Micromachined tunable optical filter with controllable finesse and passband wavelength position

Abstract

The invention provides tunable optical filters in which operating characteristics such as initial cavity length and mirror tilt, affecting passband wavelength position and filter finesse, respectively, can be controlled independently of membrane tuning bias. An illustrative embodiment incorporates a surface-micromachined plate with an opening in which a moveable frame is supported by, e.g., flexure bars or support arms. A moveable membrane with a high reflective (HR) coated mirror is supported in an opening in the moveable frame. The mirror defines one side of a Fabry-Perot (FP) filter cavity and is movable in a direction along an axis of the filter cavity. The other side of the filter cavity is defined by a second HR-coated mirror. The moveable frame has a number of electrodes arranged on a surface thereof, such that an operating characteristic of the filter, e.g., the cavity length affecting the passband wavelength position or the mirror tilt affecting the filter finesse, can be adjusted by applying signals to at least a subset of the electrodes. The use of a separate set of electrodes for controlling the moveable frame permits the operating characteristic to be adjusted independently of a tuning bias applied to one or more additional electrodes associated with the moveable membrane.

Dependencies are inferred from the claim text.