Amplification of coherent sub-THz acoustic phonons in superlattices. Fashioning and Pumping up the sound and the SASER issue LACUS Seminar
We present and demonstrate(1) a novel concept and scheme of acoustic phonon amplification at sub-THz frequency and a few nanometers wavelength range based on the photodriven acoustoelectric(AE) effect(2) with 100fs light pulses in an electrically biased semiconductor superlattice(SL) GaAs/AlGaAs; the amplification is due to stimulated Cerenkov folded zone ac-phonon(3) emission by electrons undergoing intra-miniband transport. The process is accounted for with a detailed theoretical model and extensions are discussed.
With appropriate phononic microcavity configuration it can allow the realization of the SASER (Sound Amplification by Stimulated Emission of Radiation) operation(4) the analogue of the Laser with sound. In the present configuration it is the analogue of the quantum cascade laser with sound in the sub-THz frequency and a few nm wavelength range. Such a coherent phonon source allows for investigations with very high spatial resolution, almost comparable to that of an electron microscope, e.g. in microelectronic devices or in microbiology.
1. K. Shinokita, Kl. Reimann, M. Woerner, Th. Elsaesser, R. Hey & Chr. Flytzanis,
Phys. Rev. Letts 116, 075504 (2016).
2. For a review, see N. I. Meyer and M. H. Jørgensen, in Festkörperprobleme X,
edited by O. Madelung (Vieweg, Braunschweig, 1970). pp. 21–124.
3. M. A. Stroscio and M. Dutta, Phonons in Nanostructures, Cambridge Uni Press 2001.
4. J.C. Jackson, Plasma Phys. Controlled Fusion 28, 669(1986) ; I.V Volkov,S.T. Zavtrak, I.S. Kuten,
Phys. Rev. E 56, 1097 (1997); R.P. Beardsley, A.V. Akimov, M. Henini & A.J Kent , Phys. Rev. Letts
104, 085501 (2010)