• Bulletin of the Korean Chemical Society
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• v.24 no.8
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• pp.1075-1080
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• 2003

We have investigated femtosecond coherent vibrational motions of Zn(II)-5,15-diphenylporphyrin in toluene using chirp-controlled ultrashort pulses. The oscillatory features superimposed on the temporal profiles of the pump-probe transient absorption signal are affected by the chirping and energy of excitation pulses. Using chirp- and excitation energy-controlled femtosecond pulses, we are able to obtain information on the structural changes between the electronic ground and excited states based on a comparative analysis of the Fouriertransformed frequency-domain spectra retrieved from the oscillatory components with the ground state resonance Raman spectra and normal mode calculations.

• Journal of the Optical Society of Korea
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• v.14 no.4
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• pp.424-430
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• 2010

In coherent anti-Stokes Raman scattering (CARS) microscopy reported until now, conventional microscope objectives are used, so that they are limited for introduction into a living body. Gradient-index (GRIN) rod lenses might be a solution for miniaturized microscope objectives for in-vivo CARS microscopy. However, due to the inherent large amount of chromatic aberration, GRIN rod lenses cannot be utilized for this purpose. CARS imaging catheter, composed of miniaturized microscope objective and fiber bundle, can be introduced into a living body for minimally invasive diagnosis. In order to design the catheter, we have to first investigate design requirements. And then, the optical design is processed with design strategies and intensive computing power to achieve the design requirements. We report the miniaturized objective lens system with diffraction-limited performance and completely corrected chromatic aberrations for an in-vivo CARS imaging catheter.

• Journal of the Optical Society of Korea
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• v.1 no.1
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• pp.1-4
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• 1997

The theoretical limit of the noise correlation between the signal and idler outputs of a nondegenerate optical parametric amplifier (NOPA) with a coherent state signal and vacuum state idler input can be enhanced if a non-vacuum coherent state idler input is employed. By choosing a balanced signal and idler input, the noise correlation is $1/{({\root}g + {\root}{g-1})}^2$, where g is the intensity gain of the NOPA, and that is superior to the prediced outputs with single signal input by approximately 3dB. The result is applicable to all the schemes that use the NOPA to produce a sub-shot noise light generation such as feed-back or feed-forward control.

• Korean Journal of Optics and Photonics
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• v.31 no.6
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• pp.274-280
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• 2020

In this paper, the effect of atmospheric turbulence is numerically modeled and analyzed via a phase-screen model, in regard to long-range optical energy transfer using coherent beam combination. The coherent-beam-combination system consists of three channel beams pointing at a target at a distance of 1-2 km. The phase and propagation direction of each channel beam are assumed to be corrected in an appropriate manner, and the atmospheric turbulence that occurs while the beam propagates through free space is quantified with a phase-screen model. The phase screen is statistically generated and constructed within the range of fluctuations of the structure constant Cn2 from 10-15 to 10-13 [m-2/3]. Particularly, in this discussion the shape, distortion, and combining efficiency of the 3-channel combined beam are calculated at the target plane by varying the structure constant used in the phase-screen model, and the effect of atmospheric turbulence on beam-combination efficiency is analyzed. Analysis with this numerical model verifies that when coherent beam combination is used for long-range optical energy transfer, the received power at the target can be at least three times the power obtainable by incoherent beam combination, even for maximal atmospheric fluctuation within the given range. This numerical model is expected to be effective for analyzing the effects of various types of atmospheric-turbulence conditions and beam-combination methods when simulating long-range optical energy transfer.

• Proceedings of the Optical Society of Korea Conference
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• 2009.02a
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• pp.399-400
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• 2009

• Proceedings of the Optical Society of Korea Conference
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• 2007.07a
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• pp.31-32
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• 2007

• Proceedings of the Optical Society of Korea Conference
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• 2001.08a
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• pp.230-231
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• 2001

• Proceedings of the Optical Society of Korea Conference
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• 2006.02a
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• pp.101-102
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• 2006

• ETRI Journal
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• v.34 no.6
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• pp.800-806
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• 2012

Transmission performances of direct detection-based 100-Gb/s modulation formats are investigated and compared for metro area optical networks. The effects of optical signal-to-noise ratio sensitivity, chromatic dispersion, cross-channel nonlinearity, and transmission distance on the performance of differential 8-ary phase-shift keying (D8PSK), differential phase-shift keying plus three-level amplitude-shift keying (DPSK+3ASK), and dual-carrier differential quaternary phase-shift keying (DC-DQPSK) are evaluated. The performance of coherent dual-polarization quadrature phase-shift keying (DP-QPSK) with block phase estimation and coherent DP-QPSK with digital differential detection are also presented for reference. According to our analysis, all three direct detection modulation formats could transmit a 100-Gb/s signal over several hundred kilometers of a single-mode fiber link. The results also show that DC-DQPSK outperforms D8PSK and DPSK+3ASK, and the performance of DC-DQPSK is comparable to that of coherent DP-QPSK with digital differential detection. The maximum transmission distance of DC-DQPSK is over 1,000 km, which is enough distance for metro applications.

• Korean Journal of Optics and Photonics
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• v.15 no.3
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• pp.200-213
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• 2004

The realization of partially coherent Gaussian Schell-model beams with isotropic cross section and anisotropic degree of coherence function is investigated theoretically. An optical system is devised to transform diffused light generated by passing the Gaussian beam of the He-Ne laser thorough a rotating holographic diffuser to the partially coherent Gaussian Schell-model beam with isotropic cross section and anisotropic degree of coherence function. Analytic design equations are formulated and design examples are presented.