• Title/Summary/Keyword: thin-film optics

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Polymeric Waveguide Bio Sensors with Bragg Gratings (브래그 격자 광도파로형 바이오 센서)

  • Lee, Jae-Hyun;Kim, Gyeong-Jo;Oh, Min-Choel
    • Korean Journal of Optics and Photonics
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    • v.17 no.1
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    • pp.54-59
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    • 2006
  • Biophotonic sensors based on polymer waveguide with Bragg reflection grating are demonstrated in this work. Waveguide Bragg reflectors were designed by using the effective index method and the transmission matrix method. The grating pattern was formed by exposing the laser interference pattern on a photoresist. On top of the inverted rib waveguide, the Bragg reflection grating was inscribed by the O2 plasma etching. In order to perform the bio-molecule detection experiment, a calixarene molecule was self-assembled on top of thin Au film deposited on the waveguide Bragg reflector. To measure the response of the sensor, several PBS solutions with different concentrations of potassium ion from 1 pM to $100\;{\mu}M$ were dropped on the sensor surface. The shift of Bragg reflection wavelength was observed from the fabricated sensor device, which was proportional to the concentration of potassium ion ranging from 1 pM to 108 pM.

Localized Surface-Plasmon Resonance of Ag Nanoparticles Produced by Laser Dewetting to Improve the Performance of a Sensitized TiO2 Solar Cell (레이저 Dewetting에 의해 형성된 은 나노입자의 국소 표면플라즈몬 공명을 이용한 감응형 TiO2 태양전지 성능 향상)

  • Lee, Jeeyoung;Lee, Myeongkyu
    • Korean Journal of Optics and Photonics
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    • v.29 no.5
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    • pp.215-219
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    • 2018
  • In this paper we show that the localized surface-plasmon resonance of Ag nanoparticles produced by laser dewetting can be effectively utilized for improving the photocurrent and efficiency of a dye-sensitized $TiO_2$ solar cell. An Ag thin film deposited on a conducting glass substrate was dewetted into nanoparticles by a pulsed laser. A dye-sensitized $TiO_2$ solar cell fabricated on this substrate containing the Ag nanoparticles exhibited improved photovoltaic performance, compared to a reference cell. This is attributed to the increased light trapping that arises from the localized surface-plasmon resonance of the dewetted Ag nanoparticles.

Optical and mechnical properties of ${Ta_2}{O_5}$ optical thin films by ion assisted deposition (이온 보조 증착한 ${Ta_2}{O_5}$ 광학 박막의 광학적 및 기계적 특성 분석)

  • 류태욱;김동진
    • Korean Journal of Optics and Photonics
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    • v.11 no.3
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    • pp.147-151
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    • 2000
  • We deposited the ion assisted ${Ta_2}{O_5}$ films and conventional thermal evaporated ${Ta_2}{O_5}$ films by using electron beam gun, and measured the optical properties and mechanical properties of the fabricated films according to the evaporation conditions. In the case of the TazOs films by oxygen ion assisted deposition with the anode voltage of 120 V, and current density of $50~500\muA/cm^2$, the refractive index exhibited 2.15 which was higher than the conventionally deposited film index 1.94 and the tensile stress exhibited $5.0\times10^8 dyne/cm^2$ which was lower than $7.0\times10^8 dyne/cm^2$. This properties coincided with the optical and mechanical properties of the films deposited at the elevated substrate temperature of $230^{\circ}C$. In the case of the argon ion assisted films the tensile stress was decreased but the absorption existed at the short wavelength in the visible spectral region. And all the fabricated films were found to be amorphous by the X-ray diffraction analysis. lysis.

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Thermal and temporal stabilities of a electro-optic coefficient $\gamma_{33}$ in a PI-SOT nonlinear polymer thin film (고분자 박막인 PI-SOT의 전기광학계수 $\gamma_{33}$의 열적 . 시간적 안정성)

  • Jeong, Youn-Hong;Jo, Jae-Heung;Chang, Soo;Kim, Tae;lee, Kwang-Sup
    • Korean Journal of Optics and Photonics
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    • v.10 no.3
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    • pp.188-194
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    • 1999
  • We synthesized the nonlinear optical (NLO) PI-SOT(polyimide system, 4-[N,N-bis(hydroxyethyl)amino-4,-($\beta$-cyano-$\beta$-methylsulfonyl)vinyl]azobenzene) polymer with high electro-optic coefficients as well as good thermal and temporal stabilities of the elector-optic coefficient ${\gamma}_33$ by the simple Mitsunobu reaction. By using the simple reflection method of C. C. Teng, we measured the thermal and temporal stabilities of the electro-optic coefficient ${\gamma}_33$ of corona-poled PI-SOT polymer at the wavelength of 632.8 nm and 852 nm, respectively. At the temperature of $20^{\circ}C$, the electro-optic coefficient ${\gamma}_33$ of corona-poled PI-SOT polymer were 25.12 pm/V at the wavelength of 632.8 nm and 5.40 pm/V at the wavelength of 852 nm. These values were highly stabilized for more than 60 days at 2$0^{\circ}C$ and stabilized within 6% for more than 10 hours at $100^{\circ}C$.

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Design and fabrication of temperature-independent AWG-WDM devices using polymer overcladding (폴리머 상부클래드를 이용한 온도무의존 AWG 파장분할 다중화 소자의 설계 및 제작)

  • Han, Young-Tak;Kim, Duk-Jun;Shin, Jang-Uk;Park, Sang-Ho;Park, Yoon-Jung;Sung, Hee-Kyeng
    • Korean Journal of Optics and Photonics
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    • v.14 no.2
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    • pp.135-141
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    • 2003
  • In arrayed waveguide grating (AWG) devices whose waveguides were composed of polymer with negative thermo-optic coefficient as overcladding, and silica with positive thermo-optic coefficient as both core and undercladding, we investigated the temperature dependence of the central wavelength using two-dimensional SFDM. From these results, it was confirmed that the temperature dependence can be nearly eliminated by adjusting the refractive index of the cladding and the thickness of the silica thin film upper-loaded on the core. Based on the numerical calculations, the AWG device with polymer overcladding was fabricated. and its optical characteristics were compared with those of the orginal silica AWG device. The introduction of polymer overcladding decreased the temperature dependence of the central wavelength from 0.0130 nm/$^{\circ}C$ to 0.0028 nm/$^{\circ}C$ without deteriorating the insertion loss and crosstalk characteristics.

Determination of optical properties of Pr3+-doped selenide glasses of Ge-Sb-Se system using spectroscopic ellipsometry (분광타원법을 이용한 Pr 첨가 Ge-Sb-Se 계열 셀레나이드 유리의 굴절률 결정)

  • 신상균;김상준;김상열;최용규;박봉제;서홍석
    • Korean Journal of Optics and Photonics
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    • v.14 no.6
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    • pp.594-599
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    • 2003
  • By using the spectroscopic ellipsometry, we have measured and analyzed the optical characteristics of P $r^3$$^{+}$-doped selenide glasses of Ge-Sb-Se system, a strong candidate material for U band fiber amplifiers. The ellipsometric spectra measured in the transparent wavelengths range of the material were all fitted to a model consisting of ambient/roughness/thin fil $m_strate structures to obtain simultaneously the optical properties such as refractive index, in terms of Sellmeier parameters and film structure of P $r^3$$^{+}$-doped selenide glasses. Repeated measurements on different positions in both polished faces rendered to verify positional dependence of measured spectre-ellipsometric data. Hence, the model made possible the analysis of the optical characteristics of the glasses. Even though surface roughness was mainly responsible for the position dependencies, the averaged refractive indexes were as precise as to reflect the minute compositional change tantamount to 1 mol%. The measured refractive indexes are useful for design of core and clad compositions of single-mode selenide optical fibers.

Development of a Silicon Carbide Large-aperture Optical Telescope for a Satellite (SiC를 이용한 대구경 위성용 망원경 제작)

  • Bae, Jong In;Lee, Haeng Bok;Kim, Jeong Won;Lee, Kyung Mook;Kim, Myung-Whun
    • Korean Journal of Optics and Photonics
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    • v.33 no.2
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    • pp.74-83
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    • 2022
  • The entire process, from the raw material to the final system qualification test, has been developed to fabricate a large-diameter, lightweight reflective-telescope system for a satellite observation. The telescope with 3 anastigmatic mirrors has an aperture of 700 mm and a total mass of 66 kg. We baked a silicon carbide substrate body from a carbon preform using a reaction sintering method, and tested the structural and chemical properties, surface conditions, and crystal structure of the body. We developed the polishing and coating methods considering the mechanical and chemical properties of the silicon carbide (SiC) body, and we utilized a chemical-vapor-deposition method to deposit a dense SiC thin film more than 170 ㎛ thick on the mirror's surface, to preserve a highly reflective surface with excellent optical performance. After we made the SiC mirrors, we measured the wave-front error for various optical fields by assembling and aligning three mirrors and support structures. We conducted major space-environment tests for the components and final assembly by temperature-cycling tests and vibration-shock tests, in accordance with the qualifications for the space and launch environment. We confirmed that the final telescope achieves all of the target performance criteria.

Optical Property of Super-RENS Optical Recording Ge2Sb2Te5 Thin Films at High Temperature (초해상 광기록 Ge2Sb2Te5 박막의 고온광물성 연구)

  • Li, Xue-Zhe;Choi, Joong-Kyu;Lee, Jae-Heun;Byun, Young-Sup;Ryu, Jang-Wi;Kim, Sang-Youl;Kim, Soo-Kyung
    • Korean Journal of Optics and Photonics
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    • v.18 no.5
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    • pp.351-361
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    • 2007
  • The samples composed of a GST thin film and the protective layers of $ZnS-SiO_2$ or $Al_2O_3$ coated on c-Si substrate were prepared by using the magnetron sputtering method. Samples of three different structures were prepared, that is, i) the GST single film on c-Si substrate, ii) the GST film sandwiched by the protective $ZnS-SiO_2$ layers on c-Si substrate, and iii) the GST film sandwiched by $Al_2O_3$ protective layers on c-Si substrate. The ellipsometric constants in the temperature range from room temperature to $700^{\circ}C$ were obtained by using the in-situ ellipsometer equipped with a conventional heating chamber. The measured ellipsometric constants show strong variations versus temperature. The variation of ellipsometric constants at the temperature region higher than $300^{\circ}C$ shows different behaviors as the ambient medium is changed from in air to in vacuum or the protective layers are changed from $ZnS-SiO_2$ to $Al_2O_3$. Since the long heating time of 1-2 hours is believed to be the origin of the high temperature variation of ellipsometric constants upon the heating environment and the protective layers, a PRAM (Phase-Change Random Access Memory) recorder is introduced to reduce the heating time drastically. By using the PRAM recorder, the GST samples are heated up to $700^{\circ}C$ decomposed preventing its partial evaporation or chemical reactions with adjacent protective layers. The surface image obtained by SEM and the surface micro-roughness verified by AFM also confirmed that samples prepared by the PRAM recorder have smoother surface than the samples prepared by using the conventional heater.

Study of Localized Surface Plasmon Polariton Effect on Radiative Decay Rate of InGaN/GaN Pyramid Structures

  • Gong, Su-Hyun;Ko, Young-Ho;Kim, Je-Hyung;Jin, Li-Hua;Kim, Joo-Sung;Kim, Taek;Cho, Yong-Hoon
    • Proceedings of the Korean Vacuum Society Conference
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    • 2012.08a
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    • pp.184-184
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    • 2012
  • Recently, InGaN/GaN multi-quantum well grown on GaN pyramid structures have attracted much attention due to their hybrid characteristics of quantum well, quantum wire, and quantum dot. This gives us broad band emission which will be useful for phosphor-free white light emitting diode. On the other hand, by using quantum dot emission on top of the pyramid, site selective single photon source could be realized. However, these structures still have several limitations for the single photon source. For instance, the quantum efficiency of quantum dot emission should be improved further. As detection systems have limited numerical aperture, collection efficiency is also important issue. It has been known that micro-cavities can be utilized to modify the radiative decay rate and to control the radiation pattern of quantum dot. Researchers have also been interested in nano-cavities using localized surface plasmon. Although the plasmonic cavities have small quality factor due to high loss of metal, it could have small mode volume because plasmonic wavelength is much smaller than the wavelength in the dielectric cavities. In this work, we used localized surface plasmon to improve efficiency of InGaN qunatum dot as a single photon emitter. We could easily get the localized surface plasmon mode after deposit the metal thin film because lnGaN/GaN multi quantum well has the pyramidal geometry. With numerical simulation (i.e., Finite Difference Time Domain method), we observed highly enhanced decay rate and modified radiation pattern. To confirm these localized surface plasmon effect experimentally, we deposited metal thin films on InGaN/GaN pyramid structures using e-beam deposition. Then, photoluminescence and time-resolved photoluminescence were carried out to measure the improvement of radiative decay rate (Purcell factor). By carrying out cathodoluminescence (CL) experiments, spatial-resolved CL images could also be obtained. As we mentioned before, collection efficiency is also important issue to make an efficient single photon emitter. To confirm the radiation pattern of quantum dot, Fourier optics system was used to capture the angular property of emission. We believe that highly focused localized surface plasmon around site-selective InGaN quantum dot could be a feasible single photon emitter.

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Optical properties of Nb2O5 thin films prepared by ion beam assisted deposition (이온빔 보조 증착 Nb2O5 박막의 광학적 특성)

  • 우석훈;남성림;정부영;황보창권;문일춘
    • Korean Journal of Optics and Photonics
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    • v.13 no.2
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    • pp.105-112
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    • 2002
  • We studied the optical and structural properties of conventional and ion-beam-assisted-deposition (IBAD) Nb$_2$O$_{5}$ films which were evaporated by an electron beam gun. The vacuum-to-air spectral shift and the cross sectional SEM images of the Nb$_2$O$_{5}$ films were investigated. The results show that the IBAD Nb$_2$O$_{5}$ films have a higher packing density than the conventional Nb$_2$O$_{5}$ films. The average refractive index of IBAD Nb$_2$O$_{5}$ films was increased, while the extinction coefficient was decreased compared with the conventional films. As the oxygen flow was increased, the average refractive index and extinction coefficient of the conventional and IBAD films decreased. Both the conventional and IBAD Nb$_2$O$_{5}$ films showed inhomogeneity in refractive index, and the degree of inhomogeneity of the IBAD Nb$_2$O$_{5}$ films became larger as the ion current density was increased. All Nb$_2$O$_{5}$ films were found to be amorphous by x-ray diffraction (XRD) analysis, and hence the crystal structure of Nb$_2$O$_{5}$ films was not changed by IBAD.