A novel design for fabricating the high efficacious rectangular phase grating with angle sensor by MOEMS fabrication
process is presented in this paper. The purpose of this design is for increasing the Signal-to-Noise of output signal and
reducing the size of near infrared spectrometer by using MOEMS grating. Diffraction efficiency is designed and
optimizing at first. We used Fourier optical theory and diffraction optical theory analyzed the diffraction efficiency of the
rectangular phase grating, and used the PCgrate simulated the design. After analysis and calculation, we found the best
parameter of this grating.
According the former design of infrared spectrometer by ZEMAX, the angle resolution of angle sensor is 60mV/°,
maximal angle is ±4.7° and the size of grating is 5x6mm2. Because of the large deflection angle, the electromagnetic
force is used for driving this grating. For sensing the grating deflexion angle, we design the angle sensor in the torsion
bar of this grating. This sensor is P-type piezoresistive sensor and fabricated on n-(100) high-resistance silicon wafer by
boron ion implantation. Analyses stress of torsion bar and piezoresistive angle sensor with Wheatstone bridge theory, the
scanning angle θ in a linear relation with output voltages (Vout) of Wheatstone bridge. The size of torsion bar is
2100μmx220μmx75μm, the frequency of first step model is 550Hz. The size of the sensor is 100μmx15μmx0.5μm.
Finally, the compatible fabrication process of this device is given.
The results of experiments and theory analyzing demonstrate that MOEMS phase grating could work effectively, and
angle sensor achieve the real time need. This MOEMS grating is suitable for infrared spectrometer.