Electrostatically driven optical Z-axis scanner with thermally bonded glass microlens

Abstract

This paper presents a design, fabrication and characterization results of an electrostatically-actuated microlens scanner capable of precise positioning of integrated glass ball microlens along Z-axis. The device can be used in a wide range of photonic applications, e.g. in MOEMS microscopes for active changing of focal plane during 3-D raster scanning. The scanner construction is based on parallel-plate electrostatic actuation scheme where suspended silicon platform with integrated microlens (movable electrode) is attracted to silicon cover (fixed electrode). Both parts, fabricated individually by bulk micromachining of standard silicon wafer, are vertically aligned and bonded in low-temperature process through SU-8 film. The glass microlens with diameter of 360 μm, effective focal length of about 260 μm, and numerical aperture of 0.57, is directly thermally bonded in the centre of platform. The device demonstrates vertical displacement up to 26 μm in semi-static mode and 38 μm at dynamic mode (fR=540Hz) with the max. 160 V of applied excitation voltage.