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| Identifier |
000413861 |
| Title |
Sensing resonating devices fabricated on optical fibers using multi-photon polymerization technique |
| Alternative Title |
Αισθητήριες διατάξεις αντιχείων συντονισμού εγγεγραμμένες σε οπτικές ίνες με χρήση μη γραμμικού φωτοπολυμερισμού |
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Author
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Μελισσινάκη, Βασιλεία
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Thesis advisor
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Φωτάκης, Κωνσταντίνος
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Reviewer
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Πισσαδάκης, Σταύρος
Φαρσάρη, Μαρία
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| Abstract |
The aim of this thesis is to combine standard single mode optical fibers and multi-photon lithography in order to produce robust and functional fiber-optic devices that will be exploited as fiber-optic gas or liquid sensors in the time being; also constituting basic platforms for other sensing and switching devices. Further, this study investigates in depth the advantages and disadvantages of the direct laser fabrication of micro-optical light resonating cavities onto the optical fibers.
For these reasons two different kinds of light resonating structures were fabricated by multi-photon polymerization technique directly onto single mode, telecom optical fibers. In particular, (i) fiber-optic devices based on Fabry-Perot interferometers fabricated on the endface of optical fibers and (ii) whispering-gallery mode micro-ring resonators fabricated directly onto tapered optical fibers will be demonstrated. In both cases hybrid organic-inorganic photosensitive materials were used for the fabrication of the light resonating components. For the fabrication of these fiber-optic interferometric devices new processes for the sample preparation had to be explored and developed. Furthermore, the designs of the interferometric components and their fabrication parameters had to be studied in order to produce functional structures. The spectral performance of both resonating devices was tested in the wavelength region of 1550 nm.
Initially, three different designs of fiber-optic devices based on Fabry-Perot interferometers were fabricated on the endface of optical fibers, namely, microdrum, microfunnel and microprism. Their fringe visibilities that were recorded were up to ~22 dB, while the free spectral range (FSR) was differ according to the length cavity, for example for a length cavity of ~18 μm the corresponding FSR was ~68 nm. The microprism endface FP devices were tested as vapor sensors for the detection of ethanol and chlorinated organic solvents vapors with sensitivities down to 4 ppm. Their sensitivities with respect to the surface porosity of the fabricated micro-prism sensing head were studied by reducing the pores size of the photopolymerized reflection surface using annealing treatment processes. Results show the dependence of the sensitivity and selectivity/specificity upon the porosity of the fabricated FP cavity. Moreover, the studies revealed that the operation mechanism of the fabricated sensing device did not depended only on the optical and vapor pressure characteristics of the solvents but also on their molecular structure and affinity to the sensing surfaces, thus revealing distinct spectral response versus sensing time. In addition, sensing mechanism of the devices was based on physisorption phenomena, allowing the full recover of the sensing probes to their initial spectral response (after pumping with nitrogen) and their reuse for several times. Sensitivities of ~1.5 × 103 nm/RIU were recorded in case of ethanol vapors. For the liquid sensor the device was used for the probing of substances of oily media. Experiments revealed that each of the oily liquids exhibited a distinct spectral response versus sensing time, depending on the diffusion process of the oily liquid into the photopolymerized porous reflection surface.
Regarding to the second part of this thesis, we proposed and realized for the first time the fabrication of micro-ring resonators directly onto tapered single mode telecommunication fibers by employing the multi-photon polymerization technique. Such an approach allowed the demonstration of integrated and robust tapered optical fiber WGM resonators of straightforward packaging capabilities. A fabricated ring of 20 μm diameter and thickness of ~900 nm onto a taper of 2.4 μm diameter, revealed fringe visibility of 20 dB and Q factor of 3.55 x 103 operating in TM polarization. Parallel coupled microresonators with different center to center distances were also fabricated resulting fringe visibility of 38.5 dB and Q factor of 3.82 x 103 operating in TE polarization. The single and coupled microring resonators were tested as vapor sensors for ethanol species. The sensing devices presented sensitivities down to 0.5 ppm. The parallel coupled ring sensor was also tested as a pressure sensor for the detection of inert gases (N2 and Kr). Pressures down to 50 mbar were recorded.
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| Language |
English |
| Subject |
Fabry-perot resonators |
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Fabry-perot αντιχεία |
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Fiber-optic sensors |
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Gas sensing |
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Multi-photon polymerization |
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Nonlinear lithography |
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Physisorption |
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Porous surfaces |
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Vapor sensing |
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Whispering-gallery mode resonators |
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Αισθητήρες αερίων |
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Αισθητήρες ατμών |
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Αισθητήρες ελαιωδών υγρών μέσων |
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Αισθητήρες οπτικών ινών |
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Αντιχεία τρόπων ψυθηρισμού |
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Μη γραμμική λιθογραφία |
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Πολυφωτονικός πολυμερισμός |
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Πορώδεις επιφάνειες |
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Φυσιορρόφηση |
| Issue date |
2018-01-15 |
| Collection
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School/Department--School of Sciences and Engineering--Department of Physics--Doctoral theses
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Type of Work--Doctoral theses
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| Views |
808 |
Sensing resonating devices fabricated on optical fibers using multi-photon polymerization technique
