Three dimensional electrostatic actuators for tunable optical micro cavities

The ability to fabricate micro scale structures with three dimensional features can augment the design opportunities to realise novel devices. This paper discusses the theoretical and experimental performance of a three dimensional Micro-Opto-Electromechanical systems (MOEMS) device which consists of a planar micro mirror positioned in the in-plane and out-of-plane directions by electrostatic actuators. The actuator consists of a mechanically compliant structure micromachined on a bonded Si–Glass substrate. Experimental investigation of the steady state performance of the actuator revealed that the planar mirror can be actuated about ∼3–6 μm in the in-plane direction at 90 Vdc and about ∼2 μm in the out-of-plane direction at 25 Vdc respectively. The device was found to be dynamically stable for any stray ambient excitations <1.6 kHz in air. The suitability of the device for misalignment compensation in stacked multi-layers is discussed; this will enable for realising tunable optical micro cavities for atom detection.