Coherent acoustic phonons in nanostructures investigated by asynchronous optical sampling

A new optical pump-probe technique is implemented for the investigation of acoustic phonon dynamics in the GHz to THz frequency range which is based on two asynchronously linked femtosecond lasers. Asynchronous optical sampling (ASOPS) provides the performance of on all-optical oscilloscope and allows us to record optically induced lattice dynamics over nanosecond times with 200 femtoseconds resolution at scan rates of 10 kHz. The generation of coherent acoustic phonons and their propagation and decay dynamics are investigated in semiconductor heterostructures, layered nanoscale materials of relevance for microelectronics, and X-ray mirrors. Changes of the optical properties of tailored semiconductor heterostructures associated with coherent phonon dynamics open the pathway for the modulation of optical signals at up to THz frequencies.