A Plasmonic Chip-Scale Refractive Index Sensor Design Based on Multiple Fano Resonances

Area of Science:

• Photonics and Nanophotonics
• Optical Sensing Technologies
• Integrated Optics

Background:

• Sub-wavelength metal-insulator-metal (MIM) waveguides are crucial for advanced photonic devices.
• Fano resonances in optical systems offer sharp spectral features desirable for sensing.
• Achieving multiple, high-performance Fano resonances is key for complex integrated photonic circuits.

Purpose of the Study:

• To design and investigate MIM waveguides capable of supporting multiple Fano resonances.
• To explore the potential of these structures for high-sensitivity refractive index sensing.
• To evaluate the performance of structures with an increasing number of Fano resonances.

Main Methods:

• Utilized sub-wavelength metal-insulator-metal waveguides with integrated slot cavities.
• Investigated mode interference between bright and dark modes supported by the cavities.
• Employed the finite-difference time-domain (FDTD) method for numerical simulations and performance analysis.

Main Results:

• Achieved dual Fano resonances with asymmetrical spectral responses through mode interference.
• Demonstrated high sensitivity and figure of merit for refractive index sensing.
• Successfully generated structures with three and four ultra-sharp Fano peaks by adding extra slot cavities, maintaining considerable performance.

Conclusions:

• The proposed MIM waveguide structures effectively generate multiple Fano resonances.
• These structures exhibit excellent performance metrics for refractive index sensing applications.
• The findings support the potential for on-chip optical sensing and optical communication applications in integrated photonics.