• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1330-1332
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• 2006

In the Langmuir-Blodgett (LB) technique, a monolayer on the water surface is transferred onto a substrate, which is raised and dipped through the surface. From this, multilayers can be obtained in which constituent molecules are periodically arranged. The LB technique has attracted considerable interest in the fabrication of electrical and electronic devices. Many researchers have investigated the electrical properties of monolayer and multiplayer films. Dendrimers represent a new class of synthetic macromolecules characterized by a regularly branched treelike structure. Multiple branching yields a large number of chain ends that distinguish dendrimers from conventional star-like polymers and microgels. The agobenzene dendrimer is one of the dendritic macromolecules that include the azo-group exhibiting a photochromic character. Due to the Presence of the charge transfer element of the azo-group and its rod-shaped structure, these compounds are expected to have potential interest in electronics and ptoelectronics, especially in nonlinear optics. In the present paper, we give pressure stimulation to organic thin films and detect the induced displacement current.

• Proceedings of the KIEE Conference
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• 2004.11a
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• pp.209-211
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• 2004

In the Langmuir-Boldgett(LB) technique, a monolayer on the water surface is transferred on to a substrate, which is raised and dipped through the surface, and one can obtain multilayers in which constituent molecules periodically are arranged in layer. The LB technique has attracted considerable interest in the fabrication of electrical and electronic device, e.g.. Many researchers have investigated the electrical properties of monolayer and multiplayer films. Dendrimers represent a new class of synthetic macromolecules sharacterized by a regularly branched treelike structure. Multiple branching yields a large number of chain ends, which distinguishes dendrimers from conventional starlike polymers and microgels. Azobenzene dendrimer is one of the dendritic macromolecules that includes the azo-group which exhibits a photochromic character. Due to the presence of the charge transfer part, the azo-group, and having a rod-shaped structure, these compounds are expected to have the potential interest in electronics and ptoelectronics, especially in nonlinear optics. In the present paper, we give a pressure stimulation into organic thin films and detect the induced displacement current.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.358-359
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• 2006

In the Langmuir-Blodgett (LB) technique, a monolayer on the water surface is transferred onto a substrate, which is raised and dipped through the surface. From this, multilayers can be obtained in which constituent molecules are periodically arranged. The LB technique has attracted considerable interest in the fabrication of electrical and electronic devices. Many researchers have investigated the electrical properties of monolayer and multiplayer films. Dendrimers represent a new class of synthetic macromolecules characterized by a regularly branched treelike structure. Multiple branching yields a large number of chain ends that distinguish dendrimers from conventional star-like polymers and microgels. The azobenzene dendrimer is one of the dendritic macromolecules that include the azo-group exhibiting a photochromic character. Due to the presence of the charge transfer element of the azo-group and its rod-shaped structure, these compounds are expected to have potential interest in electronics and ptoelectronics, especially in nonlinear optics. In the present paper, we give pressure stimulation to organic thin films and detect the induced displacement current.

• Korean Journal of Optics and Photonics
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• v.9 no.4
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• pp.236-239
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• 1998

We constructed a frequency doubler with a frequency-stabilized Nd:YAG Laser, a nonlinear crystal KTP, and an external resonant cavity. Using type II phase-making method and a resonant cavity, one usually have a serious problem that the second harmonic conversion efficiency is decreased greatly, for under usual circumstances ordinary ray and extraorninary ray cannot be resonated in a cavity simultaneously. With the change of temperature and incident angle of KTP, we found an optimized condition for the phase-matching and double-resonance. As a result we produced 26 mW of green light with 318 mW of fundamental laser power from a cw Nd:YAG laser.

• Korean Journal of Optics and Photonics
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• v.16 no.4
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• pp.366-375
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• 2005

A fabrication process of periodic electric field assisted poling of Ti-diffused channel waveguides in LiNbO3 (Ti:PPLN) has been developed and improved using a periodic 180o phase inversion along the z-axis. The zig for poling inversion and the Labview program of charge control have been devised. Pulse high voltage and duty cycle were adjusted based on the estimated charge required for poling inversion. Monitoring the change of leakage current under applied voltage less than the coercive voltage also minimized a breakdown.

• Korean Journal of Optics and Photonics
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• v.1 no.2
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• pp.135-141
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• 1990

Optical nonlinearity of laser heated Si with thickness of 160$\mu$m is investigated by pump-probe method. Si is heated by pdsed Nd:YAG laser of $TEM_{00}$-mode with pulse duration of 180$\mu$sec. Temperature change is monitored by observing transmittance change of probe light whose wavelength lies near band gap of Si. It is found that temperature rise is linearly proportional to incident laser intensity and the maximum temperat~re increment is measured to be $16^{\circ}C$ for the maximum incident intensity of 25KW/$\textrm{cm}^2$. From these results, the third order nonlinear susceptibility .d3) at the wavelength of 1.06$\mu$mis estimated to be $6.6\times10^{-5}$esu due to laser heating.

• Korean Journal of Optics and Photonics
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• v.22 no.3
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• pp.122-128
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• 2011

The AWG-filtering effect was investigated on a bidirectional 100-GHz-channel-spacing WDM-PON link using spectrum-sliced and RSOA-amplified light sources for downstream signals and a wavelength reuse technique for upstream signals. Signal performances of three different filtering AWGs, including Gaussian, trapezoidal, and rectangular types, were compared on link transmission with fiber nonlinear effects. As an extinction ratio of a downstream signal varied, the effect for both directional signals was analyzed and optimized. It was found that there was an optimal pass bandwidth of an AWG for the balance between relative intensity noise decrement and cross phase modulation noise increment as the bandwidth got wider.

• Current Optics and Photonics
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• v.4 no.4
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• pp.380-390
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• 2020

In this study, the traditional electron-blocking layer (EBL) in (In,Ga)N/GaN light-emitting diodes is replaced by a circular EBL that is the same size as the n-pad. The three-dimensional (3D) nonlinear Poisson, drift-diffusion, and continuity equations are adopted to simulate current transport in the LED and its characteristics. The results indicate that the local carrier-density distribution obtained for the circular EBL design is more uniform than that for the traditional EBL design. This improves the uniformity of local radiative recombination and local internal quantum efficiency (IQE) at high injection levels, which leads to a higher lumped IQE and lower efficiency droop. With the circular EBL, the lumped IQE is higher in the outer active region and lower in the active region under the n-pad. Since most emissions from the active region under the n-pad are absorbed by the n-pad, obviously, an LED with a circular EBL will have a higher external quantum efficiency (EQE). The results also show that this LED works at lower applied voltages.

• Current Optics and Photonics
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• v.5 no.5
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• pp.524-531
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• 2021

In an integral-imaging microscopy (IIM) system, a microlens array (MLA) is the primary optical element; however, surface errors impede the resolution of a raw image's details. Calibration is a major concern with regard to incorrect projection of the light rays. A ray-tracing-based calibration method for an IIM camera is proposed, to address four errors: MLA decentering, rotational, translational, and subimage-scaling errors. All of these parameters are evaluated using the reference image obtained from the ray-traced white image. The areas and center points of the microlens are estimated using an "8-connected" and a "center-of-gravity" method respectively. The proposed approach significantly improves the rectified-image quality and nonlinear image brightness for an IIM system. Numerical and optical experiments on multiple real objects demonstrate the robustness and effectiveness of our proposed method, which achieves on average a 35% improvement in brightness for an IIM raw image.

• Current Optics and Photonics
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• v.5 no.4
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• pp.458-465
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• 2021

Borate nonlinear optical crystals have been used as frequency conversion devices in many fields due to their unique transparency and nonlinearity from ultraviolet to visible spectral range. In this study, we theoretically and numerically investigate the properties of broadband second harmonic generation (SHG) in the recently reported Pna2₁-Ba₃Mg₃(BO₃)₃F₃ (BMBF) crystal. The technique is based on the simultaneous achievement of birefringence phase matching and group velocity matching between interacting waves. We discussed all factors required for broadband SHG in the BMBF in terms of two types of phase matching and group velocity matching conditions, the beam propagation direction and the corresponding effective nonlinearity and spatial walk-off, and the spectral responses. The results show that bandwidths calculated in the broadband SHG scheme are 220.90 nm (for Type I) and 165.85 nm (for Type II) in full-width-half-maximum (FWHM). The central wavelength in each case is 2047.76 nm for Type I and 1828.66 nm for Type II at room temperature. The results were compared with the non-broadband scheme at the telecom C-band.