Deformable grating apparatus for modulating a light beam and including means for obviating stiction between grating elements and underlying substrate

A modulator for modulating a beam of incident light, the modulator comprising;

• a substrate having an upper surface;
• a first planar light reflective surface formed on the upper surface of the substrate;
• a deformable grating disposed above said first reflecting surface in spaced apart relation thereto and having a second planar light reflective surface formed on its upper side facing away from the upper surface of the substrate, the deformable grating being arranged with said second reflective surface parallel to and spaced from the upper surface of the substrate, said deformable grating having a lower surface disposed in spaced apart facing relationship to said upper surface of the substrate;
• means for moving the grating towards the upper surface of the substrate while at the same time maintaining the second reflective surface of the grating substantially parallel to the first reflective surface;
• and
• means for limiting the area of contact between said lower surface and said upper surface, and preventing the grating from sticking to the substrate when the grating is moved towards the upper surface of the substrate;
• whereby, when the perpendicular spacing between the respective first and second reflective surfaces is equal to m/4 times the wavelength of the incident light bean and m=an even whole number or zero the modulator acts to reflect the incident light beam as a plane mirror and when m=an odd whole number the modulator diffracts the incident light beam as it reflects it, thereby providing the modulation of the light beam.