Optical Biosensing Techniques Using Integrated Photonic Waveguides

Optical biosensing using integrated photonic waveguides merges light–matter interaction with miniaturised platforms to detect biomolecular targets. Photonic waveguides confine light within high-index materials such as silicon or silicon nitride, generating an evanescent field that penetrates the surrounding medium. When biomolecules bind to receptor layers on the waveguide surface, they alter the local refractive index, shifting resonant wavelengths or modulating transmission intensity. Common configurations include microring resonators, Mach–Zehnder interferometers and slot waveguides, each offering trade-offs between sensitivity, footprint and integration complexity. Advances in nanofabrication have enabled subwavelength structures that enhance light confinement and surface overlap, leading to increased detection sensitivity and lower limits of detection. Label-free approaches obviate the need for fluorescent or enzymatic tags, facilitating real-time monitoring and multiplexed assays. Integrated platforms promise point-of-care diagnostics, environmental monitoring and biodefence applications by combining low cost, scalability and compatibility with complementary metal-oxide-semiconductor foundries. Recent efforts focus on enhancing analyte–photon coupling, expanding operational spectral range into the mid-infrared and integrating microfluidics for automated sample handling.

Research from Nature Portfolio

Recent studies have demonstrated the functionalisation of silicon photonic waveguides with crown ether ligands to achieve in-operando detection of lead ions. This platform employs scalable fabrication by integrating esterified linkers onto micro-ring resonators, enabling selective Pb2+ binding, a broad dynamic detection range and compatibility with field-collected water samples. The system retains a high quality factor and shows potential for cost-effective manufacturing, indicating a pathway towards widespread deployment of compact, label-free sensors for environmental contaminants.

Research from all publishers

Recent innovations include a hybrid double-slot subwavelength grating microring refractometric sensor operating in aqueous media. By engineering dual slot regions within the resonator, this design achieved sensitivity exceeding 1000 nm per refractive index unit and a quality factor above 22 000, pushing detection limits below 10⁻⁴ RIU for biomolecular assays. Another approach exploits polymer nanocomposite-based suspended slot racetrack waveguides, combining TiOx–polymer materials with slot geometries to reach sensitivities near 436 nm/RIU and detection limits of 1.4×10⁻⁴ RIU, highlighting the role of novel materials in enhancing on-chip biosensing. Foundational work on label-free silicon photonic sensors has established interferometric, microcavity and Bragg grating platforms that integrate flow-control and readout electronics into a single CMOS-compatible chip, laying the groundwork for portable diagnostics and multiplexed analyses in clinical settings.

Optical Biosensing Techniques Using Integrated Photonic Waveguides publication trend

The graph below shows the total number of articles in optical biosensing techniques using integrated photonic waveguides across all publications each year (not limited to Nature Index journals).

Technical terms

Evanescent field: A decaying electromagnetic field extending into the cladding surrounding a waveguide, sensitive to refractive index changes at the surface.

Microring resonator: A circular waveguide cavity that supports resonant modes, used to detect refractive index shifts via wavelength or intensity changes.

Slot waveguide: A structure with a low-index gap between high-index materials, concentrating light within the slot to enhance interaction with analytes.

Quality factor (Q): A measure of a resonator’s energy-storage efficiency, defined by the ratio of resonant wavelength to its spectral linewidth.

References

1. Crown ether decorated silicon photonics for safeguarding against lead poisoning. Nature Communications (2024).
2. A Review on Photonic Sensing Technologies: Status and Outlook. Biosensors (2023).
3. Design of Suspended Slot Racetrack Microring Refractive Index Sensor Based on Polymer Nanocomposite. Polymers (2023).
4. Ultrasensitive Silicon Photonic Refractive Index Sensor Based on Hybrid Double Slot Subwavelength Grating Microring Resonator. Sensors (2024).
5. Silicon Photonic Biosensors Using Label-Free Detection. Sensors (2018).