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Faculty of Graduate Studies

Heming Qin

  • MSc (Southeast University, China, 2020)
Notice of the Final Oral Examination for the Degree of Master of Applied Science

Topic

Optical Microcavity Surface Roughness Modelling

Department of Electrical and Computer Engineering

Date & location

  • Monday, January 12, 2026

  • 1:30 P.M.

  • Engineering Office Wing

  • Room 502

Reviewers

Supervisory Committee

  • Dr. Tao Lu, Department of Electrical and Computer Engineering, University of Victoria (Supervisor)

  • Dr. T. Aaron Gulliver, Department of Electrical and Computer Engineering, UVic (Member) 

External Examiner

  • Dr. Irina Paci, Department of Chemistry, University of Victoria 

Chair of Oral Examination

  • Dr. Leslee Francis Pelton, Department of Curriculum and Instruction, UVic 

Abstract

Surface roughness at the sidewalls and top surfaces of whispering-gallery mode (WGM) microdisk cavities causes scattering loss that degrades the cavity quality factor. This thesis presents a three-dimensional full-wave electromagnetic modeling framework implemented in COMSOL Multiphysics to analyze the impact of surface roughness on WGM microcavity performance. A statistical roughness generation methodology creates Gaussian-distributed surface profiles with controlled root-mean-square height and correlation length parameters, which are mapped onto complex wedge-shaped microdisk geometries. The simulation results reveal systematic trends in quality fac tor degradation with increasing surface roughness, showing more than three orders of magnitude reduction for moderate roughness levels. The scattering field extra cion formalism is also implemented, allowing detailed analysis of roughness induced scattering. Comparison with established semi-analytical models demonstrates that the three-dimensional full-wave approach captures comprehensive surface scattering interactions from all cavity surfaces, while semi-analytical models typically focus on specific dominant scattering sources such as disk-edge roughness. The results provide actionable guidance for microcavity fabrication optimization and establish a foundation for predictive modeling of surface-scattering effects in high-Q optical devices.

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