Experimentally Exploring the Interatomic Potential in a Ferroelectric Crystal via Optimal Ultrafast Lattice Control

TL;DR

This study compares resonant terahertz and nonresonant impulsive stimulated Raman scattering methods for exciting phonon-polaritons in ferroelectric lithium niobate, revealing how high-field THz pulses can probe the anharmonic lattice potential.

Contribution

It demonstrates the advantages of THz excitation over Raman scattering in selectively driving phonon modes and exploring the anharmonic potential energy surface in ferroelectric materials.

Findings

THz excitation enables high-amplitude, selective phonon-polariton driving.

High-field THz pulses probe the anharmonic regime of the lattice.

Raman excitation introduces nonlinear complications at high pump fluences.

Abstract

We present a direct comparison between resonant terahertz (THz) and nonresonant impulsive stimulated Raman scattering (ISRS) excitation of phonon-polaritons in ferroelectric lithium niobate. THz excitation offers advantages of selectively driving only the forward propagating phonon-polariton mode to exceedingly high amplitudes, without complications due to nonlinear processes at the high 800 nm pump fluences used in Raman excitation. At peak-to-peak THz electric field strengths exceeding 1 MV/cm, the ferroelectric lattice is driven into the anharmonic regime, allowing experimental determination of the shape of the potential energy surface.