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.