Study On SAW-MOEMS Strain Sensor With Light Readout Unit

Anovel structure of Micro Optical Electro-mechanical System(MOEMS) strain sensor,which combines surface acoustic wave(SAW) technology and integrated optics technologywith microelectronic crafts in one chip, is present in this thesis. This sensor can be appliedin structural testing, smart skins and safety warning of aerospace, chemical metallurgy, oiland energy, building structure. The measurement accuracy OF the sensor can be achievedmicro-strain level, it also has some advantages like strongly anti-electromagneticinterference capability, light weight, micro small, etc. Compared to silicon micromachinedstrain sensors and SAW strain sensors, this program using acousto-optic coupling design,which can avoid multimode interference noise in pure strain MEMS sensor, improve thesignal to noise ratio and their poor resistance to electromagnetic interference and poorstability, these problems have restricted the development of MEMS sensors.We propose the acousto-optic coupling design on the basis of researching on relevantinformation to the domestic and foreign. We using microelectronics technology to integrateoptical waveguide diffractive component, TE/TM mode converter and eletro-opticalmodulator in a LiNbO3substrate, and an optical readout device is added on the TE/TMmode converter. This thesis we focus on the optimal design of sound and light couplingsensing system, the optical readout detection, and the modulation and demodulation methodof light signal,etc.The concrete content of the thesis is as follows:1. On the basis of analyzing the characteristics of surface acoustic wave devices andsurface acoustic performance requirements, and through the theoretical analysis of surfaceacoustic excitation technique, we propose the design of apodization interdigital transducerand define the system parameters of the IDT. Taking into account the impact of thepiezoelectric material to the final output of the entire system, we choose lithium niobatecrystal this program used and give the specific material factor.2. By studying the collinear acousto-optic mode converter theoretical analysis, wepropose a novel SAW-MOMES strain sensor based one the conversion principle ofTE/TM polarization mode. The details of the structure and the working principle areintroduced. By establishing the mathematical model of the system, we get the final outputform. At the same time, we select the appropriate mode of sound and light coupling, set the bias point of the system, and optimize the design.of electro-optical modulator structure.3. On the basis of mathematical analysis of optical waveguide, acoustic power andother parameters of the system structure, we analysis the impact of the parameters for thesystem with Matlab simulation, and discuss the results of the simulation, thereby we definethe parameters pf this program.4. By designing and manufacturing all parts of SAW-MOEMS strain sensor structure,analyzing main influence factors of the sensor, its feasibility has been demonstratedtheoretically.