• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.06a
• /
• pp.131-131
• /
• 2010

The power of semiconductor laser diodes has been limited primarily by the heating effects which occur at high optical intensities. The actual limiting event can take one of a number of forms such as. catastrophic optical damage or filamentation. A general approach to this problem is to design a heterostructure which creates a high powered output while maintaining low internal optical intensities. A graded index separate confinement heterostructure (GRIN-SCH) is one such structure that accomplishes the above task. Here, the active region is sandwiched between graded index layers where the index of refraction increases nearer to the active layer. This structure has been shown to yield a high efficiency due to the confinement of both the optical power and carriers, thereby reducing the optical intensity required to achieve higher powers. The optical confinement also reinforces the optical beam quality against high power effects. Quantum dots have long been a desirable option for laser diodes due to the enhanced optical properties associated with the zeroth dimensionality. In our work, we use PICS3D software created by Crosslight Software Inc. to simulate the performance of In0.67A10.33As/A10.2Ga0.8AsquantumdotsusedwithaGRIN-SCH. The simulation tools are used to optimize the GRIN-SCH structure for high efficiency and optical beam quality.

• Current Optics and Photonics
• /
• v.3 no.6
• /
• pp.485-495
• /
• 2019

Photobiomodulation (PBM) using organic light emitting diodes (OLEDs) surface light sources have recently been claimed to be the next generation of PBM light sources. However, the differences between light emitting diodes (LEDs) and OLED mechanisms in vitro and in vivo have not been well studied. In vivo mouse models were used to investigate the effects of OLED irradiation on cellular function and cutaneous wound healing compared to LED irradiation. Mice in the LED- and OLED-irradiated groups were subjected to irradiation with 6 J/㎠ LED and OLED (630 nm), respectively, for 14 days after wounding, and some mice were sacrificed for the experiments on days 3, 7, 10, and 14. To evaluate wound healing, we performed hematoxylin-eosin and Masson's trichrome staining and quantified collagen density by computerized image analysis. The results showed that the size of the wound, collagen density, neo-epidermis thickness, number of new blood vessels, and number of fibroblasts and neutrophils was significantly influenced by LED and OLED irradiation. The tissue levels of interleukin (IL)-β, IL-6 and tumor necrosis factor (TNF)-α were investigated by immunohistochemical staining. LED and OLED irradiation resulted in a significant increase in the tissue IL-β and IL-6 levels at the early stage of wound healing (P < 0.01), and a decrease in the tissue TNF-α level at all stages of wound healing (P < 0.05), compared to the no-treatment group. The expression levels of the genes encoding vascular endothelial growth factor and transforming growth factor-beta 1 were significantly increased in LED and OLED-irradiated wound tissue at the early stage of wound healing (P < 0.01) compared to the no-treatment group. Thus, OLED as well as LED irradiation accelerated wound healing by modulating the synthesis of anti-inflammatory cytokines and the expression levels of genes encoding growth factors, promoting collagen regeneration and reducing scarring. In conclusion, this suggests the possibility of OLED as a new light source to overcome the limitations of existing PBMs.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.11a
• /
• pp.200-200
• /
• 2003

Polycrystalline Si(polysilicon) TFTs have opened a way for the next generation of display devices, due to their higher mobility of charge carriers relative to a-Si TFTs. The polysilicon W applications extend from the current Liquid Crystal Displays to the next generation Organic Light Emitting Diodes (OLED) displays. In particular, the OLED devices require a stricter control of properties of gate oxide layer, polysilicon layer, and their interface. The polysilicon layer is generally obtained by annealing thin film a-Si layer using techniques such as solid phase crystallization and excimer laser annealing. Typically laser-crystallized Si films have grain sizes of less than 1 micron, and their electrical/dielectric properties are strongly affected by the presence of grain boundaries. Impedance spectroscopy allows the frequency-dependent measurement of impedance and can be applied to inteface-controlled materials, resolving the respective contributions of grain boundaries, interfaces, and/or surface. Impedance spectroscopy was applied to laser-annealed Si thin films, using the electrodes which are designed specially for thin films. In order to understand the effect of grain size on physical properties, the amorphous Si was exposed to different laser energy densities, thereby varying the grain size of the resulting films. The microstructural characterization was carried out to accompany the electrical/dielectric properties obtained using the impedance spectroscopy, The correlation will be made between Si grain size and the corresponding electrical/dielectric properties. The ramifications will be discussed in conjunction with active-matrix thin film transistors for Active Matrix OLED.

• Korean Journal of Optics and Photonics
• /
• v.5 no.1
• /
• pp.100-105
• /
• 1994

We have reduced the oscillating linewidth of the commercial single mode InGaAsP visible laser diodes which emits in the 657 nm region of the spectrum down to 10 MHz by making a extended cavity employing the Littrow-type grating. The wavelength tuning characteristics of the commercial visible laser diode (CQL820D, Philips Co.) for the grating angle, laser temperature, and injection currents were measured by using the wavemeter. The proportional coefficients of the laser were found to be 1 THzlmrad, 32.4 GHz/K, and 6.14 GHz/mA, respectively.tively.

• Transactions on Electrical and Electronic Materials
• /
• v.16 no.2
• /
• pp.65-69
• /
• 2015

Low level laser therapy (LLLT) has facilitated an improvement in acupuncture treatment. In this study, we stimulated Shaochong (HT9), Dadun (LR1), Shaohai (HT3), and Yingu (KI10) acupoints with pulsed laser diodes 532 nm [green laser] and 658 nm [red laser] in rats with induced middle cerebral artery occlusion(MCAO). The animals were divided into 6 groups: intact control; MCAO control without LLLT; LLLT with red laser at HT9·LR1 and HT3·KI10 (RR); LLLT with green laser at HT9·LR1 and HT3·KI10 (GG); LLLT with green laser at HT9·LR1 and red laser at HT3·KI10 (GR); and LLLT with red laser at HT9·LR1 and green laser at HT3·KI10 (RG). We evaluated the immunohistochemical changes in the hippocampal CA1 region, and complete blood count changes. Compared to the MCAO control group, the RG group showed a significant decrease in Bax and cytochrome c levels in the hippocampus, and a significant increase in hemoglobin level, hematocrit, total white blood cell, neutrophil, lymphocyte, monocyte, and erythrocyte counts.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.11a
• /
• pp.23-23
• /
• 2003

GaN-related semiconductors are of great technological importance for the fabrication of optoelectronic devices, such as blue and ultra violet light emitting diodes (LEDs), laser diodes, and photo-detectors. One of the most important applications of GaN-based LEDs is solid-state lighting, which could replace incandescent bulbs and ultimately fluorescent lamps. For solid-state lighting applications, the achievement of high extraction efficiency in LED structures is essential. For flip-chip LEDs (FCLEDS), the formation of low resistance and high reflective p-GaN contact is crucial. So far, a wide variety of different methods have been employed to improve the ohmic properties of p-type contacts to GaN. For example, surface treatments using different chemical solutions have been successfully used to produce high-quality ohmic contacts, Metallization schemes, such as Ta/Ti contacts to p-GaN, were also investigated. For these contacts, the removal of hydrogen atoms from the Mg atoms doped n the GaN was argued to be responsible for low contact resistances.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.11a
• /
• pp.150-150
• /
• 2003

wide bind gap과 wurtzite hexagonal structure를 가지고 있으며 청색 발광 및 청자색 레이저 특성을 보이는 III-V족 화합물반도체 GaN는 laser diodes (LD) 및 light emitting diodes (LED) 재료로 주목받고있는 주요 전자재료이다. 본 연구에서는 GaN를 chemical vapor deposition (CVD) 법을 이용하여 vapor-liquid-solid (VLS) mechanisum에 의하여 GaN나노와이어 형태로 성장시켰다. 기판은 (001)Si을 사용하였고 suputtering을 이용하여 GaN와 AlN의 double buffer layer (DBL)를 증착시켰으며 촉매로는 Ni을 사용하였다. 또한, 원료로는 고순도 Ga금속과 NH$_3$ gas를, carrier gas로는 Ar을 사용하여 GaN/AlN/(001)Si 위에 GaN 나노와이어를 성장시켰다. 성장된 GaN 나노와이어는 DBL의 두께, Ga source의 양, 튜브 안의 압력, 튜브 안의 위치 등의 제 공정변수에 따라 tangled, straight 등의 다양한 형상을 보였으며 지름은 약 30~100 nm, 길이는 수 $\mu\textrm{m}$로 관찰되었다. GaN나노와이어의 결정성, 형상 및 발광특성 등을 x-ray diffraction (XRD), photoluminesence (PL), scanning electron microscope (SEM), transmision electron microscope (TEM) 등을 이용하여 측정하였으며 제 공정변수와의 상관관계를 규명하였다.

• Proceedings of the Korean Vacuum Society Conference
• /
• 1998.02a
• /
• pp.103-104
• /
• 1998

GaN is a ppromising materials fot applications in the blue/ultraviolet (UV) light emitting diodes (LEDs)[1] and laser diodes (LDs) [2] High quality ohmic contacts are very critical to these applications since the qualities of ohmic contact system pplay an impportant roles in the high efficient device opperations. For the n-GaN there have been many repports about ohmic contacts and the sppecific contact resistance were as low as from 10-8$\Omega$cm2 However for the ohmic contacts on pp-GaN much fewer study were repported and the sppecific contact resistivity was much lower than of n-GaN. In this ppapper we repport a new Ni/ppt/Au metallization scheme and discuss the mechanism of ohmic formation

• Korean Journal of Optics and Photonics
• /
• v.6 no.4
• /
• pp.359-364
• /
• 1995

A wavelength measurement system has been made using a monochromator and computer interfacing. The spectra of several light emitting diodes and the wavelength characteristics of Fabry-Perot LD and DFB LD have been measured with this system. The results show that this system can be practicalIy used in analyzing the lasing mode and the wavelength characteristics of the semiconductor lasers. asers.

• Proceedings of the KIEE Conference
• /
• 1994.07b
• /
• pp.1571-1573
• /
• 1994

In order to substitute for the conventional measuring system which could bring about technical inconveiences, measuring techniques for the fast transient high voltage upto 100 kV and small signals less than 1 V are developed by use of Laser Source with Packets cell. for the former, capacitive voltage divider was specially designed for reducing the impulse voltage less than the half-wave voltage of pockets cell. For the tatter, interferometer type was employed as a mean to removing the fluctuation of Laser output intensity. And also the main beam through the Pockels cell and the reference beam from the Laser source are seperated before being detected respectively by photo diodes. And then, these two signals are amplified and compared for detecting only the small signals applied across the Pockels cell. Throughout this work, Laser-based measuring system is likely to enable us, at this moment, to detect correctly lightning impulse voltage upto 100 kV and the small signals less than 1 V upto the 2 MHz. Such a system could be employed as a possible diagnostic measuring system at the substation.