Dielectric dispersion determining method in terahertz region using femtosecond ultrashort visible optical pulse

摘要

A dielectric dispersion determining method applying a transient grating method. The transient response of a sample is observed by the transient grating method using a femtosecond ultrashort visible optical pulse. A vibrational waveform b(t) is determined such that its square b(t) .sup.2 replicates vibrational components observed in the transient response. The vibrational waveform b(t) is converted into b(&ohgr;) through the Fourier transform. The dielectric constant &egr; (&ohgr; ) is obtained by substituting the converted value for b(&ohgr;) /&ohgr;. sup.2 on the right-hand side of the following equation (1) derived from Maxwell's equations. The dielectric constant and/or refraction index can be directly obtained from the transient response to the femtosecond ultrashort visible optical pulse without passing through the dispersion relation which leaves some ambiguity in its definition. ##EQU1##