Experimental observation of anharmonic effects in coherent phonon dynamics in diamond

摘要

We present a study of coherent optical phonon dynamics in monocrystalline and polycrystalline diamond using transient transmission spectroscopy with few-cycle laser pulses. Besides the oscillations at the fundamental phonon frequency of 40 THz we observe a signal at second harmonic frequency and four weak frequency sidebands (25.0 THz, 32.5 THz, 47.5 THz and 55.0 THz). Potential origin of these sidebands is discussed along with the dependence of the observed signal on experimental conditions (pump power, sample thickness, etc.). Phonon dephasing time in polycrystalline diamond T-2,T-poly = 6.0 +/- 0.4(ps) is found to be shorter than in monocrystalline diamond T-2,T-mono = 7.0 +/- 0.4ps.