Electrothermally Actuated Steering Micromirror with Integrated Varifocal Capability

Speaker: Jessica Morrison

When: November 7, 2014 (Fri), 10:00AM to 11:00AM (add to my calendar)
Location: PRB 365

This event is part of the Preliminary Oral Exam.

Examining Committee: David Bishop, David Campbell, John Butler, and Thomas Little (ECE)

Morrison

Morrison

Abstract: Micro-opto-electromechanical systems (MOEMS) are used for beam deflection and shaping in a wide range of applications. They are utilized as range finders, in optical coherence tomography, in optical cross connects, in projection systems and in adaptive optics. Commercially available deformable mirrors, which employ MEMS as their backbone, are now a common method of reducing astigmatisms and other aberrations to improve image resolution. A combination of macroscopic adaptive optics and a scanning micromirror was used to increase the signal to noise ratio in an optical wireless communications (OWC) setup, demonstrating the use of steerable micro-optics as a mechanism to increase speed and bandwidth in communications.

We demonstrate a novel micromirror design in which both beam steering and variable focus are integrated into one device. Our design is an electrothermally actuated gold on polysilicon micromirror. The natural parabolic shape of a thermal bimorph structure can be utilized to provide nearly aberration free imaging. The 400 µm diameter mirror has a minimum focal length of hundreds of microns which can be tuned continuously between concave to a focal length of +25 mm, convex in shape. In addition, the mirror is capable of up to ±30° beam deflection along both x- and y- axes. Such capacity can be used as a tool for color mixing in solid state lighting (SSL), to improve the signal to noise ratio in OWC with SSL, or in beam shaping such as generating super-Gaussian light needles and other non-divergent, tightly focused beams. The integration of a large range varifocal membrane and steering actuators has tremendous implications in both optical systems in research and innovative lighting products. The design simplifies what would typically be a system of multiple optical components into a single device, therefore reducing both cost and complexity.