Coherent control of gigahertz surface acoustic and bulk phonons using ultrafast optical pulses
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Results for the Si sample. (a) Experimental setup. The optical wavelength combination shown here corresponds to the first set of experiments performed with structures on the Si substrate. (b) Change in reflectivity for a uniform Al film. Inset: blowup of Brillouin oscillations. (c) Change in reflectivity for the Al grating using two pump pulses at a 44 ps interual. (d) Fourier amplitude spectrum of surface acoustic phonon mode. Inset: Fourier amplitude spectrum of Brillouin oscillations. (e) Fourier amplitude (left) and phase (right) of the surface acoustic mode vs time difference between the two pump pulses. The synthetic Fourier amplitude and phase are represented by the solid line.
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Results for the GaAs sample. Change in reflectivity when the probe polarization is (a) parallel and (b) perpendicular to the Al grating axis. Fourier amplitude vs time difference between (c) the pump pulses for the bulk mode and (d) the surface acoustic mode. The predicted Fourier amplitudes are given by the solid lines. Snapshots of the reflectivity change waveforms are given in the insets [(e)–(g)]. The solid line in (e) and (f) are predicted variations.
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