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A numerical study on the importance of non-uniform index modification during femtosecond grating inscription in microstructured optical fibers. / Baghdasaryan, Tigran; Geernaert, Thomas; Thienpont, Hugo; Berghmans, Francis.

Micro-structured and specialty optical fibres IV. Vol. 9888 SPIE, 2016. UNSP 98860A .

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Baghdasaryan, T, Geernaert, T, Thienpont, H & Berghmans, F 2016, A numerical study on the importance of non-uniform index modification during femtosecond grating inscription in microstructured optical fibers. in Micro-structured and specialty optical fibres IV. vol. 9888, UNSP 98860A , SPIE, Conference on Micro-Structured and Specialty Optical Fibres IV , Brussels, Belgium, 4/04/16. https://doi.org/10.1117/12.2229341

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@inproceedings{5b0521139dc04fd79a009296f91c3ea7,
title = "A numerical study on the importance of non-uniform index modification during femtosecond grating inscription in microstructured optical fibers",
abstract = "Fiber Bragg grating (FBG) inscription methods based on femtosecond laser sources are becoming increasingly popular owing to the (usually) non-linear nature of the index modification mechanism and to the resulting advantages. They allow, for example, fabricating fiber gratings that can survive temperatures exceeding 700 degrees C, which can be an asset in the domain of fiber sensing. However applying femtosecond laser based grating fabrication to microstructured optical fibers (MOFs) can be challenging due to the presence of the air holes in the fiber cladding. The microstructured cladding not only impedes light delivery to the core in most cases, but also causes a non-uniform intensity distribution in the MOF core. To deal with these challenges we present a modeling approach that allows simulating how the reflectivity of the grating and the nature of the index modulation are affected by the inscription conditions. We rely on transverse coupling simulations, empirical data and coupled mode analysis to model the induced index change and the resulting grating reflectivity. For IR femtosecond grating inscription we show that due to the intensity redistribution in the core region, irreversible Type II index changes can be induced in a MOF at laser peak intensities below the Type II threshold for step-index fibers. The resulting non-uniform induced index change has repercussions on the reflection spectrum of the grating as well. Our coupled mode analysis reveals, for example, that although the average index change in the core region can be high, the partial overlap of the core mode with the index change region limits the reflectivity of the grating.",
keywords = "PHOTONIC CRYSTAL FIBERS, BRAGG GRATINGS, PHASE-MASK, LASER-RADIATION, IR-GRATINGS, SILICA, TECHNOLOGY, WRITTEN, PULSES",
author = "Tigran Baghdasaryan and Thomas Geernaert and Hugo Thienpont and Francis Berghmans",
year = "2016",
month = "4",
day = "27",
doi = "10.1117/12.2229341",
language = "English",
isbn = "978-1-5106-0131-4",
volume = "9888",
booktitle = "Micro-structured and specialty optical fibres IV",
publisher = "SPIE",
address = "United States",

}

RIS

TY - GEN

T1 - A numerical study on the importance of non-uniform index modification during femtosecond grating inscription in microstructured optical fibers

AU - Baghdasaryan, Tigran

AU - Geernaert, Thomas

AU - Thienpont, Hugo

AU - Berghmans, Francis

PY - 2016/4/27

Y1 - 2016/4/27

N2 - Fiber Bragg grating (FBG) inscription methods based on femtosecond laser sources are becoming increasingly popular owing to the (usually) non-linear nature of the index modification mechanism and to the resulting advantages. They allow, for example, fabricating fiber gratings that can survive temperatures exceeding 700 degrees C, which can be an asset in the domain of fiber sensing. However applying femtosecond laser based grating fabrication to microstructured optical fibers (MOFs) can be challenging due to the presence of the air holes in the fiber cladding. The microstructured cladding not only impedes light delivery to the core in most cases, but also causes a non-uniform intensity distribution in the MOF core. To deal with these challenges we present a modeling approach that allows simulating how the reflectivity of the grating and the nature of the index modulation are affected by the inscription conditions. We rely on transverse coupling simulations, empirical data and coupled mode analysis to model the induced index change and the resulting grating reflectivity. For IR femtosecond grating inscription we show that due to the intensity redistribution in the core region, irreversible Type II index changes can be induced in a MOF at laser peak intensities below the Type II threshold for step-index fibers. The resulting non-uniform induced index change has repercussions on the reflection spectrum of the grating as well. Our coupled mode analysis reveals, for example, that although the average index change in the core region can be high, the partial overlap of the core mode with the index change region limits the reflectivity of the grating.

AB - Fiber Bragg grating (FBG) inscription methods based on femtosecond laser sources are becoming increasingly popular owing to the (usually) non-linear nature of the index modification mechanism and to the resulting advantages. They allow, for example, fabricating fiber gratings that can survive temperatures exceeding 700 degrees C, which can be an asset in the domain of fiber sensing. However applying femtosecond laser based grating fabrication to microstructured optical fibers (MOFs) can be challenging due to the presence of the air holes in the fiber cladding. The microstructured cladding not only impedes light delivery to the core in most cases, but also causes a non-uniform intensity distribution in the MOF core. To deal with these challenges we present a modeling approach that allows simulating how the reflectivity of the grating and the nature of the index modulation are affected by the inscription conditions. We rely on transverse coupling simulations, empirical data and coupled mode analysis to model the induced index change and the resulting grating reflectivity. For IR femtosecond grating inscription we show that due to the intensity redistribution in the core region, irreversible Type II index changes can be induced in a MOF at laser peak intensities below the Type II threshold for step-index fibers. The resulting non-uniform induced index change has repercussions on the reflection spectrum of the grating as well. Our coupled mode analysis reveals, for example, that although the average index change in the core region can be high, the partial overlap of the core mode with the index change region limits the reflectivity of the grating.

KW - PHOTONIC CRYSTAL FIBERS

KW - BRAGG GRATINGS

KW - PHASE-MASK

KW - LASER-RADIATION

KW - IR-GRATINGS

KW - SILICA

KW - TECHNOLOGY

KW - WRITTEN

KW - PULSES

U2 - 10.1117/12.2229341

DO - 10.1117/12.2229341

M3 - Conference paper

SN - 978-1-5106-0131-4

VL - 9888

BT - Micro-structured and specialty optical fibres IV

PB - SPIE

ER -

ID: 29134935