• Korean Journal of Optics and Photonics
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• v.16 no.1
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• pp.99-102
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• 2005

We fabricated a tunable fiber ring laser consisting of a novel strain device and fiber Bragg gratings. The lasing power and FWHM bandwidth of the optical fiber ring laser was -12dBm and 0.05nm respectively. The fiber ring laser was tuned as much as 10nm at a 8000.

• Current Photovoltaic Research
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• v.3 no.4
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• pp.126-129
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• 2015

Over the last two decades, quantum dot (QD) solar cells have attracted much attention due to the unique properties of QDs, including band gap tunability, slow hot electron cooling, and multiple exiton generation effect. However, most of the QDs employed in photovoltaic devices contain toxic heavy-metals such as cadmium or lead, which may limit the commercial application. Therefore, recently, heavy-metal-free QDs such as Cu-In-S or Cu-In-Se have been developed for application in solar cells. Here, we review the research trends in heavy-metal-free QD solar cells, mainly focusing on Cu-In-Se QD-sensitized solar cells (QDSC).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.362-363
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• 2006

In this study, the filter was designed for tuning center frequency and fabricated using ($Sr,Ba)TiO_3$ ferroelectrics and $YBa_2CuO_7$ high temperature superconductor thin film. The best result in figure of merit was 35 when the $Ba_{0.5}Sr_{0.5}TiO_3$ thin film deposition temperature was $600^{\circ}C$, the post anneal condition was $600^{\circ}C$, 10min in 1atm, $O_2$. When using $20{\mu}m$ IDC pattern gap. The higher tunability was obtained than using $30{\mu}m$ pattern gap.

• Korean Journal of Optics and Photonics
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• v.12 no.5
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• pp.401-405
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• 2001

We propose a novel channel-switching transmission filter using segmented chirped fiber Bragg gratings (CFBG's) each of which has separate transmission bands in the reflection spectrum of the CFBG. The segmented CFBG's are made by using specially designed slits. The separated reflection spectral bands of the segmented CFBG's are controlled by the attached fiber stretchers, and the controlled reflection bands are used to choose the channels independently. Tunability of the transmission spectra is experimentally demonstrated in WDM transmission experiments.

• Current Optics and Photonics
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• v.5 no.2
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• pp.134-140
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• 2021

In this paper, I introduce a novel design method of a high performance nanophotonic beam deflector providing broadband operation, large active tunability, and signal efficiency, simultaneously. By combining thermo-optically tunable vanadium dioxide nano-ridges and a metallic mirror, reconfigurable local optical phase of reflected diffraction beams can be engineered in a desired manner over broad bandwidth. The active metagrating deflectors are systematically designed for tunable deflection of reflection beams according to the thermal phase-change of vanadium dioxide nano-ridges. Moreover, by multiplexing the phase-change supercells, a robust design of actively tunable beam splitter is also verified numerically. It is expected that the proposed intuitive and simple design method would contribute to development of next-generation optical interconnects and spatial light modulators with high performances. The author also envisions that this study would be fruitful for modern holographic displays and three-dimensional depth sensing technologies.

• Current Optics and Photonics
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• v.3 no.1
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• pp.40-45
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• 2019

Adding tunability to biological light emitters offers an unprecedented technique in biological sensing and imaging. Here, we report a tunable, lithographic-free, planar, and ultrathin metal-insulator-metal (MIM) resonator capable of tuning the optical properties solely by a silk/sodium fluorescein hydrogel layer, a biocompatible light emitter. In water, the volume of the resonator was expanded by swelling, and then the resonant mode could be shifted. Simulations predicted the red-shifted resonance peak in transmission when the MIM was swollen in water. The red-shift could be attributed to the increase in the thickness of the silk hydrogel layer due to the absorbed water. The shift of the resonance could affect the fluorescence of the dye in the silk hydrogel layer.

• Current Optics and Photonics
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• v.2 no.6
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• pp.563-567
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• 2018

We propose and experimentally demonstrate a simple tunable photonic microwave band-pass filter with high resolution using a reflective semiconductor optical amplifier (RSOA) and an optical time-delay line. The RSOA is used as a gain medium for generating cross-gain modulation (XGM) effect as well as an optical source. The optical source provides narrow spectral width by self-injection locking the RSOA in conjunction with a partial reflection filter with specific center wavelength. Then, when the RSOA is operated in the saturation region and the modulated recursive signal is injected into the RSOA, the recursive signal is inversely copied to the injection locked optical source due to the XGM effect. Also, the tunability of the passband of the proposed microwave filter is shown by controlling an optical time-delay line in a recursive loop.

• Current Optics and Photonics
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• v.6 no.6
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• pp.590-597
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• 2022

We carry out numerical simulations of the responses of planar metamaterials composed of metamolecules under obliquely incident terahertz waves. A Fano-like-resonant planar metamaterial, with two types of resonance modes originating from the two meta-atoms constituting the meta-molecules, exhibits high performance in terms of resonance strength, as well as the outstanding ability to manipulate the resonance frequency by varying the incident angle of the terahertz waves. In the structure, the fundamental electric dipole resonance associated with Y-shaped meta-atoms is highly tunable, whereas the inductive-capacitive resonance of C-shaped meta-atoms is relatively omnidirectional. This is attributed to the electric near-field coupling between the two types of meta-atoms. Our work provides novel opportunities for realizing terahertz devices with versatile functions, and for improving the versatility of terahertz sensing and imaging systems.

• Current Optics and Photonics
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• v.6 no.6
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• pp.634-641
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• 2022

A frequency stable and tunable optoelectronic oscillator (OEO) incorporating an optical phase shifter and a phase-shifted fiber Bragg grating (PS-FBG) is designed and analyzed. The frequency tunability of the OEO can be realized by using a tunable microwave photonic bandpass filter consisting of a PS-FBG, a phase modulator. The optical phase compensation loop is used to compensate for the phase variations of the RF signal from the OEO by adjusting an optical phase shifter. Simulation results demonstrate that the output RF signals of the OEO can be tuned in a frequency range of 118 MHz to 24.092 GHz. When the ambient temperature fluctuates within ±3.9 ℃, the frequency drifts of the output RF signals are less than 68 Hz, the side-mode suppression ratios are more than 69.39 dB, and the phase noise is less than -92.49 dBc/Hz at a 10 kHz offset frequency.

• Molecules and Cells
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• v.45 no.1
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• pp.6-15
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• 2022

Phase separation is a thermodynamic process leading to the formation of compositionally distinct phases. For the past few years, numerous works have shown that biomolecular phase separation serves as biogenesis mechanisms of diverse intracellular condensates, and aberrant phase transitions are associated with disease states such as neurodegenerative diseases and cancers. Condensates exhibit rich phase behaviors including multiphase internal structuring, noise buffering, and compositional tunability. Recent studies have begun to uncover how a network of intermolecular interactions can give rise to various biophysical features of condensates. Here, we review phase behaviors of biomolecules, particularly with regard to regular solution models of binary and ternary mixtures. We discuss how these theoretical frameworks explain many aspects of the assembly, composition, and miscibility of diverse biomolecular phases, and highlight how a model-based approach can help elucidate the detailed thermodynamic principle for multicomponent intracellular phase separation.