• Proceedings of the Optical Society of Korea Conference
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• 2002.07a
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• pp.56-57
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• 2002

일정한 파장 간격을 가지는 다파장 광원은 WDM 시스템에서 중요한 소자중의 하나로 부각되고 있다. 다파장 광원에서 요구되는 주요 특징은 넓은 파장대역과 많은 수의 채널이며 각 채널들의 출력이 크고 균일해야 할 필요가 있다. 또한 각 채널의 파장이 ITU frequency grid와 일치해야 한다. 반도체 레이저와 광섬유레이저를 이용하여 이런 요구들을 만족하는 다파장 광원에 대한 다양한 연구들이 이루어져 왔다. (중략)

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.8
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• pp.2037-2042
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• 2014

Three methods for gain saturation tone application were compared for optical wavelength division multiplexing transmission using more than 32 channels. The methods are to use high power distributed feedback laser diodes, to use amplified light sources, and lastly to use one saturation tone and several WDM light sources. 1532.3 nm, 1545.7 nm, and 1558.2 nm for the wavelength dependency of the saturation tone were also compared. As a result, the effect of amplified spontaneous emission noise caused by an amplifier was very slight. long wavelength for a saturation tone caused 1 dB gain reduction and its reason was analyzed.

• Korean Journal of Optics and Photonics
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• v.18 no.2
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• pp.162-166
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• 2007

In this paper, we propose a WDM optical true time-delay (OTTD) beam former for phased way antenna (PAA) systems. It is composed of a delay lines matrix and a multiwavelength source with discrete DFB laser diodes. The building block of a delay lines matrix is a $2\times2$ optical MEMS switch with proper fiber-optic delay line connected between cross ports. A $4\times3$ matrix using four DFB lasers has been fabricated with unit time-delay difference of 12 ps. Maximum time-delay error was measured to be -1.74 ps and +1.14 ps at a radiation angle of $46.05^{\circ}$, corresponding to error range of $-2.87^{\circ}\sim+1.88^{\circ}$. By measuring time-delays at six different RF frequencies from 5- to 10-GHz, we verified the true time-delay characteristic of our OTTD.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.339-345
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• 2018

We investigated the curing properties of cured coatings for a multi-focal UV-LED. The coatings are for LEDs that operate at multiple UV wavelengths, unlike conventional single-wavelength UV-LEDs. Using UV-LED light sources with wavelengths of 365, 395, 420, and 450 nm, we analyzed the optical characteristics such as the direction of light flux and light source. We also analyzed the curing characteristics at each UV-LED wavelength to optimize the LED for composite wavelengths. The curing performance state was predicted through computer simulation for when the multiple wavelengths of UV light sources are superimposed, and then actual LEDs were designed and fabricated. To improve the internal high-speed curing, a multi-spot module was fabricated, in which each LED is condensed, and multiple wavelengths are synthesized and condensed at the same position. The adhesive strength, surface hardness, and internal hardness of the curing agent were tested by varying the wavelength combination conditions. The surface hardening and internal hardening were compared and analyzed using a hardness tester and FT-IR analyzer. As a result, the characteristics of the surface and internal hardness were improved by a multi-spot method in which four wavelengths were overlapped in a UV-LED rather than a single wavelength.

• Korean Journal of Optics and Photonics
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• v.8 no.6
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• pp.476-481
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• 1997

Optimum operating conditions of the 0.98 $\mu\textrm{m}$-pumped broadband erbium-doped fiber sources, where the mean wavelength variation is minimized, have been experimentally investigated. The optimum conditions for the mean wavelength stabilization were found to be different between the case of the isolated source and the case of the presence of feedback. In case of feedback, the proper pump power that yields zero slope of mean wavelength variation was found to be lower than that of the isolated case, and the mean wavelength was found nearly unchanged over the wide range of pump power. Howerer, the feedback resulted in lower output power and the mean wavelength was found to be sensitive to the variation of feedback level. In the respect of mean wavelength stability, the better performance could be obtained with some feedback, provided that the feedback level is kept constant. Thus we could also enhance the mean wavelength stability by allowing appropriate constant feedback into the source.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.102-103
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• 2000

최근 광통신 시스템에서는 파장분할다중화(WDM) 방식의 도입으로 인해, 한 개의 레이저 신호를 입사시켜 여러 개의 레이저 신호를 발생시켜 광원으로 사용하는 연구가 활발히 진행되어 왔다. Park et al.[1]은 Erbium Doped Fiber Laser(EDFL)에서 1.1nm 파장간격으로 24라인을 얻었고, Yamashita et al.[2]은 내부 에탈론 구조를 가진 EDFL에서 0.8nm 간격으로 17라인, D.Yu et al.[3]은 반사형 거울과 Circulator를 사용한 Brillouin/Erbium Fiber Laser(BEFL)에서 0.08nm 간격으로 30라인, G.J.Cowle et al.[4]은 Injection-Seed Locking을 이용한 BEFL.에서 0.09nm 간격으로 12라인 그리고 N.S.Kim et al.[5]은 내부 되먹임을 이용한 BEFL에서 0.09nm 간격으로 4라인을 각각 발생시켰다. 여기서 중요한 요소로는 발생된 레이저 신호의 안정성, 각 신호들 간의 파장간격, 레이저 신호의 수 그리고 Peak Intensity 간의 차이 등이 있는데 각 연구방식에 따라 다양한 결과를 보여준다. 본 실험에서는 향상된 되먹임 구조를 가진 BEFL에서 다파장 발생에 관한 연구를 하였다. (중략)

• Proceedings of the Optical Society of Korea Conference
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• 2000.08a
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• pp.242-243
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• 2000

매우 짧고 결맞는 극자외선 광원의 개발에 대한 기대로 강력한 레이저 장과 상호작용하는 원자에서 일어나는 비선형 다광자 현상에 대한 연구가 최근에 활발하게 전개되고 있다. 이 상호작용 과정에서 발생하는 빛은 매우 넓은 파장 영역에 걸쳐있으며, 입사 레이저의 홀수 배에 해당하는 매우 높은 차수의 조화파들을 포함하고 있다고 알려져 있다$^{(1,2)}$ . 최근의 이론 및 실험에 의하면, 강력하고 짧은 레이저 펄스를 사용하면 고차조화파의 파장에 청색변이를 일으킬 수 있다$^{(3.4.5)}$ . 실제 관측된 청색변이는 이웃하는 홀수 조화파의 간격보다 더 크다$^{(5)}$ . 따라서, 원리적으로는 매우 넓은 가변 폭을 갖고 연속적으로 파장을 조정할 수 있는 파장가변 극자외선 광원의 개발이 가능하다. (중략)

• Proceedings of the Optical Society of Korea Conference
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• 2007.07a
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• pp.349-350
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• 2007

• Korean Journal of Optics and Photonics
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• v.16 no.3
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• pp.287-294
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• 2005

In this paper, an optical true time-delay (TTD) for two-dimensional (2-D) phased array antennas (PAAs), composed of a multi-wavelength optical source and a fiber optic delay line matrix consisting of $2\times2$ optical switches with optical fiber connected between cross ports, has been proposed. A 2-bit $\times4-bit$ optical TTD for 10-GHz 2-D PAAs has been implemented by cascading a wavelength dependent TTD (WD-TTD) and a wavelength independent TTD (WI-TTD). The unit time delay for WD-TTD and WI-TTD have been chosen as ${\Delta}T=12ps$ and $\Delta\tau=6ps$, respectively. Time delay have been measured at all radiation angles. The maximum delay error for WD-TTD was measured to be 3 ps due to jitter incurred from gain switching. For the case of WI-TTD, error was within ${\pm}\;1\;ps$. The proposed optical TTD for a 2-D PAA has the following advantages: 1) higher gain compared to one-dimensional linear PAAs, 2) stabilization of optical power and wavelength by using a multi-wavelength optical source, and 3) fast beam scan and simple operation due to electronic control of the $2\times2$ optical switches matrix on a column-by-column basis.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.2
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• pp.221-227
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• 2021

Recently, interests in mask-type skin care devices using light-emitting diodes have been increasing and optical stimuli at certain wavelengths have been known to have various therapeutic effects, such as skin whitening, acne treatment, elasticity and wrinkle improvement by controlling the exposure to wavelengths of light and irradiation time. In particular, light sources of different wavelengths are applied in masks for the purpose of suppressing skin aging, inducing cell proliferation, and alleviating skin inflammation. In this paper, we developed a light-emitting diode control system that is actively used in skin regeneration masks using a microcontroller. Optical stimuli with different manners were applied to skin fibroblast cells in a single or complex wavelengths, and then confirmed how they are effective in the cell differentiation. In addition, we found a specific wavelength that has a positive effect on cell proliferation rates, and confirm the effectiveness of cell proliferation by image processing based quantitative analysis.