Design and fabrication of a MEMS high-efficiency NIR-scanning grating based on tilted (1 1 1) silicon wafer

Abstract

A MEMS high-efficiency scanning grating for near infrared micro spectrometers has been successfully developed. This paper presents its design, fabrication, and measurement results. Compared with previously reported rectangular and V-shaped groove grating scanners, the presented blazed grating scanner – in which the blazed grating can be obtained by wet anisotropic etching a tilted (1 1 1) silicon substrate, and the desired blaze angle can be easily realized by choosing the appropriate tilt angle of device silicon – has the potential to scan at higher diffraction efficiency. Moreover, an electromagnetic angle sensor is designed to detect the state of the scanning grating and supply the feedback signal for close loop control. We have demonstrated a prototype with grating constants of 4 μ m and blazed angle of 7.54°. Experimental results have showed that the diffraction efficiencies of the –1st order can reach 70% at the wavelength of 1392 nm. The output voltages of angle sensor have a good linear relationship with optical scan angle of the grating scanner, and the sensitivity of the angle sensor is 0.54 mV/° without amplifying.