Optical Waveguide Mach-Zehnder Interferometer Biochemical Sensor Based On Porous Materials

The sensing of gas is highly imperative for the fields of environment protection,industry production and human health.In order to achieve high sensitivity,fast response,and portable gas sensor,we propose a solution to integrate porous materials with optical waveguide devices,and make effort both in the materials and the devices.In the respect of material engineering,two types of porous gas-sensitive materials-Electro-Optic Polycarbonate(EOPC1)and Metal-Organic Framework materials(MOFs)are prepared and characterized,and their feasibility of integration with waveguides is studied.In device engineering,according to the properties of two porous materials,different waveguide materials are selected to be integrated with them.Then,different MachZehnder interferometer(MZI)structures are designed and fabricated to realize on-chip detection of the target gas.The main contents of the work are as follows:1.For the detection of nitroaromatic explosives,a porous EOPC1 is synthesized in this dissertation firstly.The intermolecular interaction mechanism between the electronrich D-?-A chromophore in EOPC1 and the electron-deficient nitrobenzene(NB)and 2,4-dinitrotoluene(DNT)is studied by ultraviolet-visible absorption spectrum.Then,the MZI sensor with two different arms coated with EOPC1 as the sensitive cladding layer is designed and fabricated,which simplifies the fabrication process and improves the device sensitivity.The on-chip testing is used to rapidly detect NB and DNT vapors.Our fabricated sensor can reversibly detect NB vapor much less than 300 ppm with a maximum wavelength shift of 8.61 nm.It can irreversibly detect DNT less than 100 ppb with a maximum wavelength shift of 5.31 nm.The response time of the sensor is shorter than 100 s.Our sensor has the advantages of low cost and easy fabricating,and provides a suitable approach for practical applications;2.For indoor air quality testing,we propose a silica waveguide MZI gas sensor based on MOFs materials.Firstly,the in-situ growth method is used to prepare the ZIF-8 film.And the optical loss ZIF-8 film introduced is measured to about 0.46 dB/mm by growing ZIF-8 films on straight waveguides.Then,the MZI sensor is designed and fabricated to have a length imbalance between the two arms.And by characterizing the different MZI interference spectra before and after the growth material,it is verified that ZIF-8 film makes an effect on the effective refractive index and the loss of the sensing arm.Then,we discuss the sensing test plan of the device,and conclude that the device is suitable for package testing.Finally,we make a test of indoor air quality.By placing the device in the laboratory to adsorb the volatile organic compounds gas in the environment,the interference spectrum produced a wavelength shift of 4 nm and an extinction ratio change of 10 dB.In conclusion,this work shows that the integration of ZIF-8 film with silica waveguides has the advantages of low loss and easy packaging,and lays the foundation for realizing high sensitivity gas sensors.Our approach of integrating porous materials with optical waveguides not only utilizes the excellent gas sensing performance of porous materials,but also takes advantage of optical waveguide devices which is high integration,immunity to electromagnetic interference and capability of large-scale fabrication.It provides a practical solution for low-cost,high-performance and portable optical waveguide gas sensors.