Interdependent Hot-Carrier Transient Dynamics and Active Linear/Non-Linear Optical Response in a 1D Plasmonic Crystal

Ultrafast modulation of plasmonic systems heavily rely on the nonlinear optical properties of materials. The third-order Kerr-type nonlinearity, a change in the real and imaginary component of the refractive index that is dependent on the intensity of an excitation signal, especially plays a key role in this scheme. For plasmonic systems in particular, the Kerr-type nonlinearity is highly dependent on the dynamics of hot carriers, defined as high energy electrons and holes generated through the nonradiative decay of plasmon resonances. During the decay of plasmons, high energy carriers with a non-equilibrium energy distribution are formed, which quickly thermalizes through electron-electron scattering. Electron-phonon scattering, followed by the previous sequence, then brings excited electrons to an equilibrium condition with the metal lattice. From a microscopic perspective, the Kerr nonlinearity of an optically excited plasmonic metal indeed follows the characteristic timescales attributed to the formation and relaxation of hot carriers described previously. Understanding these characteristic timescales is thus pivotal for efficient design of active plasmonic platforms.<br/><br/>In this work, we present a comprehensive picture that reveals the interplay of hot-carrier transient dynamics and the linear/nonlinear optical response of a 1D plasmonic crystal. The sensitivity of lattice resonance modes to the in-plane momentum of impinging light allows the spectral tuning of the resonance wavelength. Therefore, exploring the interdependence of hot-carrier relaxation dynamics and active linear and nonlinear resonance properties of the devised plasmonic crystal can be explored over a wide spectral range. Furthermore, spectral tuning allows the observation of interacting resonance modes. This characteristic offers the opportunity to investigate how the interaction between resonance modes modifies the mutual dependence of hot-carrier relaxation dynamics and the optical resonance properties. As prospective applications, we demonstrate the ultrafast control of resonance band separation and coherent control of light attributes through hot-carrier dynamics. We believe our results offer new design principles for designing all-optical modulation based active plasmonic devices.