Browsing by Author "Chen, H. Z."

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Domain pattern and piezoelectric response across polymorphic phase transition in strained bismuth ferrite films
(2010-12-13)
Kuo, H. Y.
;
Shu, Y. C.
;
Chen, H. Z.
;
Hsueh, C. J.
;
Wang, C. H.
A model is developed to investigate the domain pattern and piezoelectric response across the polymorphic phase transition in strained epitaxial bismuth ferrite films. The orientations of stripelike pattern of the mixed rhombohedral and tetragonal phases are predicted as the consequence of competition between elastic and depolarization energies. The abnormally large piezoelectric response is attributed to the strain-driven softening in dielectric stiffness. The results are in good agreement with recent experimental observations and provide a guidance for developing similar strain-driven polymorphic phase transition in other related perovskite material systems. (C) 2010 American Institute of Physics. [doi:10.1063/1.3525926]
Investigation of nanodomain pattern and piezoelectric behavior of mixed phases in epitaxial BiFeO(3) films
(2011-12-01)
Kuo, H. Y.
;
Shu, Y. C.
;
Chen, H. Z.
;
Hsueh, C. J.
;
Wang, C. H.
Mixed phases of rhombohedral and tetragonal ferroelectric variants have been recently observed to coexist through epitaxial constraints in bismuth ferrite films. They form stripe-like domain patterns with orientations closely parallel to the substrate edges and exhibit unusually large piezoelectric response in the stripe areas. Here a model is developed for explaining the peculiar domain orientations as well as the enhancement of piezoelectricity in the mixed phase. The former is determined by the relative magnitudes of elastic and depolarization energy, whereas the latter is ascribed to the strain-driven softening in dielectric stiffness. The predictions show the similar trend as those observed in recent experiments. (C) 2011 Elsevier Ltd. All rights reserved.
Investigation of nanodomain pattern and piezoelectric behavior of mixed phases in epitaxial BiFeO3 films
(2011-12-01)
Kuo, H. Y.
;
Shu, Y. C.
;
Chen, H. Z.
;
Hsueh, C. J.
;
Wang, C. H.
Mixed phases of rhombohedral and tetragonal ferroelectric variants have been recently observed to coexist through epitaxial constraints in bismuth ferrite films. They form stripe-like domain patterns with orientations closely parallel to the substrate edges and exhibit unusually large piezoelectric response in the stripe areas. Here a model is developed for explaining the peculiar domain orientations as well as the enhancement of piezoelectricity in the mixed phase. The former is determined by the relative magnitudes of elastic and depolarization energy, whereas the latter is ascribed to the strain-driven softening in dielectric stiffness. The predictions show the similar trend as those observed in recent experiments. (C) 2011 Elsevier Ltd. All rights reserved.
Utilizing New Erbium-Doped Fiber Laser Scheme for Long-Distance Fiber Bragg Grating (FBG) Sensor System
(2015)
Yeh, C. H.
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Chen, H. Z.
;
Chen, J. Y.
;
Chow, C. W.
;
光電工程學系
We propose and demonstrate a new erbium-doped fiber (EDF) ring laser structure for 10 km long fiber sensor application. Here, we utilize ten fiber Bragg gratings (FBGs) as fiber sensors for sensing strain change. In the experiment, we can tune the passband of tunable bandpass filter (TBF) inside a fiber ring cavity to match the Bragg wavelength of each FBG to lase corresponding wavelength. Hence, the temperature-induced shift in Bragg wavelength could be monitored. In addition, 10 km long distance single-mode fiber (SMF) can be achieved by using the proposed EDF ring laser scheme for FGB-based remote sensor system.
Utilizing simple FBG-based erbium-doped fiber architecture for remote temperature sensing
(2015-10-01)
Yeh, C. H.
;
Chow, C. W.
;
Chen, J. Y.
;
Chen, H. Z.
;
Chen, J. H.
In this work, we demonstrate experimentally an erbium-doped fiber (EDF) ring laser structure for remote temperature sensing by using fiber Bragg gratings (FBGs) in C-band. Based on the proposed EDF laser configuration, the remote temperature sensing distance is achieved at 50 km. Here, ten FBGs are employed at the remote side for temperature sensing. By tuning the optical tunable filter (TF), the corresponding Bragg wavelength from each FBG can be monitored in the proposed EDF laser. As a result, in the temperature range from 20 to 82 degrees C, the maximum drift of Bragg wavelength can be detected at 0.84 nm.