• Korean Journal of Optics and Photonics
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• v.10 no.4
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• pp.311-317
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• 1999

Unidirectional single-mode operation of a diode-pumped Nd:YAG laser with a planar semimonolithic ring cavity has been demostrated at 1064 nm. The semimonolithic cavity consists of a laser active medium placed in a magnetic field, a crystal quartz plate, and an output coupling mirror. They form an optical diode by acting each part as a Faraday rotator, a reciprocal polarization rotator and a partial polarizer, respectively. An eigenpolarization theory for the cavity configuration was presented and losses for the eigenmodes were calculated. A pump-limited single-mode output power of 155 mW and a slope efficiency of 17% were obtained when the laser was pumped by a 1.2 W, 809 nm diode-laser. A laser linewidth of less than 100 kHz is inferred from a beat note frequency spectrum between two identical laser systems and continous single-mode tuning range was more than 2 GHz.

• Current Optics and Photonics
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• v.5 no.2
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• pp.147-154
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• 2021

Microfluidic chip technology is a research focus in biology, chemistry, and medicine, for example. However, microfluidic chips are rarely applied in imaging, especially in ghost imaging. Thus in this work we propose a ghost-imaging system, in which we deploy a novel microfluidic chip modulator (MCM) constructed of double-layer zigzag micro pipelines. While in traditional situations a spatial light modulator (SLM) and supporting computers are required, we can get rid of active modulation devices and computers with this proposed scheme. The corresponding simulation analysis verifies good feasibility of the scheme, which can ensure the quality of data transmission and achieve convenient, fast ghost imaging passively.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.2
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• pp.179-188
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• 2014

Purpose: The present study was aimed to investigate the cleaning efficacy of multi-purpose solutions containing different types and content of surfactants and their effect on the visible light transmittance of soft lens. Methods: Soft lenses made of different materials (etafilcon A and hilafilcon B) were deposited tear proteins by using the artificial tear and then compared the resulting cleaning efficacy and visible light transmittance after cleaning the lens with 6 types of multi-purpose solutions containing different content of surfactants. Results: The cleaning efficacy of multi-purpose solutions was variously shown as approximately 23~43% according to the active concentration of surfactants and surface tension in multi-purpose solution when etafilcon A lens cleaned with rubbing. The highest cleaning efficacy was detected when cleaned with the multi-purpose solution containing hydrogen peroxide besides surfactant however, the amount of remaining protein was still high on the lens. After washed with multi-purpose solution, the visible light transmittance of lens was in 89.8 to 90.8%. The amount of protein deposited on hilafilcon B lens was very small compared with it on etafilcon A lens even though it was incubated in artificial tears for 7 days, which showed 5~10% of protein amount in etafilcon A lens and the decrease of visible light transmittance was also not significant. In case of rubbing with multi-purpose solution, the cleaning efficacy on hilafilcon B lens was in 45.4 to 67.4% however, the order of cleaning efficacy of multi-purpose solution was different from it on etafilcon A lens. The visible light transmittance of hilafilcon B lens has been restored to the level of new lens. Conclusions: From the result, it is concluded that the appropriate multi-purpose solution should be selected according to the lens material and the amount of protein deposit on the basis of understanding surfactants and active principle for proper care of protein deposit on soft lens and the cleaning with rubbing is more efficient for lens care regardless of manufacturer's guideline.

• Korean Journal of Food Science and Technology
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• v.43 no.1
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• pp.51-57
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• 2011

From the total methanolic extract of Gardenia jasminoides (Rubiaceae), various antioxidative characteristics were identified in terms of nitrite scavenging ability, 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical cation inhibition, superoxide dismutase (SOD)-like activity, and elongation effect of lipid peroxidation using Rancimat. After successive partitioning with n-hexane, chloroform, n-butanol, and water, potent nitrite scavenging abilities were shown in the n-butanol fraction and water fraction, and $IC_{50}$ values were 183 ppm and 194 ppm, respectively. As for ABTS radical cation inhibition, the chloroform fraction was most potent and its $IC_{50}$ was 159 ppm. SOD-like activity was slightly low in all of the fractions. The elongation effect of lipid peroxidation also increased dose-dependently and the antioxidative index (AI) of the total methanolic extract was 2.93 in 1000 ppm, which was more effective than 1.66 of butylated hydroxy anisol in the same concentration. The compounds I and II were isolated through silica gel column chromatography of the active fractions, and identified as geniposide and crocin, respectively, by $^1H-NMR$ spectral data. The $IC_{50}$ values for the nitrite scavenging abilities of geniposide and crocin were 940 ppm and 77 ppm, respectively. In ABTS radical cation inhibition, the $IC_{50}$ values of geniposide and crocin were 684 ppm and 549 ppm, respectively. And the $EC_{50}$ value for SOD-like activity of crocin was 259 ppm, which was much smaller than 453 ppm by the positive control, chlorogenic acid. The $EC_{50}$ value of geniposide could not be identified.

• Korean Journal of Food Science and Technology
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• v.39 no.1
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• pp.77-82
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• 2007

From the total methanolic extract of Chrysanthemum coronarium L. var. spatiosum (Compositae), nitrite scavenging ability and superoxide dismutase (SOD)-like activity were analyzed as antioxidative characteristics. After successive partitioning with chloroform, n-butanol, and water, the chloroform fraction showed the most significant nitrite scavenging ability with an $IC_{50}$ value of 39 ppm compared with the values of vitamin C and chlorogenic acid, 15 ppm and 36 ppm, respectively. The active fraction was subjected to silica gel and Sephadex LH-20 column chromatography, and the compound was isolated and identified as ${\beta}-sitosterol-O-{\beta}-D-glucoside$ using $^{1}H-NMR$ and $^{13}C-NMR$ spectral data. The glucoside was further hydrolyzed and confirmed as a glycosylated ${\beta}-sitosterol$. The compound and its aglycone, ${\beta}-sitosterol$, showed different nitrite scavenging and SOD-like activity. The $IC_{50}$ value of nitrite scavenging ability of the compound was 335 ppm at pH 1.5, while that of its aglycone was 41 ppm. As for the SOD-like activity, the $EC_{50}$ values of the sterol and the glucoside were 1,291 ppm and >2,000 ppm, respectively, compared with those of vitamin C and chlorogenic acid, 38 ppm and 449 ppm, respectively.

• Korean Journal of Optics and Photonics
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• v.11 no.4
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• pp.271-278
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• 2000

We have fabricated and analyzed the lasing characteristics of 1.3$\mu\textrm{m}$ Spot-Size-Converter (SSC) integrated Fabry-Perot (FP) laser diodes, which are very promising light sources for optical subscriber networks. SSC-LDs has been developed by BIB (buttjoint-built-in) coupling and selective MOVPE growth. High-performances were achieved such as the slope efficiency from the SSC facet of 0.23-0.32 mW/mA, the full-width at the half maximum of the far-field pattern (FFP) of 9.5$^{\circ}$~12.3$^{\circ}$, the alignment tolerances of $\pm$2.3$\mu\textrm{m}$ and $\pm$2.5$\mu\textrm{m}$ within the extra-coupling loss of 1 dB for the vertical and parallel directions, respectively. These experimental results were compared to theoretical ones in order to clarify the operational problems and give a good design direction of the fabricated SSC-LDs. It was revealed that an asymmetric output power from the facets, an irrelevancy of FFP and the waveguide structure around SSC facet region, and a poor temperature characteristics were originated from the scattering in the BIB and SSC sections and SHB effect in the active section for the first time.t time.

• Korean Journal of Optics and Photonics
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• v.13 no.2
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• pp.146-150
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• 2002

1.55${\mu}{\textrm}{m}$ PnpN optical thyristor as a smart optical switch has potential applications in advanced optical communication systems. PnpP optical thyristors operating at 1.55${\mu}{\textrm}{m}$ are proposed and fabricated for the first time. In the optical thyristors, we employ InGaAs/InP multiple quantum well (MQW) for the active n- and p-layers. The thyristors show sufficiently nonlinear s-shape I-V characteristics and spontaneous emission. In the OFF-state, the device has a high-impedance up to switching voltage of 4.03(V). On the other hand, it has low-impedance and emits spontaneous light as a light-emitting diode in the ON-state voltage of 1.77(V), and switching voltage is changed under several light input conditions. It can be used as a header processor in optical asynchronous transfer mode (ATM), as a hard limiter in optical code division multiple access (CDMA) and as a wavelength converter in optical WDM systems.

• Korean Journal of Optics and Photonics
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• v.28 no.6
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• pp.327-333
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• 2017

The purpose of this research was to analyze characteristics of verbal interactions of each homogeneous group in the learning of the 6th grade's 'Use of Lenses' Unit. For this research, six learning sessions were conducted in one 6th grade class composed of a high-academic-achievement group, an intermediate-academic-achievement group, and a low-academic-achievement group. All lessons were recorded, to analyze the verbal interactions of each group, and the transcribed data were analyzed using the verbal-interaction analytic framework. Results included: In the upper group, although opinions were presented more frequently, there were many negative verbal interactions in completing the tasks. The middle group was observed more specifically to accept peer opinions critically in their observational activities. The middle group's members were more active in presenting their opinions than listening to others' opinions. The lower group had difficulties in drawing conclusions because of a lack of ability to persuade peers or to respect the opinions of peers, even though the frequency of verbal interactions was higher than in other groups. Therefore, a homogeneous group structure is good for a simple activity involving a simple inquiry or an exchange of opinions, while a heterogeneous group structure is more effective in activities focused on understanding scientific concepts and knowledge.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.9
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• pp.830-837
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• 2015

Space debris has been a major issue recently for the space-active nations because its growing population is expected to increase the collision risk with operational satellites. Radar and electro-optical system has been used for space debris surveillance, which may cause unnecessary anti-collision manoeuvers due to their low tracking accuracy. So an additional tracking system is required to improve the predicted orbit accuracy and then to jude the anti-collision maneouvers more efficiently. The laser tracking system has been considered as an alternative to decrease these unnecessary manoeuvers. Korea Astronomy and Space Science Institute has been developing a space object laser tracking system which is capable of laser tracking for satellites with retro-reflectors and for space debris using high power laser, and satellite imaging using adaptive optics. In this study, the tracking capability is analyzed for space debris using high power laser based on link budget, false alarm probability and signal detection probability.

• Korean Journal of Optics and Photonics
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• v.9 no.2
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• pp.111-116
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• 1998

Thirteen InGaAs/InGaAsP separate-confinement heterostructure multiple quantum well lasers were designed such that the strain in the active layer from 0.9% compressive strain to 1.4% tensile, and their threshold current density was caluculated to see the effects of strain on the threshold current density. The well width was adjusted such that the bandgap of the quantum well is 1.55 ${\mu}{\textrm}{m}$, For the calculation of the band structure and transition matrix element needed for the gain calculation, a block diagonalized 8$\times$8 second-order $\to{k}.\to{p}$ Hamiltonian was used to incorporate the conduction band nonparabolicity and the valence band mixing. The threshold current density shows discontinuity at 0.4% tensile strain where the first heavy-hole subband and the first light-hole subband cross and at 0.5% tensile strain where the second conduction subband begins to exist. The threshold current density at room temperature has a maximum around these 0.4-0.5% tensile strains, and as strain varies in either direction it decreases first and then increases a little after a local minimum. This calculated trend is consistent with the other reported experimental results. We discussed the results of this calculation in comparison with other theoretical or experimental papers on the effect of strain.