Whispering-gallery-mode (WGM) resonators have long fascinated scientists and engineers with their ability to concentrate and manipulate light in minute circular paths, akin to the way whispering galleries focus sound waves. This unique property has led to their utilization in various sensing applications, from detecting chemical signatures to monitoring single molecules. However, their widespread adoption has been hindered by limitations such as narrow dynamic range, limited resolution, and accuracy.
A breakthrough study by Lan Yang and Jie Liao from the Preston M. Green Department of Electrical & Systems Engineering at Washington University in St. Louis introduces a transformative approach to enhance WGM resonators' sensing capabilities: optical WGM barcodes for multimode sensing. This innovative technique enables the simultaneous monitoring of multiple resonant modes within a single WGM resonator, vastly expanding the range of measurements achievable and paving the way for high-resolution optical detection in diverse fields.
WGM sensing relies on a specific wavelength of light circulating around the microresonator's perimeter numerous times. When molecules interact with the sensor, the resonant frequency of the circulating light undergoes a shift, which researchers can measure to detect and identify specific molecules. Multimode sensing enhances this process by allowing the detection of multiple resonance changes in wavelength, significantly augmenting the resolution, accuracy, and range of WGM sensing.
The study delves into the theoretical limits of WGM detection, establishing the potential of multimode sensing systems. Comparisons between conventional single-mode and multimode sensing reveal a dramatic enhancement in measurement capabilities. While single-mode sensing is constrained by a narrow range (about 20 picometers), multimode sensing offers a theoretically infinite range, limited only by the sensing apparatus. In practical terms, the experimental limit for multimode sensing surpasses conventional methods by approximately 350 times, showcasing its immense potential for high-precision optical detection.
The implications of this advancement are profound across various sectors. In biomedical applications, multimode WGM sensing can detect subtle molecular interactions with unprecedented sensitivity, enhancing disease diagnosis and drug discovery. Environmental monitoring stands to benefit from the ability to detect minute changes in parameters like temperature and pressure, enabling early warning systems for natural disasters and precise pollution monitoring.
Furthermore, the continuous monitoring of chemical reactions facilitated by multimode sensing opens avenues for real-time analysis and control in industries such as pharmaceuticals, materials science, and food production. This technology not only enhances sensitivity to detect single particles and ions but also provides a pathway to explore unknown realms, tackling ambitious projects and addressing real-world challenges.
The commercial potential of multimode WGM sensing extends to diverse applications, promising advancements in biomedical diagnostics, environmental sustainability, and industrial process control. As researchers continue to push the boundaries of optical sensing technologies, multimode WGM resonators emerge as a cornerstone of high-resolution optical detection, offering unparalleled capabilities to unlock new insights and solutions in science and industry.
The study is published in the journal IEEE Transactions on Instrumentation and Measurement.
Source: Washington University in St. Louis