• Title, Summary, Keyword: upconversion

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이중발광 코어/쉘 나노형광체

  • Jang, Ho-Seong;U, Gyeong-Ja;Im, Gi-Pil
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.132.2-132.2
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    • 2014
  • 란탄족 원소가 도핑된 세라믹 나노결정, 즉, 나노형광체는 도핑되는 원소의 종류에 따라 다양한 색을 발광할 수 있다. 일반적으로 형광체는 외부에너지에 의해 여기된 후 흡수한 에너지 보다 작은 에너지의 가시광을 발광하게 된다. 이러한 현상은 downconversion 발광으로 알려져 있다. 그러나 모체에 Yb3+와 Er3+를 도핑하는 경우 적외선을 흡수하여 가시광선을 발광하는 upconversion 현상이 관찰된다. Upconversion 형광체를 이용하여 적외선을 가시광으로 변환시키면 sub-band gap 손실을 줄임으로써 태양전지 효율을 높일 수 있고, 바이오 이미징 감도를 높일 수도 있다. 그러나, upconversion 발광기구에서는 두 개의 적외선 광자가 흡수되어 하나의 가시광 광자가 방출되기 때문에 upconversion 발광 효율은 downconversion 발광 효율에 비하여 매우 낮은 특성을 보인다. 특히 형광체의 크기가 작아져 나노미터 영역의 크기가 되면 효율이 더욱 낮아지기 때문에 upconversion 나노형광체의 경우 효율을 증가시키기 위하여 형광체 주위로 결정질 쉘을 형성시키는 것이 필요하다. 이 때, 결정질 쉘에 downconversion 특성을 보일 수 있는 란탄족 원소를 도핑하는 경우 upconversion 발광 강도가 증대될 뿐 아니라, 하나의 나노입자에서 upconversion과 downconversion 두 가지 서로 다른 발광 특성을 관찰할 수 있다. 본 발표에서는 단일 나노입자에서 upconversion과 downconversion 발광을 보이는 이중발광 코어/쉘 나노형광체의 발광 특성에 대하여 논의하고자 한다.

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Development of the Thulium Doped Upconversion Fiber Blue Laser (Thulium이 첨가된 Upconversion 광섬유 Blue Laser 개발)

  • 황대석;김규식;허창우;이영우
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • pp.439-441
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    • 2003
  • 본 연구에서는 Thulium(Tm$^{3+}$ )이 첨가된 광섬유를 이용, Upconversion blue 레이저의 개발을 위해 fiber 길이 및 파워 변화에 따른 최적화된 설계 기준 값을 찾기 위한 시뮬레이션 코드를 개발하고 그 해석을 행하였다. 1140nm의 여기광원을 이용하여 여기하였을 때 광섬유 길이 40cm에서 약 100mW의 발진 문턱값을 갖으며 1W의 여기 광원에 대해 60mW의 출력 특성이 예상된다.

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Infrared-to-blue Upconversion in Tm-doped Oxyfluoroborate Glasses (Oxyfluoroborate 유리재료에서의 적외선-청색 상방 형광발생)

  • P. Babu;Lee Seon-Gyun;Van-Thai Pham;Im Gi-Su;Seo Hyo-Jin;C. K. Jayasankar
    • Proceedings of the Optical Society of Korea Conference
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    • pp.116-117
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    • 2002
  • In recent years, there has been an increasing interest in $Tm^{3+}$ doped crystals and glasses due to their potential applications as near infrared lasers and infrared to visible upconversion lasers for use in different fields such as medical surgery, eye safe laser radar, data storage, barcode reading and so on. Thulium ions have stable excited levels suitable for emitting blue upconversion fluorescence. (omitted)

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Growth and upconversion properties of erbium doped $LiNbO_3$ single crystal fibers ($Er^{3+}$ 첨가 $LiNbO_3$ fiber 단결정의 성장 및 upconversion 특성)

  • Yang, Woo-Seok;Suh, Su-Jeong;Lee, Jong-Ho;Tsuguo Fukuda;Yoon, Dae-Ho
    • Proceedings of the Korea Association of Crystal Growth Conference
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    • pp.321-335
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    • 1999
  • Erbium(Er) doped LiNbO3(Er:LiNbO3) single crystal gibers were grown free of cracks along the c-axis by micro-pulling down method. the Er3+ concentration was distributed homogeneously along the growth axis. The samples for optical characterization were cut from as-grown single crystal fibers and polished. When the 980 nm light was incident on the sample, upconversion phenomena were observed at the green range of wavelength 510~570 nm. In addition, the intensity of upconversion was remarkably increased by increasing the concentration of Er2O3 dopant in as-grown Er:LiNbO3 crystals.

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Upconversion Mechanisms in $Tm^{3+}$-doped Glasses under 800 nm Excitation (800nm 파장 여기관에 의한 $Tm^{3+}$첨가 유리내 상향 전이 현상 기구)

  • Jeong, Hoon;Chung, Woon-Jin;Heo, Jong
    • Journal of the Korean Ceramic Society
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    • v.37 no.2
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    • pp.111-116
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    • 2000
  • 700nm red emission(3F3longrightarrow3H6) in Tm3+ ion with 800 nm(3H6longrightarrow3H4) excitation via upconversion process has been reported only in host materials which have low phonon energies such as halide crystals. However, we observed 700nm and 480nm(1G4longrightarrow3H6) upconverted emission with 800nm excitation in several oxide glasses which has never reported. With spectroscopic analyses and lifetime measurements of each nergy level of Tm3+ ion doped in various oxide glasses, following mechanisms are suggested. For red upconversion, upconversion mechanism changed with Tm3+ concentration. While direct excitation up to 3F3 level via anti-Stokes excitation was dominated at low concentration, two-step excitation via 3H6longrightarrow3H4 and 3F4longrightarrow3F3 transitions was dominated at high concentration. For blue upconversion, two step excitation mechanism up to 1G4 level was suggested as follows : electrons are exciated up to 3H5 with direct excitation with pumping light up to 3H4 followed by multiphonon relaxation, and then additional reabsorption of pumping light excites electrons up to 1G4.

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Low Noise Local Oscillator Design in K Band using Baseband Noise Upconversion Gain Analysis (저주파 잡음 상향 변화 이득 해석을 이용한 K 밴드 저잡음 국부 발진기의 설계)

  • 이영택;이문규;임종식;염인복;장동필;남상욱
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.12 no.3
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    • pp.462-469
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    • 2001
  • In this paper, local oscillator in K band using low frequency noise upconversion gain anaylsis was designed and measured. We extended Two Signal Method(TSM) to estimate upconversion gain and resulting phase noise. To confirm the validity of the proposed method, a free-running oscillator which had low upconversion gain was designed. The measured oscillation frequency was 23.42 GHz and phase noise at 1 MHz of offset was -105.2 dBc/Hz. Also, this oscillator was operated for subharmonic injection locked osci1lator(SILO). In this case, SILO showed ideal frequency multiplier phase noise characteristics at low subharmonic injection power level.

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Synthesis and Characterization of Upconversion Nanoparticles for Cancer Therapy

  • Choe, Seung-Yu;Kim, Bo-Bae;Kim, Eun-Bi;Lee, Seung-U;Jeon, Seon-A;Park, Tae-Jeong
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.420.2-420.2
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    • 2016
  • Various fields have been paid attention to upconversion nanoparticles (UCNPs) because of its unique optical properties. Moreover, to use the UC luminescent techniques through cell images for identified apoptosis/necrosis of cancer cells have been performed. They have been studied for a versatile biomedical application such as a biosensing tool, or delivery of active forms of medicines inside living cells. UCNPs have distinctive characteristics such as photoluminescence, special emission, low background fluorescence signal and good colloidal stability, which have many advantages compared with the organic dyes and quantum dots. UCNPs have not only a great potential for imaging (UC luminescence) but also therapies (photo-thermal therapy, PTT and photo-dynamic therapy, PDT) in cancer diagnostics. Therefore, we report the enhancement of upconversion red emission in NaYF4:Yb3+,Er3+ nanoparticles, synthesized via solid-state method with the thermal decomposition of trifluoroacetate as precursors and organic solvent at a high boiling point. The UCNPs have an emission in the field of near infrared wavelength, cubic shape and nano-size in length. In this study, we will further investigate it for cancer therapy with NIR optical detection onto the solid substrate.

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Synthesis and Functionalization of Upconversion Nanoparticles for Bioimaging (바이오 이미징을 위한 업컨버전 나노입자(upconversion nanoparticles)의 합성 및 특성화)

  • Cho, Hye In;Lee, Jae-Seung
    • Ceramist
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    • v.21 no.3
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    • pp.270-282
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    • 2018
  • The increasing importance of biomedical imaging technology has led to the development of a variety of luminescent materials, including molecular fluorophores, fluorescent proteins, and quantum dots. Owing to their inherent disadvantages, such as insufficient chemical stability and limited biocompatability, their utilization has been limited with imaging only under highly optimized and controlled conditions. Recently, a new class of luminescent nanoparticles, upconversion nanoparticles (UCNPs), have been emerging as a practically useful nanoprobe for various bioimaging applications. The detailed synthesis, functionalization, properties and in-vitro / in-vivo applications of the UCNPs are introduced and discussed in this Review.

Near-Infrared to Visible Upconversion Emission in Er3+and Yb3+ Codoped BaHfO3

  • Lim, Junhwi;Kim, Donghee;Lee, Y.S.
    • Journal of the Korean Physical Society
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    • v.73 no.7
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    • pp.955-959
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    • 2018
  • We report on the upconversion (UC) emission property of $Er^{3+}$ and $Yb^{3+}$ codoped $BaHfO_3$ polycrystals. We observed the green (~ 540 nm) and the red (~ 660 nm) UC emissions in $Er^{3+}$ in the host material $BaHfO_3$ with 980-nm near-infrared excitation. These emissions exhibited strong temperature evolutions. Interestingly, the UC emissions in $Er^{3+}$ were found to be controlled with the $Yb^{3+}$ doping. In $Er^{3+}$ and $Yb^{3+}$ codoped $BaHfO_3$, the intensity of the red UC emission increased dramatically while that of the green UC emission showed a non-monotonic temperature dependence. These results suggested that the UC emission process in the $Er^{3+}$ ion in $BaHfO_3$ should be temperature-sensitive.

Growth and upconversion properties of erbium doped $LiNbO_{3}$ single crystal fibers

  • Yang, Woo-Seok;Suh, Su-Jeong;Lee, Jong-Ho;Fukuda, Tsuguo;Yoon, Dae-Ho
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.9 no.4
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    • pp.377-380
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    • 1999
  • Erbium (Er) doped $LiNbO_{3}(Er:LiNbO_{3})$ single crystal fibers were grown free of creacks along the c-axis by micro-pulling down method. The $Er^{3+}$ concentration was distributed homogeneously along the growth axis. The samples for optical characterization were cut from as-grown single crystal fibers and polished. When the 980nm light was incident on the sample, upconversion phenomena were observed at the green range of wavelength 510~570nm. In addition, the intensity of upconversion was remarkably increased by increasing the concentration of $Er_{2}O_{3}$ dopant in as-grown $Er:LiNbO_{3}$ crystals.

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