MIT Department of Electrical Engineering & Computer Science

SPECIAL EECS SEMINAR

Thursday, April 20, 1995
RLE Conference Room, 36-428

Refreshments at 8:45 AM
Talk at 9:00 AM

Surface-Micromachines for Accurate and Flexible Alignment in Integrated Optics

Dr. Olav Solgaard
University of California, Berkeley

Alignment of optical components is a fundamental problem in optoelectronic integration and packaging. Submicron tolerances are typically required. To address this alignment problem, we have developed a silicon micromachining technology, the active microoptical bench, that combines microoptical elements with surface-micromachined positioners to create dynamically-aligned, reconfigurable microoptical systems on silicon.

The key to the active microoptical bench is the polysilicon-hinge technology that allows surface-micromachined elements to be rotated away from the silicon surface so that they can interact with optical beams running parallel to the surface. Based on this technology, we designed and fabricated surface-micromachined alignment mirrors with two degrees of freedom of motion, and a measured position accuracy of 0.2 micron. Using these mirrors, we achieved 45% coupling efficiency from a typical semiconductor laser (1.3 micron) to a standard single mode fiber. The stability and robustness of the alignment mirrors were demonstrated in standard shock and vibration tests.

For on-chip actuation of the micromirrors, we used electrostatic combdrives in applications that require good absolute position accuracy (0.2 micron) over a limited range of motion (10 to 20 microns). For applications requiring a substantially larger range of motion, we developed linear vibromotors with several hundred micron range of motion and a position resolution of 0.25 micron.

The accuracy, robustness and flexibility of the active microoptical bench makes it attractive for laser-to-fiber coupling as well as a number of other optical systems such as external-cavity lasers, scanning lasers, and interferometric measurement systems.