In this thesis we describe design, fabrication, and characterization of micromachined microphotonic systems on silicon. Surface-micromachining technology is used to produce movable optical components such as microreflectors and microgratings. Microhinges are used to provide high aspect-ratio structures that can interact with free-space optical beams. A linear microvibromotor, consisting of capacitive resonators driving a slider via impact, is designed for actuation of the microphotonic components. This actuator has a large travel range and sub-micron motion resolution. The vibromotor is combined with the movable microreflector and micrograting for use in self-aligning and tunable optical modules. We discuss the mechanical and optical design issues in micromachined micro-optics, and present a fabrication process for microphotonic systems.
A hybrid-integrated laser-to-fiber coupling module using the movable microreflector for alignment is described. This module provides a high coupling efficiency without the need for active fiber positioning. Silicon-optical-bench technology is used to passively place all optical components, and the microreflector is adjusted to optimize coupling. An integrated module with external actuators delivered a 40% coupling efficiency. The vibromotor-actuated microreflector was tested with discrete components producing 32% efficiency.
The concept for an integrated external-cavity grating-tunable laser is also discussed. This device uses an actuated micrograting, and can provide continuous tuning over a larger wavelength range. Optical and mechanical design criteria are discussed, and preliminary results on a fabricated movable grating structure are presented.
September 30, 1996
Daneman, M. J. (1996). Micromachined Photonic Devices and Systems on Silicon. United States: University of California, Berkeley.