Deformation Measurements of High-Speed MEMS With Combined Two-Wavelength Single-Pulse Digital Holography and Single Phase Reconstruction Using Subpicosecond Pulses

Holographic contouring of high-speed microelectromechanical system optical scanner mirrors operating at resonance frequencies close to 1 kHz is performed with ultrashort-pulse lasers containing two spectral components. These particular pulses are obtained by shaping the spectrum of sub-30 fs pulses of a Ti:sapphire laser system by an acousto-optic programmable dispersive filter. The separation of the two spectral components is adjustable within the 50-nm gain bandwidth. Single-pulse dual-wavelength contouring is achieved by an extended Twyman-Green type interferometer including two CMOS cameras. The deformation obtained from a single-wavelength interferogram is combined with the coarse-shape information deduced from the phase difference map of the two interferograms captured at different wavelengths to yield a combined reconstruction.