• Korean Journal of Optics and Photonics
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• v.11 no.3
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• pp.202-205
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• 2000

One step thermal potassium ion exchange process was carried out to form optical channel waveguides in an ErNb co-doped phosphate glass. Flowing oxygen gas into KN03 melt during ion exchange was effective to prevent glass surface damage that causes an increase of waveguide propagation loss. Amplification characteristics of the waveguides were evaluated at $1.5{\mu}m$ signal wavelength with 980 om laser diode pump. A 45 mm long waveguide whose processing parameters had been optimized exhibited a small signal net gain of 7.5 dB at the launched pump power of 160 mW.160 mW.

• Korean Journal of Optics and Photonics
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• v.23 no.3
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• pp.124-127
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• 2012

We designed and fabricated dichroic filters for high-power fiber lasers to protect the pumping laser diode from counterpropagating laser beams. The transmittance at laser diode wavelengths of 905 nm~925 nm was designed to be less than 0.1% and the transmittance at the fiber laser or Brillouin scattering wavelengths of 1020 nm ~ 1100 nm was designed to be more than 99.9%. Since oxide materials have good adhesion to the $SiO_2$ substrate, $SiO_2/Ta_2O_5$ were used as coating materials. The filter was fabricated according to our optimized design and its characteristics were compared with the theoretical design. As a result, the transmittance at laser diode wavelengths of 905 nm~925 nm was measured to be less than 0.1%, and the transmittance at the fiber laser or Brillouin scattering wavelengths of 1020 nm~1100 nm was measured to be more than 95.5%, which coincided well with the theoretical design considering processing errors. The filter was found to operate well over 1W of input laser power.

• Journal of the Optical Society of Korea
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• v.6 no.2
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• pp.48-54
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• 2002

Experimental study is performed on flashlamp-pumped Ti: sapphire lasers with single, double, and four-partial-ellipse-pump cavities aiming at improving the performance of the lasers. The output energy of 604 mJ per pulse with a width of 25 $\mu$s at a total laser efficiency of 0.13% is achieved in the laser pumped by a light pulse of 45$\mu$s without a fluorescent converter The laser output energy versus its Ti: sappy ire rod length, pumping-light pulse duration, and electrical input energy are discussed with or without using a fluorescent converter. The result shows that much more output energy is obtained il a longer Ti: sapphire-rod laser pumped by a shorter light pulse when its output coupler has an optimized transmittance. In addition, an enhancement of output energy by a factor of 7 is achieved. in the laser using a fluorescent converter LD490.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.581-586
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• 2009

Knowledge of ground thermal properties is most important for the proper design of large scale BHE(borehole heat exchanger) systems. The type, pipe size and thermal performance of the BHE is highly dependent on the ground source heatpump system-efficiency and instruction cost. Thermal response tests with mobile measurement devices were developed primarily for insitu determination of design data for large diameter BHE for triple-U spacer apply. The main purpose has been to determine insitu values of effective ground thermal conductivity and thermal resistance, including the effect of ground-water flow and natural convection in the boreholes. The test rig is set up on a some trailer, and contains a circulation pump, a inline heater, temperature sensors, flow meter, power analysis meter and a data logger for recording the temperature, fluid flow data. A constant heat power is injected into the borehole through the tripl-U pipes system of test rig and the resulting temperature change in the borehole is recorded. The recorded temperature data are analysed with a line-source model, which gives the effective insitu values of rock thermal conductivity and borehole thermal resistance of large diameter BHE for spacer apply.

• Current Optics and Photonics
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• v.2 no.6
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• pp.582-588
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• 2018

A $Nd:YVO_4$ laser dual-end-pumped by a wavelength-locked 878.6 nm laser diode is presented. At the repetition rate of 500 KHz, the absorbed pump power of 58 W, an output power of 26.1 W at 1064 nm is obtained, corresponding to an optical-optical efficiency of 45%. The pulse width is 44.2 ns. Meanwhile, the effects of traditional 808 nm pumping and 878.6 nm dual-end-pumping on the output laser beam quality and pulse width are compared and analyzed in an experiment.

• Korean journal of applied entomology
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• v.47 no.3
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• pp.287-292
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• 2008

Repellent and acaricidal activities of eucalyptus oil, permethrin, and DEET against Leptotrombidium pallidum larvae, which are a vector transmitting tsutsugamushi disease, were evaluated under laboratory conditions using a filter paper impregnated method. The $LD_{50}$ values of eucalyptus oil and DEET were 0.025 and 0.018 $mg/cm^2$, respectively while that of permethrin was higher than 0.2 $mg/cm^2$. In the repellency test of these materials at 6.14 $mg/cm^2$, eucalyptus oil gave complete repellency, and the larvae crossed the treated zone killed. But permethrin showed 60% repellency at 9.20 $mg/cm^2$ and the mites croosed the zone were not killed. The percent repellency of DEET at 0.53 $mg/cm^2$ was 8.3 and 2.8 times higher than that of permethrin and eucalyptus oil, respectively. The acaricidal activities of emulsifiable concentrates-pump sprayers containing the eucalyptus oil as an active ingredient were assayed. The emulsifiable concentrates containing 1% and 3% eucalyptus oil showed weak mortality at 1 hour after treatment, while all ones containing more than 6% oil produced 100% activity against L. pallidum larvae. The mortality also increased as exposure time to the concentrates increase. These results suggest that the potential of eucalyptus oil highly expected to be used as a control or repellent agent against L. pallidum larvae may be very high.