Design and characterization of a dual-stage, thermally actuated nanopositioner

Abstract

A nanopositioner is presented that has two stages for independent coarse and fine position control. Thermal microactuators operate both stages. The first stage includes a bistable mechanism: it travels 52 µm between two discrete positions. The second stage is mounted on the first stage and moves continuously through an additional 8 µm in the same direction as the first stage. Three approaches to the control of the second stage were evaluated in terms of accuracy and manufacturability, and one was selected for the design of the nanopositioner. The device was surface micromachined in a two-layer polysilicon process. Experiments were performed to characterize the resolution, repeatability, hysteresis and thermal drift of the second stage of the nanopositioner with open-loop control. Position measurements were obtained from scanning electron micrographs by a numerical procedure, which is described in detail. The nanopositioner demonstrated 170 nm resolution and repeatability within 124 nm. The hysteresis of the second stage was 6% of its full range. The nanopositioner drifted 25 nm in the first 60 min of operation with a time constant of about 6 min. The dual-stage nanopositioner may be useful for applications such as variable optical attenuators or wavelength-specific add–drop devices.