Performance analysis of heterostructure-based topological nanophotonic sensor

Area of Science:

• Topological nanophotonics
• Photonic crystal devices
• Optical sensing

Background:

• Conventional optical sensors face limitations in sensitivity and performance.
• Topological effects in photonic crystals offer unique properties for device applications.
• Heterostructure designs can enhance light-matter interaction for sensing.

Purpose of the Study:

• To propose and analyze a heterostructure-based topological nanophotonic structure for improved sensing.
• To demonstrate the excitation of topological interface states and cavity resonance.
• To evaluate the sensing performance, including sensitivity, Q-factor, and figure of merit.

Main Methods:

• Designing a heterostructure by connecting dissimilar 1D photonic crystals with overlapped bandgaps.
• Optimizing structural parameters to achieve opposite Zak phases and topological interface states.
• Forming a topological cavity by introducing a defect layer and analyzing mode excitation.
• Evaluating sensing performance through analytical calculations with infiltrated analytes.

Main Results:

• Robust topological interface state excitation at 1737 nm and cavity resonance at 1659 nm.
• Achieved average sensitivity of 774 nm/RIU, Q-factor of 5.2 × 10^4, and FOM of 2.6234 × 10^4 RIU^-1.
• Demonstrated significant improvements over conventional Fabry-Perot resonators: 92% higher sensitivity, 98% improved Q-factor, 206% improved FOM.

Conclusions:

• The proposed topological cavity structure exhibits excellent sensing ability over a refractive index range of 1.3-1.6.
• The design offers advantages such as high sensitivity, Q-factor, and figure of merit.
• The simple fabrication and characterization process promote the development of highly sensitive planar nanophotonic devices.