• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.95-98
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• 1999

ZnO thin films on (001) sapphire substrates have been deposited by pulsed laser deposition technique using a Nd:YAG laser with the wavelength of 355 nm. In order to investigate the effect of the deposition conditions on the properties of ZnO thin films at an oxygen pressure of 350 mTorr, the experiment has been Performed at various substrate temperatures in the range of 20$0^{\circ}C$ to $700^{\circ}C$. According to XRD, (002) textured ZnO films of high crystalline quality have been obtained and the intensity of UV emission was the highest at 40$0^{\circ}C$ substrate temperature.

• Korean Journal of Optics and Photonics
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• v.28 no.1
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• pp.22-27
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• 2017

Time-encoded near-infrared spectroscopy (NIRS) system is proposed, based on a near-infrared (NIR) swept laser source, for comparison to the conventional NIRS method using a detector-type spectrometer. The cavity of the NIR swept laser source consists of a semiconductor optical amplifier (SOA) with a gain region around 800 nm, and several fiber-optic components. To change the output wavelength in time using an applied electric radio-frequency signal, an acousto-optic tunable filter (AOTF) is introduced in the fiber ring cavity configuration. To demonstrate the feasibility of an NIR swept laser source for NIRS imaging, the spectroscopic comparison of two kinds of absorbance-measuring systems a detector-type spectrometer using a white light source, and a source-type spectrometer using an NIR swept laser is successfully performed with an NIR-absorbing dye.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.04a
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• pp.197-200
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• 2000

All-optical NOR logic device was realized by use of two pump signals with a single wavelength and a semiconductor optical amplifier(SOA). Specially, Mach-Zehnder(MZ) modulator was used for an external modulation of the pump signals. To obtain the sufficient gain saturation of the SOA, pump signals are amplified by an Er-doped fiber amplifier(EDFA) at the input of the SOA. Pump and probe signals are obtained from a DFB laser diode(${\lambda}_p$=1554 nm) and a tunable laser diode(${\lambda}_s$=1535 nm), respectively. The operation characteristics of the NOR logic device are successfully measured and demonstrated at the modulation frequency of 4.83 MHz.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.88-91
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• 2003

The crystal structure and properties of YBa$_2$Cu$_3$$O_{7-x}$(YBCO) and CeO$_2$ thin films deposited on r-plane (1(equation omitted)02) sapphire substrate by pulsed- laser deposition(PLD) have been investigated. C-axis oriented epitaxial YBCO thin films with critical temperature (Tc) of 88 K were routinely grown on (200) oriented CeO$_2$ buffer layers with thickness in the range between 20 to 80 nm. When the thickness of the (200)oriented CeO$_2$ buffer layer increases over than 80 nm, the superconducting properties of YBCO thin films on that were deteriorated. The decrease in Tc of YBCO thin films was explained by the microcrack formation in CeO$_2$ buffer layer. These results indicate that the thickness of the (200) oriented CeO$_2$ buffer layer is critical to the epitaxial YBCO thin nim growth on r-plane (1(equation omitted)02) sapphire substrate.e.

• Journal of the Semiconductor & Display Technology
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• v.6 no.1 s.18
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• pp.7-10
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• 2007

In an effort to reduce weaknesses of existing laser displacement sensor-based system, a sensing device for distance and balance of mask-substrate gap using touch-type displacement sensor was suggested. The device suggested in this study is expected to solve the problems of prices and reflections, by means of a touch-type sensor. LCD exposure equipment stage system including suggested sensing device was realized to assess the characteristics of sensing the balance and gap between mask and substrate. It was verified that a touch-type displacement sensor-based device to adjust the balance and distance of mask-substrate gap suggested in this study can be applicable to LCD expose equipment in practice.

• Journal of the Semiconductor & Display Technology
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• v.7 no.4
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• pp.1-5
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• 2008

There is a need to enlarge the mother glass substrate in OLED to raise its productivity and to realize OLED TV. On the other hand, some difficulties may arise regarding the deflection of a large glass substrate during its handling operation due to its thinness $(0.5\sim0.7t)$, which is not even enough to allow it to stand its own mass. This thesis proposes a conceptual plan for the application of the clamping- and bending-end conditions to the glass substrate handler. To verify proposed plan, the non-contact 3 dimensional measuring instrument is developed. The composition of the 3 dimensional measuring instrument measures shape of the product using X-Y stage robot and laser distance sensor. X-Y stage robot and laser distance sensor are controlled by LabVIEW language. To calibrate measuring instrument, the direction conversion of the Euler angle was used. In order to confirm deflection of the glass substrate, the experiment was carried out at the bending end boundary condition and the proposed effect was verified.

• Korean Journal of Optics and Photonics
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• v.13 no.5
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• pp.425-429
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• 2002

In this paper, we propose new simple schemes for all-optical serial-to-parallel and parallel-to-serial data format converters based on a semiconductor laser amplifier in a loop mirror (SLALOM) for all-optical data processing. They have the advantages of simple and easily expandable structure, efficient operation and easy implementation. We implement the proposed all-optical data converters. and experimentally demonstrate their operation.

• Journal of Sensor Science and Technology
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• v.27 no.5
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• pp.317-327
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• 2018

Terahertz (THz) time-domain spectroscopy(TDS), imaging techniques, and related systems have become mature technologies, widely used in many universities and research laboratories. However, the development of creative technologies still requires improved THz application systems. A few key points are discussed, including the innovative advances of mode-locking energy-emitting semiconductor lasers and better photoconductive semiconductor quantum structures. To realize a compact, low cost, and high performance THz system, it is essential that THz spectroscopy and imaging technologies are better characterized by semiconductor and nano-devices, both static and time-resolved. We introduce the THz spectroscopy and imaging systems, the OSCAT(Optical Sampling by laser CAvity Tuning) system and the ASOPS(ASynchronous Optical Sampling) system, are constructed by our research team. We report on the THz images obtained from their use.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.2
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• pp.81-86
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• 2005

This paper proposes a non-destructive ESPI technique to quantitatively evaluate defects inside a semiconductor package. The inspection system consists of the ESPI system, a thermal loading system and an adiabatic chamber. The technique is high feasibility for non-destructive testing of a semiconductor and overcomes the weaknesses of previous techniques, such as time-consumption and difficult quantitative evaluation. Most defects are classified as delamination defects, resulting from the insufficient adhesive strength between layers and from non-homogeneous heat spread. Ninety percent of the tested samples had delamination defects which originated at the corner of the chip and nay be related to heat spread design.

• Current Optics and Photonics
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• v.4 no.3
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• pp.161-173
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• 2020

Colloidal quantum dots (QDs) have gained tremendous attention as a key material for highly advanced display technologies. The performance of QD light-emitting diodes (QLEDs) has improved significantly over the past two decades, owing to notable progress in both material development and device engineering. The brightness of QLEDs has improved by more than three orders of magnitude from that of early-stage devices, and has attained a value in the range of traditional inorganic LEDs. The emergence of high-luminance (HL) QLEDs has induced fresh demands to incorporate the unique features of QDs into a wide range of display applications, beyond indoor and mobile displays. Therefore it is necessary to assess the present status and prospects of HL-QLEDs, to expand the application domain of QD-based light sources. As part of this study, we review recent advances in HL-QLEDs. In particular, based on reports of brightness exceeding 10⁵ cd/㎡, we have summarized the major approaches toward achieving high brightness in QLEDs, in terms of material development and device engineering. Furthermore, we briefly introduce the recent progress achieved toward QD laser diodes, being the next step in the development of HL-QLEDs. This review provides general guidelines for achieving HL-QLEDs, and reveals the high potential of QDs as a universal material solution that can enable realization of a wide range of display applications.