Experimental study of sensitivity dependences on waveguide position and diaphragm thickness in silicon-based guided-wave optical accelerometer

Our group has developed a silicon-based guided-wave optical accelerometer, consisting of a proof mass centered on a diaphragm and a waveguide across the diaphragm. The sensor operates based on phase retardation induced by the elasto-optic effect. Designing the sensor is considerably complicated since it is strongly suggested that sensitivity is related to many parameters, such as waveguide position, diaphragm dimensions, and size and weight of proof mass. Hence, these relations should be clearly identified to establish a design guideline. In this study, sensitivity dependences on waveguide position and diaphragm thickness were experimentally examined. Regarding sensitivity dependence on waveguide position, phase sensitivity was highest for the waveguide at the diaphragm edge and was also relatively high for the waveguide at the edge of proof mass, whereas the sensitivity was quite low around the midposition between the edges of the diaphragm and proof mass. Regarding diaphragm thickness, phase sensitivity was found to be inversely proportional to the square of the diaphragm thickness.