Study Of Infrared Filter And Application In Gas Sensors

Methane and ethane are flammable and explosive gases,they are closely related to people's daily life and production safety.Therefore,it is of great significance to realize realtime quantitative monitoring of methane and ethane.Compared with other gas sensors,nondispersive infrared gas sensor has the advantages of small size,good selectivity and short response time,so it has been widely concerned.In order to meet the detection requirements of non-dispersive infrared gas sensor,the influence of optical filter on gas detection system was analyzed,and an optical filter with central detection wavelength transmission and remaining bands cut-off was developed.By studying the infrared absorption spectra of methane and ethane,the characteristic absorption wavelength of the target detection gas was determined and the infrared light source and infrared detector were selected.Finally,a 3.3?m medium wave gas detection system was built.According to the infrared absorption coefficient of methane and ethane,intensity of light source,detector responsiveness and absorption spectra of other interfering gases,the function between the filter's bandwidth and the sensitivity and transmission intensity of gas detection system was studied,and a new evaluation function was established.The technical parameters of infrared filter were determined by using Mathcad software simulation analysis.According to the optical properties of the material,the photodiode and gallium arsenide were selected as the substrate,and Ge and Nb2O5 were used as the high and low refractive index materials respectively.According to the optical thin film theory,3.3?m?6.7?m and 7.6?m bandpass filters were designed by TFCalc software,and the samples were successfully prepared by DC pulse magnetron sputtering equipment.Film samples met the requirements of the detection system by testing the performance.At the same time,the photocurrent response test and environment test were performed on the assembled 3.3?m gas sensor.The results showed that the application of the optical filter can effectively reduce the influence of the interfering gas on the target gas detection.