Microelectromechanical spatial light modulators with integrated electronics Steven Cornelissen1, Thomas Bifano2, Paul Bierden3 1 Aerospace and Mechanical Engineering, Boston University, Boston, MA 02215 2 Manufacturing Engineering, Boston University, Boston MA 02215 3 Boston Micromachines Corp., Watertown, MA 02472 1. ABSTRACT This paper describes design and development of a microelectromechanical, micromachined spatial light modulator (pSLM) integrated with complementary metal-oxide semiconductor (CMOS) electronics, for control of optical phase in phase-only optical correlators. The jtSLM will consist of a large array of piston-motion MEMS mirror segments (pixels) each of which capable of altering the phase of reflected light by up to one wavelength for infrared ( 1 .5 jim) illumination. Results of a proof-of-concept study are presented along with an electromechanical model and details of the fabrication process for the p.tSLM KEYWORDS: spatial light modulator, MEMS, micromirror 2. INTRODUCTION A new class of spatial light modulator based on full vertical integration of CMOS electronics and surface micromachined piston mirrors is under development at Boston University's Precision Engineering Research Laboratory. The micromachined spatial light modulator (iSLM) will consist of an array of 1024 piston motion MEMS mirror segments fabricated in aluminum over a 10 mm square aperture. Each pixel will be capable of altering the phase of reflected light by up to one wavelength for visible light, controlled by an underlying multi-bit digital CMOS driver that will provide a high degree of resolution. Mirror elements will be more than 90% reflective and will be optically flat and smooth. The array will be digitally updated at a rate of 10kHz. Light modulation will be phase-only, with uniform reflected intensity. Mirror fill factor of 98% will be achievable for square pixel sizes 100 micrometers on a side. Fabrication will make use of a novel low-temperature batch surface-micromachining process integrated with commercially available low-cost foundry electronics fabrication, the device will be economical, reliable, and scalable. Figure 1 shows a schematic ofnine mirror pixels in the proposed j.tSLM. Hectrostthcally Mirror Segment Actuated Diaphragm \ At adiment Post CMOS Electronics Figure 1. Cross-sectional schematic ofthree elements in a micro-machined spatial light modulator (tSLM). In this low temperature MEMS fabrication process, patterned thin layers of structural and sacrificial materials will be built up on a substrate through sequential deposition and lithography. Ultimately, the sacrificial layers will be etched away, leaving a self-assembled, integrated opto-electromechanical device. The phase of each individual High-Resolution Wavefront Control: Methods, Devices, and Applications III, John D. Gonglewski, Mikhail A. Vorontsov, Mark T. Gruneisen, Editors, Proceedings of SPIE Vol. 4493 (2002) © 2002 SPIE. · 0277-786X/02/$15.00 184