• Korean Journal of Optics and Photonics
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• v.5 no.1
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• pp.67-73
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• 1994

The simulation code was developed to analyze the amplification properties of the regenerative amplifier, such as gain narrowing, nonlinear effect, and energy saturation. To reduce gain narrowing in the regenerative amplifier, the input pulse with a symmetrical shape and the same center wavelength of the active medium should be amplified in the active medium with a broad fluorescence linewidth. In this respect, Ti:Sapphire with a low nonlinear refractive index, a high saturation fluence, and a broad fluorescence linewidth is the most appropriate medium for the regenerative amplifier. The knowledge and the important parameters were acquired for the optimum design of the regenerative amplifier.

• Korean Journal of Optics and Photonics
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• v.7 no.1
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• pp.60-65
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• 1996

Degradation of the optical communication system due to the stimulated Brillouin scattering effect in the optical fiber is measured, and its suppression is demonstrated. In the externally modulated 2.5 Gb/s transmission experiment, bit error rate is increased due to the stimulated Brillouin scattering effect when the signal power (linewidth 3 MHz) incident into the dispersion shifted fiber is larger than 10 dBm. SBS effect is suppressed completely, up to 15 dBm of transmission power, by broadening the source linewidth to 200 MHz.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.8
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• pp.86-93
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• 1995

Linwidth enhancement factor .alpha., linwidth, chirping and differential gain characteristics were measured and compared for each DFB-LDs containing active layers composed of bulk, MQW, and S-MQW, respectively. .alpha. of 6, 4 and 3.2 and chirping measured under 2.5Gbps modulation of 1.29nm, 0.67nm and 0.48nm were given for DFB-LDs of bulk, MQW and S-MQW active layers, respectively. And S-MQW has the largest differential gin of 2.4*10$^{-15}$ cm$^{2}$ (S-MQW) compared to the of 5.4*10$^{-16}$ cm$^{2}$(bulk) and 8.6*10$^{-16}$ cm$^{2}$(MQW). Linewidth enhancement facter .alpha. of less than 2 is expected with p-type modulation doped S-MQW DFB-LD.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.6
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• pp.143-148
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• 1994

In order to study the effect of D.C resistivity of sample on electromagnetic loss of ferrite at microwave frequency, samples were prepared for having differences in resistivity of an order of two. Microwave permeability($\mu$), permitivity($\varepsilon$) and effective linewidth(${\Delta}H_{eff}$), and ferromagnetic resonance linewidth(${\Delta}$H) were characterized. Tan${\delta}{\mu}$, tan${\delta}{\varepsilon}$ and ${\Delta}H_{eff}$ were decreased with increasing the resistivity and (${\Delta}$H) was increased with increasing Fe concentration, which was due to an increase of anisotropy magnetic field (=Ha).

• Korean Journal of Optics and Photonics
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• v.10 no.3
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• pp.233-236
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• 1999

We have constructed a narrow-linewidth single-longitudinal-mode unidirectional $Er^{3+}$ -doped fiber laser using a fiber Bragg grating incorporated by a three port optical circulator with a compact configuration. Using a conventional delayed self-heterodyne detection technique with Mach-Zehnder interferometer a linewidth of 5 kHz was measured. In a single-longitudinal-mode operation, output power of up to 2.7 mW at 1548 nm were obtained for a launched pump power of 43 mW at 980 nm.

• Proceedings of the Korean Magnestics Society Conference
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• 2007.05a
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• pp.231.1-231.1
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• 2007

• Proceedings of the Optical Society of Korea Conference
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• 2005.07a
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• pp.230-231
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• 2005

• Journal of the Korea Convergence Society
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• v.11 no.7
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• pp.157-162
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• 2020

In recent years, laser induced graphene process have been intensively studied for eco-friendly electronic device such as flexible electronics or thin film based energy storage devices because of its simple and effective process. In order to increase the performance and efficiency of an electronic device using such a graphene patterned structure, it is essential to study an optimized laser patterning condition as small as possible linewidth while maintaining the graphene-specific 2-dimensional characteristics. In this study, we analyzed to find the optimal line pattern by using a Ti:sapphire femtosecond laser based photo-thermal reduction process. we tuned intensity and scanning speed of laser spot for generating effective graphene characteristic and minimum thermal effect. As a result, we demonstrated the reduced graphene pattern of 30㎛ in linewidth by using a focused laser beam of 18㎛ in diameter.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.3
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• pp.277-282
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• 2016

Effect of spectral drift in coherent fiber laser was investigated by injecting optical feedback to Fabry-Perot resonance loop. Er+3 doped fiber laser having unilateral optical feedback loop in Fabry-Perot configuration using two FBGs was fabricated. The optical feedback was found to be effective in linewidth reduction of fiber laser compared to the case without any optical feedback. The linewidth of three fiber lasers using above configuration were measured to be within 3kHz which is resolution-limited performance of self-heterodyne linewidth measurement set-up. The frequency drift measurement using Mach-Zehnder measurement set-up having 200m optical delay-line in one arm showed that the frequency drift rate of optical feedback fiber laser was measured as 300kHz/sec which was better than the case without optical feedback.

• Progress in Superconductivity
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• v.12 no.1
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• pp.51-56
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• 2010

$^{13}C$ NMR (nuclear magnetic resonance) measurements have been performed to investigate the local electronic structure of a superconducting graphite intercalation compound $CaC_6$ ($T_c$ = 11.4 K). A large number of single crystals were stacked and sealed in a quartz tube for naturally abundant $^{13}C$ NMR. The spectrum, Knight shift, linewidth, and spin-lattice relaxation time $T_1$ were measured in the normal state as a function of temperature down to 80 K at 8.0 T perpendicular to the c-axis. The $^{13}C$ NMR spectrum shows a single narrow peak with a very small Knight shift. The Knight shift and the linewidth of the $^{13}C$ NMR are temperature-independent around, respectively, +0.012% and 1.2 kHz. The spin-lattice relaxation rate, $1/T_1$, is proportional to temperature confirming a Korringa behavior as for non-magnetic metals. The Korringa product is measured to be $T_1T\;=\;210\;s{\cdot}K$. From this value, the Korringa ratio is deduced to be $\xi$ = 0.73, close to unity, which suggests that the independent-electron description works well for $CaC_6$, without complications arising from correlation and many-body effects.