• Proceedings of the KOSOMBE Conference
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• v.1996 no.11
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• pp.192-196
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• 1996

[ $1.06/1.32{\mu}m$ ] dual-wavelength medical laser was developed and preliminary clinical comparisons at these two wavelengths were performed for dental application. We could develop a compact laser system 1) by lasing two wavelengths from the same Nd:YAG rod, and 2) by introducing high-voltage switching power supply modules. Experiment on gingiva of pig jaw showed higher thermal damage at $1.32{\mu}m$. Depending on particular procedures, each wavelength has its own advantages and disadvantages. For cutting, however, using conical tips rather than bare fibers provided better results with low threshold of cutting energy and less surrounding thermal damage. Appling light-absorbing dye on target area appeared to induce more damage during laser irradiation. However, histological studies showed no significant difference whether dye was applied or not.

• Current Optics and Photonics
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• v.7 no.4
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• pp.362-377
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• 2023

Optical information processing technology is characterized by high speed and parallelism, and the light features short wavelength and large information capacity; At the same time, it has various attributes including amplitude, phase, wavelength and polarization, and is a carrier of multi-dimensional information. Therefore, optical encryption is of great significance in the field of information security transmission, and is widely used in the field of image encryption. For multi-image encryption, this paper proposes a multi-image encryption algorithm based on a modified Gerchberg-Saxton algorithm (MGSA) in the Fresnel-transform domain and computational ghost imaging. First, MGSA is used to realize "one code, one key"; Second, phase function superposition and normalization are used to reduce the amount of ciphertext transmission; Finally, computational ghost imaging is used to improve the security of the whole encryption system. This method can encrypt multiple images simultaneously with high efficiency, simple calculation, safety and reliability, and less data transmission. The encryption effect of the method is evaluated by using correlation coefficient and structural similarity, and the effectiveness and security of the method are verified by simulation experiments.

• Nuclear Engineering and Technology
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• v.55 no.12
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• pp.4642-4646
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• 2023

The Tb³⁺ or Eu³⁺-doped Lu₂Gd₁Ga₂Al₃O₁₂ phosphor were fabricated by funace at 1500 ℃ for 12 h using a solid state reaction. The XRD (X-ray diffraction_Panalytical X'Pert Pro) and FE-SEM (field emission scanning electron microscope) are measured to confirm the crystalline structure and surface morphology of the phosphor. The Tb³⁺-doped Lu₂Gd₁Ga₂Al₃O₁₂ phosphor emits the lights in 470~650 nm wavelength range due to transitions from ⁵D₄ to ⁷F_j. Therefore, it shows the green region in the CIE chromaticity diagram under both UV and X-rays excitations. The Eu³⁺-doped Lu₂Gd₁Ga₂Al₃O₁₂ phosphor emits the lights in 550~750 nm wavelength range because of ⁵D_i to ⁷F_j. The emission is confirmed to be in the red region using the CIE chromaticity diagram. The Tb³⁺ or Eu³⁺-doped Lu₂Gd₁Ga₂Al₃O₁₂ phosphor shows the characteristic f-f transition with a long decay time, which is about several milliseconds. They have the high efficiency of light emission for X-ray because of their high effective Z number (Z_eff = 58.5) and density. Therefore, they are very much promising phosphors for X-ray imaging application in medical fields.

• Nanomaterials
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• v.12 no.10
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• pp.1618-1626
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• 2022

CdS films with a wide range of substrate temperatures as deposition parameters were fabricated on Corning Eagle 2000 glass substrates using RF magnetron sputtering. The crystallographic structure, microscopic surface texture, and stoichiometric and optical properties of each CdS film deposited at various substrate temperatures were observed to be highly temperature-dependent. The grown CdS thin films revealed a polycrystalline structure in which a cubic phase was mixed based on a hexagonal wurtzite phase. The relative intensity of the H(002)/C(111) peak, which represents the direction of the preferential growth plane, enhanced as the temperatures climbed from 25 ℃ to 350 ℃. On the contrary, the intensity of the main growth peak at the higher temperatures of 450 ℃ and 500 ℃ was significantly reduced and exhibited amorphous-like behavior. The sharp absorption edge revealed in the transmission spectrum shifted from the long wavelength to the short wavelength region with the rise in the substrate temperature. The bandgap showed a tendency to widen from 2.38 eV to 2.97 eV when the temperatures increased from 25 ℃ to 350 ℃. The CdS films grown at the temperatures of 450 ℃ and 500 ℃ exhibited glass-like transmittance with almost no interference fringes of light, which resulted in wide bandgap values of 3.09 eV and 4.19 eV, respectively.

• Korean Journal of Poultry Science
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• v.37 no.4
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• pp.383-388
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• 2010

The chicken eye can discriminate light color, and different light wavelengths may affect reproduction ability. This study was carried out to identify effect of monochromatic light using light emitting diode (LED) in laying hens. Chickens were exposed to white light (WL), blue light (BL), yellow light (YL), green light (GL) and red light (RL) made by using LED as well as incandescent light (IL) (control). All light sources were equalized to a light intensity of 20 lux. The results indicated that the age of first egg laying and 50 % egg laying in laying hens treated under RL is significantly younger than under other lights (P<0.05). And the ovary weight of laying hens reared under RL is significantly heavier than under other at from 16 to 20 wks (P<0.05). The largest number of eggs production was produced in a group with treated with RL by 59 wks of age compared with any other group. The egg weight of YL was greater than other treatment groups from 26 to 45 wks (P<0.05). The egg shell from hens treated with RL was the strongest and thickest at 20 wk (P<0.05). These results suggest that the egg quality of laying hens reared in different spectrum of LED can be different and RL may enhance the laying performance.

• Horticultural Science & Technology
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• v.31 no.1
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• pp.56-64
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• 2013

Recent unusual weather due to global warming causes shortage of daily sunlight and constitutes one of the primary reasons for agricultural damages. LED light sources are frequently utilized to compensate for the shortage of sunlight in greenhouse agriculture. The present study is aimed at evaluating formations of phytochemicals as well as growth characteristics of mature strawberry fruits ('Daewang' cultivar) during cultivation in a closed growth chamber equipped with artificial LED light as a sole light source. Each LED light of blue (448 nm), red (634 and 661 nm) or mixed blue plus red (blue:red = 3:7) was separately supplied and the intensity of each light was adjusted to $200{\pm}1{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ at plant level with a photoperiod consisted of 16 hours light and 8 hours darkness. Strawberries grown under mixed LED light of blue and red wavelengths showed a higher production of fruits than those grown under other LED treatments. Fructose, one of the free sugars, increased in mixed LED light-grown fruits. Anthocyanin contents were elevated remarkably in the mixed LED light-grown fruits compared with those in other LED treatments. Contrastingly, contents of total phenolics and flavonoids were not of much different from one another among the fruits treated with various LED lights. On the other hand, ripening of strawberry fruits was found to be faster when grown under blue LED light compared with other LED treatments. Moreover, antioxidant activities of blue or red LED light-grown fruits, respectively, were significantly higher than those of mixed LED light-grown fruits. We suggest that when daylight is in shortage during cultivation in a greenhouse, supplementation of sunlight with LED light, which is composed of blue and red wavelengths, could be useful for the enhancement of productivity as well as of free sugar content in strawberry fruits. In addition, for the strawberry culture in the plant factory, selective adoption of LED light wavelength would be required to accomplish the purpose of controlling fruit maturation time as well as of enhancing contents of sugars and antioxidants of fruits.

• Journal of Bio-Environment Control
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• v.25 no.1
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• pp.42-48
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• 2016

Angelica gigas, belonging family Apiaceae, is a perennial and famous medical plant growing in Korea, Japan, and China. The aims of this study was to analyze the growth and accumulated Decursin and its precursor Decursinol angelate of A.gigas grown under fluorescent lamp and LED. A. gigas 'Manchu' were sowed and managed for seedlings stage in a glass house for 4 weeks. One hundred twenty seedlings with 3 true leafs were transplanted at an ebb & flow system with fluorescent lamp and LED [red: peak wavelength 660nm, blue: peak wavelength 455 nm, white = 3:2:4 ratio] irradiated at $180{\pm}7{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ at the top of plant canopy for 5 weeks. The number of leaves increased by 13.5% in the LED treatment, though it is not statistically significant. Leaf length/width ratio of A. gigas grown under the fluorescent lamps was 24% bigger than the LED treatment and also the stem was 13% larger. Maximum root length was similar to both groups. Fresh weight and dry weight of shoots grown under the LED increased by 50% and 42% and the both weights of roots increased by 125% and 45%, respectively. The contents of Decursin and Decursinol angelate grown under the florescent lamps were larger than LED by 188% and 27% in shoot and 78% and 8% in root. The contents of Decursin and Decursinol angelate per plant grown under LED and florescent lamps were 132mg and 122mg. In conclusion, functional materials in A. gigas were increased by florescent light and its growth was promoted by LEDs light.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.216-221
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• 2017

Reducing optical reflection in the visible light range, in order to increase the share of transmitted light and avoid the formation of ghost images in imaging, is important for polymer lens applications. In this study, polymer lenses with refractive indices of n=1.56, 1.60, and 1.67 were fabricated by the injection-molding method with a polymer lens monomer, dibutyltin dichloride as the catalyst and an alkyl phosphoric ester as the release agent. To investigate their anti-reflection (AR) effects, various AR coating structures, viz. a multi-layer AR coating structure, tri-layer AR coating structure with a discrete approximation Gaussian gradient-index profile, and tri-layer AR coating structure with a quarter-wavelength approximation, were designed and coated on the polymer lens by an E-beam evaporation system. The optical properties of the polymer lenses were characterized by UV-visible spectrometry. The material properties of the thin films, refractive index and surface roughness, were analyzed by ellipsometry and AFM, respectively. The most effective AR coating structure of the polymer lens with low refractive index, n=1.56, was the both side coating of multi-layer AR coating structure. However, both side coating of the tri-layered discrete approximation Gaussian gradient-index profile AR coating structure gave comparable results to the both side coating of the multi-layer AR coating structure for the polymer lens with a high refractive index of n=1.67.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.296-296
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• 2014

We investigate experimentally and theoretically the splitting of surface plasmon (SP) resonance peaks under TE- and TM-polarized illumination. The SP structure at infrared wavelength is fabricated with a 2-dimensional square periodic array of circular holes penetrating through Au (gold) film. In brief, the processing steps to fabricate the SP structure are as follows. (i) A standard optical lithography was performed to produce to a periodic array of photoresist (PR) circular cylinders. (ii) After the PR pattern, e-beam evaporation was used to deposit a 50-nm thick layer of Au. (iii) A lift-off processing with acetone to remove the PR layer, leading to final structure (pitch, $p=2.2{\mu}m$; aperture size, $d=1.1{\mu}m$) as shown in Fig. 1(a). The transmission is measured using a Nicolet Fourier-transform infrared spectroscopy (FTIR) at the incident angle from $0^{\circ}$ to $36^{\circ}$ with a step of $4^{\circ}$ both in TE and TM polarization. Measured first and second order SP resonances at interface between Au and GaAs exhibit the splitting into two branches under TM-polarized light as shown in Fig. 1(b). However, as the incidence angle under TE polarization is increased, the $1^{st}$ order SP resonance peak blue-shifts slightly while the splitting of $2^{nd}$ order SP resonance peak tends to be larger (not shown here). For the purpose of understanding our experimental results qualitatively, SP resonance peak wavelengths can be calculated from momentum matching condition (black circle depicted in Fig. 2(b)), $k_{sp}=k_{\parallel}{\pm}iG_x{\pm}jG_y$, where $k_{sp}$ is the SP wavevector, $k_{\parallel}$ is the in-plane component of incident light wavevector, i and j are SP coupling order, and G is the grating momentum wavevector. Moreover, for better understanding we performed 3D full field electromagnetic simulations of SP structure using a finite integration technique (CST Microwave Studio). Fig. 1(b) shows an excellent agreement between the experimental, calculated and CST-simulated splitting of SP resonance peaks with various incidence angles under TM-polarized illumination (TE results are not shown here). The simulated z-component electric field (Ez) distribution at incident angle, $4^{\circ}$ and $16^{\circ}$ under TM polarization and at the corresponding SP resonance wavelength is shown in Fig. 1(c). The analysis and comparison of theoretical results with experiment indicates a good agreement of the splitting behavior of the surface plasmon resonance modes at oblique incidence both in TE and TM polarization.

• Economic and Environmental Geology
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• v.49 no.5
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• pp.335-347
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• 2016

The mineralogical and geochemical characteristics of diverse carbonate rocks can be investigated by using VNIRSWIR(visible near infrared-short wavelength infrared) spectroscopic analysis as a rapid, nondestructive, and inexpensive tool. Comparing whole rock analysis to VNIR-SWIR spectroscopic analysis, the analytical method was investigated to estimate CaO contents, mud impurity, and whiteness of carbonate rocks involved in high-grade limestones in the field. We classify typical carbonate rocks in the upper Pungchon Formation in high-grade limestone mine area such as the Gangweon, Chungmu and Baegun mine in the Jeongseon area. The results show that powdered specimen has much higher reflectance than cutted specimen between the same sample. Whiteness is highly correlated with reflectance(0.99) for powdered specimen. The absorption of mineral mixtures shifts in position as a result of the mass ratio of calcite and dolomite in the Chungmu mine by changing to 75:25, 50:50, and 25:75. The absorption peak position in carbonate mixtures is highly correlated with CaO contents(0.98~0.99). Based on color system, the carbonate rocks are grouped into (milky) white, light grey, light brown, grey, and dark grey. The absorption peak position shifts from 2340 nm to 2320 nm as CaO contents decrease from 55.86 wt.% to 29.71 wt.%. We confirmed that absorption peak position shifts depending on the amount of Ca, which is bonded to $CO{_3}^{-2}$, Mg, and Fe contents replacing Ca. This result suggests that CaO contents in carbonate rocks can be considered to quantitative analysis in the field by spectroscopic analysis.