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Title: Tantalum pentoxide integrated photonic devices
Author: Tong, Amy Sen Kay
ISNI:       0000 0004 7967 1092
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2019
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This thesis investigates tantalum pentoxide (Ta2O5) as a material for realising integrated photonic devices on a silicon platform, as a basis for realising photonics integrated circuits with multiple functionalities on a single monolithic chip. In particular, achieving gain and lasing, and electro-optic functionalities were studied. To further investigate the integration of these functionalities onto a silicon platform, a grating-assisted coupler was explored. Ta2O5 thin films were deposited on oxidised silicon wafer using RF sputtering and waveguides were realised using lithography and ion beam milling. An optimisation of the etching process to reduce waveguide sidewall roughness was performed. Thulium-doped Ta2O5 was investigated to provide gain and lasing at around 2 μm by pumping at around 790 nm. With a thulium-doping concentration of 9x1020 ions/cm3, the highest peak photoluminescence power and lifetime was achieved with sample annealed at 650 °C for 12 hours. The excited-state lifetime of this sample was 477 ± 40 μs. Emission centred around 1.85 μm and a high emission cross-section of 2.99x10-20 cm2 was attained. The absorption cross-section were 8.05x10-21 cm2 at 792 nm and 1.09x10-20 cm2 at a wavelength of 1756 nm. Second-order nonlinearity was achieved in Ta2O5 by thermal poling, 0.46 and 0.34 pm/V was achieved with sodium-doped and undoped Ta2O5 respectively. The effect of sodium-doping and annealing on the induced second-order nonlinearity was studied. A grating-assisted coupler was designed and fabricated to couple between 750 by 750 nm Ta2O5 and a 400 by 250 nm Si channel waveguides. Simulations show that a grating period of 2.361 μm was required for coupling to occur. The results show that tantalum pentoxide is a promising medium for realising integrated lasers and amplifiers, electro-optic applications on a silicon platform.
Supervisor: Wilkinson, James Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available