Silicon bulkmicromachined piezoelectrically actuated corner cube retroflector

In this paper, a bulk-micromachined corner cube retroflector (CCR) with ultra-low voltage operation and negligible power consumption has been newly designed and fabricated for free space optical communication applications. The proposed CCR was comprised of bulk-micromachined vertical mirror which has two mutually orthogonal reflective surfaces and one piezoelectrically actuating horizontal mirror. The fabricated CCR has 300μm × 300μm of reflective surfaces. The vertical mirror with two orthogonal reflective surfaces can be obtained by using double SOI-wafer and anisotropic wet etching of (110) silicon wafer. The horizontal bottom mirror was comprised of two supporting and one actuating PZT cantilevers with meander shaped hinges. The supporting cantilevers and the meander hinges were used for accurate angular alignment of mirror by balancing and isolating the residual stresses occurred in the released PZT cantilevers after fabrication. The bottom actuated mirror exhibited a angular displacement of 1.87° at 5 volts applied with on-off switching in 276μs. The fabricated CCR can be digitally modulated up to 1kb/s.