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(a) SL sample structure, and (b) calculated folded LA phonon dispersion for the SL, is the SL period.
FFT power spectrum of the femtosecond pump-probe signal, showing a strong peak at corresponding to the first SL mini-zone center LA mode. The inset shows a zoomed section of the part of the signal for pump-probe delays between 10 and 15 ps. Oscillations in the differential transmission with a period of 790 fs are seen.
Bolometer signals for various pump photon wavelengths after subtraction of the optical (direct and PL) component, the traces have been offset for clarity. The arrival times of the LA and TA phonon signals are indicated. Notice that the LA signal dominates under resonant photoexcitation.
Integrated LA signal intensity as a function of the pump photon wavelength, showing a sharp increase when the photon energy matches the SL fundamental gap, .
Emission angle dependence of the LA bolometer signal. The angle is measured with respect to the normal to the SL layers.
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