Kyong Hon Kim

Inha University, Sŏul, Seoul, South Korea

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Publications (110)122.76 Total impact

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    ABSTRACT: We demonstrate a compactly integrated polarization beam splitter (PBS) with high polarization extinction ratios greater than 20 dB over the full C-band wavelength range based on a simple bridged silicon nanowaveguide directional coupler. The PBS device is designed via three dimensional finite-difference time-domain (3D-FDTD) simulation, and fabricated experimentally. The optimum dimension of the bridge waveguide is determined to be 7.5-μm-long and 500 nm-wide for 250-nm thick silicon core. At the 1,550-nm wavelength, the measured polarization extinction ratios (PERs) of the PBS device are 22.5 dB and 22.9 dB for TE and TM polarization modes, respectively, and its corresponding insertion losses (ILs) are about 2.1 dB and 1.8 dB, both PERs and ILs within the maximum error range of ± 2.0 dB.
    Optics Express 01/2015; 23(2):998. DOI:10.1364/OE.23.000998 · 3.53 Impact Factor
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    ABSTRACT: Enhanced four-wave-mixing (FWM) effects have been observed with the help of large group-indices near the band edges in one-dimensional (1-D) silicon photonic crystal waveguides (Si PhCWs). A significant increase of the FWM conversion efficiency of about 17 dB was measured near the transmission band edge of the 1-D PhCW through an approximate 3.2 times increase of the group index from 8 to 24 with respect to the central transmission band region despite a large group-velocity dispersion. Numerical analyses based on the coupled-mode equations for the degenerated FWM process describe the experimentally measured results well. Our results indicate that the 1-D PhCWs are good candidates for large group-index enhanced nonlinearity devices even without having any special dispersion engineering.
    Optics Express 12/2013; 21(24):30019-29. DOI:10.1364/OE.21.030019 · 3.53 Impact Factor
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    ABSTRACT: Single-longitudinal-mode (SLM) operation characteristics of an erbium-doped fiber (EDF) ring laser with an EDF saturable absorber have been measured and compared under two different-wavelength control-pump cases. The main EDF ring cavity was pumped with a conventional 977-nm-wavelength gain-pump laser diode, the EDF saturable absorber section attached to the main cavity via an optical circulator was pumped with a control-pump-laser beam of either 980-nm or 1531.9-nm wavelength to deliver the ring-laser output of 1541.4-nm wavelength. Our experimental results indicate that the control-pump-laser beam in the 1530-nm-wavelength region provides higher output power and wider wavelength range of the SLM operation of the ring laser than that in the 980-nm-wavelength region does.
    Optics Communications 11/2013; 308:15-19. DOI:10.1016/j.optcom.2013.06.008 · 1.54 Impact Factor
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    ABSTRACT: We present an experimental and numerical study of spectral profiles of effective group indices of hydrogenated amorphous silicon (a-Si:H) waveguides and of their chromatic-dispersion effect on the four-wave-mixing (FWM) signal generation. The a-Si:H waveguides of 220-nm thickness and three different widths of 400, 450 and 500 nm were fabricated by using the conventional CMOS device processes on a $2-{\mu}m$ thick $SiO_2$ bottom layer deposited on 8-inch Si wafers. Mach-Zehnder interferometers (MZIs) were formed with the a-Si:H waveguides, and used for precise measurement of the effective group indices and thus for determination of the spectral profile of the waveguides' chromatic dispersion. The wavelength ranges for the FWM-signal generation were about 45, 75 and 55 nm for the 400-, 450- and 500-nm-wide waveguides, respectively, at the pump wavelength of 1532 nm. A widest wavelength range for the efficient FWM process was observed with the 450-nm-wide waveguide having a zero-dispersion near the pump wavelength.
    Journal of the Optical Society of Korea 10/2013; 17(5). DOI:10.3807/JOSK.2013.17.5.433 · 0.96 Impact Factor
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    ABSTRACT: We have demonstrated an actively Q-switched single-longitudinal-mode (SLM) erbium-doped fiber (EDF) ring laser by using an EDF saturable absorber modulated under an external laser pulse injection. A laser output of 1531.9 nm wavelength from a distributed-feedback laser diode was amplified with an EDF amplifier and modulated with an external electro-optical modulator, and the modulated signals were used as control pulses to saturate the EDF saturable absorber for the actively Q-switched ring-type fiber laser operation. Actively Q-switched 1542 nm wavelength laser pulses of 4.5 nJ pulse energy and of 4.0μs pulse width were achieved at a repetition rate of 100 Hz. When the Q-switched laser pulse energy was reduced to about 0.54 nJ by decreasing the gain-pump power used for exciting the ring cavity and the control-pulse beam power used for bleaching out the saturable absorber, the SLM laser pulses were achieved. Further improvement of the Q-switched SLM laser pulse output can be achieved simply by using an external laser amplifier and by shortening the cavity length with short pigtailed-fiber laser components, and thus the SLM laser pulses can be useful for various applications.
    Laser Physics 08/2013; 23(9):095107. DOI:10.1088/1054-660X/23/9/095107 · 1.03 Impact Factor
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    ABSTRACT: We report on experimental measurements of the signal-wavelength conversion efficiency through the four-wave-mixing (FWM) process in a silicon strip nanowaveguide (SiNW) compared with theoretically-calculated results. The conversion efficiency has been investigated as a function of various parameters, such as the pump power and the pump and signal wavelengths. The measured and the calculated results indicate that a significant variation of the chromatic dispersion (CD) of our test SiNW device among the pump, signal and idler beam wavelengths and a high insertion loss in the device cause a very low FWM conversion efficiency. Our simulation tool can provide a direction for further improvement in the waveguide design by providing optimized CD values for the SiNW in desired ranges of the operation wavelengths.
    Journal- Korean Physical Society 02/2013; 62(3). DOI:10.3938/jkps.62.428 · 0.43 Impact Factor
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    ABSTRACT: Direct coupled-mode beam propagation analysis in the silicon-based one-dimensional photonic crystal waveguides (1D-PhCW) has been performed to explain the group-velocity-dependent enhanced four-wave-mixing (FWM) effect and to evaluate the sectional contribution of the 1D-PhCW part and its side-coupled strip waveguide parts for the FWM effect. The analyzed results indicate that the high group-index profile near the bandedge of the 1D-PhCWs provides a significantly enhanced FWM efficiency despite its high dispersion effect.
    Group IV Photonics (GFP), 2013 IEEE 10th International Conference on; 01/2013
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    ABSTRACT: We propose a simple white-light interferometric method of measuring a one-dimensional rotation angle with use of an optical plane parallel plate of standard refractive index. The phase change of the interference pattern of the interferometer during the rotation of the flat plate of known refractive index and thickness placed in one of the interferometer's arms is used for determination of the rotation angle. This method has been demonstrated for an accurate angle measurement over the angle range from 0° to 40° within a maximum uncertainty of 0.057°.
    Applied Optics 02/2012; 51(6):720-5. DOI:10.1364/AO.51.000720 · 1.69 Impact Factor
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    ABSTRACT: This paper presents our recent achievement with a simple white-light Mach-Zehnder (MZ) interferometric method to identify localized group velocity dispersion (GVD) coefficient or group delay dispersion (GDD) value of the nanostructured silicon waveguide devices (NSWDs). Conventional methods of measuring the GVD of optical fibers or waveguides are related to measurement of the total GVD of the entire fibers or NSWDs. Recently time-resolved heterodyne detection technique and the near-field scanning microscopy technique are demonstrated to measure localized group delay of the photonic crystal waveguides (PhCWs) devices, but the techniques have a limited group delay (GD) resolution depending on laser pulse-width used for the measurement. It is demonstrated that our white-light interferometric method can measure very accurate GDD value up to 0.5 fs/nm resolution. This method has been applied to determine not only the GVD or GDD profile of the entire NSWDs but also that of their localized structural sections, such as grating couplers and interface between the plain strip waveguide and single line-defect (W1) PhCW.
    Proceedings of SPIE - The International Society for Optical Engineering 02/2012; DOI:10.1117/12.910987 · 0.20 Impact Factor
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    ABSTRACT: We review the temporal dynamics of the laser output spectrum and polarization state of 1.55 μm wavelength single-mode (SM) vertical-cavity surface-emitting lasers (VCSELs) induced by external optical beam injection. Injection of an external continuous-wave laser beam to a gain-switched SM VCSEL near the resonance wavelength corresponding to its main polarization-mode output was critical for improvement of its laser pulse generation characteristics, such as pulse timing-jitter reduction, linewidth narrowing, pulse amplitude enhancement, and pulse width shortening. Pulse injection of pulse width shorter than the cavity photon lifetime into the SM VCSEL in the orthogonal polarization direction with respect to its main polarization mode caused temporal delay of the polarization recovery after polarization switching (PS), and its delay was found to be the minimum at an optimized bias current. Polarization-mode bistability was observed even in the laser output of an SM VCSEL of a standard circularly cylindrical shape and used for all-optical flip-flop operations with set and reset injection pulses of very low pulse energy of order of the 3.5~4.5 fJ.
    Advances in Optical Technologies 01/2012; 2012. DOI:10.1155/2012/247070
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    ABSTRACT: We report on a simple and direct method of measuring localized chromatic dispersion (CD) profiles of structured nanowaveguide devices using white-light interferometry. Phase change in the interference fringe of a white-light interferometer (WLI) caused by introducing a sample-under-test into one of the interferometer arms was used to determine a spectral profile of its accurate CD coefficients. This method was tested by measuring the spectral CD profiles of a localized silicon nanowaveguide and of a nonmembrane-type photonic crystal waveguide (PhCW) excluding their optical coupling sections. The measured local CD values of a 500-nm-wide single-line-defect (W1) PhCW with a lattice period of 460 nm and the hole radius of 165 nm formed on 220-nm-thick silicon layer of a silicon-on-insulator (SOI) wafer varied from 0.38 to 0.22 ps/(nm·cm) for a wavelength range from 1530 to 1570 nm. This method will be very useful in determining the accurate CD profiles of nanophotonic waveguide devices.
    Journal of Lightwave Technology 12/2011; 30(1):43-48. DOI:10.1109/JLT.2011.2177638 · 2.86 Impact Factor
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    ABSTRACT: We introduce a new measurement method of the nonlinear coefficient (NC) of a highly nonlinear fiber based on a four-wave mixing (FWM) technique. The NC along with the fiber's zero-dispersion wavelength (ZDW) was determined from the precise measurement of the pump power dependent optimum pump frequency for peak FWM signal generation conditions. The measurement errors of the NC and ZDW values determined with this method were less than 4.6% and 0.051nm, respectively.
    Optics Communications 09/2011; 284(19):4683-4686. DOI:10.1016/j.optcom.2011.05.041 · 1.54 Impact Factor
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    ABSTRACT: We present experimental and numerical study of temporal characteristics of injection-locked polarization switching of a conventional-type 1.55-μm wavelength single-mode vertical cavity surface-emitting laser (VCSEL). Delayed recovery response of the main-mode of the VCSEL was observed when short and strong optical injection pulses of an orthogonal polarization to the VCSEL's main polarization-mode were applied. Numerical analysis based on a spin-flip model describes that the relatively long upper level lifetimes compared to a short injection-pulse width and long cavity photon lifetimes cause delayed recovery response of the main-mode of the VCSEL. An optimum bias current of the VCSEL was also observed for the shortest recovery time of its free-running polarization mode after the orthogonal polarization beam pulse injection.
    Optics Express 08/2011; 19(18):16934-49. DOI:10.1364/OE.19.016934 · 3.53 Impact Factor
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    ABSTRACT: We report a white-light Mach-Zehnder interferometry method for an accurate measurement of spectral distribution of the chromatic dispersion coefficient of very short optical waveguides over a wavelength range of 1520~1560 nm. The chromatic dispersion curve of a 7.6 mm long silicon nano-waveguide of 400 nm width and 250 nm height was successfully measured by confirming the method with standard single-mode fibers up to 3 cm length, for which its total chromatic dispersion is as small as 0.51 fs/nm. This method will be very useful for determination of chromatic dispersion profile of compact nanowaveguide devices.
    Proceedings of SPIE - The International Society for Optical Engineering 02/2011; DOI:10.1117/12.874004 · 0.20 Impact Factor
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    ABSTRACT: Four-wave-mixing (FWM) efficiency of a silicon-based one-dimensional photonic crystal waveguide was measured along with its spectral profile of the group index. High FWM efficiencies were observed near the band edge compared to those at the middle sections of its transmission band despite its high dispersion effect.
    01/2011; DOI:10.1109/GROUP4.2011.6053811
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    ABSTRACT: All-optical set-reset flip-flop operations of conventional circular cylindrical-shaped 1.55-μm wavelength single-mode vertical-cavity surface-emitting lasers (VCSELs) have been demonstrated at a switching frequency of 1 GHz based on polarization bistability observed via injection current variation. The energy of set and reset pulses was lower than 4.5 fJ at a bias current of the VCSEL of 4 mA. Polarization bistable VCSELs will be useful for high-speed optical signal processing applications.
    IEEE Photonics Technology Letters 01/2011; 22(23-22):1759 - 1761. DOI:10.1109/LPT.2010.2078803 · 2.18 Impact Factor
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    ABSTRACT: We report the effect of an external injection laser wavelength on reducing the timing jitter of optical pulses generated from gain-switched single-mode 1.5-μm vertical cavity surface emitting lasers (VCSELs). Simultaneous timing jitter reduction, pulse width shortening, and spectral linewidth narrowing without any peak power penalty were observed when the injection laser wavelength was tuned near the spectral peak of the free-running VCSELs spectrum operating in a continuous wave mode. The timing jitter was reduced up to 40% of that without any injection.
    IEEE Journal of Quantum Electronics 10/2010; DOI:10.1109/JQE.2010.2046141 · 2.11 Impact Factor
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    ABSTRACT: We report simultaneous reduction of timing jitter and pulse width of gain-switched pulses from 1.55 μm-wavelength single-mode VCSELs with an external laser injection at its main and side modes of parallel and perpendicular polarizations, respectively.
    Photonics in Switching; 07/2010
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    ABSTRACT: This paper reports demonstration of a new simple white-light interferometry method for continuous dispersion curves of the thermo-optic (TO) coefficients of optical samples. Phase shifts of the interference spectra of the white-light interferometer output are measured by changing temperature of an optical sample located in the one of the interferometer arms. A continuous dispersion curve of the TO coefficient of the sample materials over the full wavelength coverage region of the white light beam is obtained from the phase shift information with the temperature change. This new method is tested with a fused silica glass material of well-known optical properties to prove its accuracy by comparing the measured results with its known TO coefficient values. This continuous dispersion information of the TO coefficients of new optical materials will be useful for fabrication of the WDM signal processing devices or functional devices in multi-wavelengths.
    Proceedings of SPIE - The International Society for Optical Engineering 02/2010; DOI:10.1117/12.842035 · 0.20 Impact Factor