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Formation of thermally stable chemical composition gratings in optical fibers
KTH, Superseded Departments, Physics.ORCID iD: 0000-0002-9207-4183
2002 (English)In: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, Vol. 19, no 8, 1759-1765 p.Article in journal (Refereed) Published
Abstract [en]

Experimental results and a discussion of possible chemical pathways in the formation of thermally stable chemical composition gratings in optical fibers are presented. Gratings are formed through high-temperature treatment of UV-exposed hydrogen-loaded fibers. The final refractive-index modulation is ascribed to variations in fluorine concentration attained by periodically increased diffusion of fluorine. The mechanism behind this increase is the formation of mobile hydrogen fluoride from chemical reactions of fluorine and UV-induced hydroxyl, which occur with the spatial periodicity of the UV pattern. A hydroxyl-assisted increase in fluorine diffusion has been verified by time-of-flight secondary-ion mass spectroscopy. Formation of ultrastable grating by periodic variation of oxygen concentration through diffusion of molecular water is also discussed.

Place, publisher, year, edition, pages
2002. Vol. 19, no 8, 1759-1765 p.
Keyword [en]
National Category
Physical Sciences
URN: urn:nbn:se:kth:diva-13201ISI: 000177430100003OAI: diva2:321810
QC 20100602Available from: 2010-06-02 Created: 2010-06-02 Last updated: 2010-06-07Bibliographically approved
In thesis
1. Photosensitivity, chemical composition gratings and optical fiber based components
Open this publication in new window or tab >>Photosensitivity, chemical composition gratings and optical fiber based components
2002 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The different topics of this thesis include high-temperaturestable fiber Bragg gratings, photosensitivity and fiber basedcomponents.

Fiber Bragg gratings (FBG) are wavelength dispersiverefractive index structures manufactured through UV exposure ofoptical fibers. Their applications range from WDM filters,dispersion compensators and fiber laser resonators fortelecommunication applications to different types of point ordistributed sensors for a variety of applications.

One aim of this thesis has been to study a new type of FBGreferred to as chemical composition grating. These gratingsdiffer from other types of FBG in that their refractive indexstructure is attributed to a change in the chemicalcomposition. Chemical composition gratings have shown to beextremely temperature stable surviving temperatures in excessof 1000 oC. Photosensitivity of pure silica and germanium-dopedcore fibers in the presence of hydroxyl groups has also beenstudied and different types of fiber based components have beendeveloped.

The main result of the thesis is a better understanding ofthe underlying mechanism of the formation of chemicalcomposition gratings and their decay behavior at elevatedtemperatures. The refractive index modulation is caused by aperiodic change in the fluorine concentration, which has beenverified through time-of-flight secondary-ion-mass spectrometryand through studies of the decay behavior of chemicalcomposition gratings. A model based on diffusion of dopants hasbeen developed, which successfully predicts the thermal decayat elevated temperatures. Studies of the dynamics of chemicalcomposition grating formation have resulted in a manufacturingtechnique that allows for reproducible gratingfabrication.

The main results regarding photosensitivity is a method tosignificantly increase the effect of UV radiation on standardtelecommunications fiber. The method, referred to asOH-flooding, has also been applied to pure-silica core fibersresulting in the first report of strong grating formation insuch fibers.

Finally, research into different schemes for developingfiber-based components has resulted in two types of singlefiber integrated Mach-Zehnder interferometers; one passiveinterferometer that can be used as an optical filter and oneactive interferometer controlled with internal metalelectrodes.

Keywords:optical fibers, fiber Bragg gratings,photosensitivity, thermal stability, fiber sensors, chemicalcomposition gratings, fiber components, Mach-Zehnderinterferometer, optical switch, optical modulator.

Place, publisher, year, edition, pages
Stockholm: KTH, 2002. xii, 77 p.
Trita-FYS, ISSN 0280-316X ; 2239
optical fibers, fiber bragg gratings, photosensitivity, thermal stability
National Category
Natural Sciences
urn:nbn:se:kth:diva-3436 (URN)91-7283-397-1 (ISBN)
Public defence
2002-12-06, 00:00
QC 20100607Available from: 2002-12-03 Created: 2002-12-03 Last updated: 2010-06-07Bibliographically approved

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