Micro-electro-mechanical variable blaze gratings

Two types of micro-electro-mechanical variable blaze gratings (VBGs) have been designed, fabricated, and tested. The gratings operate by adjusting the blaze angle of each slat so that the specular reflection of the incident light matches a particular grating diffraction order. The VBG blaze angle is adjustable with either electrostatic or thermal actuators. VBGs direct incident light in discrete directions, and are useful for steering light with beam diameters greater than 1 mm and power intensities greater than one watt. Both electrostatic and thermal VBGs were constructed from gold and polysilicon using a surface micromachining process and tested with a 20 mW continuous wave HeNe laser operating at a wavelength of 632.8 nm. Optical selectivities (the ratio of power in the selected order to power in either of the nonselected adjacent orders) were determined for both electrostatically actuated and thermally actuated VBGs. The drive voltages for both types of gratings were measured for specific blaze angles and selected diffraction orders.