Effective broadband detection of nanometer laser-induced ultrasonic surface displacements by CdTe:V adaptive photoelectromotive force detector

Abstract

Results of experiments studying the utilization of adaptive CdTe:V photoelectromotive force (photo-EMF) detector for high-sensitivity broadband detection of laser-generated ultrasound are presented. Unlike widely used GaAs photo-EMF detectors, the devices used here demonstrate no significant electron-hole competition. This ensures effective detection of ≅1 nm surface displacements with ≅0.1 mW of the signal beam power in 10 MHz detection frequency band, even in simple transverse detector configuration. For the wavelength of λ=852 nm used in the experiments, the dielectric cutoff frequency of a typical device was approaching 1 MHz. This, in principle, enables monitoring of as-processed objects moving with in-plane velocities up to 10 m/s.