• 제목/요약/키워드: optics

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3-Dimensional LADAR Optical Detector Development in Geiger Mode Operation (Geiger Mode로 동작하는 3차원 LADAR 광수신기 개발)

  • Choi, Soon-Gyu;Shin, Jung-Hwan;Kang, Sang-Gu;Hong, Jung-Ho;Kwon, Yong-Joon;Kang, Eung-Cheol;Lee, Chang-Jae
    • Korean Journal of Optics and Photonics
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    • v.24 no.4
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    • pp.176-183
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    • 2013
  • In this paper, we report the design, fabrication and characterization of the 3-Dimensional optical receiver for a Laser Detection And Ranging (LADAR) system. The optical receiver is composed of three parts; $16{\pm}16$ Geiger Mode InGaAs Avalanche Photodiode (APD) array device operated at 1560 nm wavelength, Read Out Integrated Circuit (ROIC) measuring the Time-Of-Flight (TOF) of the return signal reflected from target objects, a package and cooler maintaining the proper operational condition of the detector and control electronics. We can confirm that the LADAR system can detect the signal from a target up to 1.2 km away, and it showed low Dark Count Rate (DCR) of less than 140 kHz, and higher than 28%-Photon Detection Efficiency (PDE). This is considered to be the best performance of the $16{\pm}16$ FPA APD optical receiver for a LADAR system.

Fabrication and Characterization of Wavelength Conversion Device with Periodically Poled Ridge-type Waveguide in MgO:LiNbO3 (주기적으로 분극 반전된 MgO:LiNbO3를 이용한 리지형 광도파로 파장가변 소자 제작 및 특성)

  • Lee, H.M.;Yang, W.S.;Kim, W.K.;Lee, H.Y.;Jeong, W.J.;Kwon, S.W.;Koo, K.H.;Song, M.G.
    • Korean Journal of Optics and Photonics
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    • v.19 no.3
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    • pp.199-207
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    • 2008
  • Wavelength converting devices with a ridge-type waveguide in periodically poled $MgO:LiNbO_3$ are made and characterized. The experimental results are compared with theoretical analysis on the effects of waveguide dimension and duty ratio of the periodically poled structure. To show the relationship of the conversion efficiency to those factors, a new measurement system is configured. That experimental results show that the center wavelength, normalized conversion efficiency and full width half maximum of the conversion efficiency curve are 1067.45 nm, 90.7%/$Wcm^2$ and 0.17 nm, respectively. Also, the estimated results of the duty period and full width half maximum of the conversion efficiency from theoretical calculations agreed well with experimental results with the errors of 0.016 ${\mu}m$ and 0.01 nm.

Effect of the Reflectivity of Both Facets and the Phase of a Phase Tuning Section on the Yield Characteristics of a Multisection Complex-Coupled DFB Laser with Self-Pulsation Frequency of THz Region (양 단면 반사율과 위상 조정 영역의 위상이 Self-Pulsation 주파수가 THz 대역인 다중 영역 Complex-Coupled DFB 레이저의 수율 특성에 미치는 영향)

  • Kim, Tae-Young;Park, Jae-Woo;Kim, Boo-Gyoun
    • Korean Journal of Optics and Photonics
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    • v.19 no.3
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    • pp.208-218
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    • 2008
  • We investigate the effect in terms of yield of the reflectivity of both facets and of the phase of a phase tuning section on the self-pulsation (SP) characteristics of multisection complex-coupled (CC) DFB lasers with self-pulsation frequency of the THz region. When the grating phases on both facets of a multisection CC DFB laser are fixed as 0, the variation of SP frequency increases as the reflectivity of both facets increases, while that of SP frequency decreases as the coupling ratio (CR) and the coupling strength increase. For the coupling strength of 3, the range of the phase of a phase tuning section with yields greater than 80% decreases as the CR and the reflectivity of both facets increases. For the coupling strength of 4, the range of the phase of a phase tuning section with yields greater than 80% increases as the CR and the reflectivity of both facets increases.

Performance of CWDM Fabricated by the PLC-AWG Technology (평판형 AWG 기술을 이용한 광대역 파장다중화/역다중화 소자의 제작 및 특성)

  • Moon, H.M.;Kwak, S.C.;Hong, J.Y.;Lee, K.H.;Kim, D.H.;Kim, J.J.;Choi, S.Y.;Lee, J.G.;Lee, J.H.;Lim, K.G.;Kim, J.B.
    • Korean Journal of Optics and Photonics
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    • v.18 no.3
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    • pp.185-189
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    • 2007
  • A novel technology for CWDM (Coarse Wavelength Division Multiplexer) utilizing a PLC (Planar Lightwave Circuit)-AWG (Arrayed Waveguide Grating) fabrication process is proposed. BPM (Beam Propagation Method) Simulation results on the employed parabolic-horn-type input slab waveguide of AWG and the performance of the 20 nm-channel spacing CWDM with flattened passband are presented. Waveguides of $0.75{\triangle}%$ have been used in this experiment and the insertion loss at the peak wavelength is 3.5 dB for a Gaussian spectrum and is 4.8 dB for a flat-top spectrum. The bandwidth at 3 dB is better than 10 nm and 13 nm for Gaussian and flat-top spectra, respectively.

Measurement of Refractive Index of Liquids by the Maximum and Minimum Deviated Laser Beam (레이저광의 최대.최소 편향법을 이용한 액체의 굴절률 측정)

  • Lee, Jae-Ran;Kim, Sok-Won;Lee, Yong-San
    • Korean Journal of Optics and Photonics
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    • v.19 no.3
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    • pp.182-186
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    • 2008
  • The prism spectrometer is a standard device for the measurement of refractive index; it is used in undergraduate laboratories. Typically, however, lots of attention is required in the alignment, and the accuracy of the obtained refractive index is not so high in spite of the durability of the device. The maximum and minimum deviation method, which compensates the disadvantages of the prism spectrometer, can be composed cost effectively using a length marking tape and a rotating platform. It can measure the refractive indices accurately by utilizing a wide screen. In this study, the equal sided hollow prism whose length is 26 mm was fabricated and measured the refractive indices of seven kind of liquids (pure water, $C_3H_5(OH)_2$, $CCl_4$, $C_6H_4NH_2$, $CS_2$, $C_6H_4(CH_3)_2)$ by using the prism spectrometer and maximum and minimum deviated laser beam method at the wavelengths of He-Ne laser (${\lambda}$= 632.8 nm) and YVO4 laser (${\lambda}$= 532 nm). The result shows that the data obtained by the latter method are more accurate and precise than those obtained by the former device.

Numerical Modeling of a Short-range Three-dimensional Flash LIDAR System Operating in a Scattering Atmosphere Based on the Monte Carlo Radiative Transfer Matrix Method (몬테 카를로 복사 전달 행렬 방법을 사용한 산란 대기에서 동작하는 단거리 3차원 플래시 라이다 시스템의 수치적 모델링)

  • An, Haechan;Na, Jeongkyun;Jeong, Yoonchan
    • Korean Journal of Optics and Photonics
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    • v.31 no.2
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    • pp.59-70
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    • 2020
  • We discuss a modified numerical model based on the Monte Carlo radiative transfer (MCRT) method, i.e., the MCRT matrix method, for the analysis of atmospheric scattering effects in three-dimensional flash LIDAR systems. Based on the MCRT method, the radiative transfer function for a LIDAR signal is constructed in a form of a matrix, which corresponds to the characteristic response. Exploiting the superposition and convolution of the characteristic response matrices under the paraxial approximation, an extended computer simulation model of an overall flash LIDAR system is developed. The MCRT matrix method substantially reduces the number of tracking signals, which may grow excessively in the case of conventional Monte Carlo methods. Consequently, it can readily yield fast acquisition of the signal response under various scattering conditions and LIDAR-system configurations. Using the computational model based on the MCRT matrix method, we carry out numerical simulations of a three-dimensional flash LIDAR system operating under different atmospheric conditions, varying the scattering coefficient in terms of visible distance. We numerically analyze various phenomena caused by scattering effects in this system, such as degradation of the signal-to-noise ratio, glitches, and spatiotemporal spread and time delay of the LIDAR signals. The MCRT matrix method is expected to be very effective in analyzing a variety of LIDAR systems, including flash LIDAR systems for autonomous driving.

STATUS AND PROGRESS OF ARGO-M SYSTEM DEVELOPMENT (인공위성 레이저추적 시스템(ARGO-M) 개발 현황)

  • Park, Eun-Seo;Yu, S.Y.;Lim, H.C.;Bang, S.C.;Seo, Y.K.;Park, J.H.;Jo, J.H.;Park, J.U.;Nah, J.K.;Jang, J.G.;Jang, B.H.;Kim, K.D.;Kim, B.I.;Park, C.H.;Lee, S.H.;Ham, S.Y.;Son, Y.S.
    • Publications of The Korean Astronomical Society
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    • v.27 no.3
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    • pp.49-59
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    • 2012
  • KASI (Korea Astronomy and Space Science Institute) has developed an SLR (Satellite Laser Ranging) system since 2008. The name of the development program is ARGO (Accurate Ranging system for Geodetic Observation). ARGO has a wide range of applications in the satellite precise orbit determination and space geodesy research using SLR with mm-level accuracy. ARGO-M (Mobile, bistatic 10 cm transmitting/40 cm receiving telescopes) and ARGO-F (Fixed stationary, about 1 m transmitting/receiving integrated telescope) SLR systems development will be completed by 2014. In 2011, ARGO-M system integration was completed. At present ARGO-M is in the course of system calibration, functionality, and performance tests. It consists of six subsystems, OPS (Optics System), TMS (Tracking Mount System), OES (Opto-Electronic System), CDS (Container-Dome System), LAS (Laser System) and AOS (ARGO Operation System). In this paper, ARGO-M system structure and integration status are introduced and described.

Effect of Interlayer on TiN and CrN Thin Films of STS 420 Hybrid-Deposited by AlP and DC Magnetron Sputtering (AIP 와 스퍼터링으로 복합증착된 420 스테인리스강의 TiN과 CrN 박막에 미치는 중간층의 영향)

  • Choi, Woong-Sub;Kim, Hyun-Seung;Park, Burm-Su;Lee, Kyung-Ku;Lee, Doh-Jae;Lee, Kwang-Min
    • Korean Journal of Materials Research
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    • v.17 no.5
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    • pp.256-262
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    • 2007
  • Effects of interlayer and the combination of different coating methods on the mechanical and corrosion behaviors of TiN and CrN coated on 420 stainless steel have been studied. STS 420 specimen were tempered at $300^{\circ}C$ for 1 hr in vacuum furnace. The TiN and CrN thin film with 2 ${\mu}m$ thickness were coated by arc ion plating and DC magnetron sputtering following the formation of interlayer for pure titanium and chromium with 0.2 ${\mu}m$ thickness. The microstructure and surface analysis of the specimen were conducted by using SEM, XRD and roughness tester. Mechanical properties such as hardness and adhesion also were examined. XRD patterns of TiN thin films showed that preferred TiN (111) orientation was observed. The peaks of CrN (111) and $Cr_2N$ (300) were only observed in CrN thin films deposited by arc ion plating. Both TiN and CrN deposited by arc ion plating had the higher adhesion and hardness compared to those formed by magnetron sputtering. The specimen of TiN and CrN on which interlayer deposited by magnetron sputtering and thin film deposited by arc ion plating had the highest adhesion with 22.2 N and 19.2 N. respectively. TiN and CrN samples shown the most noble corrosion potentials when the interlayers were deposited by using magnetron sputtering and the metal nitrides were deposited by using arc ion plating. The most noble corrosion potentials of TiN and CrN were found to be approximately -170 and -70 mV, respectively.

Characteristics of TiO2 and Ag/TiO2 optical thin film by Co-sputtering method (동시 스퍼터링법에 이용하여 제작한 TiO2와 Ag/TiO2 광학 박막의 특성)

  • Kim, Sang-Cheol;Hahn, Sung-Hong;Kim, Eui-Jung;Lee, Chung-Woo;Joo, Jong-Hyun;Kim, Goo-Cheol
    • Korean Journal of Optics and Photonics
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    • v.16 no.2
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    • pp.168-173
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    • 2005
  • Ag-doped $TiO_2$ thin films were prepared by RF magnetron co-sputtering method, and their physical and chemical properties were examined as a function of calcination temperature. XRD results showed that the crystallite size of Ag-doped films was smaller than that of the $TiO_2$ thin films. SEM results showed that the particle size of $Ag/TiO_2$ film was smaller and more uniform than pure $TiO_2$ film. The films had high transparency in the visible range. The films calcined at $600^{\circ}C$ were the anatase phase, and the films calcined at $900^{\circ}C$ were a mixture of anatase and rutile phases. The absorption edge of films calcined at $900^{\circ}C$ was red-shifted. This is due to the augmented absorption resulting from the phase transformation from anatase to rutile phase. And the transmittance of films decreased by the light scattering and absorption in the films. Photocatalytic activity of $Ag/TiO_2$ thin films was higher than that of the pure $TiO_2$ thin films.

Effect of varying the coupling strength and section length on the self-pulsation characteristics of multisection index-coupled DFB lasers (다중 전극 Index-Coupled DFB 레이저에서 결합 세기 및 각 영역의 길이가 Self-Pulsation 동작 특성에 미치는 영향)

  • Kim, Sang-Taek;Kim, Tae-Young;Ji, Sung-Keun;Kim, Boo-Gyoun
    • Korean Journal of Optics and Photonics
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    • v.16 no.1
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    • pp.85-98
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    • 2005
  • 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.