Photo-acoustic terahertz phonon detection and generation within a semiconductor superlattice

Romain Legrand , Agnès Huynh (1) , Bernard Perrin

1 INSP - Institut des Nanosciences de Paris

Currently, the development of compact opto-acoustic transducers able to generate and detect acoustic wave in the terahertz wavelength is an active research subject. Superlattice made with a periodic stacking of AlAs/GaAs layers has shown the ability to be used as high frequency acoustic generators and detectors. The excitation by a femtosecond laser leads to a temporally short strain in the pattern which produces quasi-monochromatic coherent phonons up to a frequency of 1 THz related to the multilayer period (excitation near $q=0$). This superlattice is an effective phonon detector since strain causes a change of reflectivity measured with a probe light. Unfortunately, generation and detection have differents spectrals responses: generation is more efficient around $q=0$, while detection works with $q=2k$ ($k$ is the light vector). Therefore a single superlattice cannot be used to detect and generate the same wave vector. However, theory predicts a rise of $q=0$ detection in case of strong reflection at the interface between superlattice and substrate. To check this possibility we design a sample made of a 17 nm period superlattice embedded in an optical micro-cavity. We will present experiments performed at low temperatures on a sample designed to generate and detect 300 GHz acoustic waves.

Mots clés: Photo-acoustic; Superlattice; Terahertz; Semiconductor

Domaines: Acoustique [physics.class-ph]

Romain Legrand, Agnès Huynh, Bernard Perrin. Photo-acoustic terahertz phonon detection and generation within a semiconductor superlattice. Acoustics 2012, Apr 2012, Nantes, France. ⟨hal-00811094⟩