INTEGRATED OPTICS: Micromirrors make adaptive optics that could fit on the head of a pin

Oct. 1, 1996
A lithographically produced micromirror module uses electrostatic charge to modulate the phase of an incident wavefront by translating the mirror along the vertical axis.

A lithographically produced micromirror module uses electrostatic charge to modulate the phase of an incident wavefront by translating the mirror along the vertical axis. When integrated with foreoptics consisting of a diffractive microlens array to concentrate incident light onto the individual mirrors, the micromirror array can act as an adaptive optics system for real-time correction of industrial lasers or as an optically driven spatial light modulator. Each 20-µm2 micromirror of the 8 × 8 array is mounted on an octagonal pad suspended over a 20-µm-deep channel by support members that double as springs. Electrostatic capacitance between the mirror mount and the substrate below causes the mirror to deflect downward by as much as 2 µm; other designs offer deflections as high as 20 µm and significantly larger array sizes.

The micromirrors are on 300-µm centers; the addition of the diffractive microlens array yields an effective fill factor of 100%. In adaptive optics applications, the p-n junction photodiode acts as an interferometric wavefront sensor. For spatial-light-modulator applications, the photodiode receives the optical control signals to vertically reposition the mirror, introducing a wavefront phase shift.

SY Technology Inc. (Huntsville, AL) leads the micromirror development project, which is funded by the US Air Force Phillips Laboratory (Albuquerque, NM). The array shown here was designed by an SY team and produced on a standard CMOS fabrication line at Orbit Semiconductor (Santa Clara, CA); engineers at the Nanotechnology Laboratory (University of California, Los Angeles) performed additional etching procedures. SY Technology is developing other prototype micro-mechanical adaptive optics systems in collaboration with Boston University (Boston, MA), the California Institute of Technology Jet Propulsion Laboratory (Pasadena, CA), and Adaptive Optics Associates (Cambridge, MA). Approaches include a continuous membrane design for high-power systems, a small diaphragm array design, and a segmented mirror design to correct complex atmospheric distortions.

About the Author

Kristin Lewotsky | Associate Editor (1994-1997)

Kristin Lewotsky was an associate editor for Laser Focus World from December 1994 through November 1997.

Sponsored Recommendations

Request a free Micro 3D Printed sample part

April 11, 2024
The best way to understand the part quality we can achieve is by seeing it first-hand. Request a free 3D printed high-precision sample part.

How to Tune Servo Systems: The Basics

April 10, 2024
Learn how to tune a servo system using frequency-based tools to meet system specifications by watching our webinar!

Motion Scan and Data Collection Methods for Electro-Optic System Testing

April 10, 2024
Learn how different scanning patterns and approaches can be used in measuring an electro-optic sensor performance, by reading our whitepaper here!

How Precision Motion Systems are Shaping the Future of Semiconductor Manufacturing

March 28, 2024
This article highlights the pivotal role precision motion systems play in supporting the latest semiconductor manufacturing trends.

Voice your opinion!

To join the conversation, and become an exclusive member of Laser Focus World, create an account today!