Simultaneous detection of refractive index, temperature and stress realized by using a three-mode planar photonic crystal L5 cavity

A multifunctional sensor that can detect multiple parameters simultaneously is proposed in this paper. The sensor is based on a well-designed planar photonic crystal (PPC) L5 micro-cavity, which is capable of producing three resonant modes. Each mode of the cavity responds distinctively to different external perturbations, rendering the multi-mode cavity (MMC) superior capabilities for multi-parameter sensing. By using three dimensional finite difference time domain (3D-FDTD) simulation method, Q-factors and extinction ratios of these three modes are carefully optimized. Afterwards, refractive index (RI) sensing, temperature sensing, and vertical stress sensing based on the MMC are realized respectively. Finally, by constructing a sensing matrix, three parameters detection can be achieved simultaneously, and the crosstalk between sensing parameters is discussed. The multifunctional sensor can greatly improve the on-chip integration of photonic crystal sensing networks and will have broad application prospects.