Deeply-Etched MEMS Slotted Micromirrors With Controlled Transmittance

In this paper, we report the analysis, fabrication, and characterization of metallized slotted micromirrors for optical MEMS applications. A scalar model for the transmittance of the micromirror with a vertical slit using Gaussian beam analysis is developed and a closed-form expression is obtained. Detailed finite difference time domain simulation is carried out for the micromirror transmittance to understand the effect of polarization and bench mark the developed model for slit width-to-wavelength ratios in the range 0 to 8. A MEMS chip is designed comprising fiber grooves and variable slit micromirror controlled by a comb-drive actuator. The chip is fabricated using deep reactive ion etching of silicon-on-insulator substrate with 100-μm device layer height. The motion of the actuator is characterized using an opto-mechanical technique and the transmittance of the micromirror for different incident polarizations is extracted versus the slit width and compared with the theoretical predictions showing good agreement.