Fabrication and integration of diffraction gratings on electrostatic stepper motor for imaging spectrometer applications

Abstract This paper presents the development of a micromechanical rotary stepper motor with an integrated diffraction grating for miniaturized optical systems. The stepper motor is fabricated on a silicon-on-insulator wafer using micromachining techniques and provides precise, incremental rotation through electrostatic actuation, making it suitable for applications with relatively slow image sensors. The design incorporates a frictionless, flexure-based mechanism to ensure accurate operation and robust construction. A novel wafer-level replication technique enables the fabrication of customizable SU-8 diffraction gratings, including blazed profiles for enhanced light efficiency, which are seamlessly integrated with the micromotor. The diffraction grating is precisely bonded to the microactuator using a pick-and-place method with UV-curable adhesive, employing a high-precision stage and a micropipette dispensing system. Experimental characterization demonstrates reliable stepping motion and high-quality optical performance, establishing a practical approach for integrating reconfigurable optical elements with microelectromechanical systems actuators.