Highly sensitive optofluidic sensor of 2D Si Phc L3 cavity for detection of glucose and bovine serum albumin

Abstract

Photonic crystal (PhC) is promising for the application of optofluidic sensors since the voids can trap the fluid and modulate the refractive index. In this article, we modified PhC to reduce photon leakage by redesigning the cavity region and waveguide. Si PhC with L3 cavity structure on the silicon-on-insulator substrate is modelled and simulated using a finite-difference time-domain approach. The optimum Si PhC L3 cavity with hexagonal array configuration of (17 × 15) and ratio radius/lattice pitch of 0.30 is fabricated. The designed Si PhC L3 cavity structure shows a high Q-factor of approximately 15,000 and resonance wavelength, λres of around 1560 nm in ambient air. Si PhC shows a small difference in hole radius of approximately + 3.33% from the design dimension due to the proximity effect and isotropic of the dry etching process. This results in the blue shift of λres from 1560 to 1510 nm and reduces the Q-factor by 88%. The fabricated PhC L3 cavity structure demonstrated the sensitivity of 385 nm/RIU for glucose detection, while 389 nm/RIU for bovine serum albumin detection. The hydrophobicity of the analyte plays an insignificant role in determining the sensitivity of the device as both solutions can infiltrate into Si nanoholes very well. A compact, highly sensitive, and simplified fabrication process are the progress towards the development of an integrated Si optofluidic sensor system.