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Presenter: Heming Qin
Supervisor:

Date: Tue, January 20, 2026
Time: 11:00:00 - 12:00:00
Place: Zoom - see below.

ABSTRACT

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Meeting ID: 897 1618 1518
Password: 293594
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Meeting ID: 897 1618 1518
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Abstract: 

Surface roughness introduced during fabrication is a primary factor that limits the achievable quality factor of whispering gallery mode(WGM) microdisk cavities, as nanoscale imperfections on the sidewalls and top surfaces lead to additional scattering loss. In this seminar, a three dimensional full wave electromagnetic modeling framework was developed to investigate the impact of surface roughness on wedge shaped WGM microdisk resonators.

The framework integrates statistically defined Gaussian rough surface generation with full vector eigenmode simulations implemented in COMSOL Multiphysics. Surface roughness characterized by root mean square height and correlation length is applied to the surface of wedge shaped microdisks, enabling systematic studies of how fabrication induced surface statistics influence optical confinement and loss. The simulation results reveal clear and reproducible trends in quality factor degradation with increasing surface roughness, with reductions exceeding several orders of magnitude for moderate roughness levels.

Beyond quality factor analysis, the numerical framework incorporates a mode projection and overlap formalism that enables decomposition of rough surface modes into smooth and scattered field components. This approach provides physical insight into how surface roughness perturbs whispering gallery modes and contributes to radiation loss from different regions of the microdisk.

Comparisons with established semi analytical scattering models are presented to highlight the regimes where simplified theories capture dominant trends, as well as their limitations in describing fully three-dimensional geometries with multiple rough interfaces. Overall, this work demonstrates how full wave numerical modeling connects experimentally measured surface statistics with optical performance and provides guidance for the design and fabrication of high quality microcavity devices.