| dc.description.abstract | In research area of cantilever sensing element, most of approaches are based on the methodology of fiber-to-fiber coupling, which is unsuitable for the integration of laser source and photodetector (PD) into the platform of cantilever structure. In this thesis, a three-dimensional optical path on silicon optical bench (SiOB) with cantilever waveguide sensing element is proposed for the first time to overcome the bottleneck of laser and PD integration. In the proposed approach, the three-dimensional optical path consists of input 45-degree micro reflector, cantilever waveguide, and output 45-degree micro reflector. A vertical-cavity-surface-emitted-laser (VCSEL) and a PD could be easily integrated into the SiOB by three-dimensional optical path.
The proposed SiOB is realized on a silicon-on-insulator (SOI) wafer. The three-dimensional optical waveguide is fabricated on the photonic layer of SOI wafer by wet etching process, and the cantilever waveguide is defined by three kind of different deep etching processes.
The measurement result divides into optics part and vibration part. In the optics part, under the substrate thickness of 300 μm, the optical transmission efficiency is -12.168 dB, and the alignment tolerance of x-axis and z-axis at input port ranges from -4 μm to +5 μm and -4 μm to +4 μm, respectively. At output port, the alignment tolerance of x-axis ranges from -14 μm to +19 μm, and it ranges from -14 μm to +20 μm for z-axis. In the vibration part, considering that the exterior sound source levels at 1 kHz frequency are 94, 100, 105 and 108 dB, the displacement amplitude of cantilever waveguide sensing element are ±2 nm, ±4 nm, ±5.5 nm and ±10 nm, respectively.
Based on the unique optical bench design, it provides a platform to integrate optical waveguide and cantilever waveguide sensing element, and further possible to integrate laser source and PD. | en_US |