Dynamic visualization of subangstrom high-frequency surface vibrations

An optical scanning interferometer for accurate imaging of high-frequency s urface vibrations is described. Vertical-displacement (out-of-plane) resolu tion of the interferometer is similar to0.003 Angstrom, while lateral resol ution is diffraction limited, typically similar to0.5 mum. The high-frequen cy response is limited by the detector to similar to6 GHz. Both the magnitu de and phase are recorded at each point of the scan, so that an accurate me asurement of the instantaneous surface shape is obtained. Furthermore, the phase information allows one to make a slow-motion movie of the vibrating s urface. Data are presented for three examples in the frequency range 4 MHz- 2 GHz. (C) 2001 American Institute of Physics.