| dc.description.abstract | This thesis discusses the simulation analysis, waveguide fabrication, and measurement of silicon nitride micro-resonators. The simulation analysis is aimed at designing different tapered-bus waveguides to increase the coupling effect; for fabrication, this thesis addresses the conventional ultraviolet lithography technology with reverse baking of a positive photoresist for exposure and development. Finally, the cavity resonance of the silicon nitride micro-resonator will be measured and discussed.
First, we simulate waveguide propagation by the method of Finite-Difference Time-Domain. First, the fundamental transverse electric waveguide mode of the single-side-tapered and double-side-tapered bus waveguide will be analyzed under different taper widths and taper lengths. We will both analyze the waveguide propagation loss, and the coupling between waveguide and resonators under different taper widths, gaps, and resonator radius.
Second, we study the micro-resonator fabrication with conventional ultraviolet (UV) lithography, which typically has the exposure resolution limited by 1 μm. With contact exposure, the exposure time will be discussed and the fabrication optimization for waveguide width and gap will be given. In this thesis, we design both a positive photoresist region and a negative photoresist region on the mask. A positive photoresist- AZ5214 is selected to pattern the waveguide when it can also be served as a negative photoresist by the method of reverse baking. We will discuss the patterned waveguides on both regimes.
In the third part, the cavity resonance of the fabricated silicon nitride micro- resonator will be evaluated in the wavelength-dependent transmission measurement; and the corresponding free spectral range will be analyzed. We will also show the measured intrinsic quality-factor for the resonators.
Last, to overcome the lithography limitation of UV patterning and enhance the coupling between waveguide and resonators, double patterning will be introduced to avoid the optical interference during lithography. The fabricated resonator shows submicron resolution for the coupling gap. | en_US |