An open-loop nano-positioning micromechanical digital-to-analog converter for grating light modulation

We report an open-loop digitally driven precision positioning mechanism, termed micromechanical digital-to-analog converter (MDAC), and its pioneering application in a grating light modulator. A prototype grating light modulator driven by a 6-bit MDAC has been fabricated using the polysilicon multiuser microelectromechanical systems processes, achieving a total stroke of 296 nm (full-scale output) and step size [least significant bit (LSB)] of 4.7 nm in a highly repeatable and stable manner. The grating light modulator demonstrated about 13-dB contrast ratio between maximum and minimum intensity of the zeroth diffraction order. The proposed mechanism can be configured for many promising applications including digital variable optical attenuators for optical fiber communications.