Effect of anisotropy on the spectral characteristics of one-dimensional porous silicon photonic crystal microcavity for optical sensing applications

Abstract

We present a numerical study of the effect of anisotropy on the spectral characteristics of one-dimensional porous silicon microcavity (1D-PSMC) with single defect layer. These structures have strong potential applications in optical sensing of chemicals and bioanalytes. Bruggeman’s effective medium approximation (BEMA) and (4 × 4) general transfer matrix method are used for theoretical modeling of spectral response of anisotropic 1D-PSMC. The potential of this structure as a sensing material is illustrated by analyzing wavelength shift in the defect mode induced by infiltration of biochemical analytes of different refractive indices inside the pores. Observed wavelength shift is found to be linearly dependent on the refractive index of analytes. We propose two 1D-PSMC-based sensors with a microcavity wavelength around 800 and 1200 nm. An anisotropic sensor with an operating wavelength around 800 nm shows a maximum sensitivity of 190 while an isotropic sensor with the same design parameters displays a maximum sensitivity of 150. In the case of an anisotropic sensor designed around 1200 nm, the maximum sensitivity is 260; for the isotropic sensor with similar structure, maximum sensitivity of 210 is obtained. Increased sensitivity is observed in anisotropic structures as compared to the isotropic ones. Design parameters play an integral role to obtain desired sensitivity in 1D-PSMC structure for sensor applications. These sensors can be used for high precision optical sensing of chemical-analytes, bioanalytes, gases, and environmental pollutants.