The Experts below are selected from a list of 14286 Experts worldwide ranked by ideXlab platform
Zeeshan Ahmed - One of the best experts on this subject based on the ideXlab platform.
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on chip silicon waveguide bragg grating photonic temperature sensor
Optics Letters, 2015Co-Authors: Nikolai N Klimov, Sunil Mittal, Michaela Berger, Zeeshan AhmedAbstract:Resistance thermometry is a time-tested method for taking temperature measurements. In recent years, fundamental limits to resistance-based approaches have spurred considerable interest in developing photonic temperature sensors as a viable alternative. In this study, we demonstrate that our photonic thermometer, which consists of a silicon waveguide integrated with a Bragg grating, can be used to measure temperature changes over the range of 5°C-160°C, with a combined expanded uncertainty [k=2, 95% confidence level] of 1.25°C. Computational modeling of the sensor predicts the resonance wavelength and Effective Refractive Index within 4% of the measured value.
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on chip silicon waveguide bragg grating photonic temperature sensor
arXiv: Optics, 2015Co-Authors: Nikolai N Klimov, Sunil Mittal, Michaela Berger, Zeeshan AhmedAbstract:Resistance thermometry is a time-tested method for taking temperature measurements. In recent years fundamental limits to resistance-based approaches spurred considerable interest in developing photonic temperature sensors as a viable alternative. In this study we demonstrate that our photonic thermometer, which consists of a silicon waveguide integrated with a Bragg grating, can be used to measure temperature changes over the range from 5 C to 160 C with a combined expanded uncertainty [k = 2 ; 95% confidence level] of 1.25 degree C. The computational modeling of the sensor predicts the resonance wavelength and Effective Refractive Index within 4% of the measured value.
G Tsigaridas - One of the best experts on this subject based on the ideXlab platform.
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theoretical and experimental study of Refractive Index sensors based on etched fiber bragg gratings
Sensors and Actuators A-physical, 2014Co-Authors: G Tsigaridas, D Polyzos, A Ioannou, M Fakis, P PersephonisAbstract:Abstract In this work, a theoretical and experimental study of the effect of the etching process on the properties of fiber Bragg gratings (FBGs) used as Refractive Index sensors is presented. The theoretical study addresses the dependence of the Effective Refractive Index on the cladding thickness of the etched FBG. The results of this study show that as the cladding thickness is reduced, the Effective Refractive Index decreases exponentially. Based on this result, a simple analytic expression between the Effective Refractive Index and the radius of the etched FBG was developed. Thus, the radius of the FBG after the etching process can be determined directly from the shift of the Bragg wavelength, without the need of extensive numerical simulations. Also, the sensitivity of the FBG sensor in characteristic environments of practical interest has been calculated as a function of the fiber radius, and found to be described by simple analytic functions. The time evolution of the Bragg wavelength during the etching process has also been investigated, both experimentally and theoretically. By means of detailed theoretical analysis of the experimental results, the heating and the etching rate of the FBG was calculated. Finally, the etched FBGs have been used as liquid level sensors for water and oil, having Refractive indices lower and higher than the fiber core respectively. The analysis of the experimental results was based on the shift of the diffracted wavelength in the case of water and on the reduction of the reflected power in the case of oil.
Paulo André - One of the best experts on this subject based on the ideXlab platform.
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Cost Effective Refractive Index sensor based on optical fiber micro cavities produced by the catastrophic fuse effect
Measurement: Journal of the International Measurement Confederation, 2016Co-Authors: M. Fátima Domingues, Rosa Frias, Nelia Alberto, Paulo Antunes, Rute A. S. Ferreira, Paulo AndréAbstract:We propose a Refractive Index optical fiber sensor based on the micro cavities generated through the fiber catastrophic fuse effect. This sensor was tested in the measurement of solutions with Refractive indices ranging from 1.3320 to 1.4280. The linear dependence of the reflection spectra modulation period as function of the surrounding environment Refractive Index leads to a resolution of 3 × 10-4RIU. The proposed sensor is an innovative solution based on optical fiber damaged by the fuse effect, resulting in a cost Effective solution.
Noriyuki Yokouchi - One of the best experts on this subject based on the ideXlab platform.
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coupled defect photonic crystal vertical cavity surface emitting lasers
Electronics Letters, 2003Co-Authors: Aaron James Danner, J J Raftery, Noriyuki YokouchiAbstract:Photonic crystal patterns containing two defects were fabricated within a large gain area in vertical cavity surface emitting lasers. By designing Effective Refractive Index changes in the region between the defects through cavity shifts caused by photonic crystals, it was possible to coherently couple laser light output from the defects. This enables a novel way to fabricate coherently coupled laser arrays.
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etching depth dependence of the Effective Refractive Index in two dimensional photonic crystal patterned vertical cavity surface emitting laser structures
Applied Physics Letters, 2003Co-Authors: Noriyuki Yokouchi, Aaron James Danner, Kent D ChoquetteAbstract:A vertical-cavity surface-emitting laser (VCSEL) having a two-dimensional (2-D) photonic crystal structure on its surface has been investigated for single-lateral-mode operation. We evaluated the Effective Index change of a VCSEL cavity introduced by a 2-D pattern. Our experimental results showed good agreement with a theoretical model in which the influence of a finite etching depth was taken into consideration. The etching-depth dependence parameter γ, which can be explained by the optical power distribution inside a VCSEL structure, will be helpful for controlling the lateral mode of VCSEL devices.
Lei Jiang - One of the best experts on this subject based on the ideXlab platform.
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a visual and organic vapor sensitive photonic crystal sensor consisting of polymer infiltrated sio2 inverse opal
Physical Chemistry Chemical Physics, 2015Co-Authors: Yuqi Zhang, Ben Zhong Tang, Jianhua Qiu, Loujun Gao, Liping Heng, Lei JiangAbstract:A photonic crystal (PC) sensor that can selectively detect organic vapors through visual color changes has been proposed. The sensor was fabricated by infiltrating a tetraphenylethene polymer (TPEP) into the voids of SiO2 inverse opal photonic crystal. When the sensor was exposed to tetrahydrofuran or acetone vapor, a red shift of the stopband of more than 50 nm could be clearly observed; meanwhile, the film's color changed from violet to cyan. Subsequently, when exposed to air, the stopband underwent a blue shift and the color returned to violet. The reason for the observed change is that a reversible adsorption–desorption process occurs on alternate exposure of the sensor to organic vapor and air, due to the high specific surface area of the inverse opal macroporous structure and the high affinity of TPEP to tetrahydrofuran and acetone. The adsorption of vapor analyte can increase the PC's Effective Refractive Index, which will induce the stopband red shift and the resulting color change according to Bragg's Law. The reversible adsorption–desorption of organic vapors varied the Effective Refractive Index of the sensor repeatedly, causing the reversible stopband shift and color change, and providing a general method for the design of visual vapor sensors.
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a visual film sensor based on silole infiltrated sio2 inverse opal photonic crystal for detecting organic vapors
Journal of Materials Chemistry C, 2014Co-Authors: Yuqi Zhang, Ben Zhong Tang, Jianhua Qiu, Loujun Gao, Liping Heng, Miaomiao Gao, Lei JiangAbstract:The reversible color change of the silole-infiltrated SiO2 inverse opal photonic crystal (IOPC) film can be obtained by alternating its exposure to different vapor environments. When the film was put in diethyl ether or petroleum ether vapor, a stopband red shift of more than 100 nm could be clearly observed, while the color changed from green to red. When exposed to air, the stopband underwent a blue shift and the color changed back to green. The result is attributed to the silole molecules, hexaphenylsilole (HPS), which can be transformed reversibly between the crystal and amorphous state when alternately exposed to air and vapors of diethyl ether/petroleum ether. When crystal HPS changed to amorphous HPS in an atmosphere of organic vapors, both the specific surface area and Refractive Index of HPS increased. The higher specific surface area of HPS improved the adsorption behavior of organic vapors. Both the improved adsorption and higher Refractive Index of HPS increased the Effective Refractive Index of HPS-infiltrated SiO2 IOPC, which resulted in the red shift of the stopband and the color change, according to the Bragg Law. Based on the reversible aggregation state transfer and the adsorption–desorption of organic vapors, the Effective Refractive Index of the film varied repeatedly, which caused the reversible stopband shift and color change. The visual detection of organic vapors can be realized because of the remarkable color change of the IOPC film, which provides a simple route for monitoring volatile organic compounds, and is important for chemical and biological sensors.
