Study on simultaneous sensing of gas concentration and temperature in one-dimensional photonic crystal

Based on the mixed effects of the defect mode and interface state, a one-dimensional (1D) photonic crystal (PC) structure used for simultaneous gas concentration and temperature measurement is proposed. Using multiple physical field numerical module of the finite element method, the reflection spectrum with two relatively independent peaks is formed. And the wavelengths of the reflection peaks can be shifted when the concentration of the gas filled in the photonic crystal and environment temperature are changed. The defect layer thickness, metal layer thickness and period of photonic crystal are optimized. Taking the toluene as temperature-sensing medium, and the mixture of air and ethylene as gas-sensing medium, the relationships between the reflection peaks and related physical quantities are studied. Gas concentration and temperature can be measured by analyzing the relative shift of position of two reflection peaks in reflection spectrum. The results show that gas sensitivity is 500pm/1% ranging from 0% to 3% and its Q factor is 471.4. Temperature sensitivity is 88.7 pm/degrees C ranging from -20 degrees C to 70 degrees C and its Q factor is 415.7. The structure is simple, highly sensitive, and dual-parameter sensing. The study has reference value for simultaneously detecting harmful gas leakage and temperature in the polluted environment.