• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.299-302
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• 2000

In this study, we have made the large holographic surface relief gratings on amorphous chalcogenide $As_{40}$$Ge_{10}$$Se_{15}$$S_{35}$ films by two beam interference using a He-Ne laser(632.8nm) light. The film thickness was about 0.6$\mu\textrm{m}$, we could magnify beam size by using beam expander. We made use $90^{\circ}$ holder which was made of reflection mirror and sample. Formed the surface relief structures were investigated using optical microscope. The diffraction efficiency was obtained by measuring +lst order intensity. In addition we investigated grating formation and diffraction efficiency as a function of polarization states which is linear or circular polarization. The results indicate that the grating was formed by linear polarized beam is better clear than that by circular polarized beam.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.644-647
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• 2001

Amorphous As-Ge-Se-S thin films have been studied with the aim of identifying optimum etching condition which can be used to produce holographic grating structure for use as diffractive optical elements. In this study, holographic gratings have been formed using He-Ne laser(632.8nm), and fabricated by the method of wet etching using NaOH etchant with various concentration(0.26N, 0.33N, 0.40N). The diffraction efficiency was obtained by +1st order intensity of the diffracted beam. The formed grating profiles were observed by atomic force microscope and showed that the expected grating profile could be achieved by controlling the etching time. Over-etching resulted in under-cutting of the grating lines. The highest 1st order diffraction efficiency for these gratings was about 5.05%.

• Korean Journal of Optics and Photonics
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• v.23 no.5
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• pp.211-216
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• 2012

We report a resonance fiber Bragg sensor interrogation based on a Fourier domain mode-locking (FDML) laser. The FDML laser is constructed based on a conventional ring laser cavity configuration with fiber Fabry-Perot tunable filter (FFP-TF). There are two sensor parts which are composed with two FBGs inside the laser cavity. Each sensor part provides a separate laser cavity for the FDML laser. The resonance frequencies of the laser cavities are 46.687 kHz and 44.340 kHz, respectively. We applied a static and a dynamic strain on the FBG sensor system. The slope coefficients of the measured relative wavelength shift and relative time interval from the static strain are found to be $0.61pm/{\mu}{\epsilon}$ and $0.8ns/{\mu}{\epsilon}$, respectively.

• Korean Journal of Optics and Photonics
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• v.11 no.6
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• pp.429-433
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• 2000

A study of the tunable fiber DFB laser using PZT-stretcher is presented. The device has an laser ocsillator by using a fiber Bragg grating at 1559.4 nm written directly into a 3-cm long $Er^{3+}$ doped fiber. Post UV-exposure method to provide the necessary phase shift is used for a single mode operation. The device shows the single mode operation of $230\muW$ output power and has a narrow linewidth of 35 kHz. The lasing wavelength of the laser can be tuned in a range of 3 nm by stretching the grating.rating.

• Clean Technology
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• v.22 no.3
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• pp.203-207
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• 2016

Here, we report a novel fabrication technique for patchable organic lasing sheet based on non-volatile liquid organic semiconductors and freestanding polymeric film with high flexibility and patchability. For this work, we have fabricated the second-order DFB grating structure, which leads to surface emission, embedded in the freestanding polymeric film. Using an ultra-violet (UV) curable polyurethaneacrylate (PUA) mixture, the periodic DFB grating structure can be easily prepared on the freestanding polymeric film via a simple UV curing process. Due to unsaturated acrylate remained in the PUA mixture after UV curing, the freestanding PUA film provides adhesive properties, which enable mounting of the patchable organic lasing sheet onto non-flat surfaces with conformal contact. To achieve laser actions in the freestanding resonator structure, a composite material of liquid 9-(2-ethylhexyl)carbazole (EHCz) and organic laser dyes was used as the laser medium. Since the degraded active materials can be easily refreshed by a simple injection of the liquid composite, such a non-volatile liquid organic semiconducting medium has degradation-free and recyclable characteristics in addition to other strong advantages including tunable optoelectronic responses, solvent-free processing, and ultimate mechanical flexibility and uniformity. Lasing properties of the patchable organic lasing sheet were also investigated after mounting onto non-flat surfaces, showing a mechanical tunability of laser emission under variable surface curvature. It is anticipated that these results will be applied to the development of various patchable optoelectronic applications for light-emitting displays, sensors and data communications.

• Korean Journal of Optics and Photonics
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• v.13 no.3
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• pp.235-239
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• 2002

A novel ultra-narrow linewidth DFB laser in the extended FBG ring cavity having kHz linewidth is presented. The method of linewidth compression was realized by introducing an extended fiber ring cavity into the cavity between the external FBG and the Bragg grating inside a DFB laser diode. Optimum optical feedback control was achieved by using an optical circulator and a variable optical attenuator to prevent mode hopping induced by spatial hole burning. To prove the validity of the proposed scheme, a self-heterodyne measurement set-up with fiber delay line of 63 km was utilized for the ultra-narrow linewidth measurement. A 3 dB linewidth of less than 3 kHz was demonstrated, which is resolution limited performance. This linewidth is equivalent to 3 dB linewidth of 2$\times$10$^{-8}$ nm.

• Smart Structures and Systems
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• v.9 no.5
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• pp.461-472
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• 2012

This study proposes an optics-based active sensing system for continuous monitoring of underground pipelines in nuclear power plants (NPPs). The proposed system generates and measures guided waves using a single laser source and optical cables. First, a tunable laser is used as a common power source for guided wave generation and sensing. This source laser beam is transmitted through an optical fiber, and the fiber is split into two. One of them is used to actuate macro fiber composite (MFC) transducers for guided wave generation, and the other optical fiber is used with fiber Bragg grating (FBG) sensors to measure guided wave responses. The MFC transducers placed along a circumferential direction of a pipe at one end generate longitudinal and flexural modes, and the corresponding responses are measured using FBG sensors instrumented in the same configuration at the other end. The generated guided waves interact with a defect, and this interaction causes changes in response signals. Then, a damage-sensitive feature is extracted from the response signals using the axi-symmetry nature of the measured pitch-catch signals. The feasibility of the proposed system has been examined through a laboratory experiment.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.181-182
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• 2007

In this paper, we investigated the diffraction grating efficiency on $Ge_{75}Se_{25}$ and Ag-doped amorphous chalcogenide $Ag/Ge_{75}Se_{25}$ thin film for used to volume hologram. The film thickness was 2 um and diffraction efficiency was obtained from He-Ne (632.8nm) and DPSS(532nm) (P:P) polarized laser beam on $Ge_{75}Se_{25}$ and Ag/$Ge_{75}Se_{25}$ thin films. As a result. for the films, the diffraction efficiency on Ag/$Ge_{75}Se_{25}$ double layer, was better than single $Ge_{75}Se_{25}$ thin films. The recording speed of DPSS laser is higher than that of He-Ne laser.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.2
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• pp.55-60
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• 2008

Multi-wavelength Erbium-doped fiber(EDF) ring laser was developed by using a sampled fiber Bragg grating reflecting multiple wavelengths, which was formed by impressing periodical pressure on the outside of a fiber Bragg grating. The wavelength spacing was varied to 4.1nm, 1.41nm and 0.82nm, by pressing the grating with the pressure period $200{\mu}m$, $580{\mu}m$ and $1000{\mu}m$, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.133-136
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• 2001

In this paper, we investigated the diffraction efficiency of polarization holography using by amorphous $Ag/As_{40}Ge_{10}Se_{15}S_{35}$ multi-layer thin films by He-Ne laser. Multi-layer structures were formed by alternating a layer of meta1(Ag) and chalcogenide( $Ag/As_{40}Ge_{10}Se_{15}S_{35}$ ). The holographic grating in these thin flims has been formed using a linealy polarized He-Ne laser light (633nm). The diffraction efficiency was investigated the two sample of $Ag/As_{40}Ge_{10}Se_{15}S_{35}-7$ layers and $Ag/As_{40}Ge_{10}Se_{15}S_{35}-15$ layers. As the results, we found that the diffraction efficiency of $Ag/As_{40}Ge_{10}Se_{15}S_{35}-7$ layers and $Ag/As_{40}Ge_{10}Se_{15}S_{35}-15$ layers were 1.7% and 2.5% respectively.