Coherent THz frequency radiation from shock waves: A new ultrafast strain wave detection mechanism

EJ Reed and MR Armstrong and KY Kim and JH Glownia, SHOCK COMPRESSION OF CONDENSED MATTER - 2007, PTS 1 AND 2, 955, 1121-1124 (2007).

We discover that strain waves of THz frequencies can coherently generate radiation when they propagate past an interface between materials with different piezoelectric coefficients. By considering AlN/GaN heterostructures, we show that the radiation is of detectable amplitude and contains sufficient information to determine the time-dependence of the strain wave with potentially unprecedented nearly atomic time and space resolution. We demonstrate this phenomenon within the context of high amplitude THz frequency strain waves that spontaneously form at the front of shock waves in GaN crystals. We have performed proof of principle experiments that demonstrate THz signals that correlate with strain wave propagation times across Al thin films.

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