Fashioning and Pumping up the Sound. Strong Coherent THz Acoustic Phonon Amplification in Semiconductor Superlattices and the issue of SASER operation


A central issue in the growing field of phononics is the generation and amplification of pulsed beams of coherent acoustic phonons with well prescribed spatiotemporal characteristics.

We proposed and demonstrated[1] a novel amplification scheme of coherent pulsed acoustic phonon beams based on the photo-driven acousto-electric(AE) effect[2,3] involving folded zone acoustic phonons(FZAP)[4] in the near THz frequency range in semiconductor superlattices(SL).

In our scheme the strong amplification is based on the Čerenkov stimulated emission of FZA phononsby electrically driven photo-generated electrons undergoing an intra-mini-band transport with co-propagating SL acoustic phonons excited via a photo-driven displacive mechanism in the semiconductor SL. The scheme is well assessed and reproduced by theoretical calculations and extensions will be discussed .

The amplification concept holds potential for intense sources of coherent acoustic phonons in the THz frequency range and may become a key ingredient of devices based on sound amplification by stimulated emission of radiation (SASER) the analogue of the laser with sound. Phonons with THz frequencies have wavelengths in the few nanometer range, allowing for investigations with very high spatial resolution,i.e. in microelectronics, microbiology, sonochemistry, almost comparable to that of an electron microscope.

1. K. Shinokita et al, Phys. Rev. Lett 116, 075504 (2016); andPRL SynopsisFebruary 18, 2016)

2. R. H. Parmenter Phys. Rev. 89,990 (1953); G. Weinreich and H. G. White Phys. Rev. 106, 1104 (1957).

3. A. R. Hutson, Phys. Rev. Lett. 7, 237 (1961); N. I. Meyer and M. H. Jørgensen, Festkörperprobleme X,

ed. O. Madelung (Vieweg, Braunschweig, 1970). pp. 21–124.

4. A. Yamamoto, Phys. Rev. Lett. 73, 740(1994)