• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.4
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• pp.946-949
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• 2004

We obtained ultra-short single pulse with an energy of 80 uJ from Distributed feedback Dye laser. Using three stages of amplifiers constructed by two stages of dye amplifiers and one bethune cell amplifier, we obtained high power pulse and second harmonic generation with BBO in ultraviolet region.

• Proceedings of the Optical Society of Korea Conference
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• 2000.08a
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• pp.90-91
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• 2000

2차 비선형 현상인 제2고조파(Second Harmonic Generation:SHG)는 electric dipole approximation에 의하면 중심대칭성이 있는 물질에서는 발생하지 않는다. 그러나 표면에 대해서는 그 중심대칭성이 깨져 제2고조파가 발생할 수 있게 된다. 즉 bulk에서는 제2고조파가 나오지 않는 반면, 표면에서는 나오게 된다. 본 연구에서는 electric dipole approximation 이상(예를 들면 magnetic dipole, electric quadrupole)을 고려해 시료의 물리적인 성질을 실제 물질계에 가깝게 기술하고자 했다. (중략)

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.8 s.111
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• pp.719-724
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• 2006

In this paper, we designed the double conversion down mixer by using Half-LO frequency in 2.3 GHz band. The IF frequency is obtained by supplying two LO frequencies to HEMT in both gate type and resistive type. The proposed mixer uses Half-LO frequency the same way as conventional sub-harmonic mixers. However the proposed one uses fundamental component of Half-LO frequency in first stage instead of using second harmonic components of Half-LO frequency, and the IF frequency is obtained by resistive type mixer in second stage, thereby the proposed mixer can improve linearity in comparison with conventional active mixer. We can verify that the proposed mixer has an conversion loss of 5dBm and IIP3 of 16.25dBm by using 10 dBm Power.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.397-398
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• 1988

We report on the simulation results of 1)the second harmonic conversion with $1.053{\mu}m$ Nd:glass laser using monolithic KDP crystal and 2)the efficient conversion from $1.053{\mu}m$ to $0.35{\mu}m$ by the polarization-mismatch 3rd harmonic conversion in two Type-II crystals.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.6
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• pp.564-568
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• 2010

When ultrasound propagates to a crack, transmitted and reflected waves are generated. These waves have useful information for the detection of the crack lying in a structure. When a crack is under residual stress, crack surfaces will contact each other and a closed crack is formed. For closed cracks, the fundamental component of the reflected and transmitted waves will be weak, and as such it is not easy to detect them. In this case, higher harmonic components will be useful. In this paper, nonlinear characteristic of a closed crack is modeled by a continuum material having a tensile-compressive unsymmetry, and the amplitude of the second harmonic wave was obtained by spectrum analysis. Variation of the second harmonic component depending on the nonlinearity of the inclusion was investigated. Two-dimensional plane strain model is considered, and finite element software ABAQUS/Explicit is used.

• Molecules and Cells
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• v.26 no.6
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• pp.530-535
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• 2008

Optical signals based on Raman scattering, coherent anti-Stokes Raman scattering (CARS), and harmonic generation can be used to image biological molecules in living cells without labeling. Both Raman scattering and CARS signals can be used to detect frequencies of molecular vibrations and to obtain the molecular distributions in samples. Second-harmonic optical signals can also be generated in structured arrays of noncentrosymmetric molecules and can be used to detect structured aggregates of proteins, such as, collagen, myosin and tubulin. Since labeling techniques using chemical and biological reactions may cause undesirable changes in the sample, label-free molecular imaging techniques are essential for observation of living samples.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.4
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• pp.355-361
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• 2012

This paper presents an experimental study on the detection and location of nonlinear scattering source due to the presence of fatigue crack in a laboratory specimen. The proposed technique is based on a combination of nonlinear elastic wave spectroscopy(NEWS) and time reversal(TR) focusing approach. In order to focus on the nonlinear scattering position due to the fatigue crack, we employed only one transmitting transducer and one receiving transducer, taking advantage of long duration of reception signal that includes multiple linear scattering such as mode conversion and boundary reflections. NEWS technique was then used as a pre-treatment of TR for spatial focusing of reemitted second harmonic signal. The robustness of this approach was demonstrated on a cracked specimen and the nonlinear TR focusing behavior is observed on the crack interface from which the second harmonic signal was originated.

• KIEE International Transactions on Power Engineering
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• v.2A no.4
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• pp.153-159
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• 2002

Power transformer protective relay should block the tripping during magnetizing inrush and rapidly operate the tripping during internal faults. Recently, the frequency environment of power system has been made more complicated and the quantity of 2nd frequency component in inrush state has been decreased because of the improvement of core steel. And then, traditional approaches will likely be maloperate in the case of magnetizing inrush with low second harmonic component and internal faults with high second harmonic component. This paper proposes a new relaying algorithm to enhance the fault detection sensitivities of conventional techniques by using a fuzzy logic approach. The proposed fuzzy based relaying algorithm consists of flux-differential current derivative curve, harmonic restraint, and percentage differential characteristic curve. The proposed relaying was tested with relaying signals obtained from EMTP simulation package and showed a fast and accurate trip operation.

• Current Optics and Photonics
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• v.2 no.6
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• pp.606-611
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• 2018

Measurement of the nonlinear optical coefficients is not an easy task since it requires complicated experimental setup and analysis. We suggest an easy way to estimate the relative nonlinear optical tensor components by direct measurement of the output powers of the second harmonic generation and spontaneous parametric down conversion experiments. The experiments were done in quasi-phase-matched type-0 as well as type-1 interactions at similar pump wavelengths in a 5% MgO-doped periodically poled $LiNbO_3$ crystal to obtain the ratio of the nonlinear optical tensor components $d_{33}/d_{31}$ in each experiment. The obtained ratios were then compared with the previously ascertained values [J. Opt. Soc. Am. B, 14, 2268-2294 (1997)].

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.3
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• pp.299-306
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• 2016

In this paper, a vital sign sensor based on impedance variation of resonator is proposed to detect the respiration and heartbeat signals within near-field range as a function of the separation distance between resonator and subject. The sensor consists of an oscillator with a built-in planar type patch resonator, a diplexer for only pass the second harmonic frequency, amplifier, SAW filter, and RF detector. The cardiac activity of a subject such as respiration and heartbeat causes the variation of the oscillation frequency corresponding impedance variation of the resonator within near-field range. The combination of the second harmonic oscillation frequency deviation and the superior skirt frequency of the SAW filter enables the proposed sensor to extend twice detection range. The experimental results reveal that the proposed sensor placed 40 mm away from a subject can reliably detect respiration and heartbeat signals.