Surface-Micromachined MEMS Tunable Three-Leaf Trefoil-Type Corner Cube Retro-Reflector for Free-Space Optical Applications

This work has developed a three-leaf trefoil-type corner cube retro-reflector (CCR) fabricated with the MUMPs polysilicon surface micromachining process. Unlike other MEMS CCRs, this CCR's opening faces straight upward as its (1, 1, 1) direction, i.e., the direction along which the retro-reflection efficiency is maximum, is perpendicular to the substrate's surface. Simulation results show that the orthogonality of CCR plays an important role in the optical performance of the CCR. Two CCRs leaning against each other to form a CCR pair are also presented, showing the feasibility of achieving a linear CCR array. With the ability to independently set the on-off state of each CCR by employing an electrostatically actuated gap-closing mirror as one of the three reflecting “leaves,” a CCR array can be used to realize optical identification.