Unlocking Coherent Control of Ultrafast Plasmonic Interaction

Abstract

Striking a metallic nanostructure with a short and intense pulse of light excites a complex out‐of‐equilibrium distribution of electrons that rapidly interact and lose their mutual coherent motion. Due to the highly nonlinear dynamics, the photo‐excited nanostructures can generate energetic photons beyond the spectrum of the incident beam, where the shortest pulse duration is traditionally expected to induce the greatest nonlinear emission. Here, these photo‐induced extreme ultrafast dynamics are coherently controlled by spectrally shaping a sub‐10 fs pulse within the timescale of coherent plasmon excitations. Contrary to the common perception, it is shown that stretching the pulse to match its internal phase with the plasmon‐resonance increases the second‐order nonlinear emission by >25%. The enhancement is observed only when shaping extreme‐ultrashort pulses (<20 fs), thus signifying the coherent electronic nature as a crucial source of the effect. A detailed theoretical framework that reveals the optimal pulse shapes for enhanced nonlinear emission regarding the nanostructures’ plasmonic‐resonances is provided. The demonstrated truly‐coherent plasma control paves the way to engineer rapid out‐of‐equilibrium response in solids state systems and light‐harvesting applications.

Shaping Exciton Dynamics in 2D Semiconductors by Tailored Ultrafast Pulses

“…Provided that the incoming pulse duration is shorter than the resonant decoherence time scale, its temporally asymmetric nature can be probed by simply varying the pulse group delay dispersion (GDD), i.e applying a parabolic spectral phase which linearly varies the instantaneous frequency of the pulse (also referred to as Chirping, see Fig. 3.a.1) [6,32]. Our attempt to probe the temporal exciton dynamics of the 1s transition, in ambient conditions, using SFG measurements resulted in a temporally symmetric curve.…”

Temporal Dynamics of Collective Resonances in Periodic Metasurfaces

“…Since multimode resonant optical systems can exhibit complex temporal dynamics, studying their ultrafast optical response requires time-resolved methods. Examples of such systems include nanoparticle assemblies, − nonlocal diffractive metasurfaces, , anapoles, , as well as recently explored time-varying systems. − From the practical point of view, understanding and controlling the temporal dynamics can be crucial, e.g., for optimizing the efficiency of nonlinear optical processes and for tailoring their near- and far-field characteristics. − Periodic metasurfaces are especially relevant in that context, − as they can support collective resonances, in which Fano-like coupling between diffractive and localized resonances − can make the temporal dynamics nontrivial. Among various types of collective resonances, including guided-mode resonances, − surface lattice resonances (SLRs), − and waveguide-plasmon polaritons (WPPs), − of particular current interest are collective dark modes, − in which radiation loss is suppressed by destructive interference.…”

All-optical control of ultrafast plasmon resonances in the pulse-driven extraordinary optical transmission

“…Ultrashort pulses with broad spectral and temporal functional degrees of freedom offer simultaneous excitation of coherent pathways, and their interference gives rise to transient modulation in plasmonic behavior [27]. In comparison, the possibility of active tuning of ultrafast plasmon dynamics in the steady state through continuous wave (CW) excitation is quite low because of the rapid redistribution of deposited energy through the system in a short timescale [28].…”