• Journal of the Optical Society of Korea
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• v.6 no.3
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• pp.121-127
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• 2002

The operating principal of a ring laser gyroscope depends on the phase difference for the counter-propagating waves within a closed path. The reflecting mirrors mounted on the monoblock form the traveling waves. The manufacturing accuracy of the monoblock influences the traveling path of ray, the sensitivity of laser resonator for misalignments, and diffraction losses. A 3 $\times$ 3 ray transfer matrix was derived for optical components with centering and squaring errors in a ring resonator. The matrix can be utilized to predict the optical ray paths on the basis of the manufacturing errors of the monoblock as well as the misalignment of mirrors. Then the distance and orientation (o. slope) at the arbitrary plane inside the resonator along the ideal optical path can be calculated from the chain multiplication of the ray transfer matrix for each optical component in one round trip. We also show that the counter-propagating rays In a ring resonator with errors does not coincide in each round trip, which results in gain difference between two beams, and how these errors can be adjusted through the alignment procedure. Finally this 3 $\times$ 3 ray matrix formalism can be used to calculate the beam size and its displacement from the optical axis and the deviation at the diaphragm.

• Journal of the Optical Society of Korea
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• v.9 no.3
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• pp.99-102
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• 2005

Directional couplers of gradient-index plastic optical fibers were fabricated and characterized. In particular, we have employed a core-facet technique to make the directional couplers, which require mechanical side polishing and linkage. We have measured insertion loss, excess loss, and coupling ratio of the fabricated couplers as a function of polishing depth and coupling length. We found that polishing depth of $\~300{\mu}m$ and coupling length of $\~35mm$ are optimum conditions for minimizing the insertion and excess losses and for achieving 1: 1 coupling ratio.

• Proceedings of the Optical Society of Korea Conference
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• 1989.02a
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• pp.218-221
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• 1989

Buried Bragg reflectors which are immune to the contamination of the surface of an optical waveguide chip are fabricated on Si3N4-SiO2 rib optical waveguides on Si. The effective refractive indices and the bandwidths of the fabricated buried Bragg reflector waveguides are determined by transmission measurement. We show that the measured values of the effective refractive indices are consistent with the calculated values as the width of the waveguide rib varies. Propagation losses of the guided modes due to the leakage into the si substrate are also calculated.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.7
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• pp.616-621
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• 2009

Reduction of optical losses in crystalline silicon solar cells by surface modification is one of the most important issues of silicon photovoltaics. Porous Si layers on the front surface of textured Si substrates have been investigated with the aim of improving the optical losses of the solar cells, because an anti-reflection coating(ARC) and a surface passivation can be obtained simultaneously in one process. We have demonstrated the feasibility of a very efficient porous Si ARC layer, prepared by a simple, cost effective, electrochemical etching method. Silicon p-type CZ (100) oriented wafers were textured by anisotropic etching in sodium carbonate solution. Then, the porous Si layers were formed by electrochemical etching in HF solutions. After that, the properties of porous Si in terms of morphology, structure and reflectance are summarized. The structure of porous Si layers was investigated with SEM. The formation of a nanoporous Si layer about 100nm thick on the textured silicon wafer result in a reflectance lower than 5% in the wavelength region from 500 to 900nm. Such a surface modification allows improving the Si solar cell characteristics. An efficiency of 13.4% is achieved on a monocrystalline silicon solar cell using the electrochemical technique.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.295-298
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• 2007

Reduction of optical losses in crystalline silicon solar cells by surface modification is one of the most important issues of silicon photovoltaics. Porous Si layers on the front surface of textured Si substrates have been investigated with the aim of improving the optical losses of the solar cells, because an anti-reflection coating(ARC) and a surface passivation can be obtained simultaneously in one process. We have demonstrated the feasibility of a very efficient porous Si ARC layer, prepared by a simple, cost effective, electrochemical etching method. Silicon p-type CZ (100) oriented wafers were textured by anisotropic etching in sodium carbonate solution. Then, the porous Si layers were formed by electrochemical etching in HF solutions. After that, the properties of porous Si in terms of morphology, structure and reflectance are summarized. The structure of porous Si layers was investigated with SEM. The formation of a nanoporous Si layer about 100nm thick on the textured silicon wafer result in a reflectance lower than 5% in the wavelength region from 500 to 900nm. Such a surface modification allows improving the Si solar cell characteristics. An efficiency of 13.4% is achieved on a monocrystalline silicon solar cell using the electrochemical technique.

• Korean Journal of Metals and Materials
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• v.46 no.12
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• pp.835-840
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• 2008

Texturing for crystalline silicon solar cells is one of the important techniques to increase conversion efficiency by effective photon trapping. Generally, incoming wafers or alkali etched wafers are used for texturing. From this conventional etching process, $7{\sim}10{\mu}m$-sized random pyramids are formed. In this study, acid etching for removal of saw damages was practiced before texturing. This improved the resulting surface morphology, which consisted of $2{\sim}4{\mu}m$-sized pyramids. Because these pyramids covered the surface much more extensively, we obtained reduction of optical losses on the surface. In order to compare with conventional texturing, FE-SEM is used for observing surface morphology and reflectance data is analyzed by UV-VIS spectrophotometer.

• Journal of the Korean Solar Energy Society
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• v.39 no.4
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• pp.25-39
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• 2019

Luminescent solar concentrator (LSC), consisting of luminophore included glass or substrate with edge-mounted photovoltaic cell, is semi-transparent, energy harvesting devices. The luminophore absorbs incident solar light and re-emit photons, while the waveguide plate allows re-emitted photons to reach edge or bottom mounted photovoltaic cells with reduced losses. If the area of LSC is much larger than that of photovoltaic cell, this system can effectively concentrate solar light. In order to improve the performance of LSC, new materials and optical structures have been suggested by many research groups. For decreasing re-abosprion losses, it is essential to minimize the overlap between absorption and photoluminescence solar spectrum of luminophoroe. Moreover, the combination of selective top reflector and reflective optical cavity structure significantly boosts the waveguide efficiency in the LSC. As a result of many efforts, commercially available LSCs have been demonstrated and verified in the outdoor. Also, it is expected to generate electricity in buildings by replacing conventional glass to LSCs.

• Korean Journal of Optics and Photonics
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• v.13 no.3
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• pp.223-227
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• 2002

Polymeric multi-mode optical waveguides were fabricated for parallel optical interconnection. Waveguide structures were molded by a Ni mold master using a hot embossing technique. The Ni mold master was manufactured by LIGA process. Multimode optical waveguides with a 48$\times$47 ${\mu}{\textrm}{m}$$^2$cross-section were produced by a simple two-step process. The propagation losses of the multimode waveguide measured at 0.85 ${\mu}{\textrm}{m}$ and 1.3 ${\mu}{\textrm}{m}$ wavelengths were 0.38 dB/cm and 0.66 dB/cm, respectively.

• ETRI Journal
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• v.36 no.5
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• pp.841-846
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• 2014

This study proposes a novel optical sensor structure based on a refractometer combining a bend waveguide with an air trench. The optical sensor is a $1{\times}2$ splitter structure with a reference channel and a sensing channel. The reference channel has a straight waveguide. The sensing channel consists of a U-bend waveguide connecting four C-bends, and a trench structure to partially expose the core layer. The U-bend waveguide consists of one C-bend with the maximum optical loss and three C-bends with minimum losses. A trench provides a quantitative measurement environment and is aligned with the sidewall of the C-bend having the maximum loss. The intensity of the output power depends on the change in the refractive index of the measured material. The insertion loss of the proposed optical sensor changes from 3.7 dB to 59.1 dB when the refractive index changes from 1.3852 to 1.4452.

• Current Optics and Photonics
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• v.1 no.5
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• pp.468-473
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• 2017

We determined the feasibility of a fishing camera system using an optical fiber as the fishing line by testing a power-over-fiber (POF) module and multimode optical fiber. Operation of the remote camera module (RCM) without the battery was preferred because the removal of the charging or battery replacement section enabled a waterproof single-body type design. The average efficiency of the photovoltaic power converter (PPC) in the tested POF module was 32.6% at 820 nm, and thus, a high-power laser of at least 1.27 W was required for operating the developed RCM with an electrical dissipation of 413 mW. Because the optical fiber was wound on a fishing reel, composite loss composed of bending and tensile loss occurred. To mitigate the composite loss, we employed a simple holder that showed an improvement in the composite loss of 0.38 dB to 0.8 dB, which was considerably better than the losses without the holder.