The world of nanophotonics has seen remarkable progress in recent years, particularly in the development of sensors capable of detecting minute changes in their environment. Plasmonic sensors, which exploit the interaction of light with metallic nanostructures and can register changes at the scale of single molecules, are especially valued for their ability to detect extremely small variations in their surroundings. They have become increasingly important in fields ranging from medical diagnostics to food safety and environmental monitoring, offering a versatile platform that can respond to even the slightest shifts in refractive index, which is a measure of how light bends when it passes through different materials.
The research was led by Dr. Reza Kohandani and Dr. Simarjeet Saini from the University of Waterloo. Their study, published in Scientific Reports, presents a sensor based on two-dimensional gold nanogratings, which are tiny periodic patterns that can manipulate light with high precision. The device is optimized to detect subtle changes in refractive index in water-like environments, with a unique built-in feature that corrects for errors caused by temperature fluctuations.
It has been revealed that the sensor can detect extremely small shifts in surrounding conditions with impressive accuracy. Importantly, by using a special reference mode isolated from environmental interference, the resolution of the sensor improved by more than three times. This makes it especially useful in scenarios where external factors, such as temperature or vibration, could otherwise distort measurements. In this context, self-referencing means the sensor uses an internal reference signal to cancel out unwanted disturbances from the environment. As Dr Kohandani explained, “by incorporating the self-referencing mode into the sensitivity measurements, the resolution of the sensor can be improved by more than threefold.” This approach effectively reduces noise in the data, allowing the sensor to achieve more consistent results over time.
The innovation lies not only in the enhanced precision but also in the simplicity of fabrication. Unlike earlier designs that required complex, multi-step nanofabrication, this sensor was produced with a single lithography step, meaning the pattern was created in one stage rather than several, making it easier and more cost-effective to manufacture. Moreover, its polarization independence, the ability to work regardless of the orientation of the light’s electric field, adds to its practicality for real-world deployment.
Beyond the technical achievements, the implications are wide-ranging. High-sensitivity plasmonic sensors have the potential to improve medical diagnostics by detecting biomarkers, which are biological signals of disease, at very low concentrations. In food safety, they can identify contaminants before they reach consumers. Environmental monitoring could also benefit from such technology, particularly in tracking pollutants or chemical leaks in water systems.
Dr. Kohandani and Dr. Saini emphasized the promise of the work, stating, “This is the first demonstration of a high-sensitivity self-referencing plasmonic sensor with a well-defined reference mode.” Such advances may pave the way for a new generation of portable, reliable, and cost-efficient sensing platforms capable of functioning in dynamic and challenging conditions.
Journal Reference
Kohandani R., Saini S. “Self-referencing surface plasmon sensor for resolution enhancement.” Scientific Reports, 2025. DOI: https://doi.org/10.1038/s41598-025-93102-5
About the Authors
Professor Saini joined the University of Waterloo in September 2007 as an assistant professor. He received a B.Tech. (Honours) at the Indian Institute of Technology, Kharagpur (1996), and his Ph.D. from the University of Maryland, College Park (2001). His Ph.D. thesis was on the design and development of a new platform technology for monolithic integration of photonic devices called Passive Active Resonant Coupler (PARC).The resulting technology led to the founding of a start-up company Covega Corporation where Professor Saini worked as the Lead Optoelectronics Device Engineer from December 2000 to October 2004, and as Lead Applications Engineer from October 2005 to September 2007. He led the design and development of Covega’s single angled facet chips, semiconductor optical amplifiers and high power lasers.
In August 2004, Professor Saini co-founded Altanet Communications – a start-up company focused on ethernet based metro area networks with less than five ms restoration time using intelligence in the optical domain. From October 2004 to September 2005, Saini completed a post-doctoral fellowship at the University of Maryland where he worked on biochemical sensors and optical packet routing.
Reza Kohandani received his PhD in Electrical and Computer Engineering from the University of Waterloo in 2024. His doctoral research focused on nanophotonics, with an emphasis on the design, fabrication, and characterization of photonics nanostructures for biochemical sensing applications. Currently, he is a postdoctoral fellow at the Institute for Quantum Computing (IQC) at the University of Waterloo, where he has been working for over a year on the design and fabrication of superconducting qubits. With more than five years of experience in cleanroom environments and micro/nanofabrication of photonic and quantum devices, Dr. Kohandani brings a strong interdisciplinary expertise to the fields of nanophotonics and quantum technologies.
