• Current Optics and Photonics
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• v.1 no.6
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• pp.579-586
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• 2017

In this paper, we theoretically demonstrate that semiconductor optical amplifiers (SOAs) with strong wavelength dependence of gain and phase are capable of all-optical inverted and non-inverted wavelength conversion (WC) over a wide range, with the assistance of an optical filter. First, the gain dynamics and phase dynamics in a common quantum well (QW) SOA with the $In_{0.53}Ga_{0.47}As/In_{0.7322}Ga_{0.2678}As_{0.5810}P_{0.4190}$ material system are found to be strongly dependent on wavelength, which is mainly related to the wavelength dependence of the differential gain and the differential refractive-index change. Second, the wavelength dependence in an all-optical wavelength converter based on the QW SOA cascaded with a detuning band pass filter is studied. Simulations show that the quality of the converted signal has little dependence on the operation wavelength. Both inverted and non-inverted WC can be achieved, over a large wavelength range. Therefore, although the gain and phase change are strongly wavelength-dependent, the effects of this dependence can be erased by appropriate optical filtering.

• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.365-367
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• 1993

The wavelength dependence of the diffracted light in volume hologram is important in application of volume hologram, because the wavelength dependence of the diffracted light can be used to select a certain wavelength from white-light which is composed of a lot of wavelengths. Some experiments are done to analyze the wavelength dependence of diffracted lights. The coupled wave theory is used to make a theoretical approach to this model. Compared with the theoretical result, the experimental result makes a good agreement with it.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2000.08a
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• pp.13-16
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• 2000

Since stimulated Brillouin scattering (SBS) impact wavelength division multiplexing (WDM) optical transmission systems, it is important to understand the implication of SBS in the design of such lightwave systems. Therefore, Brillouin gain spectrum (BGS) is measured to characterize the effect of SBS in optical fiber. The Brillouin gain coefficient is found to vary as the wavelength and linewidth of source. Theoretically measurement of BGS shows a dependence on wavelength(λ) and on linewidth(Δν), respectively.

• Journal of Photoscience
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• v.10 no.1
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• pp.97-104
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• 2003

The excitation wavelength dependence of laser ablation dynamics of an azobenzene-containing urethane-urea copolymer film was investigated by measuring the laser fluence dependence of etch depth, transient absorbance change at each excitation wavelength, and transient absorption spectra. Moreover expansion/contraction dynamics was studied by applying nanosecond time-resolved interferometry. The threshold was determined at several excitation wavelengths from etch depth measurement, while time-integrated absorbance was obtained under excitation conditions. The photon energy required to remove the topmost of surface layer of the film did not .depend on excitation wavelength, and the penetration depth of excitation pulse dominated the etch depth. When the excitation wavelength was longer than 500 nm, permanent swelling was clearly observed but not for shorter wavelength excitation. In the latter case, photoisomerization occurred during excitation and the following photoreduction may play an important role. On the basis of the observations made in this study, a photochemical and photothermal mechanisms can explain mostly the short and long wavelength excitation results, respectively.

• Journal of the Optical Society of Korea
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• v.18 no.4
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• pp.301-306
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• 2014

A porous silicon microcavity (PSMC) sensor has been made for vapors of solvent solutions, and a method has been developed in order to obtain simultaneous determination of two volatile substances with different concentrations. In our work, the temperature of the solution and the velocity of the air stream flowing through the solution have been used to control the response of the sensor for ethanol and acetone solutions. We study the dependence of the cavity-resonant wavelength shift on solvent concentration, velocity of the airflow and solution temperature. The wavelength shift depends linearly on concentration and increases with solution temperature and velocity of the airflow. The dependence of the wavelength shift on the solution temperature in the measurement contains properties of the temperature dependence of the solvent vapor pressure, which characterizes each solvent. As a result, the dependence of the wavelength shift on the solution temperature discriminates between solutions of ethanol and acetone with different concentrations. This suggests a possibility for the simultaneous determination of the volatile substances and their concentrations.

• Korean Journal of Optics and Photonics
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• v.9 no.2
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• pp.123-126
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• 1998

We derived an equation showing the temperature dependence of the zero-dispersion wavelength and measured the temperature dependence of the zero dispersion wavelength using four-wave mixing in dispersion shifted fibers in the range of $22^{\circ}C-59^{\circ}C$ From the experimental results, we found that the zero-dispersion wavelength is increased as the temperature around DSF increases and its temperature dependence is 0.032 nm/$^{\circ}C$. Also, the calculated behavior of FWM efficiency coincided with the experimental result.

• Journal of the Optical Society of Korea
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• v.13 no.2
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• pp.267-271
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• 2009

The aim of this study is to evaluate wavelength dependence for laser-assisted lipolysis using a mathematical simulation. In this study, a Monte Carlo simulation was performed to simulate light transport in fat and dermal tissue with 3 different laser wavelengths (${\lambda}\;=\;1064\;nm$, 1320 nm, and 1444 nm) that are currently used in clinic settings for laser-assisted lipolysis. The relative rates of heat generation versus penetration depth showed that the greatest amount of heat generation was seen in the tissues at ${\lambda}\;=\;1444\;nm$. This Monte Carlo simulation may help lend insight into the thermal events occurring inside the fat and dermal tissue during laser-assisted lipolysis.

• Korean Journal of Optics and Photonics
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• v.22 no.2
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• pp.67-71
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• 2011

In the paper, we have demonstrated an azobenzene-coated fiber Bragg grating (FBG) for monitoring ultraviolet light (UV) intensity in remote measurement. The elasticity of the coated azobenzene polymer is changed by the UV light, which induces a center wavelength change corresponding to the change of the FBG's grating period. The wavelength shift resulting from both UV light and other light with the wavelength out of the UV range was about 0.18 nm. In order to improve the accuracy of the measurement, the center wavelength shift caused by radiant heat of the light source was sufficiently removed by using a thermal filter. The amount of the center wavelength shift was consequently reduced to 0.06 nm, compared to the result without the thermal filter. Also, the FBGs coated by using azobenzene polymer were produced by two different methods; thermal casting and UV curing. Considering temperature dependence, UV curing is more suitable than thermal casting in UV sensor application of the azobenzene-coated FBG. In addition, we have confirmed the wavelength dependence of the optical sensor by means of four different band pass filters. Thus, we found out that the center wavelength shift per unit intensity is 0.029 [arb. unit] as a maximum value at 370 nm wavelength region and that the absorption spectrum of the azobenzene polymer was very consistent with the wavelength dependence of the azobenzene-coated FBG.

• Proceedings of the Optical Society of Korea Conference
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• 2008.07a
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• pp.329-330
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• 2008

We experimentally demonstrate resonant-wavelength control of a series of an Si-based photonic crystal nanocavity. The cavities show a linear dependence on these parameters, a 1 nm increase of lattice constant leading to 4.2 nm increase of the resonant wavelength. The results have a small standard deviation of wavelength 1.1 nm between samples on a single chip.

• The Journal of Korean Physical Therapy
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• v.22 no.6
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• pp.77-83
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• 2010

Purpose: The aim of this study was to do numerical analysis of the wavelength dependence in low level laser therapy (LLLT) using a finite element method (FEM). Methods: Numerical analysis of heat transfer based on a Pennes' bioheat equation was performed to assess the wavelength dependence of effects of LLLT in a single layer and in multilayered tissue that consists of skin, fat and muscle. The three different wavelengths selected, 660 nm, 830 nm and 980 nm, were ones that are frequently used in clinic settings for the therapy of musculoskeletal disorders. Laser parameters were set to the power density of 35.7 W/$cm^2$, a spot diameter of 0.06 cm, and a laser exposure time of 50 seconds for all wavelengths. Results: Temperature changes in tissue based on a heat transfer equation using a finite element method were simulated and were dominantly dependent upon the absorption coefficient of each tissue layer. In the analysis of a single tissue layer, heat generation by fixed laser exposure at each wavelength had a similar pattern for increasing temperature in both skin and fat (980 nm > 660 nm > 830 nm), but in the muscle layer 660nm generated the most heat (660 nm ${\gg}$ 980 nm > 830 nm). The heat generation in multilayered tissue versus penetration depth was shown that the temperature of 660 nm wavelength was higher than those of 830 nm and 980 nm Conclusion: Numerical analysis of heat transfer versus penetration depth using a finite element method showed that the greatest amount of heat generation is seen in multilayered tissue at = 660 nm. Numerical analysis of heat transfer may help lend insight into thermal events occurring inside tissue layers during low level laser therapy.