A microelectromechanical deformable mirror device that is optically addressed and designed to
actuate at extremely low-light levels for wavefront error correction is fabricated and theoretically described.
The device consists of an optically transparent substrate, a photoconductive detector, a thin-film resistor,
and insulating posts that support a mirror. The mirror is suspended over the detector by the insulating posts
and is deformed when the detector is illuminated through the substrate. The actuation of the device is theoretically
modeled as a capacitor in series with a photoconductor under an external dc bias. Under an external 6.3 V
dc bias and when back-illuminated with 501 μW∕cm2 light at 539 nm, a total mirror deformation of 474.3 nm was
obtained and substantiated by numerical modeling. This represents the highest actuation sensitivity to date that
results in mirror deflection values in hundreds of nanometers.