Nonresonant Control of Materials

We report on a novel type of mechanism for manipulating solids via non-resonant, below gap photo-excitation, mediated by the real part of the dielectric constant. Typically, light-induced phase-changes are induced through the imaginary part of the dielectric function, associated with above-gap or resonant excitation. Here we describe two application of this non-resonant approach, first in the ferroelectric LiNbO₃where we show evidence for transient reversal of the ferroelectric polarization, and second in the chalcogenide SnSe where we observe evidence for a new type of phase-change to a higher symmetry state with long-lived and significant modulations in the optical properties. We show that both responses can be understood in terms of a non-perturbative impulsive stimulated Raman scattering response. This work defines new routes towards novel types of phase-change materials with reduced energy consumption and ultrafast switching speeds.