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Photosensitivity, chemical composition gratings and optical fiber based components
KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.ORCID iD: 0000-0002-9207-4183
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.
Series
Trita-FYS, ISSN 0280-316X ; 2239
Keyword [en]
optical fibers, fiber bragg gratings, photosensitivity, thermal stability
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:kth:diva-3436ISBN: 91-7283-397-1 (print)OAI: oai:DiVA.org:kth-3436DiVA: diva2:9235
Public defence
2002-12-06, 00:00
Note
QC 20100607Available from: 2002-12-03 Created: 2002-12-03 Last updated: 2010-06-07Bibliographically approved
List of papers
1. Formation of thermally stable chemical composition gratings in optical fibers
Open this publication in new window or tab >>Formation of thermally stable chemical composition gratings in optical fibers
2002 (English)In: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, 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.

Keyword
BRAGG GRATINGS, GERMANOSILICATE FIBER, INDEX CHANGES, PHOTOSENSITIVITY, HYDROGEN, WRITTEN, INCREASE, GLASS, DECAY, NM
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-13201 (URN)000177430100003 ()
Note
QC 20100602Available from: 2010-06-02 Created: 2010-06-02 Last updated: 2017-12-12Bibliographically approved
2. Thermal stability of chemical composition gratings in fluorine-germanium-doped silica fibers
Open this publication in new window or tab >>Thermal stability of chemical composition gratings in fluorine-germanium-doped silica fibers
2002 (English)In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 27, no 12, 1016-1018 p.Article in journal (Refereed) Published
Abstract [en]

A model based on diffusion of dopants in a periodic structure has been applied to describe thermal decay of chemical composition gratings in fluorine-germanium-doped silica fibers. The good agreement between previously reported values and the diffusion coefficients derived here from experiments and models in the 1000 - 1200 degreesC temperature range indicate that fluorine diffusion is the main mechanism of grating decay. Experimental results also indicate that the presence of phosphorous significantly increases the decay rate of chemical composition gratings.

Keyword
BRAGG GRATINGS
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-13202 (URN)000176277600010 ()
Note
QC 20100602Available from: 2010-06-02 Created: 2010-06-02 Last updated: 2017-12-12Bibliographically approved
3. Growth dynamics of chemical composition gratings in flourine-doped silica optical fibers
Open this publication in new window or tab >>Growth dynamics of chemical composition gratings in flourine-doped silica optical fibers
2002 (English)In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 27, 1974-1976 p.Article in journal (Refereed) Published
Abstract [en]

The refractive-index modulation of chemical composition gratings in fluorine-germanium-doped silica fibers as a function of thermal treatment during manufacturing has been studied. The final grating strength was found to depend strongly on an intermediate annealing step, with an optimum temperature near 600-700 degrees C, before development at a fixed temperature of 1000 degrees C. Low-temperature treatment, aimed at removing any remaining hydrogen from the fiber, performed at 100 degrees C for 20 h before the annealing step, also significantly increased the final refractive-index modulation.

National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-13203 (URN)
Note
QC 20100602Available from: 2010-06-02 Created: 2010-06-02 Last updated: 2017-12-12Bibliographically approved
4. High temperature miniature oven with low thermal gradient for processing fiber Bragg gratings
Open this publication in new window or tab >>High temperature miniature oven with low thermal gradient for processing fiber Bragg gratings
2001 (English)In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 72, no 8, 3458-3461 p.Article in journal (Refereed) Published
Abstract [en]

A miniature oven for processing fiber Bragg gratings in excess of 1000 degreesC has been projected and evaluated. The dimensions and the design of the oven allow rapid insertion and removal of the fiber during heating and minimizes mechanical degradation of the fiber. The 22 mm long oven has a flat zone at 1000 degreesC of 16 mm with a temperature variation of less than 2% and 20 mm with a temperature variation of 10%. The long term stability (hours) is +/- 20 degreesC measured at the center of the oven at 1000 degreesC. Rapid heating is possible, and heating optical fibers to 1000 degreesC shows a delay of approximately 400 ms before the core reaches thermal equilibrium.

Keyword
OPTICAL-FIBER, PHOTOSENSITIVITY
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-13204 (URN)000170046900046 ()
Note
QC 20100602Available from: 2010-06-02 Created: 2010-06-02 Last updated: 2017-12-12Bibliographically approved
5. ToF-SIMS imaging of dopant diffusion in optical fibers
Open this publication in new window or tab >>ToF-SIMS imaging of dopant diffusion in optical fibers
Show others...
2003 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 203, 648-651 p.Article in journal (Refereed) Published
Abstract [en]

Applications of optical fibers in telecommunication and sensing are rapidly emerging where the fiber properties are related to the controlled addition of dopants such as germanium, phosphorous, fluorine and erbium. The modern ToF-SIMS instrument, with its high sensitivity and high lateral resolution, has shown to be an excellent tool to directly analyze cross-sections of as-manufactured fibers. The present work describes ToF-SIMS imaging of the dopant distribution in fluorine, germanium and rare-earth doped fibers where dopants are confined to a few mum in the core. The increased fluorine diffusion in the fluorine doped fibers due to chemical reactions with hydroxyl groups was examined. This process is utilized in the manufacture of thermally stable chemical composition fiber Bragg gratings. We were able to produce ToF-SIMS elemental images with a lateral resolution around 0.5 mum showing the detailed distribution of the dopants.

Keyword
ToF-SIMS, imaging, optical fibers, fiber bragg gratings, diffusion, dopant
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-13205 (URN)000180527300145 ()
Note
QC 20100602Available from: 2010-06-02 Created: 2010-06-02 Last updated: 2017-12-12Bibliographically approved
6. Large increase in photosensitivity through massive hydroxyl formation
Open this publication in new window or tab >>Large increase in photosensitivity through massive hydroxyl formation
2000 (English)In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 25, no 5, 302-304 p.Article in journal (Refereed) Published
Abstract [en]

We report a large increase in photosensitivity of germanium-doped silicate fibers by rapid heat treatment of hydrogen-loaded fibers at 1000 degrees C before exposure of the fibers to 242-nm radiation. The increase in photosensitivity is compared with thermally induced absorption caused by introduction of massive amounts of hydroxyl species. The absorption loss was measured to be 0.02 dB/cm mol.% OH at 1.55 mu m. Strong gratings (Delta n > 1 x 10(-4)) in germanium-free phosphorous-doped fibers in the presence of 242-nm radiation have also been manufactured by this technique.

Keyword
DOPED OPTICAL FIBERS, UV PHOTOSENSITIVITY, HYDROGEN, GLASSES, GEO2
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-13222 (URN)10.1364/OL.25.000302 (DOI)000085650500008 ()
Note
QC 20100607Available from: 2010-06-07 Created: 2010-06-07 Last updated: 2017-12-12Bibliographically approved
7. Grating formation in pure silica-core fibers
Open this publication in new window or tab >>Grating formation in pure silica-core fibers
2002 (English)In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 27, no 10, 809-811 p.Article in journal (Refereed) Published
Abstract [en]

Strong grating formation in pure silica-core fibers by use of 193-nm ArF-laser radiation is reported. Unsaturated refractive-index changes of Deltan similar to 0.3 X 10(-3) were observed in nontreated fiber, and changes of Deltan similar to 0.5 X 10(-3) were observed in fibers with a high hydroxyl concentration. Possible mechanisms of photosensitivity in pure silica-core fibers are discussed.

Keyword
DOPED OPTICAL FIBERS, EXCIMER-LASER, PHOTOSENSITIVITY, GLASSES
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-13223 (URN)10.1364/OL.27.000809 (DOI)000175786100005 ()
Note
QC 20100607Available from: 2010-06-07 Created: 2010-06-07 Last updated: 2017-12-12Bibliographically approved
8. Mach-Zehnder interferometer using single standard telecommunication optical fibre
Open this publication in new window or tab >>Mach-Zehnder interferometer using single standard telecommunication optical fibre
2001 (English)In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 37, no 24, 1440-1442 p.Article in journal (Refereed) Published
Abstract [en]

It is demonstrated that a single, short-length, standard telecommunications optical fibre can function as an interferometer when subjected to hydroxyl-flooding. The interferometer is based on the mode beating effect arising from the induced-refractive index change.

Keyword
PHOTOSENSITIVITY, FIBERS
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-13224 (URN)10.1049/el:20011000 (DOI)000172687000010 ()
Note
QC 20100607Available from: 2010-06-07 Created: 2010-06-07 Last updated: 2017-12-12Bibliographically approved
9. Integrated fiber Mach-Zehnder interferometer for electro-optic switching
Open this publication in new window or tab >>Integrated fiber Mach-Zehnder interferometer for electro-optic switching
Show others...
2002 (English)In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 27, no 18, 1643-1645 p.Article in journal (Refereed) Published
Abstract [en]

Molten alloys under high pressure were used to obtain fibers with long internal electrodes that are solid at room temperature. An integrated Mach-Zehnder interferometer was constructed from a twin-core twin-hole fiber that permitted application of an electric field preferentially to one of the cores. Good stability and a switching voltage of 1.4 kV were measured with a 1-m-long fiber device with a quadratic voltage dependence.

Keyword
2ND-ORDER NONLINEARITIES, MODULATION, SILICA, FIELD
National Category
Natural Sciences
Identifiers
urn:nbn:se:kth:diva-13225 (URN)10.1364/OL.27.001643 (DOI)000177945300019 ()
Note
QC 20100607Available from: 2010-06-07 Created: 2010-06-07 Last updated: 2017-12-12Bibliographically approved

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Citation style
  • apa
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  • ieee
  • modern-language-association-8th-edition
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  • nn-NB
  • sv-SE
  • Other locale
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Output format
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