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Abstract : We present experimental results of the resonant excitation of coherent high-frequency longitudinal acoustic phonons in semiconducting doping superstructures by far-infrared laser radiation. After a grating-coupled delta-doped silicon doping superlattice is illuminated with 10 kW-mm2 nanosecond-pulsed 246 GHz laser radiation, a delayed nanosecond pulse is detected by a current-biased superconducting granular aluminum-palladium bilayer bolometer, at a time corresponding to the appropriate time of flight for ballistic longitudinal acoustic phonons across the 100 silicon substrate. The absorbed phonon power density in the microbolometer is observed to be 10 \mu W-mm2, in agreement with theory. Upon deconvolution, the phonon pulse duration matches the laser pulse duration. The absence of any delayed transverse acoustic phonon signal by the superconducting bolometer is particularly striking and implies there is little or no incoherent phonon generation occurring in the process. Attempts at: 1 1.04 THz phonon generation and 2 the use of Si:B piezo-phonon spectroscopy to measure the frequency and linewdith of the phonon distribution, will also be described.

Keywords : acoustic phonon superconducting bolometer coherent generation terahertz

Author: Thomas Wilson Michael Oehme Erich Kasper Hans-Joachim Gossmann Jörg Schulze -



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