Picosecond ultrasonics time resolved spectroscopy usinga photonic crystal fiber

We present a time resolved spectroscopy for the picosecond ultrasonics technique. Detection of picosecond coherent phonons using a wavelength continuum generation in a photonic crystal fiber with femtosecond laser pulses is introduced. Measurements are performed on two samples made of tungsten and gallium arsenide for selected wavelengths of probe pulses within a bandwidth of 250 nm with an 825 nm center wavelength. Characteristic changes of the shape of the acoustic signal due to the selection of the probe wavelength are shown.