Página 1 dos resultados de 83 itens digitais encontrados em 0.009 segundos

## Desenvolvimento de plataformas ópticas para sensoriamento de amostras biológicas; Development of optical platforms for biological samples sensing

Jonas Henrique Osório
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
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## Alternative technique for biodiesel quality control using an optical fiber long-period grating sensor

Falate,Rosane; Nike,Karen; Costa Neto,Pedro Ramos da; Cação Jr.,Eduardo; Muller,Marcia; Kalinowski,Hypolito José; Fabris,José Luís
Tipo: Artigo de Revista Científica Formato: text/html
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We report the use of an optical fiber sensor to measure the soybean oil concentration in samples obtained from the mixture of pure biodiesel and commercial soybean oil. The operation of the device is based on the long-period grating sensitivity to the surrounding medium refractive index, which leads to measurable modifications in the grating transmission spectrum. The proposed analysis method results in errors in the oil concentration of 0.4% and 2.6% for pure biodiesel and commercial soybean oil, respectively. Techniques of total glycerol, dynamic viscosity, density, and hydrogen nuclear magnetic resonance spectroscopy were also employed to validate the proposed method.

## Pressure Sensing in High-Refractive-Index Liquids Using Long-Period Gratings Nanocoated with Silicon Nitride

Smietana, Mateusz; Bock, Wojtek J.; Mikulic, Predrag; Chen, Jiahua
Fonte: Molecular Diversity Preservation International (MDPI) Publicador: Molecular Diversity Preservation International (MDPI)
Tipo: Artigo de Revista Científica
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The paper presents a novel pressure sensor based on a silicon nitride (SiNx) nanocoated long-period grating (LPG). The high-temperature, radio-frequency plasma-enhanced chemical-vapor-deposited (RF PECVD) SiNx nanocoating was applied to tune the sensitivity of the LPG to the external refractive index. The technique allows for deposition of good quality, hard and wear-resistant nanofilms as required for optical sensors. Thanks to the SiNx nanocoating it is possible to overcome a limitation of working in the external-refractive-index range, which for a bare fiber cannot be close to that of the cladding. The nanocoated LPG-based sensing structure we developed is functional in high-refractive-index liquids (nd > 1.46) such as oil or gasoline, with pressure sensitivity as high as when water is used as a working liquid. The nanocoating developed for this experiment not only has the highest refractive index ever achieved in LPGs (n > 2.2 at λ = 1,550 nm), but is also the thinnest (<100 nm) able to tune the external-refractive-index sensitivity of the gratings. To the best of our knowledge, this is the first time a nanocoating has been applied on LPGs that is able to simultaneously tune the refractive-index sensitivity and to enable measurements of other parameters.

## Long Period Gratings in Random Hole Optical Fibers for Refractive Index Sensing

Wang, Ke; Pickrell, Gary
Fonte: Molecular Diversity Preservation International (MDPI) Publicador: Molecular Diversity Preservation International (MDPI)
Tipo: Artigo de Revista Científica
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We have demonstrated the fabrication of long period gratings in random hole optical fibers. The long period gratings are fabricated by a point-by-point technique using a CO2 laser. The gratings with a periodicity of 450 μm are fabricated and a maximum coupling efficiency of −9.81 dB has been achieved. Sensing of different refractive indices in the surrounding mediums is demonstrated by applying standard liquids with refractive indices from 1.400 to 1.440 to the long period grating.

## High Temperature Long Period Grating Thermo-Mechanically Written

Lazaro, Jose Miguel; Quintela, Antonio; Lopez-Higuera, Jose Miguel
Fonte: Molecular Diversity Preservation International (MDPI) Publicador: Molecular Diversity Preservation International (MDPI)
Tipo: Artigo de Revista Científica
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An optical fiber transducer able to work in high temperature environments is experimentally demonstrated in the laboratory. It is based on a permanent long period grating (LPG) written using a new technique based on a thermo-mechanical approach. Device precision was experimentally checked by means of repetitive thermal cycles between 25 and 950 °C. In addition device stability was assured by maintaining the temperature in steady state at 800 °C during 23 hours.

## Characterization of Long-period Grating Refractive Index Sensors and Their Applications

Tsuda, Hiroshi; Urabe, Kei
Fonte: Molecular Diversity Preservation International (MDPI) Publicador: Molecular Diversity Preservation International (MDPI)
Tipo: Artigo de Revista Científica
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The influence of grating length and bend radius of long-period gratings (LPGs) on refractive index sensing was examined. Sensitivity to refractive indexes smaller than that of silica could be enhanced by bending LPGs. Bent LPGs lost sensitivity to refractive indexes higher than that of silica, whereas a 20-mm-long LPG arranged in a straight line had considerable sensitivity. These experimental results demonstrated that the sensitivity characteristics of LPGs to refractive index could be controlled by grating length and bend radius.

## Chemical Sensing Sensitivity of Long-Period Grating Sensor Enhanced by Colloidal Gold Nanoparticles

Tang, Jaw-Luen; Wang, Jien-Neng
Fonte: Molecular Diversity Preservation International (MDPI) Publicador: Molecular Diversity Preservation International (MDPI)
Tipo: Artigo de Revista Científica
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A simple and effective method is proposed to improve spectral sensitivity and detection limit of long period gratings for refractive index or chemical sensing, where the grating surface is modified by a monolayer of colloidal gold nanoparticles. The transmission spectra and optical properties of gold nanospheres vary with the different refractive index of the environment near the surface of gold nanospheres. The sensor response of gold colloids increases linearly with solvents of increasing refractive index. The results for the measurement of sucrose and sodium chloride solutions are reported, which show that this type of sensor can provide a limiting resolution of ∼10-3 to ∼10-4 for refractive indices in the range of 1.34 to 1.39 and a noticeable increase in detection limit of refractive index to external medium.

## Highly Sensitive Refractive Index Sensor Based on Adiabatically Tapered Microfiber Long Period Gratings

Ji, Wen Bin; Tjin, Swee Chuan; Lin, Bo; Ng, Choong Leng
Fonte: Molecular Diversity Preservation International (MDPI) Publicador: Molecular Diversity Preservation International (MDPI)
Tipo: Artigo de Revista Científica
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We demonstrate a refractive index sensor based on a long period grating (LPG) inscribed in a special photosensitive microfiber with double-clad profile. The fiber is tapered gradually enough to ensure the adiabaticity of the fiber taper. In other words, the resulting insertion loss is sufficiently small. The boron and germanium co-doped inner cladding makes it suitable for inscribing gratings into its tapered form. The manner of wavelength shift for refractive indices (RIs) differs from conventional LPG, and the refractive index detection limit is 1.67 × 10−5.

## Initial results on the fabrication of long-period fiber Bragg gratings with a CO₂ laser; Initial results on the fabrication of long-period fiber Bragg gratings with a CO(2) laser

Armitage, J.; Hsu, M.; Munch, J.; Corbett, K.; Grant, K.; Jewell, C.
Fonte: S P I E - International Society for Optical Engineering Publicador: S P I E - International Society for Optical Engineering
Tipo: Artigo de Revista Científica
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Long-period fiber Bragg gratings (LPG) where the grating period is much longer than the wavelength of light have many unique characteristics and find uses in gain-flattening filters and mode converters. This paper describes the characteristics of the initial LPGs fabricated at the University of Adelaide using an infrared CO2 laser. The optical system implemented promotes uniform irradiation of the full circumference of the fiber, avoiding many of the non-uniformities, associated with a single sided system. Some initial gratings have been made using this method, which typically show an attenuation of 10dB within a wavelength range (FWHM) of 8 nm. Work is now focused on improving these devices through an understanding of the writing process and its effect on the transmitted spectrum.; John C. Armitage, Magnus T. L. Hsu, Jesper Munch, Kerry A. Corbett, Kenneth J. Grant and Chris Jewell

## Intensity-based optical fiber strain sensor using long-period fiber gratings and a core mode blocker

Hwang, D.; Nguyen, L.V.; Moon, D.S.; Chung, Y.
Fonte: IOP Publishing Publicador: IOP Publishing
Tipo: Artigo de Revista Científica
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We report an intensity-based fiber strain sensor using a pair of long-period fiber gratings (LPFGs) and an in-line core mode blocker. By inserting a core mode blocker fabricated by the arc discharge method between two LPFGs, a band-pass filter can be formed. We used an LED and an optical power meter to measure the transmittance near the resonance wavelength of the LPFGs and we obtained a relation between the axial strain applied on one of the LPFGs and the transmitted power. The measurement results indicate that the sensitivity of the power meter output voltage to the applied strain is 6.37 pV με−1.; Dusun Hwang, Linh Viet Nguyen, Dae Seung Moon, and Youngjoo Chung

## Virtual long-period gratings

Jáuregui Misas, César; López Higuera, José Miguel
Fonte: Optical Society of America Publicador: Optical Society of America
Tipo: info:eu-repo/semantics/article; publishedVersion
ENG
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A theoretical prediction of a new fiber grating structure is presented. This new device is achieved when a high-birefringence fiber is heavily twisted. It behaves like a long-period grating, but its spectral response can be controlled with the input state of polarization of the light. Since there is no permanent index change, but the index change is instead a product of the polarization evolution along the fiber, this device is called a virtual long-period grating.

## High temperature long period grating thermo-mechanically written

Lázaro Urrutia, José Miguel; Quintela Incera, Antonio; López Higuera, José Miguel
Tipo: info:eu-repo/semantics/article; publishedVersion
ENG
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An optical fiber transducer able to work in high temperature environments is experimentally demonstrated in the laboratory. It is based on a permanent long period grating (LPG) written using a new technique based on a thermo-mechanical approach. Device precision was experimentally checked by means of repetitive thermal cycles between 25 and 950 ºC. In addition device stability was assured by maintaining the temperature in steady state at 800 ºC during 23 hours.

## Virtual long-period fiber gratings

Jáuregui Misas, César; Quintela Incera, María Ángeles; Márquez, P.; López Higuera, José Miguel; Cobo García, Adolfo; González Fernández, Daniel Aquilino
Fonte: SPIE Society of Photo-Optical Instrumentation Engineers Publicador: SPIE Society of Photo-Optical Instrumentation Engineers
Tipo: info:eu-repo/semantics/conferenceObject; publishedVersion
ENG
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In this paper a theoretical prediction of a new kind of in-fiber devices is presented. They behave essentially like long-period Bragg gratings except for the fact that they are not permanent but volatile. This is because these devices are not formed by the UV-induced increment of the refractive index but by the twisting of a pristine HiBi fiber. This way, a long period fiber grating whose characteristics can be modified by changing the polarization of the incoming light is obtained.

## Grabado termo-mecánico de redes de difracción de periodo largo permanentes; Thermo-mechanical fabrication of permanent long period grating

Lázaro Urrutia, José Miguel; Quintela Incera, Antonio; Quintela Incera, María Ángeles; Lomer Barboza, Mauro Matías; Cobo García, Adolfo; López Higuera, José Miguel
Tipo: info:eu-repo/semantics/conferenceObject; publishedVersion
SPA
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RESUMEN: Las redes de difracción de periodo largo (RDPL) tienen un gran número de atractivas propiedades que pueden ser explotadas en una gama variada de aplicaciones entre las que se encuentran la detección y medida. Existen diferentes técnicas para su grabado. En este artículo se muestra una modificación de la técnica de presión mecánica. Esta modificación permite el grabado de RDPLs permanentes sin necesidad de utilizar láseres intensos y costosos. La técnica se ha demostrado comparando las medidas experimentales con los resultados de las simulaciones comprobando su concordancia.; ABSTRACT: Long period gratings (LPG) have a number of attractive properties that may be exploited in a wide range of applications like detection and measure. There are different writing techniques. In this paper a modification of the mechanical technique is shown. This modification allows the writing of permanent LPGs without the necessity of use intense and expensive lasers. The measured results are compared with simulated results in order to check the concordance.

## Fabricación de redes de periodo largo en fibras ópticas plásticas perfluoradas; Fabrication of long-periods grating in perfluorinated-core plastic optical fibers

Castrellón Uribe, Jesús; Lomer Barboza, Mauro Matías; Shokry Girgis Roufael, Hany; López Higuera, José Miguel
Tipo: info:eu-repo/semantics/conferenceObject; publishedVersion
SPA
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RESUMEN: En este documento se propone la fabricación y caracterización de redes de periodo largo (RPL) en fibras ópticas plásticas multimodo perfluoradas de gradiente de índice (PF-GI-POF) y comercialmente disponibles. Las redes han sido realizadas mediante el método de grabado punto a punto en la cubierta de la fibra utilizando un láser pulsado UV en la longitud de onda de 355 nm. El haz laser es focalizado en el eje de la fibra y se crea un periodo en la cubierta por ablación y por desplazamiento de la fibra se graban los otros periodos. Se presentan los resultados experimentales de una LPG realizados en una fibra perfluorada de 50/500 µm de diámetro de núcleo/cubierta y con peridos de 75 µm. El LPG presenta un rechazo de 15 dB a la longitud de onda de resonancia de 910 nm.; ABSTRACT: In this paper we describe the fabrication and characterization of long-period grating in perfluorinated GI-POF commercially available. To make the grating in PF-GI-POF has used the technique of writing point-by-point. This technique consists of a pulsed laser wavelength of 355 nm which is focused on the center of the fiber and creates a single period by ablation in the fiber cladding. Then, by longitudinal displacement of the fiber other periods are written in succession . That is...

## Development and Characterization of Polysiloxane Polymer Films for Use in Optical Sensor Technology

Plett, KRISTA
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado Formato: 2571901 bytes; application/pdf
EN; EN
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A novel sensor using a polymer coated long-period grating (LPG) has been proposed for monitoring levels of organic contaminants in air or water systems. The sensor operates by detecting refractive index changes in the polymer coating as analytes partition in. Polymer coatings used must be able to reversibly and reproducibly absorb contaminants of interest from the sample and have a refractive index just below that of the fiber cladding. The synthesis and characterization of several chemically selective polysiloxanes is described. Pre-polymer materials are made through the catalyzed condensation of silane monomers. Different functional groups are incorporated either through polymerizing functionalized monomers, or by post-functionalizing the polymer through a platinum-catalyzed hydrosilylation reaction. The pre-polymer materials are crosslinked into elastomeric films using titanium(IV) tetraisopropoxide. The polymer refractive index is controlled through altering the ratios of functional groups within the polymer or changing the loading levels of titanium. Four polymers were made, having different functional groups and optimized refractive indices for use on the proposed sensor. The partition coefficients for the polymers with a variety of solvents are calculated and compared. Each polymer was found to have a slightly different chemical selectivity pattern...

## Rapid and accurate detection of Cyanobacterial toxin microcystin-LR using fiber-optic long-period grating based immunosensor

Tripathi, Saurabh Mani; Bock, Wojtek J.; Mikulic, Predrag; Mishra, Garima
Tipo: Artigo de Revista Científica
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In this paper we present a label-free, stable and highly sensitive fiber-optic sensor for detection of environmental toxin microcystin-LR (MC-LR). Thiolated MC-LR-targeting aptamer covalently immobilized on dual-resonance long-period fiber gratings (DR-LPFG) is used as MC-LR recognition element and the spectral response of the DR-LPFG is monitored for various concentrations of MC-LR. Sensitivity of the DR-LPFG is optimized by coating an appropriate thickness of gold layer to the fiber surface. Gold coating serves two purposes, first it locally supports a surface-Plasmon mode associated with the modified cladding modes and second it helps covalently immobilize the MC-LR targeting aptamer to the sensor surface. Monitoring both the resonance wavelengths of our ultra sensitive DR-LPFGs (3891.5 nm/RIU) we study the aptamer and MC-LR binding to the sensor surface. Real-time, efficient MC-LR molecular binding to the sensor surface is also confirmed using atomic force microscopy. The detection limit of our sensor, limited by the molecule size of MC-LR, its fractional surface coverage of the sensor, and sensor length, is 5 ng/mL, which can be further improved by increasing the fractional MC-LR coverage on the sensor surface by (i) reducing the LPFG length (ii) increasing grating strength...

## Highly sensitive refractometer with photonic crystal fiber long-period grating

Rindorf, Lars; Bang, Ole
Tipo: Artigo de Revista Científica
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We present highly sensitive refractometers based on a long-period grating in a large mode area PCF. The maximum sensitivity is 1500 nm/RIU at a refractive index of 1.33, the highest reported for any fiber grating. The minimal detectable index change is $2\times 10^{-5}$. The high sensitivity is obtained by infiltrating the sample into the holes of the photonic crystal fiber to give a strong interaction between the sample and the probing field.; Comment: 4 pages, 3 figures, journal paper, submitted

## Experimental realization of transverse mode conversion using optically induced transient long-period gratings

Hellwig, Tim; Schnack, Martin; Walbaum, Till; Dobner, Sven; Fallnich, Carsten
Tipo: Artigo de Revista Científica
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We present the experimental realization of transverse mode conversion in an optical fiber via an optically induced long-period grating. The transient gratings are generated by femtosecond laser pulses, exploiting the Kerr effect to translate intensity patterns emerging from multimode interference into a spatial refractive index modulation. Since these modulations exist only while the pump beam is present, they can be used for optical switching of transverse modes. As only a localized part of the grating was written at a time and the probe beam was co-propagating with the pump beam the required pulse energies could be reduced to 120\,nJ which is about a factor of 600 lower than in previous quasi-continuous-wave experiments. Accompanying numerical simulations allow a better understanding of the involved effects and show excellent agreement to the experimental results.

## Refractometric sensors based on long period optical fiber gratings

Flores Llamas,I; Kolokoltsev,O; Svyryd,V