• Journal of the Korean Institute of Telematics and Electronics
• /
• v.8 no.4
• /
• pp.17-24
• /
• 1971

Laser light which modulated and transmitted through one-meter water bath and one-kilometer transmission distances in atmospheric media is detected by method of direct photo-detection. Also, it is analyzed as a square law detection and the experimental apparatus are designed and constructed. Consequently, in spite that the quantitative analysis remains, the availability of coherent optical communication is understood. The average attenuation with the conditions of weather is about -25dB, and the average attenuation coefficient of water is about 0.4(m-1).

• Proceedings of the Optical Society of Korea Conference
• /
• 2001.02a
• /
• pp.54-55
• /
• 2001

Recently, there has been much interests in InGaN/GaN multiple-quantum-well (MQW) structures due to their applicability as optoelectronic devices such as light-emitting diodes (LEDs) and laser diodes [1]. Their ultrafast and physical properties are also of significant interests. Anomalously large acoustic phonon oscillations have been observed using ultrafast lasers in InGaN MQWs [2]. In this study, we have peformed femtosecond pump-probe experiments in the reflection geometry on 5 periods InGaN/GaN MQW LED structure with well width of 20$\AA$ and barrier width of 100$\AA$ at room temperature. (omitted)

• Electronics and Telecommunications Trends
• /
• v.39 no.1
• /
• pp.48-61
• /
• 2024

The integration of high-capacity terrestrial networks with non-terrestrial communication using satellites has become essential to support seamless low-latency services based on artificial intelligence and big data. Tunable light sources have been instrumental in resolving the complexity of channel management in wavelength division multiplexing (WDM) systems, contributing to increased network flexibility and serving as optical sources for long-distance coherent systems. Recently, these light sources have been applied to beam-steering devices in laser communication and sensing applications across ground, aerial, and satellite transport. We examine the utilization and requirements of tunable lasers in WDM networks and describe the relevant development status. In addition, performance requirements and development directions for tunable lasers used in optical interference systems and beam-steering devices are reviewed.

• Journal of The Korean Digital Architecture Interior Association
• /
• v.13 no.4
• /
• pp.13-23
• /
• 2013

Steven Holl is outstanding architect who has been applied his phenomenological thinking to his works. he has been reported that he had adhered to focus his interest on coherent phenomenological theme and sublimated his architectural concept succesfully. This study focuses on relationship how phenomenological concept has common ground with architectural parts and with the study on phenomenological application methodology of architectonics of Steven Holl. In the case of Holl, with the theme of sense and flesh, he molds phenomenologically sensitive space. His works contains coherent phenomenolgical concepts such as distrust of rationality, synthesis of consciousness, and qeustions of perception. The Methodologies of connection with environment(nature or bridge), regional values, placeness, light and time are considered in his works(books and architectural works) as anchoring, interwining and parallax for phenomenological process in his concepts. His methodologies of enlisted works contain many valuable concepts of phenomenological intuition and would be applicable to contemporary and future architecture for humanism.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.2
• /
• pp.465-469
• /
• 2013

Proton transfer reaction is one of the most fundamental processes in chemistry and life science. Excited state intramolecular proton transfer (ESIPT) has been studied as a model system of the proton transfer, since it can be conveniently initiated by light. We report ESIPT reaction dynamic of 1-hydroxy-anthraquione (1-HAQ) in solution by highly time-resolved fluorescence. ESIPT time of 1-HAQ is determined to be $45{\pm}10$ fs directly from decay of the reactant fluorescence and rise of the product fluorescence. High time resolution allows observation of the coherent vibrational wave packet motion in the excited state of the reaction product tautomer. The coherently excited vibrational mode involves large displacement of the atoms, which shortens the distance between the proton donor and the acceptor. With the theoretical analysis, we propose that the ESIPT of 1-HAQ proceeds barrierlessly with assistance of the skeletal vibration, which in turn becomes excited coherently by the ESIPT reaction.

• Korean Journal of Optics and Photonics
• /
• v.35 no.3
• /
• pp.107-114
• /
• 2024

In this study, the feasibility of using the covariance-matrix-adaptation-evolution-strategy (CMA-ES) algorithm in a multichannel coherent-beam-combining (CBC) system was experimentally verified. We constructed a multichannel CBC system utilizing a spatial light modulator (SLM) as a multichannel phase-modulator array, along with a coherent light source at 635 nm, implemented the stochastic-parallel-gradient-descent (SPGD) and CMA-ES algorithms on it, and compared their performances. In particular, we evaluated the characteristics of the CMA-ES and SPGD algorithms in the CBC system in both 16-channel rectangular and 19-channel honeycomb formats. The results of the evaluation showed that the performances of the two algorithms were similar on average, under the given conditions; However, it was verified that under the given conditions the CMA-ES algorithm was able to operate with more stable performance than the SPGD algorithm, as the former had less operational variation with the initial phase setting than the latter. It is emphasized that this study is the first proof-of-principle demonstration of the CMA-ES phase-control algorithm in a multichannel CBC system, to the best of our knowledge, and is expected to be useful for future experimental studies of the effects of additional channel-number increments, or external-phase-noise effects, in multichannel CBC systems based on the CMA-ES phase-control algorithm.

• Journal of the Korean housing association
• /
• v.16 no.5
• /
• pp.75-81
• /
• 2005

The purpose of this study is to shed light on the field dynamics of 'lived space' in the light of our intuitive experiential contents by way of investigating three properties of space. While finding inspirations in the field theory of modern physics, investigation of our intuitive responses to the physical and spatial environment leads us to a coherent view of matter and space. We find then that our lived world is more than a system of inert matter; it is a dynamic environment of life in which feeling and mood, spiritual meaning and value, are perpetually infused with matter. Any concept of space, if it is to be meaningful to lift has to somehow acknowledge this fact. Empty space and matter cannot be conceived as mutually exclusive and independent as in classical physics. Rather they should be seen as two different manifestations of an underlying dynamism which permeates the world. The 'properties' of space can only be understood in terms of the 'impact' of material presence. The object cannot be seen as an isolated entity, but the 'conditioning' of its surrounding space has to be understood as an integral part of its being. Lived space can thus be viewed as an emotionally charged field, or a field of emotional energy, whose properties may be described in terms of concentration, mobility and resonance.

• The Bulletin of The Korean Astronomical Society
• /
• v.43 no.1
• /
• pp.72.2-72.2
• /
• 2018

The Opposition Effect (OE) is an enhancement of the brightness of a reflecting light as the phase angle (the Sun-target-observer angle) approaches zero. The mechanisms have been studied both theoretically and experimentally and nowadays recognized that there are two major mechanisms, namely, coherent backscattering OE (CBOE) and shadow hiding OE (SHOE). From data analyses of an S-type asteroid Itokawa taken with the Hayabusa spacecraft onboard camera, it is suggested that the CBOE would be dominant at phase angle smaller than ~ 1.4 deg, while SHOE dominates at larger phase angles (M. Lee & M. Ishiguro, under review). The study on the physical parameters which affect the OE, such as size and composition, will lead us to find a way to disentangle each of them from observation. The experiments in lab, however, faces two major difficulties: (a) the detector blocks the incident light if phase angle is nearly zero and (b) incident and emission angles must be controlled with high angular resolution to prevent blurring of OEs at different phase angles in one measurement. In this presentation, we introduce a new apparatus which has been installed at Seoul National University to investigate the OE in our lab, and summarize the initial results. It will be a valuable starting point to establish infrastructure in Korea, and will shed light on the investigation of OE physics using laboratory simulants.

• Korean Journal of Optics and Photonics
• /
• v.20 no.6
• /
• pp.334-338
• /
• 2009

Recently, with increasing demand for flat-panel display product, methods for large area patterning are required. TIR (total internal reflection) holographic photo-lithography isstudied as one of the methods of large area lithography. In conventional TIR holography, light sources for hologram recording and image reconstruction are coherent beams such as laser beams. If the image is reconstructed with an incoherent light source such a UV lamp, the image noise from the coherence of light will be reduced and the UV lamp will be a better light source for large area exposure. We analyzed the effect of spectral bandwidth and angular bandwidth of the light source in image reconstruction and verified image blurring with experiments. For large area patterning which has micro-scale line width, it is expected that TIR holographic photo lithography by UV lamp will become a low-noise and low-priced technique.

• Journal of Advanced Navigation Technology
• /
• v.2 no.2
• /
• pp.126-131
• /
• 1998

In optical scanning holography, 3-D holographic information of an object is generated by 2-D active optical scanning. The optical scanning beam can be a time-dependent Gaussian apodized Fresnel zone plate. In this technique, the holographic information manifests itself as an electrical signal which can be sent to an electron-beam-addressed spatial light modulator for coherent image reconstruction. This technique can be applied to 3-D optical remote sensing especially for identifying flying objects. In this paper, we first briefly review optical scanning holography and analyze the resolution achievable with the system. We then present mathematical expression of real and virtual image which are responsible for holographic image reconstruction by using Gaussian beam profile.