A Real Pivot Structure for MEMS Tunable Lasers

This paper presents the design of a real pivot formed by a double-clamped beam for the rotational tuning structures in microelectromechanical systems (MEMS) tunable lasers. Micromechanical properties such as beam deformation, pivot position and pivot shift are investigated and compared with the virtual pivot formed by a cantilever beam. It is shown that the real pivot has negligible shift when subjected to load and fabrication error owing to its feature of structural symmetry, while the virtual pivot suffers from significant pivot shift, which would severely limit the wavelength tuning range. The two pivot designs are implemented into MEMS tuning structures that are fabricated by deep etching and released using a dry release approach. The real pivot measures a depth variation of 16% over the double-clamped beam but maintains the symmetry to the midpoint, and is still able to produce a rotation angle of 4.7deg. In contrast, the virtual pivot has a depth reduction of 4% over the cantilever beam, but achieves only a 2.4deg rotation due to the pull-in problem originated from the severe pivot shift. The real pivot design is more suitable for the MEMS tunable lasers as it is simple, symmetric, robust, and suitable for single-chip integration