• Bulletin of the Korean Chemical Society
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• v.27 no.8
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• pp.1186-1188
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• 2006

In this paper a new theory is presented to treat the problem of stimulated absorption and emission of photons between energy levels from the standpoint of discrete quantum jumps. In order to implement the theory a scheme to avoid the quantum Zeno effect is proposed. Numerical simulations are performed to demonstrate that this approach does not contradict the principles of the standard wave mechanics. It is shown that with this approach one can obtain photon observation statistics as well.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1994.11a
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• pp.50-53
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• 1994

In this study. we report the properties of optically pumped stimulated emission at room temperature (RT) from column-III nitride semiconductors of GaN, GaInN, AlGaN/GaN double hetero-structure (DH) and AlGaN/GaInN DH which grown by low pressure metal-organic vapor phase epitaxy on sapphire substrate using an AIN buffer-layer. The peak wavelength of the stimulated emission at RT from AlGaN/GaN DH is 370nm and the threshold of excitation pumping power density (P$\_$th/) is about 89㎾/$\textrm{cm}^2$, and they from AlGaN/GaInN DH are 403nm and 130㎾/$\textrm{cm}^2$, respectively. The P$\_$th/ of AlGaN/GaN and AlGaN/GaInN DHs are lower than the bulk materials due to optical confinement within the active layers of GaN and GaInN. The optical gain and the polarization of stimulated emission characteristics are presented in this article.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.10
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• pp.784-789
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• 1998

In this work, the optical properties of freestanding GaN single crystalline substrate grown by hydride vapor phase epitaxy(HVPE) were investigated. The low temperature PL spectrum in freestanding GaN consists of free and bound exciton emissions, and a deep DAP recombination around at 1.8eV. The optically-pumped stimulated emission in freestanding GaN substrate was observed at room temperature. At the maximum power density of 2MW/$\textrm{cm}^2$, the peak energy and FEHM of stimulated emission were 3.318 eV and 8meV, respectively. The excitation power dependence on the integrated emission intensity indicates the threshold pumping power density of 0.4 MW/$\textrm{cm}^2$.

• Electrical & Electronic Materials
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• v.8 no.3
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• pp.272-277
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• 1995

We report the properties of optically pumped stimulated emission at room temperature (RT) from column-III nitride semiconductors of GaN, AlGaN/GaN double heterostructure (DH) and AlGaN/GaInN DH which prepared on a sapphire substrate using an AIN buffer-layer by the nietalorganic vapor phase epitaxy (MOVPE) method. The peak wavelength of the stimulated emission at RT from AIGaN/GaN DH is 369nm and the threshold of excitation pumping power density (P$\_$th/) is about 84kW/cm$\^$2/, and they from AlGaN/GaInN DH are 402nm and 130kW/cm$\^$2/ at the pumping power density of 200kW/cm$\^$2/, respectively. The P$\_$th/ of AIGaN/GaN and AlGaN/GaInN DHs are lower than the single layers of GaN and GaInN due to optical confinement within the active layers of GaN and GaInN, respectively.

• 전기의세계
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• v.18 no.6
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• pp.58-63
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• 1969

필자는 메이서와 레이서에 대하여 되돌고이면 평이하게 정성적으로 기술하려고 한다. "Maser"란 말은 Microwave Amplification by Stimulated Emission of Radiation. 또 "Laser"란 Light Amplification by Stimulated Emission of Radiation의 약자이다. 이 메이서나 레이서는 진공관 원리에서 사용되는 자유전자대신 원자의 구속전자를 사용하여 에너지를 발생하든가 증폭작용을 하고 있다. 자극방사 (Stimulated emission)란 말은 원자에서 에너지 방사가 있기 위해서는 구속전자에 자극을 줘야하기 때문에 생긴 것이다. microwave란 말을 붙인 것은 전자에너지중 이 주파수범위내에 해당되는것에만 이용된다는 것이고 이와 마찬가지로 광(light)은 전자복사중 이 빛의 파장범위에서 작용된다는 것을 말한다. 따라서 이 메이서나 레이서는 매우 높은 주파수 범위에서 사용되는 에너지 발생장치 또는 증폭기라고 생각할 수 있다. 이 메이서나 레이서의 동작원리는 진공관증폭기의 동작원리와 다르므로 따라서 그 동작원리를 이해하려면 새로운 개념이 필요하게된다. 과학기술의 발달과 함께 과거의 전자기긱의 성능은 그 한계에 도달하게 되었고 통신, 천문학, 의학, 산업, 과학연구분야등에서 이 메이서와 레이서는 새로운 기회와 가능성을 제시해주고 있다.운 기회와 가능성을 제시해주고 있다.

• Applied Science and Convergence Technology
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• v.26 no.4
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• pp.79-85
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• 2017

The crack-free AlGaN template has been successfully grown by using selective area growth with triangular GaN facet. The triangular GaN stripe structure was obtained by vertical growth rate enhanced mode with low growth temperature of $950^{\circ}C$ and high growth pressure of 500 torr. The lateral growth rate enhanced mode of AlGaN for crack-free and flat surface was also investigated. Low pressure of 30 torr and high V/III ratio of 4400 were favorable for lateral growth of AlGaN. It was confirmed that the $4{\mu}m$ -thick $Al_{0.2}Ga_{0.8}N$ was crack-free over entire 2-inch wafer. The dislocation density of $Al_{0.2}Ga_{0.8}N$ was as low as ${\sim}7.6{\times}10^8/cm^2$ measured by cathodoluminescence. Based on the high quality AlGaN with low dislocation density, the ultraviolet laser diode epitaxy with cladding, waveguide and GaN/AlGaN multiple quantum well (MQW) was grown by metalorganic chemical vapor deposition. The stimulated emission at 349 nm with full width at half maximum of 1.8 nm from the MQW was observed through optical pumping experiment with 193 nm KrF laser. We also have fabricated the deep ridge type ultraviolet laser diode (UV-LD) with $5{\mu}m-wide$ and $700{\mu}m-long$ cavity for electrical properties. The turn on voltage was below 5 V and the resistance was ${\sim}55{\Omega}$ at applied voltage of 10 V. The amplified spontaneous emission spectrum of UV-LD was also observed from pulsed current injection.

• Proceedings of the Optical Society of Korea Conference
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• 2001.08a
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• pp.30-31
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• 2001

• ETRI Journal
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• v.29 no.6
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• pp.779-784
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• 2007

In this paper, we report the experimental results of a hybrid wideband fiber amplifier. The amplifying medium is a concatenated hybrid fiber consisting of Er-doped fiber (EDF) and dispersion compensating fiber (DCF). The gain mechanisms are based on stimulated emission in the EDF and stimulated Raman scattering (SRS) in the DCF. Since we simultaneously use optical amplification by the two processes, the gain bandwidth is easily expanded over 105 nm by a two-tone pumping scheme. Using an experimental setup constructed with a hybrid structure of EDF-DCF-EDF, we analyzed the spectral behavior of amplified spontaneous emission for pumping powers. We achieved an optical gain of over 20 dB in the wavelength range from 1,500 to 1,600 nm under optimized pumping conditions to make the spectral gain shape flat.

• Rapid Communication in Photoscience
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• v.4 no.4
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• pp.76-78
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• 2015

We report on the photoluminescence (PL) properties of poly[2,7-(9-9-dioctylfluorene)] (PF) thin film under strong optical pumping using a streak camera system. When the excitation energy density increases above $72{\mu}J{\cdot}cm^{-2}$, the emission spectrum becomes narrower and PL decay curve comes to be faster simultaneously. These behaviors are clear evidence of Amplified Spontaneous Emission (ASE) due to a waveguided Stimulated Emission in slab structure of thin film. ASE threshold of $72{\mu}J{\cdot}cm^{-2}$ is comparable with previous reports and PF is attractive as a gain medium for plastic lasers.

• Clean Technology
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• v.14 no.2
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• pp.95-102
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• 2008

In order to choose alternative environmental-friendly cleaning agents, it is very important in the present point that the systematic selection procedures should be introduced and applied to the industry through the evaluation of their cleaning ability, environmental characteristics, and economical factors, and that the objective and effective evaluation methods of cleanliness should be established for the industry. Thus, a novel cleaning evaluation method utilizing optically stimulated electron emission (OSEE) among various methods of cleaning ability was studied in this study. The contaminants used in this cleaning experiments were flux, solder, grease, cutting oil, and mixed soil of 35% grease and 65% cutting oil. The cleaning agents developed or prepared in our laboratory were employed and their cleaning ability were comparatively evaluated by the OSEE, gravimetry and contact angle methods. The experimental results in this work showed that flux cleaning efficiency measured by the OSEE method was similar to that of the gravimetric method, but that the OSEE method could not be compared with gravimetric method for the case of solder or grease cleaning because the contaminants radiate or absorb ultra-violet light. In case of cutting oil cleaning, the gravimetric method indicated its limitation of cleaning efficiency of cutting oil since it showed cleaning efficiency of 100%, even though residual soil remaining on the substrate surface a little after its cleaning. The comparative experimental results of cleaning ability evaluated by the OSEE- and contact angle measurement methods showed that they were similar in case of cleaning of flux, mixed soil and cutting oil. It was judged that the contact angle measurement method could evaluate the cleaning ability more precisely than the OSEE method for cleaning solder and grease.