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.
 
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