2015 Volume 70 Issue 3 Pages 200-205
The detection-energy dependence of the coherent longitudinal optical phonon in a (001)-CdTe semiconductor crystal has been investigated using a spectrally resolved pump-probe method. When the center energy of laser pulses is tuned to the transparent region, the detection-energy dependence of the phonon amplitude has two peaks at the energies shifted by one-phonon energy of CdTe from the center energy of the laser pulses. On the other hand, the detection-energy dependence of the amplitude at the excitation in the opaque region shows two peaks at the energies shifted by' about twice the phonon energy. The energy shifts in the detection-energy dependence imply that the emission and absorption of phonons take part in coherent phonon generation. We discuss the detection-energy dependence of the coherent phonon from the viewpoint of third-order nonlinear susceptibility based on the impulsive stimulated Raman scattering process under nonresonant and resonant conditions.