A novel structure of optical fiber accelerometer based on MEMS torsional micro-mirror is introduced, including MEMS
torsional micro-mirror and optical signal detection. The micro-mirror is a non-symmetric one, which means that the
torsional bar supporting the micro-mirror is not located in the axis where the center of the micro-mirror locates. The
optical signal detection is composed of PIN diode and dual fiber collimator, which is very sensitive to the coupling angle
between the input fiber and output fiber. The detection principle is that acceleration is first transformed into torsional
angle of the micro-mirror, then, optical insertion loss of the dual fiber collimator caused by the angle can be received by
PIN. So under the flow of acceleration to torsional angle to optical signal attenuation to optical power detection, the
acceleration is detected. The theory about sensing and optical signal detect of the device are discussed in this paper. The
sensitive structure parameters and performance parameters are calculated by MATLAB. To simulate the static and modal
analysis, the finite element analysis, ANSYS, is employed. Based on the above calculation, several optimization methods
and the final structure parameters are given. The micro-mirror is completed by using silicon-glass bonding and deep
reactive ion etching (DRIE). In the experiment, the acceleration is simulated by electrostatic force and the test results
show that the static acceleration detection agrees with the theory analysis very well.
Fabrication of flat, free-standing silicon diaphragms as micromirrors using etching processes is the key in the
development of optical Micro-Elecro-Mechanical System(MEMS) devices, such as tunable F-P(Fabry-Perot) filters. It is
very important for etching process to get smooth surface and uniform depth because they greatly affect the performance
of the final device. In this paper, we report the experimental results about roughness and flatness of silicon micromirror
fabricated by wet and dry etching processes. The investigated process involved wet-etching process in self-prepared
KOH solution, and dry etching process with such machines as ALCATEL 601E DRIE(Deep Reactive Ion Etching) and
STS ICP (Inductivity Coupling Plasma). It was found that wet etching process could supply more uniform etching depth,
whereas the better surface roughness was gotten by dry etching. For a 30μm target depth, surface roughness less than
3-nm and maximal depth difference less than 0.3-μm were obtained by STS ICP and KOH respectively.
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