• Korean Journal of Optics and Photonics
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• v.13 no.1
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• pp.73-78
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• 2002

We have investigated the lasing characteristics of intracavity second harmonics of a Nd:YAG laser pumped by a laser diode. Through the analysis of the scalings of laminar phases, we verify that the second harmonics are generated through on-off intermittency. The intermittent behavior can be reproduced by a numerical simulation with rate equations.

• Korean Journal of Optics and Photonics
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• v.12 no.6
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• pp.496-502
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• 2001

We generated a nondiffracting beam and investigated its intensity profile on propagation. We first obtained an annular output beam from Nd:YAG laser with a negative branch unstable ring resonator and, using a 1m focal length lens, we generated a Bessel- Gauss beam. The inner radius of the annular output beam was 2.57 mm and the ring width was 0.145 mm. The intensity profile of the nondiffracting beam did not show any appreciable diffraction up to 33 m distance from the focal lens. This result was compared with the theory.

• Korean Journal of Optics and Photonics
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• v.13 no.1
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• pp.70-72
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• 2002

Amplified pulsed laser beam with narrow linewidth was generated from CW laser beam with narrow linewidth by using frequency doubled Nd:YAG laser beam and Bethune cell. The degree of the frequency chirping of the amplified pulse laser was measured by using the heterodyne method and obtained by calculating instantaneous phase change from heterodyne beating signals. The frequency chirping of amplified pulsed laser beam from CW laser beam with sub-MHz linewidth by 10 ns pulse was 80 MHz so that pulsed laser beam with very narrow linewidth was obtained.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.69.2-69.2
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• 2011

The discovery of dark energy from Type Ia supernovae (SN Ia) is based on the implicit assumption that the look-back time evolution of SN Ia luminosity, after light-curve corrections, would be negligible. A strong support for this assumption was the apparent insensitivity of SN Ia distances across the host galaxy morphologies. However, Hicken et al. 2009 (H09) shows a systematic difference in the Hubble residual (HR) of $0.144{\pm}0.070$ mag between the E-S0 and Scd/Sd/Irr galaxies, after light-curve corrections. If true, this indicates that the light-curve fitters used by the SN Ia community can not correct for the population age (and therefore the evolution) effect. In order to confirm this, we have combined nearby SN Ia samples and the first-year SDSS-II SN Survey. The SNANA package was used for analyzing SN Ia light-curve, both for the MLCS2k2 and SALT2 fitters. We find a systematic difference in the HR of $0.10-0.13{\pm}0.030$ mag between E-S0 and Scd/Sd/Irr galaxies, which is in agreement with the result of H09, but now at the 3-5 ${\sigma}$ level. Considering the significant difference in the mean age of stellar population between these morphological types, the difference in the HR reported here suggests that the evolution effect of SN Ia luminosity should be considered in the cosmological application of SN Ia data.