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Typical SEM images of the GaAs nanopillars. (a) Top view. (b) Oblique view.
(a) Experimental setup. PBS: Polarizing beam splitter. (b) Measured relative reflectivity variation δR(t)/R. Inset: Background subtracted data. (c) Moduli of the temporal Fourier transforms for δR(t)/R (solid line) and forthe simulated displacements: Uz (dotted line) and Ux (dashed line), both normalized (the latter enhanced by a factor of 9). The bright horizontal line segment in the inset was used to average the Fourier transform moduli.
(a) Simulated maps of the x- and z-directed motion from moduli of the temporal Fourier transforms. The sections are vertical cuts in the [1 −1 0] direction. (b) Sections of the mode deformations in anti-phase.
The 7 simulated peak frequencies (a) vs. 1/a, with d and h fixed at the sample nominal values; (b) vs. 1/d for constant a and h; (c) vs. h for constant a and w. Arrows show nominal sample values. The dashed curves in (a) are fits, labelled by reciprocal lattice vector indices (i, j) (Ref. 6), based on an empty-lattice model. The dashed curves in (b) are guides to theeye.
Fitting parameters for the experimental δR(t)/R using a sum over five terms in the form Ai cos(2πfit + ψi )exp(− 2πfit/Qi ). (i)-(iv) refer to vibrations, whereas “Bulk” refers to the Brillouin peak whose Q-factor is determined by the optical penetration of probe beam.
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