The Experts below are selected from a list of 3258 Experts worldwide ranked by ideXlab platform
David J Webb - One of the best experts on this subject based on the ideXlab platform.
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time dependent variation of pof bragg Grating Reflectivity and wavelength submerged in different liquids
Optics and Laser Technology, 2017Co-Authors: Andreas Pospori, Carlos Marques, David J WebbAbstract:In this work, we investigate the time-dependent variation of both the Reflectivity and resonance wavelength of microstructured polymer optical fiber Bragg Grating (mPOFBG) array sensors embedded in silicone rubber and polyurethane resin diaphragms in contact with water and aircraft fuel, respectively. The array sensors were inscribed using two different phase masks with pitches of 557.5 and 580 nm and the thermal annealing of the inscribed fiber was used to change the Bragg wavelengths. Both the reflection and the resonance wavelength shift were monitored over 90 days submerged in liquid and two studies were investigated. In the first study, in addition to the mPOFBGs coated with the diaphragm, also the rest of the fiber is totally protected between the sensors with the same material used for diaphragms. On the other hand, in the second study, the fiber between sensors is unprotected – in direct contact with liquid. PMMA and TOPAS fibers were used and this study suggests that TOPAS fiber should be a good option for long-term liquid monitoring applications.
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time dependent variation of fiber bragg Grating Reflectivity in pmma based polymer optical fibers
Optics Letters, 2015Co-Authors: D Saezrodriguez, Kristian Fog Nielsen, Ole Bang, David J WebbAbstract:In this paper we investigate the effects of viscoelasticity on both the strength and resonance wavelength of two fibre Bragg Gratings (FBGs) inscribed in microstructured polymer optical fibre (mPOF) made of undoped PMMA. Both FBGs were inscribed under a strain of 1% in order to increase the material photosensitivity. After the inscription the strain was released and the FBGs spectra were monitored. We initially observed a decrease of the reflection down to zero after which it began to increase. After that, strain tests were carried out to confirm the results and finally the Gratings were monitored for a further 120 days, with a stable reflection response being observed beyond 50 days.
J S Wilkinson - One of the best experts on this subject based on the ideXlab platform.
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superstrate index control of waveguide Grating Reflectivity
Optics Letters, 2002Co-Authors: Stavros Pissadakis, M N Zervas, D A Sager, J S WilkinsonAbstract:Control of Reflectivity of a relief Grating in a high-index film overlaid on a monomode glass waveguide was achieved by adjustment of the superstrate refractive index with liquids. Weak Gratings reflecting at 1531 nm were inscribed by UV laser ablation. The Grating Reflectivity was measured as the ratio of the transmission outside the reflection band, at 1536 nm, to that at the Bragg wavelength. Reflectivity with an air superstrate was <0.3 dB for both polarizations. In the TE polarization the Grating strength increased to 20.5 dB after application of a liquid of index 1.45. In the TM polarization the strength increased to 27 dB with a superstrate index of 1.50. Good agreement was found with a theoretical model based on beam propagation.
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superstrate index control of waveguide Grating Reflectivity
Conference on Lasers and Electro-Optics, 2001Co-Authors: Stavros Pissadakis, M N Zervas, D A Sager, J S WilkinsonAbstract:Waveguide Gratings reflecting at wavelengths near 1530 nm were fabricated by laser ablation of thin Ta/sub 2/O/sub 5/ films on glass waveguides. Variation of Reflectivity from 0.3 dB to 34 dB was achieved by alteration of the superstrate refractive index.
M N Zervas - One of the best experts on this subject based on the ideXlab platform.
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ultra wide detuning planar bragg Grating fabrication technique based on direct uv Grating writing with electro optic phase modulation
Optics Express, 2013Co-Authors: Chaotan Sima, James C Gates, Christopher Holmes, Paolo L Mennea, M N Zervas, Helen Rogers, P G R SmithAbstract:A direct UV Grating writing technique based on phase-controlled interferometry is proposed and demonstrated in a silica-on-silicon platform, with a wider wavelength detuning range than any previously reported UV writing technology. Electro-optic phase modulation of one beam in the interferometer is used to manipulate the fringe pattern and thus control the parameters of the Bragg Gratings and waveguides. Various Grating structures with refractive index apodization, phase shifts and index contrasts of up to 0.8×10-3 have been demonstrated. The method offers significant time/energy efficiency as well as simplified optical layout and fabrication process. We have shown Bragg Gratings can be made from 1200 nm to 1900 nm exclusively under software control and the maximum peak Grating Reflectivity only decreases by 3dB over a 250 nm (~32THz) bandwidth.
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superstrate index control of waveguide Grating Reflectivity
Optics Letters, 2002Co-Authors: Stavros Pissadakis, M N Zervas, D A Sager, J S WilkinsonAbstract:Control of Reflectivity of a relief Grating in a high-index film overlaid on a monomode glass waveguide was achieved by adjustment of the superstrate refractive index with liquids. Weak Gratings reflecting at 1531 nm were inscribed by UV laser ablation. The Grating Reflectivity was measured as the ratio of the transmission outside the reflection band, at 1536 nm, to that at the Bragg wavelength. Reflectivity with an air superstrate was <0.3 dB for both polarizations. In the TE polarization the Grating strength increased to 20.5 dB after application of a liquid of index 1.45. In the TM polarization the strength increased to 27 dB with a superstrate index of 1.50. Good agreement was found with a theoretical model based on beam propagation.
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superstrate index control of waveguide Grating Reflectivity
Conference on Lasers and Electro-Optics, 2001Co-Authors: Stavros Pissadakis, M N Zervas, D A Sager, J S WilkinsonAbstract:Waveguide Gratings reflecting at wavelengths near 1530 nm were fabricated by laser ablation of thin Ta/sub 2/O/sub 5/ films on glass waveguides. Variation of Reflectivity from 0.3 dB to 34 dB was achieved by alteration of the superstrate refractive index.
Stavros Pissadakis - One of the best experts on this subject based on the ideXlab platform.
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superstrate index control of waveguide Grating Reflectivity
Optics Letters, 2002Co-Authors: Stavros Pissadakis, M N Zervas, D A Sager, J S WilkinsonAbstract:Control of Reflectivity of a relief Grating in a high-index film overlaid on a monomode glass waveguide was achieved by adjustment of the superstrate refractive index with liquids. Weak Gratings reflecting at 1531 nm were inscribed by UV laser ablation. The Grating Reflectivity was measured as the ratio of the transmission outside the reflection band, at 1536 nm, to that at the Bragg wavelength. Reflectivity with an air superstrate was <0.3 dB for both polarizations. In the TE polarization the Grating strength increased to 20.5 dB after application of a liquid of index 1.45. In the TM polarization the strength increased to 27 dB with a superstrate index of 1.50. Good agreement was found with a theoretical model based on beam propagation.
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superstrate index control of waveguide Grating Reflectivity
Conference on Lasers and Electro-Optics, 2001Co-Authors: Stavros Pissadakis, M N Zervas, D A Sager, J S WilkinsonAbstract:Waveguide Gratings reflecting at wavelengths near 1530 nm were fabricated by laser ablation of thin Ta/sub 2/O/sub 5/ films on glass waveguides. Variation of Reflectivity from 0.3 dB to 34 dB was achieved by alteration of the superstrate refractive index.
D Saezrodriguez - One of the best experts on this subject based on the ideXlab platform.
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time dependent variation of fiber bragg Grating Reflectivity in pmma based polymer optical fibers
Optics Letters, 2015Co-Authors: D Saezrodriguez, Kristian Fog Nielsen, Ole Bang, David J WebbAbstract:In this paper we investigate the effects of viscoelasticity on both the strength and resonance wavelength of two fibre Bragg Gratings (FBGs) inscribed in microstructured polymer optical fibre (mPOF) made of undoped PMMA. Both FBGs were inscribed under a strain of 1% in order to increase the material photosensitivity. After the inscription the strain was released and the FBGs spectra were monitored. We initially observed a decrease of the reflection down to zero after which it began to increase. After that, strain tests were carried out to confirm the results and finally the Gratings were monitored for a further 120 days, with a stable reflection response being observed beyond 50 days.
