The Study Of Silicon Nitride Waveguide Biochemical Sensor Based On Functional Polymer

With the development of social productivity,the discharge of a large number of pollutants from industrial production has caused serious air pollution and threatened human life and health.Due to the awareness of public health,the development of Volatile Organic Compounds(VOC)sensors to achieve rapid and sensitive detection of pollutant VOCs in the air has become a current research hotspot in biochemical sensing.Optical waveguide device based on refractive index sensing is an important platform for on-chip VOC detection.It is an integrated sub-device that integrates optical elements on the same substrate in the form of thin film by means of Complementary Metal Oxide Semiconductor(CMOS)technology.Such an integrated optical sensor not only has the advantages of anti-strong electromagnetic interference,compact structure,small size,high sensitivity,etc.,but also facilitates data collection and transmission,and conforms to the development trend of modern sensors in miniaturization,intelligence,and networking.The innovative research work of this thesis includes the following:1.All polymer waveguides based on functional polymers are used for explosive vapor detection.The UV bleaching and explosive-sensitivity of an Electro-Optic Polycarbonate(EOPC)containing dipole molecules were systematically studied.On this basis,a non-equal width Mach-Zehnder interferometer(MZI)structure was designed.Through a simple process of lithography/development,combined with photo-bleaching to control the refractive index of EOPC,we fabricate the all-polymer MZI and regulate the evanescent field and group refractive index of the two arms of the interferometer.As a result,the refractive index sensing sensitivity of the MZI sensor has been increased from 7022 nm/RIU to 11624 nm/RIU.Finally,through the test of Nitrobenzene(NB)explosive vapor,it is found that the detection sensitivity of MZI after photo-bleaching for 80 min is significantly improved,and the wavelength drift is as high as 6.8 nm under 2.3 ppm NB atmosphere.This research work not only combines the advantages of low cost and simple manufacturing process of polymer waveguides,but also utilizes the photobleaching-induced refractive index changes and explosive-sensitivity properties of functional polymers,demonstrating innovative ideas and practical prospects.2.Silicon nitride(Si₃N₄)waveguide based on functional polymer is used for pyridine vapor detection.The Si₃N₄ waveguide based on the CMOS manufacturing process has the advantages of small transmission loss,small device size,strong stability,low cost and easy mass production.However,for the practical application in biochemical sensing,it is necessary to solve the problem of the on-chip functionalization of the Si₃N₄ waveguide and the polarization dependence of waveguide sensitivity.For this reason,this thesis uses a simple strategy to spin-coat functional polymer on the surface of Si₃N₄ waveguide to achieve specific detection of VOC gas pyridine;At the same time,an ultra-high sensitivity MZI structure with refractive index sensing sensitivity greater than 30000 nm/RIU in both TE and TM polarizations was rationally designed based on functional polymers and Si₃N₄.The fabrication of functionalized Si₃N₄ waveguide sensor chip was completed by photolithography,etching and spin-coating,and the device packaging and VOC sensing performance were studied.The test results show that the Si₃N₄ waveguide sensor has high sensitivity(15.5pm/ppm)and large dynamic range(0 ppm-450 ppm)for VOC pyridine sensing.In summary,this thesis successfully combines the advantages of optical waveguide technology and functional polymer materials,and the systematic study from device design,fabrication to packaging and testing provides important ideas and solutions for practical on-chip VOC detection.