Design of 1D photonic crystals for colorimetric and ratiometric refractive index sensing

• Main Authors: Simone Normani, Nicholas Dalla Vedova, Guglielmo Lanzani, Francesco Scotognella, Giuseppe M. Paternò
• Format: Article
• Language: English
• Published: Elsevier 2020-12-01
• Series: Optical Materials: X
• Subjects: Photonic crystals; Distributed Bragg reflectors; Refractive index; Sensing
• Online Access: http://www.sciencedirect.com/science/article/pii/S2590147820300127

Photonic crystals can be employed effectively as simple and low-cost colorimetric sensors for monitoring variation in the environmental refractive index. In most cases, the photonic colorimetric approach relies on the use of porous and permeable materials to highlight refractive index (RI) modulation, although a fine control over the size distribution and free volume can be complex to achieve. Here, we propose nonporous low-layer count distributed Bragg reflectors (DBRs) as simple optical devices for colorimetric refractive index sensing. In our feasibility study, we simulated the reflectance of DBRs consisting of two to five SiO2/TiO2 bilayers upon variation of the external refractive index. We found that the 2-bilayers sample exhibits the highest sensitivity to RI variations, and identified the ratio between the first and third order reflectance intensity as simple yet efficient ratiometric parameter to discern analytes with different refractive indices. This approach can provide a promising perspective for the development of cheap and portable devices for environmental detection of a wide range of substances.