Surface micro-machined SU-8 2002 membrane mirrors for focus control

We have built 1 mm circular and 1 mm × 1.4 mm elliptical surface micro-machined SU-8 2002 deformable mirrors for focus control. The SU-8 2002 membrane layers are 2.25 μm thick with gold as the reflective coating on their surfaces. Three annular electrodes were used for electrostatic actuation. Stable deflection was observed up to 6.8 μm for a 1 mm × 1.4 mm elliptical mirror with an air gap of 14 μm. The frequency response of the membrane exhibited a 3 dB frequency larger than 10 kHz