증폭된 광 귀환을 가자는 다중 전극 복소 결합 DFB 레이저에서 발생되는 self-pulsation 특성 해석

김상택,김태영,김부균,임영안,박경현,Kim, Sang-Taek,Kim, Tae-Young,Kim, Boo-Gyoun,Leem, Young-Ahn,Park, Kyung-Hyun 한국광학회 2005 한국광학회지 Vol.16 No.6

하나의 DFB 영역, 위상 조정 영역과 이득 영역으로 구성된 다중 전극 DFB 레이저의 pulsation 동작 특성을 살펴본다. Anti-phase (AP) complex-coupled (CC) DFB 구조를 사용한 경우가 in-phase CC DFB 구조나 index-coupled DFB 구조를 사용한 경우에 비하여 안정된 pulsation 동작이 발생하는 이득 영역과 위상 조정 영역의 전류 범위가 큼을 알 수 있다. AP CC DFB 구조를 사용한 경우 결합 세기가 커질수록, 이득 결합 계수가 커질수록 안정된 pulsation 동작이 발생하는 이득 영역의 전류 범위가 증가하고 pulsation 주파수의 튜닝 영역이 커짐을 볼 수 있다. 또한 위상 조정 영역의 위상 변화에 의한 pulsation주파수의 튜닝 영역도 커짐을 볼 수 있다. 고정된 결합 세기에서 DFB 영역의 길이가 증가할수록 pulsation 동작이 발생하는 위상 조정 영역과 이득 영역의 전류 범위가 증가하여 pulsation 주파수 튜닝 영역이 넓어짐을 볼 수 있다. We investigate the pulsation characteristics in a multi-section DFB laser which is composed of one DFB section, phase tuning section, and gain section. Multi-section DFB lasers with anti-phase (AP) complex-coupled (CC) DFB structure show wide current ranges of gain and phase tuning sections fer stable pulsations compared to those with in-phase CC DFB structure or index-coupled DFB structure. For multi-section DFB lasers with AP CC DFB structure, the current range of a gain section for stable pulsations increases and the tuning range of the pulsation frequency increases as a coupling strength or a gain coupling coefficient increases Also, the tuning range using the phase variation in a phase tuning section increases. For a fixed coupling strength, the current ranges of gain and phase tuning sections for stable pulsations increase and the tuning range of the pulsation frequency increases as the length of a DFB section increases.

Total Cross Sections for Neutron Nucleus Scattering

S. V. Suryanarayana,H. Naik,S. Ganesan,S. Kailas,R. K. Choudhury,김귀년 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23

Ramsauer model is well known and widely applied to understand systematics of neutron nucleus total cross sections. In this work, we examined the role of nuclear effective radius parameter (r_0) on Ramsauer model fits of neutron total cross sections. We examined the Ramsauer model global analysis of the experimental neutron total cross sections reported by W. P. Abfalterer, F. B. Bateman, et. al., from 20 MeV to 550 MeV for nuclei ranging from Be to U. The global fits predict within ±8% deviation to data.It has been observed that a finer adjustment of r_0 parameter alone can give very good Ramsauer model description of neutron total scattering data within ±4% deviation. The required r_0 values for Ramsauer model fits are provided as a function of nuclear mass number. In optical model study, we have modified the real part of Koning-Deleroche potentials to fit the neutron total cross sections using SCAT2 code. The modified potentials have a different energy dependence beyond 200 MeV of neutron energy and fit the neutron total cross sections from C to Bi.

Theoretical Investigation of Electron Impact Total Ionization Cross Sections for N(CH_3)_3, NH(CH_3)_2, NH_2CH_3, P(CH_3)_3, PH(CH_3)_2, and PH_2CH_3 Molecules

Harshad Bhutadia,Minaxi Vinodkumar,Bobby Antony 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.41

Calculations of the electron impact total ionization cross sections for N(CH_3)_3, NH(CH_3)_2,NH_2CH_3, P(CH_3)_3, PH(CH_3)_2, and PH_2CH_3 were performed in the energy range from ionization threshold to 2 keV. In this work we have made use of a spherical complex optical potential in the Schr¨odinger equation, which is solved through the partial wave approximation to obtain the total inelastic cross sections. The total inelastic cross sections thus obtained are then used to derive the total ionization cross sections by employing the complex spherical potential-ionization contribution method.

다중 전극 Index-Coupled DFB 레이저에서 결합 세기 및 각 영역의 길이가 Self-Pulsation 동작 특성에 미치는 영향

김상택,김태영,지성근,김부균,Kim, Sang-Taek,Kim, Tae-Young,Ji, Sung-Keun,Kim, Boo-Gyoun 한국광학회 2005 한국광학회지 Vol.16 No.1

두 개의 DFB 영역과 위상 조정 영역으로 구성된 다중 전극 index-coupled DFB 레이저에서 self-pulsation 동작 특성을 수치 해석으로 분석하였다. 금지 대역폭 내에 존재하는 전체 공진기 모드 수가 감소할수록 두 DFB 영역의 브래그 파장 차이인 $\Delta$λ$_{B}$가 변화할 때 발진 모드의 호핑이 발생하는 경우의 수가 적어져 pulsation 주파수가 불연속적으로 변화하는 경우의 수가 감소한다. 또한 고정된 $\Delta$λ$_{B}$에 대하여 위상 조정 영역의 위상이 변화할 때 pulsation 주파수가 연속적으로 변화한다. 결합 세기와 위상 조정 영역의 길이가 고정되어 있을 때 금지 대역폭 내에 존재하는 전체 공진기 모드의 수는 DFB 영역의 길이가 길수록 감소한다. 반면에 DFB 영역의 결합 세기와 길이가 고정되어 있을 때 금지 대역폭 내에 존재하는 전체 공진기 모드의 수는 위상 조정 영역의 길이가 작을수록 감소한다. 따라서 결합 세기 및 각 영역의 길이를 적절히 조정하면 $\Delta$λ$_{B}$ 또는 위상조정 영역의 위상이 변화하여도 모드 호핑이 발생하지 않아 안정된 pulsation 동작을 얻을 수 있음을 보였다.을 보였다. As the number of compound cavity modes within the stopband of DFB sections decreases, the frequency of mode hopping decreases for the variation of $\Delta$λ$_{B}$, which represents the difference between the Bragg wavelengths of two DFB sections, so that the number of abrupt changes of pulsation frequencies decreases. In addition, the pulsation frequency varies continuously for the variation of the phase in a phase tuning section for a fixed $\Delta$λ$_{B}$. The number of compound cavity modes within the stopband decreases as the length of DFB sections increases and the length of a phase tuning section decreases. Thus stable self-pulsation operations for the variation of $\Delta$λ$_{B}$ and the phase in a phase tuning section could be obtained by proper selection of the coupling strength and the length of each section.ction.

GPU 기반의 TSM-RT를 이용한 풍력 블레이드의 동적 RCS 계산

최영재(Young-Jae Choi),최인식(In-Sik Choi) 한국전자파학회 2020 한국전자파학회논문지 Vol.31 No.3

다수의 풍력 블레이드에 의하여 발생하는 동적 RCS를 계산하기 위해서는 샘플링 시간별로 이동된 표적의 3차원 메쉬에 대한 RCS를 계산하는 과정이 필요하다. 본 논문에서는 물리광학법을 사용하여 이러한 동적 RCS를 계산하는 방법을 제안하였다. 광선추적법을 가속하기 위하여 GPU 기반의 TSM-RT 방법을 적용하여 계산 속도를 향상시켰으며, 제안한 방법의 성능을 상용 전자파 해석 소프트웨어인 FEKO와 비교하여 검증하였다. 마지막으로 제안된 방법을 사용하여 서로 다른 회전 속도를 갖는 두 개의 풍력 블레이드의 동적 RCS를 계산하였다. It is necessary to calculate the RCS generated by several wind blades for the three-dimensional mesh analysis of a target moved for each sampling time. In this paper, we propose a method of calculating dynamic RCS through physical optics. The computational speed was improved by applying the graphics processing unit-based two-scale-model ray-tracing method to enhance the ray tracing efficiency. Finally, the proposed method was used to calculate the dynamic RCS of two wind blades at different rotational speeds.

함정용 통합 마스트의 레이다 단면적 분석

신호근(Hokeun Shin),이석곤(Seokgon Lee),박동민(Dongmin Park),신진우(Jinwoo Shin),정명수(Myungsoo Chung),박상현(Sanghyun Park),박용배(Yong Bae Park) 한국전자파학회 2017 한국전자파학회논문지 Vol.28 No.7

본 논문에서는 함정용 통합 마스트의 레이다 단면적을 분석한다. 레이다 단면적 분석을 위한 물리 광학법 및 물리광학 회절이론 기반의 계산 프로그램을 개발하고, 상용 시뮬레이터와 비교를 통해 계산의 정확도를 확인한다. 함정용 마스트의 형상과 입사각, 편파에 따른 레이다 단면적 변화를 계산하고 분석한다. 마스트의 측면 기울기 변화 및 모따기가 있는 마스트 구조를 통해 레이다 단면적을 감소시킬 수 있고, 이것을 저 RCS 함정 마스트 개발에 활용할 수 있음을 확인한다. In this paper, the radar cross section of the integrated mast module for battleship is analyzed. The computation program based on physical optics and physical theory of diffraction is developed and the computed results are compared with those of commercial simulator to check the accuracy of computations. The radar cross section is calculated in terms of the mast shape, incident angle, and polarization. The radar cross section can be reduced through the change of the mast slope and the chamfered mast, which can be applied to a mast with a low radar cross section.

Optical Tracking of Three-Dimensional Brownian Motion of Nanoparticles

C. K. Choi,K. D. Kihm 한국가시화정보학회 2005 한국가시화정보학회지 Vol.3 No.1

Novel optical techniques are presented for three-dimensional tracking of nanoparticles; Optical Serial Sectioning Microscopy (OSSM) and Ratiometric Total Internal Reflection Fluorescent Microscopy (R-TIRFM). OSSM measures optically diffracted particle images, the so-called Point Spread Function (PSF), and determines the defocusing or line-of-sight location of the imaged particle measured from the focal plane. The line-of-sight Brownian motion detection using the OSSM technique is proposed in lieu of the more cumbersome two-dimensional Brownian motion tracking on the imaging plane as a potentially more effective tool to nonintrusively map the temperature fields for nanoparticle suspension fluids. On the other hand, R-TIRFM is presented to experimentally examine the classic theory on the near-wall hindered Brownian diffusive motion. An evanescent wave field from the total internal reflection of a 488-㎚ bandwidth of an argon-ion laser is used to provide a thin illumination field of an order of a few hundred nanometers from the wall. The experimental results show good agreement with the lateral hindrance theory, but show discrepancies from the normal hindrance theory. It is conjectured that the discrepancies can be attributed to the additional hindering effects, including electrostatic and electro-osmotic interactions between the negatively charged tracer particles and the glass surface.

Enhanced Airborne Optical Sectioning Design via HSV Color Space for Detecting Human Object Under Obscured Aerial Image Environment

KangSoo Ryu,Byungjin Lee,Dong-Gyun Kim,Sangkyung Sung 제어·로봇·시스템학회 2023 International Journal of Control, Automation, and Vol.21 No.11

This paper aims to develop an algorithm to identify the obscured target from the aerial image encountered in a general complex flight environment. For this, an airborne optical sectioning (AOS) and synthesizing technique is newly adapted for the purpose of preliminary data processing. Specifically, the proposed algorithm consists of several image processing stages. In a foliage-rich environment, the majority of an image may be occupied by trees, where it is difficult to detect a person hidden under foliage. To resolve this, the preprocessing stage in the HSV color space removes the tree parts while preserving the person, and the processed images are combined to construct the AOS, which reveals the person hidden under the trees. Then the exposed person is identified using the machine learning technique that accurately recognizes human shapes. Consequently, the proposed optical sectioning and synthetic process suggests to expand the application field of typical vision-based mission system under complex airborne environment. The performance of the proposed algorithm is demonstrated through the airborne data from a high fidelity process-in-the-loop simulator, where sensor and vision measurement are constructed and provided to a level of practical flight environment.

Microscopic Optical Model Potential of Isospin Dependent Nucleon, Deuteron and Helium-3

Yinlu Han,Hairui Guo,Qingbiao Shen 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23

The microscopic optical model potentials for isospin-nucleon, deuteron and helium-3 are obtained by the one-particle, two-particle and the three-particle Green function method through nuclear matter approximation and local density approximation based on the Skyrme interactions. The calculated results are compared with the experimental data by the microscopic optical model potentials. Good agreement is generally obtained for elastic scattering angular distributions. Good agreement is obtained for the reaction cross sections of some nucleus.

Optical Tracking of Three-Dimensional Brownian Motion of Nanoparticles

Choi C. K.,Kihm K.D. The Korean Society of Visualization 2005 한국가시화정보학회지 Vol.3 No.1

Novel optical techniques are presented for three-dimensional tracking of nanoparticles; Optical Serial Sectioning Microscopy (OSSM) and Ratiometric Total Internal Reflection Fluorescent Microscopy (R-TIRFM). OSSM measures optically diffracted particle images, the so-called Point Spread Function (PSF), and dotermines the defocusing or line-of-sight location of the imaged particle measured from the focal plane. The line-of-sight Brownian motion detection using the OSSM technique is proposed in lieu of the more cumbersome two-dimensional Brownian motion tracking on the imaging plane as a potentially more effective tool to nonintrusively map the temperature fields for nanoparticle suspension fluids. On the other hand, R-TIRFM is presented to experimentally examine the classic theory on the near-wall hindered Brownian diffusive motion. An evanescent wave field from the total internal reflection of a 488-nm bandwidth of an argon-ion laser is used to provide a thin illumination field of an order of a few hundred nanometers from the wall. The experimental results show good agreement with the lateral hindrance theory, but show discrepancies from the normal hindrance theory. It is conjectured that the discrepancies can be attributed to the additional hindering effects, including electrostatic and electro-osmotic interactions between the negatively charged tracer particles and the glass surface.