E1 ULTRASONIC DETECTION FROM PICOSECOND SURFACE VIBRATIONS

We present measurements with a new optical technique for the detection of picosecond ultrasonic pulses in thin opaque films by direct time-resolved detection of ultrafast vibrations of the film surface. For thin films of tungsten and a three-layer Cr/a-Si/W sample we show how the strain pulse shape in the film can be measured without significant distortion at frequencies around 100 GHz.