Design Of Structure And Fabrication Technology Of High Sensitivity Displacement Sensor Based On Micro Ring Resonator

A novel displacement sensor based on micro ring resonator is described, which can be used for atomic force microscope. In this design, a bus waveguide couples to a micro ring resonator and they are integrated on a cantilever with GaAs/Al0.6Ga0.4As/GaAs membrane structure. The displacement of the sensor can be obtained by means of monitoring the changes in the transmission spectrum of the ring resonator. It has high precision and high sensitivity of optical sensors, and compactness and potential for mass production of the MEMS sensors.In this paper, firstly, the feasibility is proved for displacement sensor by theory analysis and fiber ring experiment. It is concluded that the radius of resonator and the coupling efficiency of straight waveguide and ring resonator are very important for sensor's capability. And based on these two factors, the structures of cantilever and ring resonator are studied systematically. In our design, the length, width and height of cantilever are 400μm, 50μm, 60μm, the width and height of waveguide are 1μm and 0.6μm, and the gap of straight waveguide and ring resonator is about 0.05μm, respectively. Secondly, after the experiment of E-beam exposure condition, the etching method of coupling gap by Focused Ion Beam (FIB) is introduced in detail. Further more, the whole manufacturing process is also presented. And finally, the general planning for sensor's test is put forward. Through the problems in it, the shortcoming and the improvement method of structure and fabrication are discussed in detail.In this paper, as a kind of novel sensitive element, the ring resonator is used to feedback the displacement of cantilever by means of monitoring the changes in the transmission spectrum of the ring resonator. It is expected to break through the detection limit of traditional MEMS sensors. Further more, FIB is presented to etch the coupling gap accurately after E-beam. They are very useful for the further study of displacement sensor and the fabrication of other similar device.