• Korean Journal of Optics and Photonics
• /
• v.34 no.6
• /
• pp.225-234
• /
• 2023

Mode-locked pulse lasers have a temporal periodicity up over a short period of time. However, in the time-frequency domain, a pulsed laser with temporal periodicity is described as an optical frequency comb with constant frequency spacing. Each frequency component of the optical frequency comb in the frequency domain is then a continuous-wave (CW) laser with hundreds of thousands of single-frequency-component CW lasers in the time domain. This optical frequency comb was developed approximately 20 years ago, enabling the development of the world's most precise atomic clocks and precise transmission of highly stable optical frequency references. In this review, research on the selective extraction of the single-frequency components of optical frequency combs and the control of the frequency components of optical combs is introduced. By presenting the concepts and principles of these optical frequency combs in a tutorial format, we hope to help readers understand the properties of light in the time-frequency domain and develop various applications using optical frequency combs.

• Journal of Korean Ophthalmic Optics Society
• /
• v.3 no.1
• /
• pp.151-165
• /
• 1998

We investigated the optical properties of 3-component zoom camera lens whose character is being compact and having wide angle. Also, we calculated paraxial design condition and locus of each component by using Gaussian Bracket.

• Journal of the Optical Society of Korea
• /
• v.16 no.3
• /
• pp.215-220
• /
• 2012

In an earlier work, we proposed the chromatic dispersion monitoring technique of non-return to zero (NRZ) signal based on clock-frequency component (CFC) through numerical simulations. However, we have not yet shown any experimental demonstration or analytic derivation of it. In this paper, we show an experimental demonstration and analytic derivation of the proposed chromatic dispersion monitoring technique. We confirm that the experimental results and the analytic results correspond with the simulation results. We also demonstrate that monitoring range and accuracy can be improved by using a simple clock-extraction method.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.32-32
• /
• 2011

Plasma etching is used in microelectronic processing for patterning of micro- and nano-scale devices. Commonly, optical emission spectroscopy (OES) is widely used for real-time endpoint detection for plasma etching. However, if the viewport for optical-emission monitoring becomes blurred by polymer film due to prolonged use of the etching system, optical-emission monitoring becomes impossible. In addition, when the exposed area ratio on the wafer is small, changes in the optical emission are so slight that it is almost impossible to detect the endpoint of etching. For this reason, as a simple method of detecting variations in plasma without contamination of the reaction chamber at low cost, a method of measuring plasma impedance is being examined. The object in this research is to investigate the suitability of using plasma impedance monitoring (PIM) with statistical approach for real-time endpoint detection of $SiO_2$ etching. The endpoint was determined by impedance signal variation from I-V monitor (VI probe). However, the signal variation at the endpoint is too weak to determine endpoint when $SiO_2$ film on Si wafer is etched by fluorocarbon plasma on inductive coupled plasma (ICP) etcher. Therefore, modified principal component analysis (mPCA) is applied to them for increasing sensitivity. For verifying this method, detected endpoint from impedance analysis is compared with optical emission spectroscopy (OES). From impedance data, we tried to analyze physical properties of plasma, and real-time endpoint detection can be achieved.

• Journal of the Optical Society of Korea
• /
• v.17 no.5
• /
• pp.454-460
• /
• 2013

We present qualitative and quantitative component analyses on compound explosives via Terahertz time-domain spectroscopy (THz-TDS) based on a combination of wavelet thresholding and wavelength selection. Despite its importance, the field of signal processing of THz signals of compound plastic explosives is relatively unexplored. In this paper, experiment results from explosives Composition B-3 and Pentolite are newly presented, suggesting a novel signal processing procedure for in situ compound explosives detection. The proposed signal processing method demonstrates effective component analysis even in noisy and humid environments, showing significant decrease in component concentration percentage error of approximately 22.7% for Composition B-3 and 48.8% for Pentolite.

• Proceedings of the IEEK Conference
• /
• 2003.11c
• /
• pp.109-112
• /
• 2003

Wavelength division multiplexing technology is a promising solution for the next generation optical networks. Optical buffer is a key component for optical packet switching system. It can be used to hold optical packets and to resolve the contention of optical packets. In this paper, we implemented a optical buffer using optical wavelength converters and demonstrated that optical packets are delayed successfully.

• Proceedings of the Optical Society of Korea Conference
• /
• 1998.08a
• /
• pp.220-221
• /
• 1998

An optical implementation of higher order neural networks based on based principal component analysis and time integration has been described. The principal component analysis combined with time integration allows larger input size than fully spatial neural networks at the cost certain amount of time consumption. This time-integration usage actually breaks down the barrier of the maximum space-bandwidth product that optical systems can offer.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2015.11a
• /
• pp.242-243
• /
• 2015

Fault detection using optical emission spectra with modified K-means cluster analysis and principal component anal ysis are demonstrated for inductive coupl ed pl asma cl eaning processes. The optical emission spectra from optical emission spectroscopy (OES) are used for measurement. Furthermore, Principal component analysis and K-means cluster analysis algorithm is modified and applied to real-time detection and sensitivity enhancement for fluorocarbon cleaning processes. The proposed techniques show clear improvement of sensitivity and significant noise reduction when they are compared with single wavelength signals measured by OES. These techniques are expected to be applied to various plasma monitoring applications including fault detections as well as chamber cleaning endpoint detection.

• Proceedings of the Optical Society of Korea Conference
• /
• 2008.07a
• /
• pp.179-180
• /
• 2008

Optical Mechanical splice is essential component to construct for FTTH. Optical Mechanical splice is executed many countries' FTTH including Korea. In this paper, we have designed Optical Mechanical splice using UV and completed a series of mechanical and environmental tests on the optical Mechanical splice. And the results of tests and Bellcore-requirements for optical Mechanical splice will be presented. Accordingly, evaluation method of optical Mechanical splice has gained power to improve the quality and stability of it.

• Proceedings of the KIEE Conference
• /
• 2007.04a
• /
• pp.363-365
• /
• 2007

Novel concept of sensor mat and its signal processing method is proposed for patient monitoring in medical application. Proposed sensor mat structure has sensing inner layer which has cross-linked arrangement using plastic optical fiber(POF). Large core diameter of plastic optical fiber behaved as band pass filter by averaging the noise component. caused by unwanted environmental factors. Signal processor followed by sensor output added noise immune performance by filtering out unwanted component. Fail-proof patient breath monitoring scheme was realized by using intelligent decision algorithm. Unlike the conventional approach by using mechanical sensor, which have high sensitivity both to intruder and to environmental noise, our approach provided reliable breath motion detection.