• Journal of the Optical Society of Korea
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• v.5 no.4
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• pp.131-135
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• 2001

We report experiemtnal results demonstrating the electromagnetically induced transparency (EIT) in trapped Cs atoms. EIT occurs at the Λ-type configuration where the re0-pumping laser simultaneously plays a role as the coupling laser in the presence of a magneto-optical trapping and weak magnetic fields. Dependences of EIT signal on both the intensity and the detuning of the coupling laser were investigated. Linear absorption spectra for cold cesium atoms in the magneto-optical trap have been observed and shown the pronounced dispersion-like structure with sub-natural linewidth of 1 MHz due to the cooling laser.

• Korean Journal of Optics and Photonics
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• v.5 no.2
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• pp.260-265
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• 1994

In the three-level atom interacting with a single mode radiation field, two-photon excitation between the ground state and the upper most excited state is investigated. Using the resolvant theory, the effective resolvant, containing the ground state and the final excited state, is found and the coupling constant and the detuning being taken as parameters, the excitation mechanism is analyzed. In particular. by introducing an ensemble of effective two-level atoms, a consistent interpretation in terms of inteference phenomena is pursued. rsued.

• Proceedings of the Optical Society of Korea Conference
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• 2009.10a
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• pp.359-360
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• 2009

This paper reports experimental results on temporal characteristics of injection-locked polarization switching of a conventional type 1.55-${\mu}m$ wavelength single-mode vertical-cavity surface-emitting laser (VCSEL). The polarization of external injection beam was kept orthogonal to main mode of VCSEL. The relation for variation of intensity of two polarization modes of VCSEL with wavelength detuning for various repetition rates of injection pulse is reported.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.4
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• pp.811-815
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• 2005

We theoretically studied synchronization of chaotic oscillation in semiconductor lasers with chaotic light injection feed-back induced chaotic light generated from a master semiconductor laser was injected into a solitary slave semiconductor laser. The slave laser subsequently exhibited synchronized chaotic output for a wide parameter range with strong injection and frequency detuning within the injection locking scheme. We also analytically examined chaos synchronization based on a linear stability analysis from the view point of synchronization based on a linear stability analysis from the view point of modulation response of injection locked semiconductor lasers to chaotic light signal.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.1
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• pp.67-73
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• 1996

Subsynchronous resonance(SSR) causes a torsional shaft torque on the generator. Damages resulting from the uncontrolled SSR have resulted in the breakdown in the shaft and costs for replacement power. This paper is to determine the feasibility of controlling SSR by the fast modulation of series compensation capacitors. The presence of subsynchronous currents in the system was detected by a subsynchronous relay which was modeled by the transient analysis of control systems(TACS) in electromagnetic transients program (EMTP). The capacitor segments were switched by bi-directional thyristor switches. These were modeled into EMTP. The strategy to switch the capacitors were modeled as a closed loop system. The paper proves that effective control of SSR can be obtained only by the detuning of the system and the removal or blocking of subsynchronous energy from the system. (author). refs., figs., tabs.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.434-436
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• 1995

This paper was to determine the feasibility of controlling subsynchronous resonance(SSR) by the fast modulation of series compensation capacitors. The presence of subsynchronous currents in the system was detected by a subsynchronous relay which was modeled by the transient analysis of control systems (TACS) in the electromagnetic transients program (EMTP). The capacitor segments were switched by bi-directional thyristor swtiches. The paper proved that effective control of SSR can be obtained only by the detuning of the system and the removal or blocking of subsynchronous energy from the system.

• The Journal of Natural Sciences
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• v.12 no.1
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• pp.23-30
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• 2002

Atomic coherences induced by the interaction with light provide new physical properties and optical phenomena. Even though two-photon resonances play important roles in build-up of atomic coherences, only approximate formula for two-photon resonance condition has often been used. In this paper, we present the more accurate two-photon resonance condition and confirm it using numerical simulation. We also studied the effects of laser frequency detuning and intensity on the two-photon resonance .

• Korean Journal of Optics and Photonics
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• v.2 no.4
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• pp.197-202
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• 1991

The real time autocorrelator has been developed in order to measure the pulse widths of ultrashort laser pulses using the SHG method. The scanning range of the autocorrelator is 142 ps, and inserting a delay block in one arm of the autocorrelator, the scanning range can be extended to 250 ps. The shortest pulse width was measured to be 20 ps, when the cavity length was well matched to the RF frequency of the mode-locker, and broadened to be 39 ps and 47 ps as the cavity length was detuned.

• Bulletin of the Korean Chemical Society
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• v.17 no.2
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• pp.188-192
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• 1996

It is shown that the inversion of the undamped Bloch equation for an amplitude-modulated broadband π/2 pulse can be precisely treated as an inverse scattering problem for a Schrodinger equation on the positive semiaxis. The pulse envelope is closely related to the central potential and asymptotically the wave function takes the form of a regular solution of the radial Schrodinger equation for s-wave scattering. An integral equation, which allows the calculation of the pulse amplitude (the potential) from the phase shift of the asymptotic solution, is derived. An exact analytical inversion of the integral equation shows that the detuning-independent π/2 pulse amplitude is given by a delta function. The equation also provides a means to calculate numerically approximate π/2 pulses for broadband excitation.

• Korean Journal of Optics and Photonics
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• v.15 no.4
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• pp.375-384
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• 2004

Switching phenomenon of a three-waveguide optical coupler was analyzed by using the coupled mode theory, and the coupling-length of the device was calculated by means of the FDM. CPW traveling-wave electrodes were designed by the CMM and SOR simulation techniques so as to satisfy the conditions of phase-velocity and impedance matching. Traveling-wave modulators were fabricated on a z-cut LiNbO$_3$ substrate. Ti was in-diffused in LiNbO$_3$ to make waveguides and Au electrodes were built on the waveguides by the electroplating technique. Insertion loss and switching voltage of the optical modulator were about 4 ㏈ and 15.6V. Network analyzer was used to obtain S parameters and corresponding RF response. From the measurement, parameters of the traveling-wave electrodes were extracted as such Z$_{c}$=39.2 $\Omega$, Neff=2.48, and a0=0.0665/cm((GHz) (1/2)). The measured optical response R(w) was compared with the theoretically estimated and both responses were shown to agree well. The measurement results revealed that the ㏈ bandwidth turned out to be about 13 GHz.