The Experts below are selected from a list of 22674 Experts worldwide ranked by ideXlab platform
Dongning Wang - One of the best experts on this subject based on the ideXlab platform.
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femtosecond laser inscribed long period gratings in all solid photonic bandgap fibers
IEEE Photonics Technology Letters, 2010Co-Authors: Changrui Liao, Ying Wang, Dongning WangAbstract:Long-period fiber gratings are inscribed in all-solid photonic bandgap fibers by use of a femtosecond laser with the line-scanning method. The coupling from the fundamental core mode to LP11 core mode can be readily obtained and the Resonant Wavelength of the grating is found to be highly sensitive to tensile strain while being nearly insensitive or only slightly sensitive to temperature, curvature, and external refractive index. Such gratings can be effectively used in stable spectral filters and optical fiber sensors with largely reduced cross-sensitivity.
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fiber bragg gratings with enhanced thermal stability by residual stress relaxation
Optics Express, 2009Co-Authors: Yuhua Li, Dongning Wang, Minwei Yang, Jian Lu, K T V GrattanAbstract:Fiber Bragg gratings with greatly enhanced thermal stability have been fabricated by the use of femtosecond laser pulse irradiation on optical fibers with relaxed residual stress, through using high temperature annealing treatment. The grating reflectivity and Resonant Wavelength can be maintained for periods up to 20 hours using isothermal measurements and temperatures up to 1200 °C. No hysteresis was observed in the Wavelength response when the gratings were annealed and the temperature cycled repeatedly between room temperature and 1200 °C.
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long period gratings in air core photonic bandgap fibers
Optics Express, 2008Co-Authors: Yiping Wang, Hoi Lut Ho, Jian Ju, Limin Xiao, Haifeng Xuan, Dongning WangAbstract:Long period fiber gratings in hollow-core air-silica photonic bandgap fibers were produced by use of high frequency, short duration, CO2 laser pulses to periodically modify the size, shape and distribution of air holes in the microstructured cladding. The Resonant Wavelength of these gratings is highly sensitivity to strain but insensitive to temperature, bend and external refractive index. These gratings can be used as stable spectral filters and novel sensors.
Siddharth Ramachandran - One of the best experts on this subject based on the ideXlab platform.
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highly sensitive optical response of optical fiber long period gratings to nanometer thick ionic self assembled multilayers
Applied Physics Letters, 2005Co-Authors: Zhiyong Wang, James R Heflin, Rogers H Stolen, Siddharth RamachandranAbstract:Ionic self-assembled multilayers deposited on long period fiber gratings (LPGs) yield dramatic Resonant-Wavelength shifts, even with nanometer-thick films. Fine control of the refractive index and the thickness of these films was achieved by altering the relative fraction of the anionic and cationic materials combined with layer-by-layer deposition. We demonstrate the feasibility of this highly controllable deposition technique for fine-tuning grating properties. In addition a variety of biological and chemical sensing agents can easily be incorporated into these films, which makes this an attractive platform for realization of high-performance LPG-based sensors.
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analysis of optical response of long period fiber gratings to nm thick thin film coatings
Optics Express, 2005Co-Authors: Zhiyong Wang, James R Heflin, Rogers H Stolen, Siddharth RamachandranAbstract:We have theoretically and experimentally demonstrated that the Resonant Wavelength of long period fiber gratings (LPG) can be shifted by a large magnitude by coating with only a nm-thick thin-film that has a refractive index higher than that of the glass cladding. The Resonant Wavelength shift can result from either the variation of the thickness of the film and/or the variation of its refractive index. These results demonstrate the sensitivity of LPG-based sensors can be enhanced by using a film of nm-thickness and refractive index greater than silica. This coating schematic offers an efficient platform for achieving high-performance index-modulating fiber devices and high-performance index/thickness-sensing LPG-based fiber sensors for detecting optical property variations of the thin-film coating.
Jayaraj Thillaigovindan - One of the best experts on this subject based on the ideXlab platform.
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optical nanomechanical sensor using a silicon photonic crystal cantilever embedded with a nanocavity resonator
Applied Optics, 2009Co-Authors: Chengkuo Lee, Jayaraj ThillaigovindanAbstract:We present in-depth discussion of the design and optimization of a nanomechanical sensor using a silicon cantilever comprising a two-dimensional photonic crystal (PC) nanocavity resonator arranged in a U-shaped silicon PC waveguide. For example, the minimum detectable strain, vertical deflection at the cantilever end, and force load are observed as 0.0133%, 0.37 mum, and 0.0625 muN, respectively, for a 30 mum long and 15 mum wide cantilever. In the graph of strain versus Resonant Wavelength shift, a rather linear relationship is observed for various data derived from different cantilevers. Both the Resonant Wavelength and the Resonant Wavelength shift of cantilevers under deformation or force loads are mainly a function of defect length change. Results point out that all these mechanical parameters are mainly dependent on the defect length of the PC nanocavity resonator. This new PC cantilever sensor shows promising linear characteristics as an optical nanomechanical sensor.
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Si nanophotonics based cantilever sensor
Applied Physics Letters, 2008Co-Authors: Jayaraj Thillaigovindan, Xian Tong Chen, Ya-ting Chao, Wenfeng Xiang, Aibin Yu, Hanhua Feng, Chii-chang Chen, Guo-qiang LoAbstract:We present design and simulation results of a novel nanomechanical sensor using silicon cantilever embedded with a two-dimensional photonic crystal microcavity resonator. Both of Resonant Wavelength and Resonant Wavelength shift could be measured as a function of various physical parameters such as applied force, strain, and displacement. Rather linear relationship is derived for strain and Resonant Wavelength shift. This new nanomechanical sensor shows promising features for biomolecules detection.
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design and modeling of a nanomechanical sensor using silicon photonic crystals
Journal of Lightwave Technology, 2008Co-Authors: Chengkuo Lee, Jayaraj Thillaigovindan, Chii-chang Chen, R Radhakrishnan, N BalasubramanianAbstract:Conventionally a line defect in the photonic crystal (PhC) is used to create a waveguide for light propagation through the PhC. A PhC based filter is designed by introducing micro-cavities within the line defect so as to form the Resonant bandgap structure for PhC. Such a PhC waveguide (PhCWG) filter shows sharp Resonant peak in output Wavelength spectrum. We proposed a suspended silicon bridge structure comprising this PhCWG filter structure. Since the output Resonant Wavelength is sensitive to the shape of air holes and defect length of the micro-cavity. Shift of the output Resonant Wavelength is observed for suspended PhCWG beam structure under particular force loading. In other words, the induced strain modifies the shape of air holes and the spacing among them. Such an effect leads to shift of Resonant Wavelength. Under optical detection limitation of 0.1 nm for Resonant Wavelength shift, the sensing capability of this nanomechanical sensor is derived as that vertical deformation is 20-25 nm at the center and the smallest strain is 0.005% for defect length. This innovative design conceptualizes a new application area for PhCs, i.e., the nanometer-scale physical sensors for strains and forces.
Chii-chang Chen - One of the best experts on this subject based on the ideXlab platform.
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optimization and comparison of photonic crystal resonators for silicon microcantilever sensors
Sensors and Actuators A-physical, 2011Co-Authors: Trong Thi Mai, Fu-li Hsiao, Wenfeng Xiang, Chii-chang Chen, Chengkuo Lee, W K ChoiAbstract:Abstract Microcantilever sensors have been known as a fundamental design used in force sensors, strain sensors and biochemical sensors. The fast-growing applications in nanoelectromechanical systems (NEMS) lead to strong demands in new sensing mechanism in order to downsize the sensing elements to nanometer scale. Photonic crystal (PC) based resonators have been investigated as promising solutions because the bandgap structure and resonator characteristics are extremely sensitive to the deformation and position shift of holes in PC resonators. In addition to the well-known nano-cavity resonator (NCR), we proposed hexagonal nano-ring resonators (NRR) of two different layout configurations. When a microcantilever under different force loads, both of the Resonant Wavelength and the Resonant Wavelength shift can be measured as a linear function of force load. The linear relationship between Wavelength shifts and strain is observed as well. The minimum detectable force and detectable strain for NRR configuration 1 is derived as small as 0.0757 μN and 0.0023%. The outstanding sensing capability renders PC resonators as a promising nanomechanical sensing element to be integrated in various transducers for NEMS applications.
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Si nanophotonics based cantilever sensor
Applied Physics Letters, 2008Co-Authors: Jayaraj Thillaigovindan, Xian Tong Chen, Ya-ting Chao, Wenfeng Xiang, Aibin Yu, Hanhua Feng, Chii-chang Chen, Guo-qiang LoAbstract:We present design and simulation results of a novel nanomechanical sensor using silicon cantilever embedded with a two-dimensional photonic crystal microcavity resonator. Both of Resonant Wavelength and Resonant Wavelength shift could be measured as a function of various physical parameters such as applied force, strain, and displacement. Rather linear relationship is derived for strain and Resonant Wavelength shift. This new nanomechanical sensor shows promising features for biomolecules detection.
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design and modeling of a nanomechanical sensor using silicon photonic crystals
Journal of Lightwave Technology, 2008Co-Authors: Chengkuo Lee, Jayaraj Thillaigovindan, Chii-chang Chen, R Radhakrishnan, N BalasubramanianAbstract:Conventionally a line defect in the photonic crystal (PhC) is used to create a waveguide for light propagation through the PhC. A PhC based filter is designed by introducing micro-cavities within the line defect so as to form the Resonant bandgap structure for PhC. Such a PhC waveguide (PhCWG) filter shows sharp Resonant peak in output Wavelength spectrum. We proposed a suspended silicon bridge structure comprising this PhCWG filter structure. Since the output Resonant Wavelength is sensitive to the shape of air holes and defect length of the micro-cavity. Shift of the output Resonant Wavelength is observed for suspended PhCWG beam structure under particular force loading. In other words, the induced strain modifies the shape of air holes and the spacing among them. Such an effect leads to shift of Resonant Wavelength. Under optical detection limitation of 0.1 nm for Resonant Wavelength shift, the sensing capability of this nanomechanical sensor is derived as that vertical deformation is 20-25 nm at the center and the smallest strain is 0.005% for defect length. This innovative design conceptualizes a new application area for PhCs, i.e., the nanometer-scale physical sensors for strains and forces.
Yiping Wang - One of the best experts on this subject based on the ideXlab platform.
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long period gratings in air core photonic bandgap fibers
Optics Express, 2008Co-Authors: Yiping Wang, Hoi Lut Ho, Jian Ju, Limin Xiao, Haifeng Xuan, Dongning WangAbstract:Long period fiber gratings in hollow-core air-silica photonic bandgap fibers were produced by use of high frequency, short duration, CO2 laser pulses to periodically modify the size, shape and distribution of air holes in the microstructured cladding. The Resonant Wavelength of these gratings is highly sensitivity to strain but insensitive to temperature, bend and external refractive index. These gratings can be used as stable spectral filters and novel sensors.
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asymmetric long period fiber gratings fabricated by use of co2 laser to carve periodic grooves on the optical fiber
Applied Physics Letters, 2006Co-Authors: Yiping Wang, D N Wang, Wei Jin, Yunjiang Rao, Gangding PengAbstract:An asymmetric long period fiber grating (LPFG) with a large attenuation of −47.39dB and a low insertion loss of 0.34dB is fabricated by use of focused CO2 laser beam to carve periodic grooves on one side of the optical fiber. Such periodic grooves and the stretch-induced periodic microbends can effectively enhance the refractive index modulation and increase the average strain sensitivity of the Resonant Wavelength of the LPFG to −102.89nm∕me. The Resonant Wavelength and the peak attenuation of the LPFG can be tuned by ∼12nm and ∼20dB, respectively, by the application of a stretching force.