• Title/Summary/Keyword: High refractive index

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Beam Profile Analysis of DFB Laser for High Speed Communications (고속 통신용 DFB 레이저의 빔 분포 해석)

  • Kwon, Keeyoung
    • The Journal of the Convergence on Culture Technology
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    • v.6 no.3
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    • pp.419-425
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    • 2020
  • In this paper, when a refractive index grating and a gain grating are simultaneously present in a DFB (Distributed Feedback) laser for a 1.55 um wavelength with two mirror surfaces without an anti-reflective coating, an analysis program was developed to determine the beam distribution of the oscillation mode in the longitudinal direction. As the phases of the index and gain gratings on the mirror faces are varied, the lasing gain and the beam profiles |R(z)| and |S(z)| of the lasing mode with the emitted power ratio Pl/Pr are analyzed and examined in case of δL<0. In order to reduce the threshold current of a oscillation mode and enhance the frequency stability, κL should be greater than 8, regardless of the grating phase values at the mirror surface.

940-nm 350-mW Transverse Single-mode Laser Diode with AlGaAs/InGaAs GRIN-SCH and Asymmetric Structure

  • Kwak, Jeonggeun;Park, Jongkeun;Park, Jeonghyun;Baek, Kijong;Choi, Ansik;Kim, Taekyung
    • Current Optics and Photonics
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    • v.3 no.6
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    • pp.583-589
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    • 2019
  • We report experimental results on 940-nm 350-mW AlGaAs/InGaAs transverse single-mode laser diodes (LDs) adopting graded-index separate confinement heterostructures (GRIN-SCH) and p,n-clad asymmetric structures, with improved temperature and small-divergence beam characteristics under high-output-power operation, for a three-dimensional (3D) motion-recognition sensor. The GRIN-SCH design provides good carrier confinement and prevents current leakage by adding a grading layer between cladding and waveguide layers. The asymmetric design, which differs in refractive-index distribution of p-n cladding layers, reduces the divergence angle at high-power operation and widens the transverse mode distribution to decrease the power density around emission facets. At an optical power of 350 mW under continuous-wave (CW) operation, Gaussian narrow far-field patterns (FFP) are measured with the full width at half maximum vertical divergence angle to be 18 degrees. A threshold current (Ith) of 65 mA, slope efficiency (SE) of 0.98 mW/mA, and operating current (Iop) of 400 mA are obtained at room temperature. Also, we could achieve catastrophic optical damage (COD) of 850 mW and long-term reliability of 60℃ with a TO-56 package.

A Study on the Optimization of the SiNx:H Film for Crystalline Silicon Sloar Cells (결정질 실리콘 태양전지용 SiNx:H 박막 특성의 최적화 연구)

  • Lee, Kyung-Dong;Kim, Young-Do;Dahiwale, Shailendra S.;Boo, Hyun-Pil;Park, Sung-Eun;Tark, Sung-Ju;Kim, Dong-Hwan
    • Journal of the Korean Vacuum Society
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    • v.21 no.1
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    • pp.29-35
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    • 2012
  • The Hydrogenated silicon nitride (SiNx:H) using plasma enhanced chemical vapor deposition is widely used in photovoltaic industry as an antireflection coating and passivation layer. In the high temperature firing process, the $SiN_x:H$ film should not change the properties for its use as high quality surface layer in crystalline silicon solar cells. Initially PECVD-$SiN_x:H$ film trends were investigated by varying the deposition parameters (temperature, electrode gap, RF power, gas flow rate etc.) to optimize the process parameter conditions. Then by varying gas ratios ($NH_3/SiH_4$), the hydrogenated silicon nitride films were analyzed for its optical, electrical, chemical and surface passivation properties. The $SiN_x:H$ films of refractive indices 1.90~2.20 were obtained. The film deposited with the gas ratio of 3.6 (Refractive index=1.98) showed the best properties in after firing process condition. The single crystalline silicon solar cells fabricated according to optimized gas ratio (R=3.6) condition on large area substrate of size $156{\times}156mm$ (Pseudo square) was found to have the conversion efficiency as high as 17.2%. Optimized hydrogenated silicon nitride surface layer and high efficiency crystalline silicon solar cells fabrication sequence has also been explained in this study.

Gemological Characterization of B. C. Jade (비씨 제이드의 보석학적 연구)

  • Kim, Won-Sa;Wight, Willow
    • Journal of the Mineralogical Society of Korea
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    • v.21 no.2
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    • pp.177-182
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    • 2008
  • The Gemological characteristics of B.C. jade from Cassiar Mine, British Colombia, Canada, have been investigated, using polarizing microscopy, Mohs' hardness, refractive index and density measurements, X-ray powder diffraction, X-ray fluorescence spectrometry, ICP-MS, Infrared absorption spectrometry, and DTA/TGA. The B.C. jade is deeply green (spinach peen or olive green) in color and is translucent. It shows a resinous or waxy luster. The principal mineral of the material is tremolite-actinolite solid solution and minor amount of Cr-garnet and unidentified opaque minerals are accompanied. Mohs' hardness value ($5.5{\sim}6$). refractive index (1.62), and specific gravity (3.01) are measured. It is very highly tough and shows hackly fracture. The high Fe content ($Fe_2O_3\;4.14{\sim}4.66\;wt%$) in B.C. jade is attributable to a deepening of green color of the material. The B.C. jade starts to dehydrate at v and dehydration is completed at $1000.8^{\circ}C$, transforming tremolite-actinolite solid solution to enstatite, diopside, quartz, and water in its place. This possible reaction is supported by the weight loss of B.C. jade (1.93 wt%) at $1000.8^{\circ}C$ indicated by TGA curve.

Fabrication of Optically Encoded Images on Porous Silicon (다공성 실리콘을 이용한 암호화된 광학이미지 제작)

  • Koh, Young-Dae;Kim, Sung-Jin;Kim, Jong-Hyeon;Rheu, Seong-Ok;Bang, Hyeon-Seok;Jeong, Yun-Sik;Park, Bo-Kyeong;Sohn, Hong-Lae
    • Journal of the Korean Vacuum Society
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    • v.17 no.1
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    • pp.46-50
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    • 2008
  • Optical images on the porous silicon exhibiting Febry-Perot fringe pattern have been prepared by using an electrochemical etching of p-type silicon wafer (boron-doped,<100> orientation, resistivity $0.8{\sim}1.2m{\Omega}-cm$) and beam projector. The images remained in the substrate displayed an optical images correlating to the optical pattern and could be useful for optical data storage. A decrease in the effective optical thickness of the Febry-Perot layers was observed, indicative of a change in refractive index induced by exposing of porous silicon to the white light. This provides the ability to fabricate complex optical encoding in the surface of silicon.

Optical reflectance of TiO2/SiO2 multilayer coating flat mirrors (TiO2/SiO2 다층 박막 평판 mirror의 광학적 반사)

  • Lee, Chanku;Lee, Sudae;Joung, Maengsig
    • Journal of Korean Ophthalmic Optics Society
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    • v.7 no.1
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    • pp.75-78
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    • 2002
  • Thirty three layer $TiO_2/SiO_2$ coating mirrors with high reflectance through a 620~820nm wavelength range have been designed and fabricated by electron beam evaporation method. Multilayer films were deposited on glass(BK7) and sequentially. The high reflector design is based on alternating high and low refractive index layers. $n_H$ and $n_L$ such that a "stopband"(or area of high reflectivity) is created that is centered around the design wavelength. ${\lambda}_0$. The measured transmittance spectrum with an incident wavelength at an incident angle of $40^{\circ}{\pm}7^{\circ}$ exhibited a reflectance of 99.9% at the wavelength of 620~820nm but high peak transmittance in the wavelength region from 700 to 740nm.

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An in Depth Study of Crystallinity, Crystallite Size and Orientation Measurements of a Selection of Poly(Ethylene Terephthalate) Fibers

  • Karacan Ismail
    • Fibers and Polymers
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    • v.6 no.3
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    • pp.186-199
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    • 2005
  • A selection of commercially available poly(ethy1ene terephtha1ate) fibers with different degrees of molecular alignment and crystallinity have been investigated utilizing a wide range of techniques including optical microscopy, infrared spectroscopy together with thermal and wide-angle X-ray diffraction techniques. Annealing experiments showed increased molecular alignment and crystallinity as shown by the increased values of birefringence and melting enthalpies. Crystallinity values determined from thermal analysis, density, unpolarized infrared spectroscopy and X-ray diffraction are compared and discussed in terms of the inherent capabilities and limitations of each measurement technique. The birefringence and refractive index values obtained from optical microscopy are found to decrease with increasing wavelength of light used in the experiments. The wide-angle X-ray diffraction analysis shows that the samples with relatively low orientation possess oriented non-crystalline array of chains whereas those with high molecular orientation possess well defined and oriented crystalline array of chains along the fiber axis direction. X-ray analysis showed increasing crystallite size trend with increasing molecular orientation. SEM images showed micro-cracks on low oriented fiber surfaces becoming smooth on highly oriented fiber surfaces. Excellent bending characteristics were observed with knotted fibers implying relatively easy fabric formation.

Fabrication of Metal-insulator-metal Capacitors with SiNx Thin Films Deposited by Plasma-enhanced Chemical Vapor Deposition

  • Wang, Cong;Kim, Nam-Young
    • Transactions on Electrical and Electronic Materials
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    • v.10 no.5
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    • pp.147-151
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    • 2009
  • For integrated passive device (IPD) applications, we have successfully developed and characterized metalinsulator-metal (MIM) capacitors with 2000 $\AA$ plasma-enhanced chemical vapor deposition (PECVD) silicon nitride which are deposited with the $SiH_4/NH_3$ gas mixing rate, working pressure, and RF power of PECVD at $250^{\circ}C$. Five PECVD process parameters are designed to lower the refractive index and lower the deposition rate of $Si_3N_4$ films for the high breakdown electric field. For the PECVD process condition of gas mixing rate (0.957), working pressure (0.9 Torr), and RF power (60 W), the atomic force microscopy (AFM) root mean square (RMS) value of about 2000 $\AA$ $Si_3N_4$ on the bottom metal is lowest at 0.862 nm and the breakdown electric field is highest at about 8.0 MV/cm with a capacitance density of 326.5 pF/$mm^2$. A pretreatment of metal electrodes is proposed, which can reduce the peeling of nitride in the harsh test environment of heat, pressure, and humidity.

Enhanced Anti-reflective Effect of SiNx/SiOx/InSnO Multi-layers using Plasma Enhanced Chemical Vapor Deposition System with Hybrid Plasma Source

  • Choi, Min-Jun;Kwon, O Dae;Choi, Sang Dae;Baek, Ju-Yeoul;An, Kyoung-Joon;Chung, Kwun-Bum
    • Applied Science and Convergence Technology
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    • v.25 no.4
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    • pp.73-76
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    • 2016
  • Multi-layer films of $SiN_x/SiO_x$/InSnO with anti-reflective effect were grown by new-concept plasma enhanced chemical vapor deposition system (PECVD) with hybrid plasma source (HPS). Anti-reflective effect of $SiN_x/SiO_x$/InSnO was investigated as a function of ratio of $SiN_x$ and $SiO_x$ thickness. Multi-layers deposited by PECVD with HPS represents the enhancement of anti-reflective effect with high transmittance, comparing to the layers by conventional radio frequency (RF) sputtering system. This change is strongly related to the optical and physical properties of each layer, such as refractive index, composition, film density, and surface roughness depending on the deposition system.

A Study on the Thermal Characteristics of Tunable All-Optical Filter Using Fiber Bragg Grating (광섬유 브래그 격자를 이용한 파장가변 형 전광 필터의 온도특성에 관한 연구)

  • Son, Yong-Hwan;Won, Yong-Yuk;Kim, Jae-Wook;Han, Sang-Kook
    • Journal of IKEEE
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    • v.12 no.2
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    • pp.102-109
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    • 2008
  • In this paper, the thermal characteristics of a tunable all-optical fiber Bragg grating(FBG) filter was investigated by numerical analysis. From the results, it is possible to tune a Bragg center wavelength along temperature variation because a Bragg center wavelength is varied linearly according to its operating temperature, however, the reflectivity of a Bragg center wavelength was reduced over a limited high temperature. Accordingly, it is possible to obtain the stability of a tunable all-optical FBG filter within $600^{\circ}C$, but it is difficult to tune a Bragg center wavelength over this temperature.

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