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Identifier

000341870

Title

Inscription of Bragg Gratings in highly transparent optical fibres using ultrafast ultraviolet radiation

Alternative Title

Εγγραφή φραγμάτων ανάκλασης Bragg σε οπτικές ίνες υψηλής διαπερατότητας με χρήση υπεριώδους ακτινοβολίας υπερβραχέων παλμών

Author

Λιβιτζιής, Μιχάλης

Thesis advisor

Φωτάκης, Κωνσταντίνος

Abstract

The photosensitivity mechanisms of the pristine silicate glass and the inscription of Fiber Bragg Gratings (FBGs) in highly transparent, step-index and microstructured optical fibers, using ultrafast, ultraviolet radiation, are presented in this thesis. The photosensitivity of pure and hydrogenated silica is investigated by examining the evolution curves of average and modulated refractive index changes versus accumulated energy density, for Bragg grating inscriptions in fluorine depressed cladding, pure silica core optical fibers, using 248nm, 5ps, 500fs and 120fs laser radiation. An important achievement of this work was the recording of strong FBG (20dB) in pristine fiber, by employing a double phase mask interferometer in order to apply high intensity laser pulses at 248nm. Thermal annealing results are also examined for understanding of the underlying photosensitivity mechanism. In addition, the possibility of inscribing Bragg gratings in high purity all-silica microstructured optical fiber is investigated. Weak Bragg gratings (~1dB) were recorded in both hydrogenated and pristine fibers and the differentiation between inscriptions in them and the aforementioned step index fibers are discussed. Finally, the first as far as we know, Type IIA Bragg Gratings in microstructured optical fiber are reported in this work. Strong Bragg gratings were recorded in MOF with highly Ge-doped core using 10ns 193nm excimer laser radiation. These gratings maintain the 50% of their strength up to temperatures of 700^οC. Higher order notches were also observed in the transmission spectrum and considering that, the overlap of the guiding modes with the topology of the fiber is discussed.

Physical description

87 σ. : εικ. ; 30 εκ.

Language

English

Subject

Bragg gratings

Φράγματα περίθλασης Bragg

φωτοευαισθησία

Issue date

2009-04-02

Collection

School/Department--School of Sciences and Engineering--Department of Physics--Post-graduate theses