Ultrafast control of material optical properties via the infrared resonant Raman effect

TL;DR

This paper demonstrates that resonant excitation of IR and Raman phonons can rapidly and significantly alter a material's optical properties, enabling dynamic control over a broad frequency range through nonlinear lattice effects.

Contribution

It introduces a new pathway involving nonlinear lattice polarizability for light-matter interactions, expanding the understanding of ultrafast optical property control in crystalline insulators.

Findings

Giant shifts in refractive index induced by IR and Raman phonon excitation

Discovery of new optical constants forbidden in equilibrium structures

Control of optical properties across a broad frequency range

Abstract

The Raman effect -- inelastic scattering of light by lattice vibrations (phonons) -- produces an optical response closely tied to a material's crystal structure. Here we show that resonant optical excitation of IR and Raman phonons gives rise to a Raman scattering effect that can induce giant shifts to the refractive index and induce new optical constants that are forbidden in the equilibrium crystal structure. We complete the description of light-matter interactions mediated by coupled IR and Raman phonons in crystalline insulators -- currently the focus of numerous experiments aiming to dynamically control material properties -- by including a forgotten pathway through the nonlinear lattice polarizability. Our work expands the toolset for control and development of new optical technologies by revealing that the absorption of light within the terahertz gap can enable control of optical properties of materials over a broad frequency range.