The Experts below are selected from a list of 270 Experts worldwide ranked by ideXlab platform
Raman Kashyap - One of the best experts on this subject based on the ideXlab platform.
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demonstration of a 3 mw threshold er doped random fiber laser based on a unique fiber bragg Grating
Optics Express, 2009Co-Authors: Mathieu Gagne, Raman KashyapAbstract:We demonstrate a novel random laser based on a single fiber Bragg Grating. A long fiber Bragg Grating Fabrication technique allows the insertion of a large number of randomly distributed phase errors in the structure of the Grating which induces light localization. By writing such a Grating in a polarisation maintaining Er-doped fiber, a random laser is demonstrated by pumping the fiber with 976 and 1480 nm pump lasers. The number of emitted modes is observed to be a function of the length of the Grating and of the pump power and single-mode operation is shown to be possible. The random fiber laser shows low-threshold (~3 mW) and measured ~0.5 pm emission linewidth at a wavelength of around 1534 nm.
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novel custom fiber bragg Grating Fabrication technique based on push pull phase shifting interferometry
Optics Express, 2008Co-Authors: Mathieu Gagne, Lucian Bojor, Romain Maciejko, Raman KashyapAbstract:A new UV-writing technique is proposed for fabricating custom fiber Bragg Gratings (FBGs). A continuously moving fringe pattern is generated by use of two electro-optical UV modulators and synchronized with a moving fiber. This scheme potentially enables the Fabrication of infinitely long FBGs with arbitrary profiles and chirp without any mechanical perturbation of the writing interferometer. Preliminary results of this technique are presented and discussed.
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fiber bragg Gratings
1999Co-Authors: Raman KashyapAbstract:* Provides an overview of Fiber Bragg Gratings (FBGs), from fundamentals to applications* Evaluates the advantages and disadvantages of particular applications, methods and techniques* Contains new chapters on sensing, femtosecond laser writing of FBGs and poling of glass and optical fibers* Includes a special version of the photonic simulator PicWave(tm), allowing the reader to make live simulations of many of the example devices presented in the book. This fully revised, updated and expanded second edition covers the substantial advances in the manufacture and use of FBGs in the years since the publication of the pioneering first edition. It presents a comprehensive treatise on FBGs and addresses issues such as the merits of one solution over another; why particular Fabrication methods are preferred; and what advantages a user may gain from certain techniques. Beginning with the principles of FBGs, the book progresses to discuss photosensitization of optical fibers, Bragg Grating Fabrication and theory, properties of Gratings, specific applications, sensing technology, glass poling, advances in femtosecond laser writing of Bragg Gratings and FBG measurement techniques. In addition to material on telecommunications usage of FBGs, application areas such as fiber lasers and sensors are addressed in greater detail. This special version of Picwave is limited to modelling only the passive fibre devices covered in this book. However the full PicWave package is capable of modelling other non-linear and active devices such as laser diodes and SOAs as discussed in Chapter 8. More information about PicWave can be found at www.photond.com/products/picwave.htm. In addition to researchers, scientists, and graduate students, this book will be of interest to industrial practitioners in the field of Fabrication of fiber optic materials and devices. Raman Kashyap, Canada Research Chair holder on Future Photonics Systems, and Professor at cole Polytechnique, University of Montr al since 2003, has researched optical fibers and devices for over 30 years. He pioneered the Fabrication of FBGs and applications in telecommunications and photonics. * Provides an overview of Fiber Bragg Gratings (FBGs), from fundamentals to applications* Evaluates the advantages and disadvantages of particular applications, methods and techniques* Contains new chapters on sensing, femtosecond laser writing of FBGs and poling of glass and optical fibers* Includes a special version of the photonic simulator PicWave(tm), allowing the reader to make live simulations of many of the example devices presented in the book.
Yiping Wang - One of the best experts on this subject based on the ideXlab platform.
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residual stress induced helical long period fiber Gratings for sensing applications
Optics Express, 2018Co-Authors: Shen Liu, Zhiyong Bai, Yan Zhang, Zhongyuan Sun, Xueya Liu, Yiping WangAbstract:We demonstrate a high-efficiency Grating Fabrication system, which can be used to inscribe a high-quality helical long period fiber Grating (HLPFG) on single-mode fiber by means of hydrogen-oxygen flame. Such the HLPFG can be produced in enormous quantities with a uniform Grating parameters and good reproducibility of Grating inscription. Possible mechanisms for refractive index modulation in the HLPFG can be attributed to residual stress concentration by solidifying the periodic twisting stress under a fused status of optical fiber. Moreover, the HLPFG exhibits an excellence performance of high temperature sensing with a high sensitivity of ~132.8 pm/°C and a measuring range from room temperature to 900 °C. Comparing to the traditional LPFG fabricated by CO2 laser or arc discharge technique, the HLPFG has a low the bending and tensile strain sensitivity of 1.94 nm/(1/m) and 1.41 pm/μe, respectively. So the proposed HLPFG could have a great potential in special applications as optical high-temperature sensors.
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orbital angular momentum mode converter based on helical long period fiber Grating inscribed by hydrogen oxygen flame
Journal of Lightwave Technology, 2017Co-Authors: Shen Liu, Ying Wang, Changrui Liao, Zhiyong Bai, Yan Zhang, Kaiming Yang, Yiping WangAbstract:A high-efficiency Grating Fabrication method was, for the first time, demonstrated to inscribe helical long period fiber Gratings (H-LPFGs) in small numbers by means of twisting a standard single-mode fiber (SMF) during hydrogen-oxygen flame heating and then cutting the helical fiber into in series of sections. Each section of the helical fiber was a desired LPFG whose resonant wavelength, i.e., Grating pitch, can be changed by adjusting the twist rate of the helical fiber. The H-LPFG inscribed in a standard SMF could be used to generate orbital angular momentum (OAM) modes, i.e., OAM+1 mode, with a purity of 91% and a conversion efficiency of 87% within a large wavelength range from more than the cutoff wavelength of an SMF, which is highly advantageous to all-fiber optical communications based on the OAM mode-division multiplexing technique.
Chaotan Sima - One of the best experts on this subject based on the ideXlab platform.
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terahertz bandwidth photonic hilbert transformers based on synthesized planar bragg Grating Fabrication
Optics Letters, 2013Co-Authors: Chaotan Sima, James C Gates, Christopher Holmes, Paolo L Mennea, M N Zervas, Pete SmithAbstract:Terahertz bandwidth photonic Hilbert transformers are proposed and experimentally demonstrated. The integrated device is fabricated via a direct UV Grating writing technique in a silica-on-silicon platform. The photonic Hilbert transformer operates at bandwidths of up to 2 THz (~16nm), which is at least ten fold greater bandwidth than any previously reported experimental approaches. Achieving this performance requires detailed knowledge of the system transfer function of the direct UV Grating writing technique, this allows improved linearity, and yields THz bandwidth Bragg Gratings with improved spectral quality. By incorporating a flat-top reflector and Hilbert Grating with a waveguide coupler an ultra wideband all-optical single-sideband filter is demonstrated.
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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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phase modulation technique for high modulation wide band planar bragg Grating Fabrication
International Quantum Electronics Conference, 2013Co-Authors: Chaotan Sima, James C Gates, Christopher Holmes, Helen L Rogers, Paolo L Mennea, M N Zervas, Pete SmithAbstract:Direct UV Grating Writing (DGW) is effective route for fabricating high quality Bragg Gratings, similar to fiber Bragg Gratings, in a planar geometry. We will present a phase modulation controlled DGW method using an Electro-Optical Modulator for planar Bragg Grating Fabrication that offers improved performance. This new approach not only provides much greater modulation depths for stronger and shorter Bragg Gratings but also offers greater Fabrication speed and a higher fidelity of control than previous amplitude modulation methods [1].
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phase modulated direct uv Grating writing technique for ultra wide spectrum planar bragg Grating Fabrication
Proceedings of SPIE, 2013Co-Authors: Chaotan Sima, James C Gates, Christopher Holmes, Helen L Rogers, Paolo L Mennea, M N Zervas, Pete SmithAbstract:Direct UV Grating Writing (DGW) is an attractive technique for simultaneously fabricating integrated Bragg Grating devices in a silica-on-silicon platform, yielding losses as low as 0.03dB/cm. Previously, an Acousto-Optical Modulator has been used for writing planar Bragg Gratings; in this new work we demonstrate a new phase modulation Fabrication technique that offers improved performance. We report a novel phase control DGW method using an Electro-Optical Modulator for planar Bragg Grating Fabrication. We phase modulate one laser beam in a focusing interferometer as a photosensitive silica-on-silicon sample is translated under the spot to give a moving fringe pattern that allows high quality Bragg Gratings and waveguides to be fabricated in a single step. This new approach has allowed us to achieve a 1mm long uniform Bragg Grating with ~70% reflectivity and a 1.4nm 3dB bandwidth; while a 3mm long Grating has 100% top flat reflectivity and a 1.22nm 3dB reflection bandwidth - refractive index changes of up to 0.001 can be achieved. Since there is neither laser power reduction nor writing speed variation, the method offers significantly faster writing speeds. The simplified optical layout offers greater laser power on sample and furthermore the design coding is simplified. By applying Gaussian apodisation to the Grating design we can achieve sidelobe suppression of >15dB. Using Grating detuning and this new phase control method we have shown that Bragg Gratings can be written from 1200nm to 1900nm on a single chip under software control and with less than 3dB variation across a 250nm bandwidth high chemical stability, which makes these materials very interesting for active photonics applications. In particular, Yb3+-doped RTP exhibits a broad fluorescence spectrum that has been exploited to demonstrate ultrafast operation, with pulses as short as 155 fs being generated [1]. Recently, planar waveguiding has been demonstrated in an (Yb3+, Nb5+):RTP film grown by liquid phase epitaxy [2], opening the possibility of planar integrated devices based on this highly functional material.
Changrui Liao - One of the best experts on this subject based on the ideXlab platform.
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orbital angular momentum mode converter based on helical long period fiber Grating inscribed by hydrogen oxygen flame
Journal of Lightwave Technology, 2017Co-Authors: Shen Liu, Ying Wang, Changrui Liao, Zhiyong Bai, Yan Zhang, Kaiming Yang, Yiping WangAbstract:A high-efficiency Grating Fabrication method was, for the first time, demonstrated to inscribe helical long period fiber Gratings (H-LPFGs) in small numbers by means of twisting a standard single-mode fiber (SMF) during hydrogen-oxygen flame heating and then cutting the helical fiber into in series of sections. Each section of the helical fiber was a desired LPFG whose resonant wavelength, i.e., Grating pitch, can be changed by adjusting the twist rate of the helical fiber. The H-LPFG inscribed in a standard SMF could be used to generate orbital angular momentum (OAM) modes, i.e., OAM+1 mode, with a purity of 91% and a conversion efficiency of 87% within a large wavelength range from more than the cutoff wavelength of an SMF, which is highly advantageous to all-fiber optical communications based on the OAM mode-division multiplexing technique.
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Asymmetric microhole-structured long-period fiber Gratings
Sensors and Actuators B-chemical, 2011Co-Authors: Ying Wang, D.n. Wang, Minwei Yang, Changrui LiaoAbstract:Abstract Asymmetric microhole-structured long period fiber Grating fabricated in single mode, fiber and photonics crystal fiber by use of femtosecond laser pulse drilling is, presented. The periodically structured microholes positioned a few microns away, from the central fiber axis can effectively couple the fundamental core mode into the, forward-propagating cladding mode, thus forming a long period fiber Grating. The, results obtained show that the asymmetrical-drilling method can effectively improve, the reliability of the Grating Fabrication when compared with the symmetrical-drilling, method, owing to the increased tolerance in geometric error of laser pulse, micromachining.
D N Nikogosyan - One of the best experts on this subject based on the ideXlab platform.
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multi photon high excitation energy approach to fibre Grating inscription
Measurement Science and Technology, 2007Co-Authors: D N NikogosyanAbstract:Amongst the most important and frequently used fibre devices, fibre Bragg and long-period Gratings are conventionally fabricated by low-intensity (I < 107 W cm?2) UV quanta with an energy of about 5 eV, which coincides with the maximum of the absorption band of defects in germanosilicate glass (the usual material of a fibre core). Such a single-quantum photochemical technique produces refractive index changes in the fibre core and not in the fibre cladding. The use of single-quantum excitation with high-energy vacuum UV photons with 157 nm wavelength or two-quantum 193 nm excitation through the real intermediate state results in a higher excitation energy (7.9 and 12.8 eV, respectively) and significantly increases the efficiency of Grating inscription. However, neither of these high-energy approaches is free of disadvantages: the 157 nm radiation is strongly absorbed by practically all optical materials and even by air; the application of the second approach is based on the existence of an intermediate state, i.e. presence of absorption at the irradiation wavelength. The new multi-photon high-excitation-energy approach to fibre Grating Fabrication is based on refractive index change modification by high-intensity (I ~ 1011?1013 W cm?2) femtosecond UV, near-UV or IR laser radiation applied to fibre, which acquires a total excitation energy of about 8?12 eV via two-, three- or even five-photon (through the intermediate virtual state/states) absorption processes. Such a high value of excitation energy exceeds the band-gap energy values for both the fibre core and the cladding, which could result in asymmetric light energy deposition inside the fibre and even inside the fibre core. We will consider the advantages of this novel technique such as Grating Fabrication in fibres of any content, including photonic crystal ones; the writing of extremely stable Gratings with erasing temperatures above 1000 ?C; the point-by-point inscription of Bragg Gratings, including non-uniform 'chirped' ones; the creation of fibre Gratings with high polarization properties; etc.
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single quantum mechanism of bragg Grating inscription in a ge b codoped fibre by high intensity 264 nm femtosecond pulses
Measurement Science and Technology, 2007Co-Authors: T Ernst, D N NikogosyanAbstract:We studied fibre Bragg Grating Fabrication in Ge/B codoped photosensitive fibre using high-intensity (60−230 GW cm−2) 264 nm, 220 fs laser pulses The ratio of the refractive index modulation to the incident fluence was found to be independent of the irradiation intensity which points to a single-quantum mechanism of Bragg Grating Fabrication under the stated experimental conditions.
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two photon photochemical long period Grating Fabrication in pure fused silica photonic crystal fiber
Optics Letters, 2006Co-Authors: Gilberto Brambilla, A A Fotiadi, Stephen A Slattery, D N NikogosyanAbstract:We report what is to our knowledge the first photochemical Fabrication of a long-period Grating in a pure-fused-silica photonic crystal fiber. The inscription technique is based on a two-photon absorption mechanism and does not require a specially designed photonic crystal fiber with a photosensitive Ge-doped core. The characteristic fluence value for the inscription is an order of magnitude less than that for a standard telecom fiber irradiated under similar conditions with the same Grating parameters.
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long period fiber Grating Fabrication by high intensity femtosecond pulses at 211 nm
Journal of Lightwave Technology, 2005Co-Authors: Alexey I Kalachev, D N Nikogosyan, Gilberto BrambillaAbstract:Using high-intensity (110-200 GW/cm/sup 2/) 250-fs 211-nm laser pulses and a point-by-point technique, the efficiency of long-period Grating inscription in H/sub 2/-loaded standard telecom Corning SMF-28 and H/sub 2/-free photosensitive B-codoped Fibercore fibers was studied and compared with those at other existing recording methods (low-intensity 157-nm, 193-nm, 248-nm or high-intensity 264-nm Fabrications). It was shown that at high-intensity 211-nm laser inscription, two-quantum photoreactions are responsible for long-period fiber Grating (LPFG) formation, which results in a significant photosensitivity enhancement in comparison with conventional low-intensity 248-nm exposure (by 45 times for SMF-28 fiber). It was found that the Grating strength in the case of SMF-28 fiber, irradiated with high-intensity 211-nm pulses, reaches 28 dB, which is the highest value among all known photochemical approaches. The thermal studies of the recorded Gratings were also conducted.
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long period fibre Grating Fabrication with femtosecond pulse radiation at different wavelengths
Microelectronic Engineering, 2003Co-Authors: P G Kryukov, D N Nikogosyan, Yu V Larionov, A A Rybaltovskii, K A Zagorulko, Adrian Dragomir, Albert A RuthAbstract:The Fabrication of long-period fibre Gratings (LPFGs) in optical fibres by femtosecond pulses at different wavelengths is reported. Several types of fibres were used and it was found that LPFGs with strong attenuation peaks (more than 20 dB) can be induced in hydrogen-loaded germanosilicate fibres using the second harmonic of a femtosecond Ti:sapphire laser without the use of an amplifier (400 nm, 70 fs and 2.5 nJ) and amplified, frequency-quadrupled pulses from a Nd:glass laser (264 nm, 220 fs and 0.4 mJ). Low 'out-of-band' losses and results of isochronal annealing for the fabricated Gratings suggest that the photoinduced refractive index change is not accompanied by damage to irradiated fibres.
