Spiegelarrays

Spiegelarrays are programmable arrays of miniature reflective elements used to shape and control optical wavefronts. The term combines spiegel, the German word for mirror, with array, reflecting their function as a mosaic of individually addressable mirrors that collectively mold light. Each element can adjust angle or phase, enabling dynamic beam steering and the synthesis of complex intensity distributions.

Construction and architecture typically involve microfabricated mirrors mounted on a silicon or glass substrate. Actuation is commonly electrostatic, piezoelectric, or magnetic, allowing rapid and precise control of each mirror. Some designs employ curved or segmented surfaces to provide focusing power or to reduce aberrations. Control electronics address the individual elements to achieve a desired phase or tilt across the array, and software translates optical objectives into mirror patterns.

Operation is based on coherent addition or interference of light reflected from the array elements. By coordinating the response of many mirrors, a spiegelarray can implement wavefronts corresponding to holographic fields, beam shaping, or targeted illumination patterns. Operation modes may be binary, with mirrors in on/off states, or analog, providing continuous phase control for finer modulation.

Applications span adaptive optics, laser beam shaping for materials processing, holography, optical trapping, and imaging techniques such as structured illumination or digital holography. Spiegelarrays can offer fast response times and high optical damage thresholds compared with some other spatial light modulators, though they entail calibration challenges and potential inter-element crosstalk.

See also: spatial light modulator, MEMS mirror, digital micromirror device, wavefront shaping, holography.