Adriatic Research Institute

Monolithic high aspect ratio silicon micromirror devices were demonstrated with fully isolated vertical comb drives micromachined from the back side and front side of a 50-/spl mu/m silicon-on-insulator device layer. The devices are suspended by torsional support beams and exhibit bidirectional single-axis rotation, as well as independent up- and down-pistoning actuation. The comb drives are fabricated with initial comb-finger preengagement of up to 10 /spl mu/m for constant force actuation and have accurately self-aligned comb-fingers. Device 1 with a 30-/spl mu/m-thick support beam measured static optical beam deflection from -20/spl deg/ to 19/spl deg/ and bidirectional pistoning motion from -7.5 to 8.25 /spl mu/m. Device 2 utilizes a highly compliant 10-/spl mu/m-thick support beam and measured static optical beam deflection from -14/spl deg/ to 16/spl deg/ and downward pistoning motion to -12.5 /spl mu/m, all at <70 V.

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 m to allow future implementation of large arrays with <100 sec 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 m down to 400 m 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 m x 500 m dimensions achieves optical deflection angles beyond -20 to 20 for both axes and greater than -12 m to 12 m pistoning, at <80V actuation. In comparison, a larger low field-factor device with a 600 m 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 m to 30 m pistoning.