Date of Award

Spring 5-15-2023

Author's School

McKelvey School of Engineering

Author's Department

Electrical & Systems Engineering

Degree Name

Doctor of Philosophy (PhD)

Degree Type



Optical whispering-gallery-mode (WGM) microresonators can trap photons within a small volume for extended periods, resulting in strong interactions between light and matter. This makes WGM resonators an ideal platform for photonic sensors. In the past, WGM resonator sensors relied on analyzing and monitoring a single resonance. This thesis focuses on the study of optical WGM microresonators with ultra-high Q-factors and their diverse sensing applications exploiting multimode resonances. By leveraging the unique spectral properties of WGM resonators and the principles of information theory, the thesis aims to extract maximum information from the sensor’s signal to improve sensing performance and capabilities.The thesis first establishes an information-theoretic framework for WGM sensors, verifying improved accuracy and dynamic range with the use of a multimode spectrum. To demonstrate the effectiveness of the proposed framework, this thesis presents experiments using a barcode technique, which shows improved sensing performance in terms of sensitivity, resolution, and dynamic range. Furthermore, this thesis demonstrates how artificial intelligence (AI) techniques can be utilized to extract additional information from the multimode spectrum, enabling a single sensing element to achieve multi-parameter sensing by considering each individual resonance as an effective individual sensor.This thesis focuses on three areas of application for WGM sensors. Firstly, it demonstrates the potential of WGM sensors in vibration sensing, including high-performance acoustic sensors for hearing aids, wearable vibration sensors for pulse, respiration, and tremor monitoring, and endoscopic WGM microprobe for ultrasound sensing. Secondly, it introduces an optofluidic label-free WGM sensor for biosensing to detect biomolecules and biomarkers for early-stage disease diagnosis, including conventional sensing based on the evanescent field and novel all-optical photoacoustic sensing with high throughput. Thirdly, it explores microbial sensing in water to monitor water quality.This thesis also introduces new structures, i.e., cascaded microbubble resonators, which allow the exploration of new physics, such as optical coupling and optomechanical interactions between two resonators. Additionally, the thesis demonstrates the WGM resonator as a robust photonic physical unclonable function (PUF) with high randomness for information security and confidentiality devices, leveraging the dense spectral feature of WGM resonators. This thesis showcases the potential of multimode WGM sensors as a powerful tool for sensing and information processing.


English (en)


Lan Yang

Committee Members

Shantanu Chakrabartty, Song Hu, Chuan Wang, Yong Wang,

Available for download on Saturday, April 25, 2026