• Journal of the Korean Magnetics Society
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• v.27 no.3
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• pp.77-81
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• 2017

The rotatable anisotropy effect was observed in the ferromagnetic resonance measurement in exchange coupled ferromagnetic/antiferromagnetic thin films and it was due to rotation of antiferromagnetic layer by the exchange coupling energy. We analyzed the CoFe thickness dependence of rotatable anisotropy field and ferromagnetic resonance linewidth in exchange coupled $CoFe(t_F)/MnIr(2.5nm)$ thin films. The rotatable anisotropy field was inversely propositional to the CoFe thickness and it was well fitted by the rotatable anisotropy energy of $0.96erg/cm^2$. The ferromagnetic resonance linewidth were linearly propositional to the rotatable anisotropy field in $t_F$ < 50 nm, while it was more dominated by the eddy current effect in $t_F$ > 50 nm.

• Current Optics and Photonics
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• v.8 no.1
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• pp.45-55
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• 2024

A fiber spool with ultra-low vibration sensitivity has been demonstrated for the ultra-narrow-linewidth fiber-stabilized laser by the multi-object orthogonal experimental design method, which can achieve the optimization object and analysis of influence levels without extensive computation. According to a test of 4 levels and 4 factors, an L₁₆ (4⁴) orthogonal table is established to design orthogonal experiments. The vibration sensitivities along the axial and radial directions and the normalized sums of the vibration sensitivities are determined as single objects and comprehensive objects, respectively. We adopt the range analysis of object values to obtain the influence levels of the four design parameters on the single objects and the comprehensive object. The optimal parameter combinations are determined by both methods of comprehensive balance and evaluation. Based on the corresponding fractional frequency stability of ultra-narrow-linewidth fiber-stabilized lasers, we obtain the final optimal parameter combination A3B1C2D1, which can achieve the fiber spool with vibration sensitivities of 10^-12/g magnitude. This work is the first time to use an orthogonal experimental design method to optimize the vibration sensitivities of fiber spools, providing an approach to design the fiber spool with ultra-low vibration sensitivity.

• Korean Journal of Optics and Photonics
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• v.21 no.3
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• pp.123-128
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• 2010

Sum frequency generation was utilized to obtain a yellow laser with the wavelength of 578.4 nm for a probe laser of an Yb lattice clock. The output of an Nd:YAG laser with wavelength of 1319 nm and that of an Yb-fiber laser with wavelength of 1030 nm were passed through a waveguided periodically-poled lithium niobate (WG-PPLN) for sum frequency generation. It is required that the probe laser has a linewidth of the order of 1 Hz to fully resolve the Yb lattice clock transition. Thus, the linewidth of the probe laser was reduced by stabilizing the frequency to a super-cavity. This was made of ULE with a low thermal expansion coefficient, and was mounted on an active vibration-isolation table at the optimal point for the reduced sensitivity to vibration. Also, this was installed in a vacuum chamber, and the temperature was stabilized to 1 mK level. This system was installed in an acoustic enclosure to block acoustic noise. The finesse of the super-cavity was measured to be 380 000 from the photon life time of the cavity.

• Proceedings of the Optical Society of Korea Conference
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• 2009.10a
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• pp.94-95
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• 2009

• Proceedings of the Optical Society of Korea Conference
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• 1996.09a
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• pp.68-68
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• 1996

• Journal of Magnetics
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• v.2 no.4
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• pp.123-125
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• 1997

We have studied a series of I2-doped poly [2-buthoxy-5-methoxy-1, 4-phenylenevinylene] (PBMPV) conducting polymers by means of electron paramagnetic resonance (EPR) measurements. In this work, the EPR linewidth and spin density were obtained from the EPR intensity and studied as a function of the degree of doping.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.11a
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• pp.139-139
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• 2004

• Korean Journal of Optics and Photonics
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• v.3 no.1
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• pp.11-15
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• 1992

In this work we analyze effects on the spectra of an integrated-mirror etalon by the absorption in a spacer layer, scattering loss at the interfaces between layers, and the focusing of incident beam.

• Applied Chemistry for Engineering
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• v.2 no.1
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• pp.1-11
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• 1991

Xenon-129 NMR technique has been developed since 1980 as a new method for the characterization of microporous materials such as zeolites, activated carbons and alumina by using chemical shift and linewidth variations in $^{129}Xe$ NMR of adsorbed xenon gas. This NMR technique has been known to be very effective to probe the locational and the chemical changes of the supported metallic species as well as the physicochemical change of the support material. Recently, this method has been successfully applied for the characterization of amorphous materials such as activated carbons, silica and alumina. Basic principles, experimental techniques and recent applications of the $^{129}Xe$ NMR method for the study of heterogeneous catalysts are introduced in this paper.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.2
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• pp.350-356
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• 2012

The tension effect on fiber Bragg gratings was analyzed and the linearity of 1.24 nm/10kpsi was obtained when Bragg wavelength was varied within 3 nm by applied tension. Using tension control method, different center wavelength fiber Bragg grating(FBG) were fabricated by only single period phase mask. These serially connected four FBGs showed the transmission spectrum of 1.5 nm linewidth as a 3 dB bandwidth which was twice that of a conventional FBG.