Two-phonon Raman-scattering probe of nonequilibrium, high-frequency acoustic phonons: The TA-phonon bottleneck in GaAs

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Abstract
Two-phonon Raman spectroscopy is shown to be a viable probe of nonequilibrium, high-frequency acoustic phonons. These excess phonons were generated in GaAs at ∼25 K by intense Nd: YAlG (neodymium-doped yttrium aluminum garnet) laser pulses, and the same beam was used, in situ, for 90° Raman scattering. From the modulation of the overtones and the difference frequency combinations, the first direct and comprehensive information was obtained on both the frequencies and populations of excess phonons in the TA-phonon bottleneck.