Porous silicon photonic crystal-based interferometric chemical sensor

Area of Science:

• Optoelectronics and Photonics
• Chemical Sensing Technology
• Materials Science

Background:

• Porous silicon photonic crystals offer tunable optical properties.
• Existing chemical sensors can be bulky and expensive.
• Need for rapid, cost-effective analyte detection systems.

Purpose of the Study:

• To investigate an interferometric chemical sensor utilizing porous silicon photonic crystals.
• To develop a fast, inexpensive sensing system with a narrow spectral response.
• To analyze analyte adsorption/desorption kinetics efficiently.

Main Methods:

• Fabrication of porous silicon photonic crystals with modulated optical bandgap parameters.
• Utilized a single, narrow spectral response photodetector for rapid measurements.
• Employed the transfer matrix method for reflectance spectra computation, varying refractive indices and bilayer numbers (Nbi).

Main Results:

• Reflectance oscillation frequency was found to be proportional to analyte refractive index and evaporation rate.
• Short fast Fourier transformation (FFT) generated analyte-specific spectrograms for ethanol and isopropanol.
• Sensitivity was enhanced in photonic structures designed at shorter wavelengths and was independent of Nbi.

Conclusions:

• The proposed interferometric sensor demonstrates a viable, cost-effective method for chemical sensing.
• The system offers advantages in studying analyte kinetics due to its speed and simplicity.
• Optimized photonic structures can enhance sensor sensitivity for specific analytes.