Research On Optical Pressure Sensor Of Micro-Opto-Electro-Mechanical System Based On MZI

Light pressure plays a very important role in the field of micro optical device manufacturing.Micro-Opto-Electro-Mechanical Systems(MOEMS)have been applied to the field of measuring optical pressure with the advantages of small size and high precision.However,there are still some problems such as low sensitivity and low linearity in the measurement of light pressure by MOEMS pressure sensor.In order to improve the performance of MOEMS pressure sensor,the working principle analysis,structural design optimization and physical preparation of the sensor are carried out in this paper.The specific research contents and results are as follows:(1)Structure design and research of pressure sensor optical waveguide.Based on the principle of Mach-Zehnder interferometer(MZI),a ridge optical waveguide pressure sensor is designed with silicon on insulator(SOI)as material.Based on the transmission principle of light wave in the waveguide,the size of the sensor is determined as ridge height 2μm,outer ridge height 1.5 μm and ridge width 5 μm.Using COMSOL 5.6,under the premise of single-mode transmission,the light wave transmission energy is concentrated in the core layer when the effective mode refractive index is 3.44.Finally,the law of low loss of waveguide transmission and low power difference of output port is studied.The results show that when the bending radius of optical waveguide is 500 μm and the length of directional coupler waveguide is 100 μm,the loss of optical waveguide is 3.8%,and the design of optical waveguide meets the performance requirements.(2)Structural design and research of elastic diaphragm of pressure sensor.Based on the theory of film deformation,aluminum is used as the elastic diaphragm material,and the finite element simulation is used to determine that when the radius of the diaphragm is 52 μm and the thickness is 2.1 μm,the phase difference of the optical waveguide sensing arm changes the most.After applying 0-1000Pa light pressure,the simulation results are linearly fitted in ORIGIN 2022.The sensitivity of the pressure sensor is 2.2×10-3 W/kPa,and the linear relationship R2 is 99.6%.(3)Structure design and research of grating coupler.Based on the period formula of the grating coupler,it is determined that the period with the best coupling effect is 0.486 μm when the fiber incident angle is 10°.The coupling efficiency of the grating coupler is studied by using the FDTD optical finite element software and the orthogonal experiment method.The results show that when the groove depth is 1.5 μm,the total length of the groove is 10 μm,and the optimal incident position x of the fiber is 1 μm,the coupling efficiency is the highest,reaching 53.6%,the coupling loss is less than 3 dB,indicating that the grating coupler design meets the performance requirements.(4)Preparation of pressure sensor.Based on the MOEMS processing flow,the process steps of the pressure sensor were determined,including lithography,etching,inductively coupled plasma etching(ICP)and magnetron sputtering.The sensor was fabricated and the manufacturing error of the sensor was analyzed by microscope.The results show that the manufacturing error of ridge width is 0.6μm,the manufacturing error of ridge height is 0.7 μm,and the sensitivity of the optical pressure sensor is 1.7×10-3 W/kPa,and the linear relationship is 99.7%.The influence on the performance of the optical pressure sensor is small,all within a reasonable range,which meets the manufacturing requirements.An MZI-based SOI ridge-shaped optical waveguide pressure sensor was designed.This structure has the following advantages:smaller structure size,higher sensitivity,less linearity and the ability to measure tiny pressure.Compared with other methods of measuring optical pressure,the method of measuring optical pressure with this pressure sensor is more suitable.