• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.3
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• pp.238-242
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• 1988

It is analyzed how performance of phase-locked loop driven by photodetector current in optical receiver will be changed under the condition that Gaussian thermal noise, pattern noise and shot noise are present and the loop has the nonzero detuning frequency. The phase error variance cahnges with the circuit configuration and the produced noise models. The analyzed results are applied to the previously implemented 90.194Mbps optic system whose loop filter is the improved active noninverting 1-st order lag-lead type.

• Journal of Electrical Engineering and information Science
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• v.2 no.3
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• pp.95-98
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• 1997

A nonlinear optical-microwave interaction is carried out in an uniplanar CPW-to-Slotline ring resonator on the semi-insulating GaAs substrate, in which a Schottky photodetector is monolithically integrated as a coupling gap. When the capacitive reactance of the detetor is modulated, the parametric amplification effect of the mixer occurs. In this device structure, the parametric amplification gain of 20 dB without the applied bias in RF signal is obtained. This microwave optoelectronic mixer can be used in the fiber-optic communication link.

• Journal of the Optical Society of Korea
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• v.16 no.3
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• pp.277-281
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• 2012

We measured small optical beam deflection in an image rotating Sagnac interferometer. We used a weak value measurement scheme that involves a pre-selection, weak perturbation, and a post-selection procedure to obtain the amplified value of beam deflection. The amplification factor of the measured beam deflection varied from 11 to 63 depending on the settings of the post-selection polarizer in front of the photodetector and the settings of polarization compensator in the interferometer.

• Proceedings of the KIEE Conference
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• 1987.07a
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• pp.64-67
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• 1987

We demonstrate the optical bistability and multistability using light emitting devices, a photodetector, and transistors under the positive electro optic feedback. Its operating principle and high speed operation Scheme are also described.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2300-2302
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• 2005

Metal-Semiconductor-Metal type photodetector was fabricated with AlGaAs/InGaAs Quantum Well FET structures using simplified processing steps. The DC and RF responses were measured by 850nm wavelength injection laser. A DC responsivity in the quasisaturated regime was 0.45 A/W in CW measurements, and a bandwidth measured using a 850nm 40 ps pulsed laser was 16GHz. An electrical equivalent circuit model was extracted from measured S-parameter.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.11
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• pp.2219-2222
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• 2009

A new touch-sensitive hydrogenated amorphous silicon(a-Si:H) display with embedded optical sensor arrays is presented. The touch-sensitive panel operation was successfully demonstrated on a prototype of 16-in. active-matrix liquid crystal display (AMLCD). The proposed system provides the finger touched point without the real-time image processing of information of the captured images. Due to the simple architecture of the system, we expect the introduction of large-area touch-sensitive display panels.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.244.1-244.1
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• 2015

The Ag Nanowire is one of the materials that are widely studied as alternatives to ITO and is available for large area, low cost process and the flexible transparent electrode. However, Ag nanowire can have the problem of a lack of stability at high temperatures, making this impossible to form a film. Using a structure of ITO/AgNW/ITO in photodetector device, we improved the properties of the ITO in the IR region and improved the thermal stability of the AgNW. The structure of ITO/AgNW/ITO has a high transmittance value of 89% at a wavelength of 900 nm and provide a good electrical property. The AgNWs embedded ITO film has a high transmittance, this is because of the light scattering from the AgNW. The thermal stability of the developed ITO/AgNWs/ITO films were investigated and found AgNWs embedded ITO films posses considerable high stability compared to the solo AgNWs on the Si surface. The ITO/AgNWs/ITO device showed a improved photo-response ratio compared to those of the conventional TC device in IR region. This is attributed to the high transmittance and low sheet resistance. We suggest an effective design scheme for IR-sensitive photodetection by using an AgNW embedded ITO.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.860-863
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• 2003

Pulse oximetry has gained wide spread clinical acceptance in the latter part of the 21st century. The principle of pulse oximetry is based on the red and infrared light absorption features and uses a light emitter with red and infrared LEDs that shines through a reasonably translucent site with good blood flow. There are two methods of sending light through the measuring site : transmission and reflectance. After the transmitted red and infrared signals pass through the measuring site and received at the photodetector, the red/infrared ratio is calculated. But, pulse of oximeters are so sensitive that they may detect pulses when pressure is too low to provide adequate tissue blood flow, that is, SpO2 may decrease due to O2 consumption by the finger of the pulsing but stagnant arterial blood at low pressure or with vasoconstriction. This project has the limitations of pulse oximetry. Therefore, this paper is focused on the resuction of motion artifact that caused by moving when someone measures with SpO2 system.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.234-234
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• 2010

The PR transitions in asymmetric dot-in-double-quantum-well (DdWELL) photodetector is identified by bias-dependent spectral behaviors. Discrete n-i-n infrared photodetectors were fabricated on a 30-period asymmetric InAs-QD/[InGaAs/GaAs]/AlGaAs DdWELL wafer that was prepared by MBE technique. A 2.0-monolayer (ML) InAs QD ensemble was embedded in upper combined well of InGaAs/GaAs and each stack is separated by a 50-nm AlGaAs barrier. Each pixel has circular aperture of 300 um in diameter, and the mesa cell ($410{\times}410\;{\mu}m^2$) was defined by shallow etching. PR measurements were performed in the spectral range of $3{\sim}13\;{\mu}m$ (~ 100-400 meV) by using a Fourier-transform infrared (FTIR) spectrometer and a low-noise preamplifier. The asymmetric photodetector exhibits unique transition behaviors that near-/far-infrared (NIR/FIR) photoresponse (PR) bands are blue/red shifted by the electric field, contrasted to mid-infrared (MIR) with no dependence. In addition, the MIR-FIR dual-band spectra change into single-band feature by the polarity. A four-level energy band model is proposed for the transition scheme, and the field dependence of FIR bands numerically calculated by a simplified DdWELL structure is in good agreement with that of the PR spectra. The wavelength shift by the field strength and the spectral change by the polarity are discussed on the basis of four-level transition.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.3
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• pp.45-54
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• 2004

Microwave characteristics of ridge type CPW traveling-wave(TW) electroabsorption modulator and photodetector are affected by the thickness of intrinsic layer, width of guiding layer, and the separation of signal and ground electrodes. These factors are determined effective index of microwave and characteristic impedance due to changing of capacitance(C) and inductance(L) of device. However, conventional equivalent circuit of TW-structure is approximated to microstrip and CPW transmission line by distribution of electric and magnetic fields, respectively. In this paper, we analyzed microwave characteristics of TW-structure and found more accurate value of C and L by using finite difference time domain (FDTD) method. These values are adopted circuit element of equivalent circuit. Microwave characteristics obtained by the FDTD and equivalent circuit model show good agreement.