Scale-reduction rule for diaphragm dimensions to miniaturize a silicon-based integrated optic pressure sensor without reducing sensitivity

摘要

In this paper, an original scale-reduction rule without sensitivity loss in integrated optic pressure sensors based on the elasto-optic effect is described. The sensor has a rectangular diaphragm as a pressure-sensitive mechanical structure and a sensing waveguide on the diaphragm. In this type of sensor, sensitivity is theoretically known to be strongly dependent on the dimensions of the diaphragm. According to the theoretical results, the sensitivity can be kept constant even if the diaphragm dimensions are reduced as long as both the side length ratio and the characteristic length remain constant. Here, the characteristic length is introduced as the cube of the shorter side length of the diaphragm divided by the square of the thickness. Such a scale-reduction rule would be very significant in the miniaturizing of a sensor without reducing sensitivity, but it has not been experimentally confirmed. In this study, the scale-reduction rule was experimentally examined using three fabricated sensors, which had the same side length ratio and the same characteristic length. The exact dimensions of the sensors were 2.0 mmX10 mmX35μm, 2.5 mmX 12.5 mmX49 μm and 3.0 mmX 15 mmX64μm. The measured sensitivities of the three sensors were quite similar to each other as theoretically predicted.