• Title/Summary/Keyword: Photon

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실리콘 박막 태양전지를 위한 CdSe계 양자점 광변환구조체

  • Sin, Myeong-Hun
    • Proceedings of the Korean Vacuum Society Conference
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    • 2014.02a
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    • pp.135.2-135.2
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    • 2014
  • Photon conversion technology for thin film solar cells is reviewed. The high-energy photons which are hardly absorbed in solar cells can be transformed the low energy photon by the photon conversion process such as down conversion or down shift, which can improve the solar cell efficiency over the material limit. CdSe-based quantum dot materials commonly used in LED can be used as the photon conversion layer for Si thin film solar cells. The photon conversion structure of CdSe-based quantum dot for Si thin film solar cells will be presented and the pros and cons for the Si thin film solar cells integrated with the photon conversion layers will be discussed.

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Photon Counting Linear Discriminant Analysis with Integral Imaging for Occluded Target Recognition

  • Yeom, Seok-Won;Javidi, Bahram
    • Journal of the Optical Society of Korea
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    • v.12 no.2
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    • pp.88-92
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    • 2008
  • This paper discusses a photon-counting linear discriminant analysis (LDA) with computational integral imaging (II). The computational II method reconstructs three-dimensional (3D) objects on the reconstruction planes located at arbitrary depth-levels. A maximum likelihood estimation (MLE) can be used to estimate the Poisson parameters of photon counts in the reconstruction space. The photon-counting LDA combined with the computational II method is developed in order to classify partially occluded objects with photon-limited images. Unknown targets are classified with the estimated Poisson parameters while reconstructed irradiance images are trained. It is shown that a low number of photons are sufficient to classify occluded objects with the proposed method.

Differences in Design Considerations between InGaN and Conventional High-Brightness Light-Emitting Diodes

  • Lee, Song-Jae
    • Journal of the Optical Society of Korea
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    • v.2 no.1
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    • pp.13-21
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    • 1998
  • Based on the escape cone concepts, high-brightness light-emitting diodes (LEDs) have been analyzed. In AlGaAs or InGaAlP LEDs, photon absorption in the ohmic region under the electrode is known to be significant. Thus, ins general, a thick window layer (WL) and a transparent substrate (TS) would minimize photon shielding by the electrodes and considerably improve photon output coupling efficiency. However, the schemes do not seem to be necessary in InGaN system. Photon absorption in ohmic contact to a wide bandgap semiconductor such as GaN may be negligible and, as a result, the significant photon shielding by the electrodes will not degrade the photon output coupling efficiency so much. The photon output coupling efficiency estimated in InGaN LEDs is about 2.5 - 2.8 times that of the conventional high-brightness LED structures based on both WL and TS schemes. As a result, the extenal quantum efficiency in InGaN LEDs is as high as 9% despite the presumably very low internal quantum efficiency.

Detection of Intracellular Free Metal Ions with Molecular Two-Photon Sensors (이광자 분자센서를 이용한 생체 내 금속이온 검출)

  • Kim, Hwan-Myung
    • Clean Technology
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    • v.17 no.3
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    • pp.231-237
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    • 2011
  • Two-photon microscopy (TPM) is attracting much attention in biological imaging due to the capability of imaging deep inside the living tissues for a long period of time. For maximum utilization of TPM, it is essential to develop efficient twophoton sensors. Regarding this, many research groups are developing two-photon sensors for specific applications. In this review, we summarize recent results on selected examples of two-photon sensors for intracellular free metal ions in the live cells and tissues to provide a guideline for various imaging applications.

Vibronically Induced Two-Photon Transitions in Benzene

  • Chung, Gyu-Sung;Lee, Duck-Kwan
    • Bulletin of the Korean Chemical Society
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    • v.10 no.3
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    • pp.298-302
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    • 1989
  • The strengths of two-photon transitions from the ground state to excited vibronic states in benzene are calculated by using the CNDO/2-U wave functions. The role of vibronic coupling in two-photon absorption process is discussed. The $A_{1{\bar{g}}}-A_{2g}^+$ two-photon transitions, which are forbidden by the identity-forbidden selection rule in single frequency two-photon absorption, are too weak to be experimentally observed even when two photons of different energies are used. It is because the transitions are forbidden also by the pseudo-parity selection rule which are applicable for alternant hydrocarbons such as benzene. It is also shown that the vibronic coupling is not very effective in altering the pseudo-parity property of the electronic state. The strength of the vibronically induced two-photon absorption is strongly affected by the presence of an electronic state from which two-photon absorption can borrow the intensity. It is pointed out that the pseudo-parity selection rule may be violated in such cases.

Two-photon probes for biomedical applications

  • Lim, Chang Su;Cho, Bong Rae
    • BMB Reports
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    • v.46 no.4
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    • pp.188-194
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    • 2013
  • Two-photon microscopy (TPM), which uses two photons of lower energy as the excitation source, is a vital tool in biology and clinical science, due to its capacity to image deep inside intact tissues for a long period of time. To make TPM a more versatile tool in biomedical research, we have developed a variety of two-photon probes for specific applications. In this mini review, we will briefly discuss two-photon probes for lipid rafts, lysosomes, mitochondria, and pH, and their biomedical applications.

Remarks on Single-Frequency Two-Photon Absorption$^\dag$

  • Lee, Duck-Hwan
    • Bulletin of the Korean Chemical Society
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    • v.8 no.4
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    • pp.338-340
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    • 1987
  • The single-frequency two-photon absorption tensor is carefully rederived and examined. It is pointed out that the conventionally used tensor, which has been formally deduced from the different-frequency two-photon absorption tensor, can give an incorrect absolute two-photon absorption rate. The identity forbidded selection rule and the polarization ratio expressions are also examined with the new tensor.

Comparisons of Object Recognition Performance with 3D Photon Counting & Gray Scale Images

  • Lee, Chung-Ghiu;Moon, In-Kyu
    • Journal of the Optical Society of Korea
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    • v.14 no.4
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    • pp.388-394
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    • 2010
  • In this paper the object recognition performance of a photon counting integral imaging system is quantitatively compared with that of a conventional gray scale imaging system. For 3D imaging of objects with a small number of photons, the elemental image set of a 3D scene is obtained using the integral imaging set up. We assume that the elemental image detection follows a Poisson distribution. Computational geometrical ray back propagation algorithm and parametric maximum likelihood estimator are applied to the photon counting elemental image set in order to reconstruct the original 3D scene. To evaluate the photon counting object recognition performance, the normalized correlation peaks between the reconstructed 3D scenes are calculated for the varied and fixed total number of photons in the reconstructed sectional image changing the total number of image channels in the integral imaging system. It is quantitatively illustrated that the recognition performance of the photon counting integral imaging system can be similar to that of a conventional gray scale imaging system as the number of image viewing channels in the photon counting integral imaging (PCII) system is increased up to the threshold point. Also, we present experiments to find the threshold point on the total number of image channels in the PCII system which can guarantee a comparable recognition performance with a gray scale imaging system. To the best of our knowledge, this is the first report on comparisons of object recognition performance with 3D photon counting & gray scale images.

Search for Dark Photon in e+e- → A'A' Using Future Collider Experiments

  • Kihong Park;Kyungho Kim;Alexei Sytov;Kihyeon Cho
    • Journal of Astronomy and Space Sciences
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    • v.40 no.4
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    • pp.259-266
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    • 2023
  • The Standard Model (SM) does not provide an information for 26% of dark matter of the universe. In the dark sector, dark matter is supposed to be linked with the hypothetical particles called dark photons that have similar role to photons in electromagnetic interaction in the SM. Besides astronomical observation, there are studies to find dark matter candidates using accelerators. In this paper, we searched for dark photons using future electron-positron colliders, including Circular Electron Positron Collider (CEPC)/CEPC, Future Circular Collider (FCC-ee)/Innovative Detector for Electron-positron Accelerator (IDEA), and International Linear Collider (ILC)/International Large Detector (ILD). Using the parameterized response of the detector simulation of Delphes, we studied the sensitivity of a double dark photon mode at each accelerator/detector. The signal mode is double dark photon decay channel, e+e- → A'A', where A' (dark photon with spin 1) decaying into a muon pair. We used MadGraph5 to generate Monte Carlo (MC) events by means of a Simplified Model. We found the dark photon mass at which the cross-sections were the highest for each accelerator to obtain the maximum number of events. In this paper we show the expected number of dark photon signal events and the detector efficiency of each accelerator. The results of this study can facilitate in the dark photon search by future electron-positron accelerators.

Improved Progressive Photon Mapping Using Photon Probing (포톤 탐사법을 이용한 개선된 점진적 포톤 매핑)

  • Lee, Sang-Gil;Shin, Byeong-Seok
    • Journal of the Korea Computer Graphics Society
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    • v.16 no.3
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    • pp.41-48
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    • 2010
  • Photon mapping is a traditional global illumination method using many photons emitted from the light source for photo-realistic rendering. However, this method needs a lot of resources to perform tracing of millions of photons. Progressive photon mapping solves this problem. Typical progressive photon mapping performs ray tracing at first to find the hit points on diffuse surface of objects. Next, light source repeatedly emits a small number of photons in photon tracing pass, and power of photons in each sphere that has a fixed radius with the hit points in the center is accumulated. This method requires less resources than previous photon mapping, but it spends much time for gathering enough photons since each of photons progresses through a random direction and rendering high quality image. To improve the method, we propose photon probing that calculates variance of photons in the sphere and controls radius of sphere. In addition, we apply cone filter in radiance estimation step for reducing aliasing at the edges in result image.