the occurrence of a stopband phenomenon when an acoustic wave propagates through periodically corrugated ducts is discussed using theoretical and BEM analyses. A 2-D duct with sinusoidally corrugated upper and lower walls is considered. When the magnitude of the sinusoidal corrugation is sufficiently small compared to the duct's height, the wave equation is solved with the multiple scaling perturbation method. Then stopbands for Bragg and non-Bragg resonances are computed from the condition where frequency becomes a complex number. A 2-D BEM analysis is performed to compute insertion loss of the duct, and stopbands are confirmed as predicted by analytical analysis.