• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.487-488
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• 2006

Picosecond (ps) laser micro-machining has emerged as an attractive method of fabricating high-precision microstructures, especially in metals. In this paper, a metallic mold for diffraction gratings is fabricated with a mode-locked 12 Ps $Nd:YVO_4$ laser. Laser pulses with a wavelength of 355nm are irradiated on the surface of NOK 80, a mold material, to generate line patterns. In order to minimize the line width, laser power is set just above the ablation threshold of NOK 80. Results show that the spectrum from the fabricated mold is good enough for some industrial application.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.8
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• pp.387-391
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• 2006

The Ag photodoping effect in amorphous $As_{40}Ge_{10}Se_{15}S_{35}$ chalcogenide thin films for holographic recording has been investigated using a He-Ne laser (${\lambda}$=632.8 nm). The chalcogenide films thickness prepared in the present work were thinner in comparison with the penetration depth of recording light ($d_p=1.66{\mu}m$). It exhibits a tendency of the variation of the diffraction efficiency (${\eta}$) in amorphous chalcogende films, independently of the Ag photodoping. That is, ${\eta}$ increases rapidly at the beginning of the recording process and reaches the maximum (${\eta}_{max}$) and slowly decreases slowly with the exposed time. In addition, the value of ${\eta}_{max}$ depends strongly on chalcogenide film thickness(d) and its maximum peak among the films with d = 40, 80, 150, 300, and 633 nm is observed 0.083% at d = 150 nm (approximately 1/2 ${\Delta}n$), where ${\Delta}$n is the refractive index of chalcogenide thin film (${\Delta}n=2.0$). The ${\eta}$ is largely enhanced by Ag photodoping into the chakogenides. In particular, the value of ${\eta}_{max}$ in a bilayer of 10-nm-thick Ag/150-nm-thick $As_{40}Ge_{10}Se_{15}S_{35}$ film is about 1.6%, which corresponds to ${\sim}20$ times larger than that of the single-layer $As_{40}Ge_{10}Se_{15}S_{35}$ thin film (without Ag). And we obtained the diffraction pattern according to the formation of (P:P) polarization holographic grating using Mask pattern and SLM.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.3
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• pp.145-152
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• 1989

Volume phase diffraction grating is formed in 5${mu}m$ Agfa 8E75 photographic emulsion film using He-Ne laser. It is dependent on the chemical processing rather than materials themselves that high diffraction efficiency can obtained in silver halide emulsions. With potassium dichromate bleach and alcohol drying, overall efficiency of 71% (81% after allowing for reflection at the two surfaces) has been achieved at an exposure of 180${mu}J/cm^2.$ Dichromate cross-linkage and air void by rapid dehydration increase refractive index modulation depth. The grating is swollen, which is newly identified by Scanning Electronic Microscope(SEM) photography, and it causes on-Bragg at larger angle than the recording angle. It is pointed out that controlling the emulsion thickness has an important role as a potential source for high diffraction efficiency.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.1
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• pp.247-252
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• 2019

The diffraction properties of optical signals by multi-layered periodic structures is formulated in two-dimensional space by using Fourier expansions associated with basic grating profile. The fields in each layer are then expressed in terms of characteristic modes, and the complete solution is found rigorously by using a modal transmission-line theory(MTLT) to address the pertinent boundary-value problems. Such an approach can treat periodic arbitrary gratings containing arbitrarily shaped dielectric components, which may generally have optical properties along directions that are parallel or perpendicular to the multi-layers. This paper illustrates the present approach by comparing our numerical results with data reported in the past for simple periodic circular 2D structures. In addition, this proposed theory can apply easily for more complex configurations, which include multiple periodic regions with several possible canonic shapes and high dielectric constants.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.456-459
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• 2003

In this thesis, We observed the characteristic of the diffraction efficiency according to the wave length of the chalcogenide thin films. The used an $Ag(200{\AA})/As_{40}Ge_{10}Se_{15}S_{35}$ thin film. We made grating formation by each wave length 325nm, 442nm, 632.8nm. After measure diffraction efficiency of the time. We expressed the maxium saturation value at fast time as were the short wavelength and stable characteristic. On the other hand we appeard to the by a maxium diffraction efficiency the 1.7% in 325nm, 0.8% in 442nm, 0.27% in 632.8nm. The maximum diffraction efficiency expressed high value as were the long wavelength.

• Korean Journal of Optics and Photonics
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• v.21 no.1
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• pp.1-5
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• 2010

In this study, we propose a grating structure using guided-mode resonance (GMR) to increase the absorption efficiency of a silicon solar cell. The proposed solar cell design consists of a one-dimensional diffraction grating and a planar waveguide layer of poly-silicon deposited on a silver reflector. We investigate the influence of structure parameters such as grating period, waveguide thickness, grating width and grating depth. Optimal parameters are found using the particle swarm optimization (PSO) algorithm. In the optimized GMR-assisted solar cell, absorption efficiency up to 65.8% is achieved in the wavelength range of 300 nm~750 nm.

• Korean Journal of Optics and Photonics
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• v.7 no.4
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• pp.314-321
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• 1996

In this paper, the chemical process of each step in fabricating the holographic phase diffraction grating with silver salt sensitive materials has been studied in detail. A new analysis of the bleaching methods have been made through the study. The result shows that among the types of bleaching methods, the reversal bleach can not be reacted chemically. And the experiments about the chemical reactions, the characteristics of the reaction products and the refractive modulation types by the bleaching methods have been done to prove the theory. It is investigated that the exposure acts as the catalyst of developing reaction and affects the developing reaction time conspicuously. At the optimum developing reaction times, which could be taken from the experiments, the holographic diffraction gratings with high diffraction efficiency over 70% could be obtained in the range of the exposure quantity 50~350 [$\mu$J/ $\textrm{cm}^2$]. From the experiments about the correlation of the chemical processing conditions of the composition of developers, the exposure, and the developing reaction time, it has proved that the enhancement of the diffraction efficiency is impossible in the limited exposure energy and conventional constant chemical reaction time.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.04a
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• pp.127-130
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• 2003

We have carried out two-beam interference experiment to form holographic grating on amorphous $As_{40}Ge_{10}Se_{15}S_{35}$ single-laver, $MgF_{2}/As_{40}Ge_{10}Se_{15}S_{35}$ muliti-layer. In this study holographic grating formed using He-Ne laser(632.8nm) under different polarization state(intensity, phase polarization holography). The diffraction efficiency was obtained by first order intensity. The maximum diffraction efficiency of $As_{40}Ge_{10}Se_{15}S_{35}$ single-laver was 0.8% and The maximum diffraction efficiency of $MgF_{2}/As_{40}Ge_{10}Se_{15}S_{35}$ multi-layer(multi-layer I, multi-layer II) were 1.4% and 3.1%.

• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.385-387
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• 1994

Optical interconnections are more attractive than electronic interconnections because of their higher speed, freedom from planar constraints, immunity to electromagnetic interference effects and higher interconnection capacity. Volume hologram is one of the best way to implement optical interconnections. Diffraction efficiency and crosstalk effect are very important things for ensuring independent interconnections. Recently, a general systematic method that can handle a large number of superposed volume gratings in anisotropic host material is presented. In this study for numerical analysis of diffraction, above method is programmed in general form near Bragg angle. Diffraction orders for variation of grating strength are determined by comparing with the coupled-mode method. The effects of parameter variation are considered. Parameters include vertical and azimuthal incident angle, wavelength and interaction length. Diffraction analyses are also performed for intra-mode and inter-mode diffractions.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.3
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• pp.212-215
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• 2005

Modified illumination techniques have been used to enhance the resolution of the sub-wavelength lithography. But, since they shield the central part of incident light, the light efficiency is seriously degraded, which in turn reduces the throughput of a lithography process. In this research, we introduced an annular illumination structure that enhances the light efficiency with a concentric circular grating at the backside of a photomask. The efficiency of the structure was theoretically analyzed.