Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE credits
Recently, unique combination of electro- and magneto-optic, piezoelectric, and coupled acousto-optic properties makes complex metal oxide films to be important players in emerging heterogeneous integration technologies. Nowadays, bulk-single crystal- quality thin film heterostructures can be fabricated directly on a semiconductor platform. Integration of dissimilar classes of high performance functional materials into a single system enables optical and electrical signal processing and storage: e.g., waferlevel integration of tunable narrowband lasing sources, electro-optic modulators, magneto-optic isolators, logic and memory devices. As a result, well-known photonic materials own new functionalities. In addition, interesting effect of so called resistive switching is observed in several transition metal oxide films might be also considered for the application in novel optical devices. Functional properties of transition metal oxide films can be tailored in a wide range. Standard plasma dry etching technique can be employed to pattern these films to fabricate optical waveguides and optical integrated circuits. Therefore, a complex research program that includes films processing, characterization, theoretical modelingand device simulation is required for material validation and cost efficiencyand should precede further practical exploration.
Three kinds of dielectric oxide films, Er2O3, WO3, and Ta2O5 were deposited on a transparent borosilicate glass substrate via radio-frequency magnetron sputtering. Optical properties of grown films were characterized by ellipsometer technique within the range 1.5-6eV(850 -200 nm) and using optical transmissionspectrometer 1.1 -6 eV(200-1100nm). Inherent transition peaks at 379 and 524nm caused by a single trivalentEr3+ion is observed in transmission spectrum of Er2O3film. Two different approaches, computation using the ellipsometer DeltaPsi 2 software and Matlab simulation based on the microscopic electric dipole theory wereemployed to obtain dispersion relations of refractive index and extinction coefficient. We found and explained several mismatches of refractive indexes and extinction coefficientsobtained by these two methods.
Optical characteristics were obtained with a reasonable precision and wereset into optical waveguide simulationsas input parameters. Modeling of light propagation in 2D planar waveguide with different widthsyields requirements for an optical insertion loss. We compared the performance of the waveguides made from the fabricated functional oxides with currently achieved optical properties. Variation of processing parameters leads to the variation of film stoichiometry, critically influences film refractive index and strongly effects a light confinement. With Comsol multiphysics we modeledC-bandlight amplification in 2D waveguides made from Er-dopedTa2O5and WO3.The threshold values of the fractional population of 4I13/2 level of Er3+-ions were found for currently achieved Ta2O5and WO3film properties.
Advanced device modeling and design should include a tailoring of optical films properties through the optimization of processing conditions furnished with a detailed feedback of comprehensive films characterization.
2013. , 108 p.