Influence of terahertz pulse width on two-dimensional terahertz spectroscopy

摘要

The influence of the width of terahertz (THz) pulses on two-dimensional THz spectroscopy (2DTS) has been studied theoretically via a classical method in which the expressions for the second-order nonlinear polarizations with different nonlinear sources are derived by using a perturbation approach. Compared to the common disposal method in which the THz pulse is treated as a delta function, some terms that were of unknown physical meaning or vanished will come into force when the width is considered. Three types of nonlinear sources, i.e. anharmonicity, nonlinear damping and nonlinear coupling, are considered for a single mode system. The simulation results demonstrate that the width of the incident THz pulse can markedly affect the properties of 2DTS and that different sources have different influences. This study reveals a more practical insight for 2DTS and could provide much information, such as the optimal width and interval of THz pulses, to guide possible future experiments.