| The development of integrated photonic sensing provides the way to miniaturization,high sensitivity,and low detection limit of gas sensors.As an organic solvent and industrial raw material,acetone is widely used in industry and experiments,but acetone gas is a mildly hazardous pollutant,which may explode under certain conditions,and will seriously endanger human health after being inhaled by the human body.Realizing the detection of acetone gas concentration helps to ensure personal safety in production and experiments.In addition,the detection of acetone gas also has great value in the fields of animal husbandry and medical detection.Therefore,the low limit,high sensitivity detection of acetone at room temperature has attracted the attention of researchers in the fields of industry,agriculture and scientific research.Aiming at the problems of large volume,high cost,high operating temperature and low sensitivity of the existing acetone sensor,this paper proposes a combination of branched polyethyleneimine and aminated graphene oxide based on a waveguide with a high-sensitivity Mach-Zehnder interferometer structure.As a gas-sensitive film,the composite film is combined with a high-sensitivity integrated optical sensing structure to realize an on-chip acetone gas sensing method.The experimental results show that at room temperature,the fabricated sensor has good selectivity to acetone gas,can be used repeatedly,and has good stability for long-term use.It has high sensitivity in the environment of 20 ppm acetone,and the detection limit can reach 0.76 ppm.The main contents of this paper include:1.The sensor model of the waveguide structure of the Mach-Zehnder interferometer is designed and simulated.The structural parameters of the waveguide were determined by Comsol Multiphysics simulation based on the finite element method.In the incident light wavelength=633 nm,in TM mode,to ensure single-mode confinement,the width W and depth D of the waveguide were designed to be 2μm and10 nm,respectively.Through Rsoft Beam PROP software simulation,it is determined that the designed Y-coupler aperture angle is 2.52°,and the waveguide spacing is 42μm.2.In the process of sensor fabrication,this paper also summarizes a set of fabrication methods.Through L-edit,the reticle for two times of lithography was designed,and the conditions of lithography were explored by changing the exposure time and development time to find the most perfect lithography conditions.3.The experimental configuration of the sensor test is built,and the performance indicators of the sensor are tested.This procedure was performed on sensors covered with a single-layer polyethyleneimine film and a composite film covered with polyethyleneimine and aminated graphene oxide,respectively,and the sensitivity and detection limit of the sensors were calculated.4.The performance of the sensor has been further optimized.By changing the concentration of the aqueous solution of the PEI film,the sensitivity of the sensor is increased to 8.72×10-3rad/ppm,which is 3.2 times higher than that of the PEI single-layer film.And the detection limit can reach 0.76 ppm,the estimated response time is 44 s,and the recovery time is 106 s.In 20 cycles of 36 days,the overall drift of the output intensity is not large,and the output intensity of the sensor tends to stabilize after about 30 days. |
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