Decay time of coherent longitudinal optical phonons in GaAs estimated with the use of ultrafast optical pump–probe spectroscopy employing femtosecond laser pulses optically transparent to GaAs

We performed ultrafast reflection-type pump-probe spectroscopy of coherent longitudinal optical (LO) phonons in a (001)-oriented semi-insulating GaAs crystal using femtosecond laser pulses optically transparent to GaAs. From the temporal oscillatory profile as a function of time delay, the decay time of the coherent LO phonons was estimated to be (4.4±0.15) ps. The present estimated decay time agrees with the decay time estimated with the use of coherent anti-Stokes Raman scattering spectroscopy: (4.2±0.4) ps [Phys. Rev. B49, 2460 (1994)10.1103/PhysRevB.49.2460]. The above-mentioned results indicate that the coherent LO phonons, which are observed using ultrafast pump-probe with femtosecond laser pulses transparent to the samples, have the same decay time obtained by coherent anti-Stokes Raman scattering spectroscopy.