Generation of terahertz acoustic waves in semiconductor quantum dots using femtosecond laser pulses

We present experimental results demonstrating that the generation of terahertz acoustic waves using femtosecond laser pulses is possible in quantum dots (QDs). Very short and strong pulses are emitted from a buried QD layer and detected at the sample surface. By tuning the laser wavelength we can detect, at room temperature, frequencies above 1 THz using a photoelastic mechanism. A theoretical model supports such a capability and shows that around an interband transition the bandwidth of the photoelastic detection can be greatly improved. These results suggest that QD can be an ultrahigh-frequency acoustic transducer needed for nanoscale acoustics.