Moving vibrational measurement techniques, methodologies, and concepts from macroscopic applications to the microworld

Abstract

The damping in so-called high Q silicon paddle oscillators is considered with emphasis on near room temperature behavior. New measurements of the spatial distribution of oscillator motion using scanning laser doppler vibrometry (LDV) are presented, and these are used to examine the damping caused by energy loss at the attachment of the oscillator to the base structure. Two approaches - one based on shape optimization and the other on stop band design - are presented for reducing attachment loss. These studies are then extended to silicon micro-oscillators by using a scanning LDV microscope which we have developed having 2 micron spatial resolutions. The Q's found here, as well as those reported in the literature on other micro-oscillators, are several orders of magnitude below what we estimate based on intrinsic silicon absorption. This, together with the LDV scans which show large motions of the supporting structure, indicates straightforward improvements in the design should result in significant increases in Q. Finally, for micro-oscillators with sufficiently high Q's we examine whether quantum mechanical behavior might be observable through such optical measurements, and we describe progress we have made on a super-resolution LDV using the nearfield of a tapered optical fiber.