Compact optical delay line based on scanning surface micromachined polysilicon mirrors

The rapid scanning optical delay (RSOD), which is based on femtosecond pulse shaping technology, was developed to overcome the speed limitations of traditional approaches. In an RSOD the traditional translating mirror is replaced by a scanning mirror with a rotation angle of a few degrees. We present the integration of a scanning silicon micromirror into a compact RSOD geometry only about 5 cm in length. We demonstrate a 40 ps rapid scanning optical delay of 100 fs time scale optical pulses. Our RSOD is based on a surface micromachined tilt-up mirror. The polysilicon mirror is connected to a supporting frame with torsional polysilicon beams and is dynamically driven by an electrostatic comb-drive actuator. The rectangular mirror face is 760 μm by 500 μm, with a resonant frequency of 1060 Hz and a measured range of deflection of 16 degrees optical. The residual stress gradients give the micromirror a measured convex radius of curvature of 34 cm. The RSOD is characterized using a Michelson interferometer. The frequency and deflection characteristics of the micromirror are presented