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Synthesis of Ca₊Ba₁₋₊Nb₂O₅ Thin Films on Lattice Matched Gd₃Ga₅O₁₂ substrate by Pulsed Laser Deposition.


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Kabir, S. M. Humayun (2017). Synthesis of Ca₊Ba₁₋₊Nb₂O₅ Thin Films on Lattice Matched Gd₃Ga₅O₁₂ substrate by Pulsed Laser Deposition. Mémoire. Québec, Université du Québec, Institut national de la recherche scientifique, Maîtrise en sciences de l'énergie et des matériaux, 106 p.

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The accelerating increase in information traffic demands higher data transfer for the telecommunications. Thin film materials with high electro-optic (EO) coefficient are attractive towards the fabrication of high performance photonic devices, such as EO modulators for telecommunications applications. The ferroelectric Tetragonal Tungsten Bronze (TTB) family material SrxBa1-xNb2O6 (SBN) has shown high electro-optic coefficient both in the bulk and thin film form. With compared to commercially available conventional lithium niobate (LiNbO3, LN), SBN has forty times higher electro-optic coefficient. But, due to the low Curie temperature (below 80°C) SBN is not suitable to use as active layer in EO modulators operating at hundreds of GHz. On the other hand, CaxBa1-xNb2O6 (CBN), which also belongs to TTB family has high electro-optic coefficient (130 pm/V) and Curie temperature (above 200°C), and hence a potential candidate for next generation electro-optic devices applications. Epitaxial CBN thin films have been synthesized on various substrates including MgO, Nb:SrTiO3, as well as on Silicon. However, epitaxial CBN films have to be achieved on a lattice matched and device fabrication compatible substrates (refractive index of the substrate should be lower than that of CBN) before they can be integrated in high-performance devices. This work focuses on the synthesis of CBN thin films on lattice matched Gadolinium Gallium Garnet (Gd3Ga5O12, GGG) substrate. In the first part of our work, we have investigated structural and optical properties of CBN thin film. In our experiment, we have done the optimization of CBN thin film on GGG substrate. XRD, XPS and AFM measurements were performed for the structural, compositional, and surface properties measurements. After that ellipsometric measurements were taken for the optical properties analysis. We found a high optical transmittance of 85% for epitaxial CBN films deposited at a 50 mTorr oxygen pressure. The promise of nanophotonic devices is controlled by the large size difference between much smaller photonic waveguides and comparatively large optical fibers, which causes an unacceptable amount of loss without a mode size conversion solution. One such solution to overcome the huge loss is the vertical grating coupler which allows light to be efficiently coupled from the top of a device. In the second part of our work, we have successfully fabricated and demonstrated light coupling through a CBN thin film based optical grating coupler to CBN thin film based waveguides on GGG substrate.

Type de document: Thèse Mémoire
Directeur de mémoire/thèse: Chaker, Mohamed
Informations complémentaires: Titre en français: Synthèse par ablation laser de couches minces de Ca₊Ba₁₋₊Nb₂O₅ sur un substrat de GGG (réseau cristallin compatible avec le CBN). Résumé avec symboles
Mots-clés libres: Tetragonal Tungsten Bronze; Thin film materials; high electro-optic (EO) coefficient; CaxBa1-xNb2O6(CBN); Gadolinium Gallium Garnet substrate; nanophotonic devices; ferroelectric material; ferroelectric thin films.
Centre: Centre Énergie Matériaux Télécommunications
Date de dépôt: 27 nov. 2017 21:12
Dernière modification: 27 nov. 2017 21:12
URI: http://espace.inrs.ca/id/eprint/6514

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