Slit-Gradient Phoxonic Crystal Sensor for Detecting the Solution Concentration

This study proposes a slit-gradient phoxonic crystal sensor for detecting the changes in concentration during biochemistry reactions. A slit-gradient cavity is designed in the periodic structure and calculates the finite element method (FEM) of the sensing characteristics under different parameters. Considering the effect of viscosity on the acoustic sensing performance, we found that viscosity broadens the acoustic resonance peaks and decreases the acoustic quality factor. Based on the thermos-optical effect on the sound velocity and refractive index, the sensing performance parameter changes with temperature are analyzed. By changing the solution temperature, phononic and photonic sensitivities can reach 9.21 MHz/K and −47 pm/K, and this sensor successfully detects different solutions with the same concentration. The sensor has the advantages of multiparameter detection and miniaturization, and it exhibits accurate acousto-optic (AO) detection, which is expected to become a potential micro-nano device for measuring the solution concentration.