Picosecond optical generation and detection of phonon waves in a‐As2Te3

Using the pump and probe technique we have observed oscillations of photoinduced transmission in thin films of a‐As2Te3. The oscillations have periods of 70‐240 ps, depending on sample thickness. We ascribe these to phonon propagation in the films. Thermal expansion and carrier deformation potentials are discussed as the origin of these waves. Their velocity in a‐As2Te3 is measured to be v=1.6×105 cm/s. The effect on transmission of heating by the laser pulse is estimated and compared to experiment.