High-sensitivity quasi-periodic photonic crystal biosensor based on multiple defective modes

Area of Science:

• Photonics
• Nanotechnology
• Biosensing

Background:

• Quasi-periodic photonic crystals (QPCs) offer unique optical properties.
• Defective modes in photonic crystals can be highly sensitive to environmental changes.
• Biosensors are crucial for dynamic monitoring of biological analytes.

Purpose of the Study:

• To theoretically investigate the sensitivities of octagonal QPC defective modes for biosensing applications.
• To optimize QPC design for maximum refractive index sensitivity and minimal detection limits.
• To analyze the influence of protein thickness on resonant wavelength shifts.

Main Methods:

• Theoretical study of octagonal QPC defective modes.
• Design of defect structures within silicon column arrays in a liquid background.
• Analysis of localized modes with varying spatial symmetries and field profiles.
• Optimization of central rod size for sensitivity and detection limit.

Main Results:

• Maximum refractive index sensitivity of 800 nm/RIU achieved around 1500 nm transmission peak with a 100 nm central rod.
• Detection limit of 0.00042 demonstrated.
• Minimum detectable protein thickness of less than 10 nm achieved with a 400 nm central rod.
• Spatial field profiles analyzed to correlate with sensitivity.

Conclusions:

• Octagonal QPC biosensors exhibit high sensitivity for detecting protein concentration in liquid environments.
• The design allows for convenient, dynamic monitoring of liquid analytes.
• Optimized QPC structures can achieve ultra-low detection limits and detect minute changes in analyte thickness.