• 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.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.10
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• pp.461-466
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• 2006

In the present work, we investigated the photodissolution and photodiffusion effect on the interface of Ag/chalcogenide $As_{40}Ge_{10}Se_{15}S_{35}$ thin film by measuring the absorption coefficient, the optical density, the resistance change of Ag layer. It was found that the photodissolutioniphotodiffution ratio depends on the magnitude of photon energy absorbed in the chalcogenide thin film and the depth of photodiffution was proportional to the square root of the exposed time. Also, we have investigated the holographic grating formation with P-polarization states on chalcogenide $As_{40}Ge_{10}Se_{15}S_{35}$ thin film and $As_{40}Ge_{10}Se_{15}S_{35}/Ag$ double layer structure thin film. Holographic gratings have been formed using He-Ne laser (632.8 nm) which have a smaller energy than the optical energy gap, $E_g\;_{opt}$ of the film, i. e., an exposure of sub-bandgap light $(h{\upsilon} under P-polarization. As the results, we found that the diffraction efficiency on $As_{40}Ge_{10}Se_{15}S_{35}/Ag$ double layer structure thin film was more higher than that on single $As_{40}Ge_{10}Se_{15}S_{35}$ thin film. Also, we obtained that the maximum diffraction efficiency was 0.27 %, 1,000 sec on $As_{40}Ge_{10}Se_{15}S_{35}\;(1{\mu}m)/Ag$ (10 nm) double layer structure thin film by (P: P) polarized recording beam. It will offer lots of information for the photodoping mechanism and the analyses of chalcogenide thin films.

• Proceedings of the Optical Society of Korea Conference
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• 1996.09a
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• pp.73-73
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• 1996

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.490-493
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• 2003

We have carried out two-beam interference experiment to form holographic grating on amorphous $As_{40}Ge_{10}Se_{15}S_{35}/Ag$ double-layer. In this study holographic grating formed using He-Ne laser(632.8nm) under non-polarization state and p-polarization state and we confirm that the diffraction efficiency depend on thickness of Ag. The diffraction efficiency was obtained by first order intensity. We got the maximum diffraction efficiency that thickness of Ag was $600{\AA}$. The maximum diffraction efficiency was 13.5% in (P:P) polarization state.

• Journal of the Optical Society of Korea
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• v.7 no.4
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• pp.269-274
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• 2003

In this paper, a Gaussian apodization technique applied to a transmission volume hologram for holographic demultiplexer is proposed. The Gaussian apodized grating of 15 mm ${\times}$ 11mm size, $38{\mu}m$ thickness and 3.2 mm horizontal standard deviation of the Gaussian index modulation profile was fabricated. A 22-channel demultiplexer based on that grating has been optically demonstrated. The channel spacing, the interchannel cross-talk level and the channel uniformity of 0.8 nm, -30 dB and 1.5 dB, respectively, were obtained.

• Journal of Information Display
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• v.2 no.3
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• pp.6-12
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• 2001

Formation of intensity gratings was studied with two s-polarized (s+s) configuration in polymer liquid crystals (PLCs) containing a photochromic moiety (azobenzene) and a mesogenic unit (tolane, T-AB; cyanobiphenyl, CB-AB) by photoinduced alignment of PLCs. Remarkable differences were observed between the two PLCs. T-AB showed a faster response to the change in the diffraction intensity than CB-AB. In T-AB, alignment change took place faster than that of CB-AB. By introducing the tolane unit at the side chain, we obtained a diffraction efficiency of 30 % in the Raman-Nath regime

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.218-218
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• 2006

A number of new ideas have been implemented to control the droplet morphology and electrooptic properties of holographic polymer dispersed liquid crystal (HPDLC). Doping of conductive fullerene particles to the conventional HPDLC induced dual effects of reducing both droplet coalescence and operating voltage. Chain transfer agent gave higher gel content with lower crosslink density, less dark reactions and less grating shrinkage with much smooth LC-polymer interfaces. Addition of octanoic acid (OA) to the formulation of HPDLC gave a decrease in droplet size and monotonic increase of the off state diffraction throughout the OA content.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.5
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• pp.868-873
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• 1987

Holographic diffraction gratings which are the core element of the optical instruments such as a spectrophotometer have been fabricated using the photoresist as a recording material. A 488nm line from an argon laser is used in making the gratings. Transmission type surface-relief phase grating and reflection type which is fabsricated by coating the aluminum on the transmission type with thickness 2000\ulcornerare fabricated, the spatical frequency of which are 1200 lines/mm. Diffraction efficiency, scattered light and wave-front aberratin are measured to test the performance of the developed gratings. A marimum diffraction efficiency is given when light is incident at the Bragg angle. Theoretical efficiency is about 80%, but measured efficiency of the transmission type and reflection type is 50% and 45%, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.12
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• pp.1353-1361
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• 1992

Holographic optical element(HOE) is fabricated with the properties of lightweight, thin thickness and interconnectivity for free space. Particularly, HOE for optical interconnection and multiple image processing should have a high efficiency and equal spot intensity, Nonlinear equations for 2-dimensional binary phase grating(BPG) structure is solved by computer simulation based on modified Newton method. Computer-generated pattern drawn by plotter is scaled down and translated into the microfilm. After contact printing between the microfilm and silver halide hologram film, phase diffraction grating produces the $5{\times}5$ multiple spots. Experimental results are shown that bleached phase grating has a high efficiency and equal focused beams except central zero order.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.10
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• pp.934-940
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• 1991

A modified quantizing method is introduced to teach single layer learning algorithm, which is implemented optically. The proposed optical system consists of input masks, holographic diffraction grating. LCD and CCD camera. The 2 dimensional interconnections between input neurons and output neurons are realized using holographic phase grating, which is fabricated for equal intensity distribution of diffraction orders. The two gray levels of LCD act as binary weights for each interconnection. The weights are compensated according to the learning algorithm in which the amount of weights to be compensated is determined by comparing the output patterns with target patterns. The learning process is iterated until the predetermined conditions are satisfied. Optical experiments are performed for two learning rates, 0.5 and 0.9 and the experimental results show that the proposed system is useful for optical neural networks.