• Title/Summary/Keyword: Laser threshold

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Random Signal Characteristics of Super-RENS Disc (Super-RENS Disc의 Random 신호 특성)

  • Bae, Jae-Cheol;Kim, Joo-Ho;Kim, Hyun-Ki;Hwang, In-Oh;Park, Chang-Min;Park, Hyun-Soo;Jung, Moon-Il;Ro, Myong-Do
    • Transactions of the Society of Information Storage Systems
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    • v.2 no.1
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    • pp.38-42
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    • 2006
  • We report the random pattern characteristics of the super resolution near field structure(Super-RENS) write once read-many(WORM) disc at a blue laser optical system(laser wavelength 405nm, numerical aperture 0.85) and the Super-RENS read only memory(ROM) disc at a blue laser optical system(laser wavelength 659nm, numerical aperture 0.65). We used the WORM disc of which carrier-to-noise ratio(CNR) of 75nm is 47dB and ROM disc of which carrier-to-noise ratio(CNR) of 173nm is 45dB. We controlled the equalization(EQ) characteristics and used advanced partial-response maximum likelihood(PRML) technique. We obtained bit error rate(bER) of 10-3 level at 50GB WORM disc and bite error rate of 10-4 level at 50GB level ROM disc. This result shows high feasibility of Super-RENS technology for practical use.

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Analysis on Design and Fabrication of High-diffraction-efficiency Multilayer Dielectric Gratings

  • Cho, Hyun-Ju;Lee, Kwang-Hyun;Kim, Sang-In;Lee, Jung-Hwan;Kim, Hyun-Tae;Kim, Won-Sik;Kim, Dong Hwan;Lee, Yong-Soo;Kim, Seoyoung;Kim, Tae Young;Hwangbo, Chang Kwon
    • Current Optics and Photonics
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    • v.2 no.2
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    • pp.125-133
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    • 2018
  • We report an in-depth analysis of the design and fabrication of multilayer dielectric (MLD) diffraction gratings for spectral beam combining at a wavelength of 1055 nm. The design involves a near-Littrow grating and a modal analysis for high diffraction efficiency. A range of wavelengths, grating periods, and angles of incidence were examined for the near-Littrow grating, for the $0^{th}$ and $-1^{st}$ diffraction orders only. A modal method was then used to investigate the effect of the duty cycle on the effective indices of the grating modes, and the depth of the grating was determined for only the $-1^{st}$-order diffraction. The design parameters of the grating and the matching layer thickness between grating and MLD reflector were refined for high diffraction efficiency, using the finite-difference time-domain (FDTD) method. A high reflector was deposited by electron-beam evaporation, and a grating structure was fabricated by photolithography and reactive-ion etching. The diffraction efficiency and laser-induced damage threshold of the fabricated MLD diffraction gratings were measured, and the diffraction efficiency was compared with the design's value.

A Study on Structural-Thermal-Optical Performance through Laser Heat Source Profile Modeling Using Beer-Lambert's Law and Thermal Deformation Analysis of the Mirror for Laser Weapon System (Beer-Lambert 법칙을 적용한 레이저 열원 프로파일 모델링 및 레이저무기용 반사경의 열변형 해석을 통한 구조-열-광학 성능 연구)

  • Hong Dae Gi
    • Journal of Aerospace System Engineering
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    • v.17 no.4
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    • pp.18-27
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    • 2023
  • In this paper, the structural-thermal-optical performance analysis of the mirror was performed by setting the laser heat source as the boundary condition of the thermal analysis. For the laser heat source model, the Beer-Lambert model considering semi-transparent optical material based on Gaussian beam was selected as the boundary condition, and the mechanical part was not considered, to analyze the performance of only the mirror. As a result of the thermal analysis, thermal stress and thermal deformation data due to temperature change on the surface of the mirror were obtained. The displacement data of the surface due to thermal deformation was fitted to a Zernike polynomial to calculate the optical performance, through which the performance of the mirror when a high-energy laser was incident on the mirror could be predicted.

Design of 850 nm Vertical-Cavity Surface-Emitting Lasers by Using a Transfer Matrix Method (전달 행렬 방법을 이용한 850 nm수직 공진기 레이저 구조의 최적설계)

  • Kim Tae-Yong;Kim Sang-Bae
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.41 no.1
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    • pp.35-46
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    • 2004
  • In comparison with edge-emitting lasers(EELs), predicting the output power and slope efficiency of Vertical-Cavity Surface-Emitting Lasers(VCSELs) is very difficult due to the absorption loss in DBR layers. However, by using transfer matrix method(TMM), we've made possible to calculate such parameters of multi-layer structures like VCSELs. In this paper, we've calculated the threshold gain, threshold current and slope efficiency through the methodology based on TMM. Also TMM is the way of customizing the VCSEL structure for the desired threshold current and slope efficiency by changing the number of DBR mirror layers.

Effects of structural nonidealities on the lasing characteristics of $\lambda$/4 phase-shifted DFB lasers ($\lambda$/4 위상천이 DFB 레이저 다이도드에서 grating 구조상의 비이상성이 발진특성에 미치는 영향)

  • 조종섭;김상배
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.33A no.7
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    • pp.245-252
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    • 1996
  • $\lambda$/4 phase-shifted DFB lasers with nonideal grating structure have been studied by using an effective-index transfer matrix method where material dispersion, vwaveguide dispersion and waveguide-structuredependent loss are taken into consideration. Nonideal grating structure in the center phase-shift region does not incur serous degradation of laser characteristics. Phase-shift error from the ideal shift of $\pi$ causes a decrease in the threshold gain difference and lasing wavelength shift and should be less than $\pi$/4 when residual facet reflectivity is 0.7%. also, positional error of the phase-shift should be less than 9% of the cavity length in order for the threshold gain difference to be decreased less than 10%.

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Lasing characteristics of 1.3??m GaInAsP/InP DH Lasers Grown By LPE (LPE에 의한 1.3$\mu$m GaInAsP/InP DH 레이저의 제작 및 발진특성)

  • 신동혁;유태환
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.22 no.4
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    • pp.72-75
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    • 1985
  • 1.3$\mu$m double-heterostructure GaInAsP/InP wafers have been grown by LPE and broad contact laser diodes have been fabricated. Electrical and optical characteristics of these lasers under pulsed lasing operation at room temperature are described. Typical threshold currents are below 2 Amp. corresponding to threshold current densities of 3 - 6 KAmp./$\textrm{cm}^2$ and peak lasing wavelength is shown to be at 1.315 $\mu$m.

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Depleted optical thyristor - Laser Diode using surface-normal injection method (표면 수직 입사 방식의 완전 공핍 광 싸이리스터 레이저 다이오드)

  • choi, Yoon-Kyung;Kim, Doo-Keun;Choi, Young-Wan;Lee, Suk;Woo, Duck-Hwa;Byun, Young-Tae;Kim, Jae-Hun;Kim, Sun-Ho
    • Proceedings of the Optical Society of Korea Conference
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    • 2004.07a
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    • pp.26-27
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    • 2004
  • We present the first demonstration of the vertical-injection depleted optical thyristor laster diode with InGaAs/InGaAsP multiple quantum well structure. The measured switching voltage and current are 3.36 V and 10 A respectively. The holding voltage and current are respectively 1.37 V, 100 A. The lasing threshold current is 131 mA at 25 C. The output peak wavelength is at 1578 nm at a bias current equal to 1.22 times threshold.

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Nano-Second Periodically Poled Lithium Niobate Optical Parametric Oscillator with Planar Cavity Mirrors

  • Kim, Hong-Ki;Rhee, Bum--Ku
    • Journal of the Optical Society of Korea
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    • v.5 no.4
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    • pp.136-139
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    • 2001
  • We investigated a high-output ower, periodically poled lithium niobate(PPLN) optical parametric oscillator(OPO) pumped by a Q-switched Nd:YAG laser. Given the low optical damage threshold and the limited aperture (0.5mm thick) of PPLN, we tried to maximize the signal output power in a linear cavity consisting of two flat mirrors with a loosely focused pump beam. It is found that this simple cavity structure allowed a robust OPO operation, which was not sensitive to alignment compared with the conventional ones using concave mirrors. A maximum energy of 100$\mu$J/pulse was achieved for the signal at 1.36${\mu}{\textrm}{m}$, while the oscillation threshold was 0.3 mJ/pulse for the pump at 1064 nm.

Highly-Efficient Optical Gating in Vanadium Dioxide Junction Device

  • Lee, Yong-Wook
    • Journal of Sensor Science and Technology
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    • v.20 no.4
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    • pp.230-233
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    • 2011
  • In this paper, highly-efficient optical gating in a junction device based on vanadium dioxide($VO_2$) thin film grown by a sol-gel method was investigated as a gate terminal of a three-terminal device using infrared light with a wavelength of ~1554.6 nm. Due to the photoinduced phase transition, the threshold voltage of the $VO_2$ junction device, at which the device current abruptly jumps, could be tuned with a sensitivity of ~96.5 V/W by adjusting the optical power of the infrared light directly illuminating the device. Compared with the tuning efficiency of the previous device fabricated using $VO_2$ thin film deposited by a pulsed laser deposition method, the threshold voltage of this device could be tuned by ~76.8 % at an illumination power of ~39.8 mW resulting in a tuning efficiency of ~1.930 %/mW, which is ~4.9 times larger than the previous device.

Implementation Mode Image Segmentation Method for Object Recognition (물체 인식을 위한 개선된 모드 영상 분할 기법)

  • Moon, Hak-Yong;Han, Wun-Dong;Cho, Heung-Gi;Han, Sung-Ryoung;Jeon, Hee-Jong
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.51 no.1
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    • pp.39-44
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    • 2002
  • In this paper, implementation mode image segmentation method for separate image is presented. The method of segmentation image in conventional method, the error are generated by the threshold values. To improve these problem for segmentation image, the calculation of weighting factor using brightness distribution by histogram of stored images are proposed. For safe image of object and laser image, the computed weighting factor is set to the threshold value. Therefore the image erosion and spread are improved, the correct and reliable informations can be measured. In this paper, the system of 3-D extracting information using the proposed algorithm can be applied to manufactory automation, building automation, security guard system, and detecting information system for all of the industry areas.