• Title/Summary/Keyword: Laser diodes

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Analysis of Lateral-mode Characteristics of 850-nm MQW GaAs/(Al,Ga)As Laser Diodes (850 nm GaAs/AlGaAs MQW LD의 Lateral-mode 특성 연구)

  • Yang, Jung-Tack;Kwak, Jung-Geun;Choi, An-Sik;Kim, Tae-Kyung;Choi, Woo-Young
    • Korean Journal of Optics and Photonics
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    • v.32 no.2
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    • pp.55-61
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    • 2021
  • The lateral-mode characteristics of 850-nm GaAs/(Al,Ga)As multiple-quantum-well laser diodes and their influence on the kinks in output optical power are investigated. For the investigation, self-consistent electro-thermal-optical simulation and measurement of fabricated devices are used. From this investigation, the optimal P-cladding thickness that provides single-lateral-mode operation is determined, so that high beam quality can be achieved even at high output powers.

Geometric error assessment system for linear guideway using laser-photodiodes (레이저-수광소자를 이용한 선형 이송측의 기하학적 오차측정 시스템)

  • Pahk, H.J.;Chu, C.N.;Hwang, S.W.
    • Journal of the Korean Society for Precision Engineering
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    • v.11 no.5
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    • pp.180-188
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    • 1994
  • Error assessment and evaluation for machine for machine tool slides have been considered as essential tools for improving accuracy. In this paper, a computer aided measurement technique is proposed using photo pin diodes of quadrant type and laser source. In thedeveloped system, three photo diodes are mounted on a sensor mounting table, and the sensored signal is processed by specially designed signal conditioner to give fine resolution with minimum noise. A micro computer inputs the processed signal, and the geometric errors of five degree of freedoms are successfully evaluated. Pitch, roll, yaw, vertical and horizontal straightness errors are thus assessed simultaneously for a machine tool slide. Calibration techniques such as optics calibration, photo diode calibration are proposed and implemented, giving precise calibration for the measurement system. The developed system has been applied to a practical machine tool slide, and has been found as one of efficient and precise technique for machine tool slide.

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Development of GaInP-AlGaInP High Power Red Laser Diodes

  • Kim, Ho-Gyeong;Kim, Chang-Ju;Choe, Jae-Hyeok;Bae, Seong-Ju;Song, Geun-Man;Sin, Chan-Su;Go, Cheol-Gi
    • Proceedings of the Korean Vacuum Society Conference
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    • 2013.02a
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    • pp.118-119
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    • 2013
  • High power, short wavelength red laser diodes (LDs) have attracted significant interests in a variety of fields due to their advantages in terms of reliability, compactness and cost. The higher brightness for human eyes is required, the shorter wavelength like 630 nm is necessary with higher output power. In this respect, LDs are promising as alternative candidates of gas or dye lasers for such applications due to their small size, high optical/electrical power conversion efficiency, robustness and so on. The crystalline quality of GaInP-AlGaInP multiple quantum wells (MQWs) and AlInP cladding layers is a crucial part in the device performance of GaInP red LDs. Here, we first investigated the effect of Si diffusion on the optical properties of GaInP-AlGaInP MQWs grown with different growth temperatures. Secondary ion mass spectroscopy (SIMS) measurements revealed that both the Mg and Si diffusion into MQW active region was significant. To reduce such diffusion, we employed undoped Mg and Si diffusion barrier and could improve the properties.Without both Mg and Si diffusion barriers, no lasing emission was observed. However, lasing emission was observed clearly for the red LDs with both Mg and Si diffusion barriers. We then investigated the temperature dependent optical properties of MQW layers grown with different well thicknesses (6, 8 and 10 nm). When the well thickness was 10 nm, the better crystalline quality was obtained. However, the observed LD performances were similar, probably due to the defects and impurities in the AlGaInP layer. Further investigation with the detailed analyses will be presented later.

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Effects of 630-nm Organic Light-emitting Diodes on Antioxidant Regulation and Aging-related Gene Expression Compared to Light-emitting Diodes of the Same Wavelength

  • Mo, SangJoon;Kim, Eun Young;Ahn, Jin Chul
    • Current Optics and Photonics
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    • v.6 no.3
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    • pp.227-235
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    • 2022
  • To investigate the aging-related physiological functions of organic light-emitting diodes (OLEDs), we examined mRNA expression changes in aging-related genes due to oxidative stress inhibition by 630-nm red light OLEDs. As a result of irradiating 630-nm OLED with an intensity of 5 mW/cm2 for 15 min, the viability of dermal fibroblasts significantly increased by 1.3-fold. In addition, reactive oxygen species generated by H2O2 were significantly reduced about 4.9-fold by irradiation with 630-nm OLED. Quantitative reverse-transcription polymerase chain reaction results showed that 630-nm OLEDs altered aging-related gene mRNA expression levels through antioxidant activity. The mRNA expression levels of matrix metalloproteinase1 (MMP1) and MMP9 decreased significantly, by about 2.2- and 2.5-fold, compared to the control group, whereas those of collagen, type I, and alpha 1 increased significantly, by 4.9-fold. The mRNA expression levels of cancer suppression genes p16 and p53 in dermal fibroblasts were also significantly reduced by 630-nm OLED irradiation, by about 1.4- and three-fold, respectively, compared to the control. Overall, it was confirmed that 630-nm OLED irradiation lowered the level of ROS formation induced by H2O2 in dermal fibroblasts, and that this antioxidant effect could regulate the mRNA expression levels of aging- and tumor suppression-related genes. This study shows a link between 630-nm OLED irradiation and anti-aging physiological functions such as antioxidant function, and suggests the potential of OLEDs as a useful light source for skin care.

Broadband Wavelength-swept Raman Laser for Fourier-domain Mode Locked Swept-source OCT

  • Lee, Hyung-Seok;Jung, Eun-Joo;Jeong, Myung-Yung;Kim, Chang-Seok
    • Journal of the Optical Society of Korea
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    • v.13 no.3
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    • pp.316-320
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    • 2009
  • A novel broadband wavelength-swept Raman laser was used to implement Fourier-domain mode locked (FDML) swept-source optical coherence tomography (SS-OCT). Instead of a conventional semiconductor optical amplifier, this study used broadband optical fiber Raman amplification, over 50 nm centered around 1545 nm, using a multi-wavelength optical pumping scheme, which was implemented with the four laser diodes at the center wavelengths of 1425, 1435, 1455 and 1465 nm, respectively, and the maximum operating power of 150 mW each. The operating swept frequency of the laser was determined to 16.7 kHz from the FDML condition of 12 km optical fiber in the ring cavity. The OCT images were obtained using the novel broadband wavelengthswept Raman laser source.

Application of Voltage-Controlled 12-Laser Diode Array in the Optical Fiber Communication (전압에 의하여 구동 가능한 12-Laser Diode Array의 광통신에의 응용)

  • Lee, Shang-Shin;Jhee, Yoon-Kyoo
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.27 no.11
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    • pp.1-8
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    • 1990
  • We made a 12-Laser Diode Array consisting of 12 Graded Index Separate Confinement (GRINSCH) InGaAs/Inp Buried Heterostructure 4 Quantum Well Laser Diodes and examined the potential of controlling lasing operation of each laser diode by the voltage to its electroabsorption region. Using Si V-Groove with 12 V-grooves, a 12-Laser Diode Array, and 12 optical fibers, we investigated the various characteristics of each laser diode by changing the voltage to its electro-absorption region. Finally, we thought over the promising way of implementing optical local area communication between electric circuit boards or between subscribers and a central office using a 12-Laser Diode Array, Si V-groove, and optical fibers.

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Generation of coherent bulk and folded acoustic phonon oscillations in InGaN light-emitting diodes structure (InGaN LED 구조에서 결맞는 bulk phonon과 folded acoustic phonon의 생성)

  • Yang Ji-Sang;Jo Yeong-Dal;Lee Gi-Ju;O Eun-Sun;Kim Dae-Sik
    • Proceedings of the Optical Society of Korea Conference
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    • 2001.02a
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    • pp.54-55
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    • 2001
  • Recently, there has been much interests in InGaN/GaN multiple-quantum-well (MQW) structures due to their applicability as optoelectronic devices such as light-emitting diodes (LEDs) and laser diodes [1]. Their ultrafast and physical properties are also of significant interests. Anomalously large acoustic phonon oscillations have been observed using ultrafast lasers in InGaN MQWs [2]. In this study, we have peformed femtosecond pump-probe experiments in the reflection geometry on 5 periods InGaN/GaN MQW LED structure with well width of 20$\AA$ and barrier width of 100$\AA$ at room temperature. (omitted)

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In-line Dual-Mode DBR Laser Diode for Terahertz Wave Source

  • Chung, Youngchul
    • Current Optics and Photonics
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    • v.4 no.6
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    • pp.461-465
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    • 2020
  • A dual-mode laser terahertz source consisting of two in-line distributed Bragg reflector (DBR) laser diodes (LD) is proposed. It is less susceptible to residual reflections from facets than an in-line dual-mode distributed feedback (DFB) LD. The characteristics of the proposed terahertz source are theoretically investigated using a split-step time-domain simulation. It is shown that terahertz waves of frequencies from 385 GHz to 1725 GHz can be generated by appropriate thermal tuning of two DBR LDs. The dual-mode DBR LD terahertz source exhibits good spectral quality for residual facet reflectivity below 0.02, but facet reflectivity of the in-line dual-mode DFB LD terahertz source should be below 0.002 to provide similar spectral quality.

Effect of Photobiomodulation on the Mesenchymal Stem Cells

  • Yoo, Shin Hyuk
    • Medical Lasers
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    • v.9 no.2
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    • pp.119-125
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    • 2020
  • Photobiomodulation forms the basis of photomedicine and is defined as the effect of coherent or non-coherent light sources, such as low-level lasers and light-emitting diodes, on cells and tissues. This treatment technique affects cell functions, proliferation, and migration, and plays an important role in tissue regeneration. Mesenchymal stem cells (MSCs) are known to be beneficial for tissue regeneration, and the combination of stem cell therapy and laser therapy appears to positively affect treatment outcomes. In general, a low-power laser has a positive effect on MSCs, thereby facilitating improvements in different disease models. This study elucidates the mechanisms and effects of low-power laser irradiation on the proliferation, migration, and differentiation of various MSCs that have been examined in different studies.

Channel Orientation Dependent Electrical Characteristics of Low Temperature Poly-Si Thin-film Transistor Using Sequential Lateral Solidification Laser Crystallization

  • Lai, Benjamin Chih-ming;Yeh, Yung-Hui;Liu, Bo-Lin
    • 한국정보디스플레이학회:학술대회논문집
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    • 2007.08b
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    • pp.1263-1265
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    • 2007
  • The electrical characteristics of low temperature poly-Si (LTPS) thin-film transistors (TFT) with channel parallel and perpendicular to the direction of lateral growth were studied. The poly-Si film was crystallized using sequential lateral solidification (SLS) laser crystallization technique. The channel orientation dependent turn-on characteristics were investigated by using gated-diodes and capacitance-voltage measurements

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