Device for acoustic pulse echo experiments in the subterahertz range

International audience; We present experimental results on the light-to-sound transduction by a superlattice embedded in an optical microcavity, using picosecond ultrasonics. Experiments on the ability to generate and detect phonons at 0.3 and 0.6 THz were performed at low temperature. Finally, we demonstrate that such a device can detect the acoustic burst that it has generated and which has propagated through the substrate, been reflected on the backside of the substrate and has returned to the device. We study the efficiency of this detection by varying independently the laser wavelength of the pump and probe, by means of asynchronous optical sampling.