Tip-Tilt-Piston Actuators for High Fill-Factor Micromirror Arrays

Abstract

Tip-tilt-piston actuators for optical phased arrays with large deflection angle, large piston range, and fast update rates are demonstrated. The devices include bonded low-inertia micromirrors on top of actuators aimed to achieve >96% fillfactor arrays. The gimbal-less design methodology enables scaling devices down to a few 100 µm to allow future implementation of large arrays with <100 µsec update. Several different design architectures have been successfully fabricated and tested as individual devices, and as a 2x2 element array. Devices with square layouts are demonstrated with 800 µm down to 400 µm on a side. In each case the devices consist of 4 vertical combdrive rotators connected by 2 degree-of-freedom (DoF) linkages to a central stage. Each actuator can rotate bidirectionally to raise or lower its linkage, giving the stage the required 3 DoF. The stage is used as a platform for bonding of a thin, low-inertia mirror plate which then completely covers the actuator. A representative high field-factor actuator of 500 µm x 500 µm dimensions achieves optical deflection angles beyond -20° to 20° for both axes and greater than -12 µm to 12 µm pistoning, at <80V actuation. In comparison, a larger low field-factor device with a 600 µm diameter integrated micromirror is also demonstrated which utilizes 3 bi-directional actuators radially offset by 120° to achieve tip-tilt-piston actuation with -10° to 10° deflection in all axes and -30 µm to 30 µm pistoning.

A microelectrostatic repulsive-torque rotation actuator with two-width fingers

“…Among them, the electrostatic actuator has the advantages of low power consumption, fast response, high compatibility with semiconductor processes, and simple and diverse structure. Out-of-plane electrostatic actuators are widely used in microoptical switches [16][17][18], optical attenuators [19,20], tunable optical filters [21], and scanning displays [22][23][24][25]. For these applications, a large rotation angle, i.e.…”

“…Electrostatic repulsive-force actuators have been reported in [30][31][32][33][34], combining large displacement with high operation stability. Repulsive-force actuators have a two-layer [20][21][22][23] or three-layer thin-film structure [34]. Applications of the two-layer repulsive-force actuator include the micromirror based laser vector display [33,35] and its application to automotive head-up displays (HUDs) [36].…”

A novel ultra-planar, long-stroke and low-voltage piezoelectric micromirror

“…Electrostatic actuators are currently the most widely used. Although these are low power, non-resonant structures require high voltages and achieve limited stroke lengths [4][5][6][7]. Piezoelectric thin films, on the other hand, provide the desirable combination of long-stroke actuation at low voltages combined with low power consumption [8].…”

A micromachined dual-axis beam steering actuator for use in a miniaturized optical space communication system

“…There is a wide range of scanning micromirrors for displays, imaging, adaptive optics, optical switching and laser beam steering. The actuation principles are electrostatic [10][11][12][13][14], electrothermal [15][16][17], electromagnetic [18][19][20] and piezoelectric [21]. Miniaturized FSO systems based on MEMS technology have been proposed for communication in smart sensor networks [17,22], micro air vehicles [13] and for microspacecraft [14,23].…”