• Korean Journal of Materials Research
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• v.8 no.5
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• pp.419-423
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• 1998

The conditions for optimizing mass transport for making buried heterostructure (BH) InGaAsP/lnP lasers are discussed. The double heterostructure InGaAsP/lnP laser structures were grown by Liquid Phase Epitaxy (LPE) and etched into mesas. The active layer was selectively etched along [llO] and the mass transport was carried out in the LPE reactor to cover the sides of the active layer and form a BH structure. The threshold temperature for the appreciable mass transport is measured to be 670$670^{\circ}C$ when the holding time is set to 40 min. The width of the region re¬filled by mass transport is observed to increase as the temperature increases.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.6
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• pp.773-782
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• 2016

The performance of the CT-TDLAS (computed tomography-tunable diode laser absorption spectroscopy) is strongly dependent upon the line broadening functions. The line of the laser beam used in the TDLAS is scattered by the natural broadening, the collisional broadening and the doppler broadening. The influence of the natural broadening to the experimental spectra obtained in the TDLAS is negligible. The influences of the collisional broadening and the doppler broadening to the experimental spectra are relatively large, in high pressure gas flows and in high temperature low pressure gas flows, respectively. In this study, optimal coefficients are proposed for the doppler broadening function by using the experimental data obtained in a flat burner test. The optimal coefficients were ${\gamma}_j=0.16$ and n=0.37. Using these coefficients, the temperature and concentration distributions at the engine exhaust gas pipe have been calculated showing their validities.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.37 no.1
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• pp.27-34
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• 2000

In this paper, carrier transport mechanism and modulation response for SCH(Separate Confinement Heterostructure) SQW(Single Quantum Well) laser diodes were studied. In order to explain carrier transport mechanism, both carrier density and current density were calculated. The recombination current density in the quantum well as a function of the SCH length was also calculated. For the modulation response, linearizing the rate equation, we calculated the bandwidth, relaxation oscillation frequency, damping factor, and the K-factor.

• Transactions of the Society of Information Storage Systems
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• v.2 no.2
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• pp.138-143
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• 2006

We developed a numerical simulator in order to study the Super-RENS/ROM (Super REsolution Near-Field Structure, Read Only Memory) using 3-dimensional FDTD (finite difference time domain) method. The simulation can be performed by three steps. In the first step, we utilized the vector-diffraction theory to calculate the characteristics of incident laser beam from the object-lens to the surface of the disk. At the second step, we fed the calculated result as an input for the main FDTD simulations on the optical layers in the disk structure. After performed the FDTD simulations, we took near-to-far field transformation for the reflected signal, from the surface of the disk to the detector. Finally, we can get reflected signal at the photo-diode. Using this developed simulator, we were able to study about the reading signal from various disk structures as a function of a laser beam position. We calculated reading signals for various pit sizes for Super-ROM structure, and it is found that the simple optical diffraction theory can not explain the reading mechanism of Super-ROM, and more complicated temperature dependent physics must be involved.

• Korean Journal of Optics and Photonics
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• v.3 no.1
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• pp.43-49
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• 1992

A microwave free electron laser which consists of Marx generator, vacuum diode, bifilar helical wiggler, and guide solenoid was designed and constructed. The analysis of the magnetic field distributions of the bifilar helical wiggler and computer simulation of electron trajectories with the perpendicular effect of space charges led to the conclusion that the magnetic field distributions are suitable for the electron beam injection. Output frequency in a single $TE_{11}$

• Current Optics and Photonics
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• v.5 no.3
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• pp.298-305
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• 2021

Modern distance sensing methods employ various measurement principles, including triangulation, time-of-flight, confocal, interferometric and frequency comb. Among them, the triangulation method, with a laser light source and an image sensor, is widely used in low-cost applications. We developed an omnidirectional two-dimensional (2D) distance sensor based on the triangulation principle for indoor floor mapping applications. The sensor has a range of 150-1500 mm with a relative resolution better than 4% over the range and 1% at 1 meter distance. It rotationally scans a compact one-dimensional (1D) distance sensor, composed of a near infrared (NIR) laser diode, a folding mirror, an imaging lens, and an image detector. We designed the sensor layout and configuration to satisfy the required measurement range and resolution, selecting easily available components in a special effort to reduce cost. We built a prototype and tested it with seven representative indoor wall specimens (white wallpaper, gray wallpaper, black wallpaper, furniture wood, black leather, brown leather, and white plastic) in a typical indoor illuminated condition, 200 lux, on a floor under ceiling mounted fluorescent lamps. We confirmed the proposed sensor provided reliable distance reading of all the specimens over the required measurement range (150-1500 mm) with a measurement resolution of 4% overall and 1% at 1 meter, regardless of illumination conditions.

• International Journal of Korean Welding Society
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• v.1 no.2
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• pp.23-29
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• 2001

In this study, a preview-sensing visual sensor system is constructed far weld seam tracking in GMA welding. The visual sensor system consists of a CCD camera, a diode laser system with a cylindrical lens, and a band-pass-filter to overcome the degrading of image due to spatters and/or arc light. Among the image processing methods, Hough transform method is compared with the central difference method from a viewpoint of the capability for extracting the accurate feature position. As a result, it was revealed that Hough transform method can more accurately extract the feature positions and it can be applied to real time weld seam tracking. Image processing which includes Hough transform method is carried out to extract straight lines that express laser stripe. After extracting the lines, weld joint position and edge points are determined by intersecting the lines. Even though the image includes a spatter trace on it, it is possible to recognize the position of weld joint. Weld seam tracking was precisely implemented with adopting Hough transform method, and it is possible to track the weld seam in the case of offset angle is in the region of $\pm$ $15^{\circ}$.

• Clinical and Experimental Reproductive Medicine
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• v.28 no.2
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• pp.147-153
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• 2001

Objective: The present study was performed to investigate the efficiency of partial laser assisted hatching (p-LAH; lased 1/2 ZP width from ZP edge) on hatching of mouse blastocysts. Methods: We used non-contact $1.48{\mu}m$ diode laser (MTM, Switzland) to create a precise hole on zona pellucida. 2-cell embryos were collected from the mouse (ICR) oviduct at 48 hours after hCG administration. Collected 2-cell embryos were cultured in the P-1 medium supplemented with 0.4% BSA. For experiments, embryos at 8-cell stage were used after $20{\sim}22$ hours in culture. After conventional (c-LAH) or partial laser assisted hatching, the embryos were further cultured in P-1 medium supplemented with 0.4% BSA for 3 days. To compare efficiency of complete and partial laser assisted hatching, hatching rate, hatching time and blastocyst diameter and zona pellucida thickness at hatching time were investigated. Embryos were examined every 12 hours. Blastocyst diameter and zona pellucida thickness at hatching time were measured with an ocular micrometer. Results: Hatching rates of p-LAH group (84.2%) was significantly higher than that of control group (39.3%), but there was no difference between the p-LAH (84.2%) and c-LAH (91.2%). p-LAH group was hatched 12 hours earlier than control group, but hatched 12 hours later than c-LAH group. The diameter of blastocyst at hatching time of p-LAH group ($113.1{\pm}6.4{\mu}m$) was smaller than that of control group ($122.2{\pm}5.0{\mu}m$), but larger than that of c-LAH group ($102.2{\pm}2.7{\mu}m$). Zona pellucida thickness at hatching time of p-LAH group ($6.4{\pm}0.9{\mu}m$) was thicker than that of control group ($4.5{\pm}1.5{\mu}m$), but thinner than that of c-LAH group ($10.0{\pm}0.8{\mu}m$). Conclusion: These results suggest that p-LAH may maintains the cell arrangement of early embryos to ensure successful development and prevent precocious hatching of blastocyst when compare to c-LAH and conventional (acidic tyrode) AH. Thus, p-LAH may provide a valuable and effective AH technique for human ART program.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.391-392
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• 2012

In these days, the desire for the precise and tiny displays in mobile application has been increased strongly. Currently, laser displays ranging from large-size laser TV to mobile projectors, are commercially available or due to appear on the market [1]. In order to achieve a mobile projectors, the semiconductor laser diodes should be used as a laser source due to their size and weight. In this presentation, the continuous etch characteristics of Pd and AlGaN/GaN superlattice for the fabrication of blue laser diodes were investigated by using inductively coupled $CHF_3$ and $Cl_2$ -based plasma. The GaN laser diode samples were grown on the sapphire (0001) substrate using a metal organic chemical vapor deposition system. A Si-doped GaN layer was grown on the substrate, followed by growth of LD structures, including the active layers of InGaN/GaN quantum well and barriers layer, as shown in other literature [2], and the palladium was used as a p-type ohmic contact metal. The etch rate of AlGaN/GaN superlattice (2.5/2.5 nm for 100 periods) and n-GaN by using $Cl_2$ (90%)/Ar (10%) and $Cl_2$ (50%)/$CHF_3$ (50%) plasma chemistry, respectively. While when the $Cl_2$/Ar plasma were used, the etch rate of AlGaN/GaN superlattice shows a similar etch rate as that of n-GaN, the $Cl_2/CHF_3$ plasma shows decreased etch rate, compared with that of $Cl_2$/Ar plasma, especially for AlGaN/GaN superlattice. Furthermore, it was also found that the Pd which is deposited on top of the superlattice couldn't be etched with $Cl_2$/Ar plasma. It was indicating that the etching step should be separated into 2 steps for the Pd etching and the superlattice etching, respectively. The etched surface of stacked Pd/superlattice as a result of 2-step etching process including Pd etching ($Cl_2/CHF_3$) and SLs ($Cl_2$/Ar) etching, respectively. EDX results shows that the etched surface is a GaN waveguide free from the Al, indicating the SLs were fully removed by etching. Furthermore, the optical and electrical properties will be also investigated in this presentation. In summary, Pd/AlGaN/GaN SLs were successfully etched exploiting noble 2-step etching processes.

• Journal of Dental Rehabilitation and Applied Science
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• v.40 no.2
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• pp.55-63
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• 2024

Purpose: This study aimed to assess the antimicrobial efficacy of an 810-nm infrared diode laser with indocyanine green (ICG) against Staphylococcus aureus on sandblasted, large grit, and acid-etched (SLA) titanium surfaces, comparing its effectiveness with alternative chemical decontamination modalities. Materials and Methods: Biofilms of S. aureus ATCC 25923 were cultured on SLA titanium disks for 48 hours. The biofilms were divided into five treatment groups: control, chlorhexidine gluconate (CHX), tetracycline (TC), ICG, and 810-nm infrared diode laser with ICG (ICG-PDT). After treatment, colony-forming units were quantified to assess surviving bacteria, and viability was confirmed through confocal laser-scanning microscope (CLSM) imaging. Results: All treated groups exhibited a statistically significant reduction in S. aureus (P < 0.05), with notable efficacy in the CHX, TC, and ICG-PDT groups (P < 0.01). While no statistical difference was observed between TC and CHX, the ICG-PDT group demonstrated superior bacterial reduction. CLSM images revealed a higher proportion of dead bacteria stained in red within the ICG-PDT groups. Conclusion: Within the limitations, ICG-PDT effectively reduced S. aureus biofilms on SLA titanium surfaces. Further investigations into alternative decontamination methods and the clinical impact of ICG-PDT on peri-implant diseases are warranted.