Reconfigurable compound diffraction grating

Abstract

A reconfigurable compound diffraction grating is fabricated using microelectomechanical systems (MEMS) technology. The compound grating structure can be viewed as the superposition of two separately configured gratings. A common lower electrode is placed beneath selected beam elements, known as deflectable beams, to achieve the desired grating configuration (i.e. every other, every third, every fifth, etc.) of the beams in the primary grating. These deflectable beams alone comprise a secondary, lower resolution grating structure. The beam elements are linked to a common upper electrode. Voltage applied across the electrodes creates an electrostatic force that pulls the selected beams down toward the underlying electrode. Changing the vertical position of the selected beams with respect to the other stationary beams presents a different ruling spacing distribution to the incoming radiation. By changing this distribution, the diffracted power among individual diffraction orders of the wavelengths is altered. Controlling the diffracted signal in this way allows for specific diffraction passbands to be fixed on a particular detector or a particular area of a detector. Automated adjustments to the rulings can be very rapidly, which would significantly simplify and reduce the time necessary for complete spectral analysis previously achieved by mechanical movement of diffraction gratings.