• Journal of the Optical Society of Korea
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• v.6 no.3
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• pp.59-71
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• 2002

Photonic band gap structures have a high potential for nearly zero-threshold lasers. This paper describes new-types of low-threshold photonic crystal lasers fabricated in InGaAsP slab waveguides free-standing in air. Two-types of photonic crystal lasers are studied. One is a single-cell nano-cavity laser formed in a square array of air holes. This photonic band gap laser operates in the smallest possible whispering gallery mode with a theoretical Q >30000 and exhibits low threshold pump power of 0.8 mW at room temperature. The nther laser does not have any cavity structure and the lasing operation originates from the enhanced optical density of states near photonic band edges. A very low threshold of 35 $\mu$W (incident pump power) is achieved from this laser at 80 K, one of the lowest values ever reported. This low threshold is benefited from low optical losses as well as enhanced material gain at low temperature.

• Korean Journal of Optics and Photonics
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• v.16 no.4
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• pp.366-375
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• 2005

A fabrication process of periodic electric field assisted poling of Ti-diffused channel waveguides in LiNbO3 (Ti:PPLN) has been developed and improved using a periodic 180o phase inversion along the z-axis. The zig for poling inversion and the Labview program of charge control have been devised. Pulse high voltage and duty cycle were adjusted based on the estimated charge required for poling inversion. Monitoring the change of leakage current under applied voltage less than the coercive voltage also minimized a breakdown.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.391-394
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• 2003

Laser direct writing process is developed 3rd harmonic Diode Pumped Solid State Laser with the near visible wavelength of 355 m sensitive polymer is irradiated by UV laser and developed using polymer solvent to obtain quasi-3D. It is important to reduce line width for image mode waveguides, so some investigations will be carried out in various conditions of process parameters such as laser power, writing speed, laser focus and optical properties of polymer. This process could be to fabricate a single mode waveguide without expensive mask projection method. Experimentally, the patterns of trapezoidal shape were manufactured into dimension of 8.4 mm width and 7.5 mm height. Propagation loss of straight waveguide measured 3 dB/cm at 1,550 nm.

• Korean Journal of Optics and Photonics
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• v.13 no.1
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• pp.21-26
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• 2002

In the conventional star coupler, a certain amount of loss should be expected because lateral diffraction is used for the power distribution. In this paper, we propose a new design of a low loss star coupler which employs UV-written tapered waveguides and an AWG based on the low loss star couplers, and investigate their various characteristics. The loss of the UV-written star coupler is lower than that of the conventional star coupler, and the AWG device based on the UV-written star couplers shows low loss characteristics.

• Korean Journal of Optics and Photonics
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• v.7 no.3
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• pp.272-279
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• 1996

A simple transfer matrix algorithm to analyze the properties of 2 dimensional waveguides is introduced. We applied this algorithm to strained InGaAs/InGaAsP GINSCH MQW laser structures. We studied how optical confinement factor and effective refractive index, which are important in calculating the modal gain, depend on the structure parameters such as waveguide width, shape of GRIN, and number of quantum wells. Especially we suggested that the concept of effective waveguide width is very useful in understanding the GRINSCH waveguide.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.123-126
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• 2004

We have demonstrated the fabrication of patterned 3D photonic crystals by holographic lithography in conjunction with soft lithography. Holographic lithography created 3D ordered macroporous structures and soft lithography made tailored defects. Because the hard baked photoresist pattern possessed high resistance against the uncured photoresist solution and the refractive index did not change appreciably by hard baking, a crosslinked photoresist was used as a relief pattern for the holographic fabrication of patterned 3D photonic crystals. More complicated defect geometries might be easily obtained with more complicated patterns on PDMS stamps. Moreover, the present results might be used as templates for 3D PCs of highindex defects that can be exploited as optical waveguides and optical circuits.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.1
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• pp.72-78
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• 1998

Polarization mode converters have been produced by utilizing Ti:LiNbO$_{3}$ channel waveguide and strain-optic effect. Shear strain for periodic perturbations of optical channel waveguides and phase matching can be obtained by an evaporated periodic SiO$_{2}$ thin film at 300.deg. C. The electrodes located on the either side of waveguide provide a means to electro-optically tune the wavelength for maximum polarization conversion via the electrooptic effect. The maximum conversion effeciency was observed at 21.deg. C for V=0 and 46.deg. C for V=30V aro the device having 7 .mu.m waveguide wiith and 350 periodic pads. The dependence of the number of pads on conversion efficiency was observed experimentally.fficiency was observed experimentally.

• Journal of the Optical Society of Korea
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• v.15 no.4
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• pp.398-402
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• 2011

In this paper, we have proposed a principle to design wideband, low dispersion and temperature stabilized slow light structure in slotted photonic crystal waveguide (SPCW). The infiltration of the silicon photonic crystal with polymer will enhance the slow light and increase the group index, whereas the different signs of thermo-optic coefficients of polymer and silicon make the proposed structure stable on temperature variation over $60^{\circ}C$ and improves the group index-bandwidth products of the designed structure. The SPCW structure is modified to maximize the slow light effect and minimize the dependence of the group index and hence the group velocity dispersion to temperature.

• Journal of the Optical Society of Korea
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• v.12 no.1
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• pp.13-18
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• 2008

We numerically investigate by the finite-difference time-domain method the effects of surface termination on directional emission exiting a photonic crystal waveguide. The directed power and far-field beam profile for the original proposal [E. Moreno et al., Phys. Rev. B 69, 121402 (2004)] and its enhancement [S. K. Morrison et al., Appl. Phys. Lett. 86, 081110 (2005)] are computed for different values of some important parameters. We find another surface termination condition with a positive surface displacement in the structure of the original proposal which has a negative surface displacement. Our surface termination is more effective than the original structure, and nearly as effective as the termination for the enhancement, for directional emission. Besides, our termination is simpler than that for the enhancement. We confirm the effectiveness of directional emission from our termination in its far-field beam profile, radiation intensity distribution, and additionally the wave-vector space representation by the Fourier analysis.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.4
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• pp.87-93
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• 1997

An electro-optic polymer digital optical switch with a coupling region modified for optimum mode coupling is proposed, and it is analyzed by using the beam propagation method combined with the effective index method. Its modified coupling region is adiabatically introduced along the propagation direction from the branching point of the two waveguides. The structure of the modified coupling region and its refractive index profiles are designed to optimize the mode coupling in the Y-branch waveguide. Therefor, the switching performance of the device may be enhanced with a fixed device length. It is confirmed from the numerical calculation that the drive voltage is reduced by more than 30 percents and te crosstalk is improved by about 8dB.