The aim of this thesis is to demonstrate novel or improved photonic devices based on the CMOS based photonics processes. Methods to obtain application-specific optical mode characteristics through design, fabrication and post-processing are proposed. Focus is on devices attainable within the capabilities of 130 nm CMOS node tool-set, thereby ensuring manufacturability of photonic devices studied in this thesis.Compared to the widely studied 1D polarization sensitive slot waveguides, we demonstrate novel designs for 2D slot waveguides with high confinement for both polarizations of the fundamental optical mode (quasi-TE and quasi-TM). It is shown that on the basis of required optical mode characteristics such as effective index, birefringence, confinement and mode overlap; cross-slot waveguide, closed 2D slot waveguide, open 2D slot waveguide or u-slot waveguide can be used. It is also shown that angled sidewall in vertical slot waveguide aides void-less filling of the narrow vertical slot waveguide and enhances interaction with the non-linear slot. Asymmetric vertical slot waveguides to achieve non-reciprocal phase shift are also discussed. Furthermore, unprecedented reduction of optical propagation loss is demonstrated for the shorter wavelength regime (980 nm) in the CMOS based silicon nitride material system. This is realized through CMOS compatible ALD based wafer-scale post-processing technique.
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