Development of MEMS Programmable Diffraction Gratings for Spectroscopic Applications in the Visible, Near- and Mid-Infrared

This work presents the development of two MEMS programmable diffraction gratings designed for spectroscopic applications in the visible, near- and mid-infrared. These devices have been developed to limit distortion of their optical surfaces at rest and throughout actuation in order to improve their optical performance. In the first part of this thesis, we present the development of a fully programmable micro diffraction grating (F-PMDG): a linear array of individually addressable micromirrors that can be vertically displaced by up to 1.6 µm. The F-PMDG design maintains a simple mechanical structure, avoiding a complicated fabrication procedure while limiting distortion of the micromirrors during actuation. This is achieved through in-plane separation of the electrostatic actuators and the optical surfaces of the micromirrors. Vertical displacement of the micrormirrors is controlled by electrostatic actuators placed on either side of the central micromirror. Actuators with two types of flexures have been implemented in the design of the F-PMDG: classical clamped-clamped (CC) flexures and center-symmetric serpentine flexures. Through analytical and numerical simulation, it has been shown that serpentine flexures reduce the dependence of the actuator on length and thickness allowing the mirrors to be designed with shorter actuators and thicker device layers. Rotational stiffness remains an issue for the serpentine flexures, requiring a high degree of lateral alignment during fabrication; however, as the mirror width is reduced down to 20 µm the rotational stiffness is shown to approach that of CC flexures. F-PMDG arrays with 4-64 micromirrors, 700 µm long and 20-120 µm wide, have been successfully fabricated using anodic bonding to transfer a single crystal silicon (SCS) layer from an SOI wafer onto a prepatterned electrode array. By varying the bonding conditions, the residual stress in the device layer has been limited to 2 MPa leading to flat SCS micromirrors exhibiting a peak-to-valley curvature of ∼ 7 nm over the length of the micromirrors (ROC=8 m). Surface profile measurements performed on fully actuated micromirrors reveal peak-to-valley curvatures of