Influence of pulse width and detuning on coherent phonon generation

TL;DR

This paper explores how pulse width and detuning influence coherent phonon generation, revealing the simultaneous occurrence of ISRS and IA processes and their dependence on experimental parameters.

Contribution

It presents a new formulation showing the combined roles of ISRS and IA in phonon generation and how pulse width and detuning affect the process.

Findings

ISRS is negligible for short pulses and increases with pulse width.

The initial phase depends on pulse width and detuning.

Both ISRS and IA contribute to phonon wave packets.

Abstract

We investigated the coherent phonon generation mechanism by irradiation of an ultrashort pulse with a simple two-level model. Our derived formulation shows that both impulsive stimulated Raman scattering (ISRS) and impulsive absorption (IA) simultaneously occur, and phonon wave packets are generated in the electronic ground and excited states by ISRS and IA, respectively. We identify the dominant process from the amplitude of the phonon oscillation. For short pulse widths, ISRS is very small and becomes larger as the pulse width increases. We also show that the initial phase is dependent on the pulse width and the detuning.