• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.8
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• pp.1833-1841
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• 1997

Rectangular dielectric waveguides, the most fundamental and indispensible elements in integrated optics, have been investigated by many researchers with various approaching methods including from the relatively approximate techniques to the numerical method. In this paper, the optimum equivalent waveguide model is adopted which is determined by a perturbation feedback process for analyzing the propagation constant by means of computer simulation, we have ascertained that the propagation constant from perturbation feedback method gives the best approximate value because it coincide with more exact value than obtained by other approximating methods. The technique also provides analytical expression for the modal field profile that should be useful in the design of various integrated optical devices.

• 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.

• Korean Journal of Optics and Photonics
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• v.17 no.5
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• pp.469-474
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• 2006

A $1{\times}16$ thermo-optic switch with small excess loss using multimode interference(MMI) couplers is designed, fabricated, and measured. This paper introduces the proposed $1{\times}16$ thermo-optic switch, and discusses the measurement results. The $1{\times}16$ thermo-optic switch is farmed as 4-stage which consists of 15 unit devices. The unit devices are the $2{\times}2$ thermo-optic switches with Mach-Zehnder interferometer(MZI) structure. The characteristics of the $1{\times}16$ thermo-optic switch depends strongly on each unit device. The unit deviceconsists of two 3-dB general interference MMI couplers and two single mode waveguide arms as a phase shifter. First of all, the 3-dB optical splitter and $2{\times}2$ MZI thermo-optic switch have been tested to confirm the characteristics of the unit devices of the $1{\times}16$ MZI thermo-optic switch. Using the measurement results of the unit devices, the $1{\times}16$ MZI thermo-optic switch can be produced with better characteristics. The resultant structure of the MMI coupler with the optical light source of wavelength of 1550nm for the $1{\times}16$ thermo-optic switch is that the width and the optimized length are $25{\mu}m\;and\;1580{\mu}m$, respectively. The smallest excess loss fur the unit device is -0.5dB and the average excess loss is -0.7dB.

• International Journal of Vascular Biomedical Engineering
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• v.4 no.2
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• pp.1-6
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• 2006

Microsystems create new opportunities for conventional cell analysis by combining microfluidics and flow cytometry. This article describes recent developments in conventional flow cytometers and related microfluidic flow cytometers to detect, analyze, and sort cells or particles. Flow cytometry strongly consisted of fluidics, optics and electronics requires a large space to equip various components, which are mostly the fluidic components such as compressor, fluid handling system. Adopting microfluidics into flow cytometry enables volume- and power-efficient, inexpensive and flexible analysis of particulate samples. In this paper, we review various efforts that take advantage of novel techniques to build microfluidic cell analysis systems with high-speed analytical capability. Highly integrated microfluidic cytometry shows great promise for basic biomedical and pharmaceutical research, and robust and portable point-of-care devices could be used in clinical settings.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.408-410
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• 2009

First demonstrators of bi-directional OLED microdisplay devices have been developed and integrated into see-through HMD optics. The device combines 'display' and 'imaging' by nested OLED pixels and photodetectors in a single CMOS chip. Major aim of this integration is to provide capabilities for eyetracking to achieve gaze-based human-displayinteraction.

• Korean Journal of Optics and Photonics
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• v.27 no.5
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• pp.174-180
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• 2016

A tunable optical delay line is designed, fabricated, and characterized. The tunable delay line consists of four polymer-ring add/drop filters with delay waveguides between adjacent ones. The polymer waveguide is a buried structure, designed to be square with core width and height of $1.8{\mu}m$. The refractive indices of the core and cladding polymer are 1.48 and 1.37 respectively. The large index difference and small cross section of the waveguide enable us to realize a compact device using a small radius of curvature. Four pairs of electrodes are evaporated above the add/drop filters to provide heating currents for thermal tuning. In measurements we can identify variable time delays of 110, 225, and 330 ps in proportion to the number of delay lines.

• Korean Journal of Optics and Photonics
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• v.19 no.3
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• pp.224-228
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• 2008

A highly sensitive integrated photonic temperature sensor was proposed and developed incorporating a polymeric microring resonator. The change in the ambient temperature was estimated by observing the shift in the resonant wavelength of the resonator induced via the thermooptic effect. For the purpose of enhancing its sensitivity, the sensor was built by implementing a polymeric resonator exhibiting a high thermooptic coefficient on a silicon substrate with a small coefficient of thermal expansion. For the range of from $20^{\circ}C$ to $30^{\circ}C$ near the room temperature, the fabricated sensor yielded a sensitivity of as high as 165 ${\pm}/^{\circ}C$ and a resolution of better than $0.1^{\circ}C$. And its performance was found to be hardly affected by the variation in the refractive index of the target analyte, which was applied to the surface of the sensor. It is hence expected that the sensor could be integrated with other refractormetric optical sensors, thereby compensating for the fatal error caused by the change in the ambient temperature.

• Korean Journal of Optics and Photonics
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• v.10 no.4
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• pp.342-347
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• 1999

As the waveguide width and the radius of curvature get smaller for the effort of monolithic fabrication of integrated photonic devices, the waveguide characteristics change significantly according to the change of the waveguide width or the radius of curvature. Especially, variation of the waveguide width due to fabrication process errors induces a phase error for each waveguide from the change of the propagation constant. Therefore, it is important to quantify these variation effects on the device characteristics for the design and fabrication of highly integrated photonic devices. Here, we analyze four different types of waveguides to get general characteristics in propagation constant change by utilizing the effective index method and the analytic solution method. Futhermore, the output characteristics of two AWG(Arrayed Waveguide Grating) devices are simulated by a highly-functional computer code. The simulated results have been found to be similar to the realistic device characteristics. The required fabrication error limit for the ridge-type InP-AWG device should be smaller than 0.02 ${\mu}{\textrm}{m}$ to get better channel crosstalk than-25 dB, while the required fabrication error limit for rib-type silica-AWG devices may be allowed up to 0.1 ${\mu}{\textrm}{m}$ to obtain better crosstalk than -30 dB.

• Korean Journal of Optics and Photonics
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• v.16 no.5
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• pp.469-475
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• 2005

An integrated photonic microwave bandpass filter has been proposed and demonstrated incorporating a coherently coupled microring resonator in low-loss polymers. The proposed device may feature compact site, simple structure, tuning via the thermooptic and electrooptic effect, and flexible integration with other electrical and optical devices. The resonator was designed to have an extremely small bandwidth so that it could be used to selectively pass the optical signal carrying the microwave signal to attain efficient bandpass filtering. We made and tested two resonators with a single ring and double rings, and performed a theoretical fitting of their measured transfer curves to predict the performance of the microwave filters based on them precisely. It was found that as the number of the rings used for the resonator increases, the bandwidth gets smaller, the rolloff sharper, and the band rejection higher. Finally our filter exhibited the center frequency of 10GHz, the 3-dB bandwidth of 1.0GHz, the corresponding quality (Q) factor of 10, and the rejection outside of the passband of more than 25dB.

• Korean Journal of Optics and Photonics
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• v.13 no.1
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• pp.32-37
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• 2002

Passive polarization mode splitters at λ= 1.55 ${\mu}{\textrm}{m}$ were designed and fabricated based on Ti:x-cut LiNbO$_3$ single-mode optical waveguide and two-mode interference theory. The splitting ratio with waveguide width 8 ${\mu}{\textrm}{m}$, branching angle 0.55$^{\circ}$ and interfering length 470 ${\mu}{\textrm}{m}$ showed 16.18 dB, 21.25 dB for TE and TM input polarization modes, respectively. Polarization cross-talk of -16.28 dB and -21.28 dB for TE and TM modes was achieved. Total insertion losses of 2.24 dB/cm (TE) and 2.41 dB/cm (TM) were also measured. The devices operated nearly wavelength independently over a range or 30 nm.