Dear Esteemed Colleagues,

An optical microring resonator (MRR) is a set of miniature optical waveguides, at least one of which is a closed loop coupled to some light input and output. Besides MRR structures, other optical resonant structures such as microdisk, microsphere and microtoroid resonators have also been studied. The MRR structures can range from a “simple” single ring to a cascaded design consisting of multiple rings. There has also been research into MRR structures incorporating plasmonics and photonic crystal engineering, exploiting the enhanced optical characteristics facilitated by these complementary disciplines.

The humble MRR structure has been utilized to perform optical filtering, including add-drop multiplexing, electro-optic modulation and switching, and even optical frequency comb generation, exploiting Kerr nonlinear effects in silicon photonics. Moreover, its optical characteristics have been exploited for sensing applications including biological sensors, chemical sensors, environmental sensors for monitoring temperature and humidity, current sensors, and magnetometers. Due to the enhanced lightwave interaction via the resonating structure, the utilization of MRRs in sensing applications is evidently extensive.

MRR-based sensing in the optical domain relies on the shift in the user-selected MRR’s optical resonance in the presence of a measurand. In recent years, MRR-based sensing has been explored in the interdisciplinary field combining microwave and optical engineering known as microwave photonics. Improved sensitivity has been demonstrated by translating the optical behaviors to the microwave regime. The utilization of MRR structures in microwave photonics has also seen these devices applied in sensor concepts to perform the frequency measurement of unknown incoming microwave signals, demonstrating a compact capability suitable for addressing size, weight, and power constraints in specific applications.

The Special Issue on Microring Resonator Sensors focuses on the applications of MRR structures for sensing and sensor designs. The Guest Editor graciously encourages the scientific community to showcase and share their original research on utilizing MRRs, including microdisk, microsphere and microtoroid resonators, for sensing and sensor designs.

This Issue will accept high-quality articles that contain original research results, and review articles, that will allow readers to learn more about MRR-based sensing technologies and their potential. Articles reporting recent advances in MRR-based sensing properties, MRR-based sensor devices and systems, novel MRR design and fabrication, novel material platforms for MRR fabrication to achieve enhanced sensing performance, interdisciplinary engineering for MRR-based sensors, and other closely related topics, are therefore warmly welcomed.

Dr. Linh Nguyen
Dr. Fathi Abdelmalek
Guest Editors

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• Optical sensor device and system
• Miniature optical sensor
• Microring resonator
• Microdisk resonator
• Microsphere resonator
• Microtoroid resonator
• Novel optical resonator structure
• Chemical sensor
• Biological sensor
• Environmental sensor
• Temperature sensor
• Humidity sensor
• Current sensor
• Magnetometer
• Magnetosensor
• Microwave photonics
• Interdisciplinary engineering
• Integrated photonics
• Photonic integrated circuits
• Silicon photonics
• Group III-V
• Hybrid integration
• Plasmonics
• Photonic crystal
• Photonic bandgap structure