In the past 20 years, we have reached a broad understanding of many light-driven phenomena in nanoscale systems. The temporal dynamics of the excited states are instead quite challenging to explore, and, at the same time, crucial to study for understanding the origin of fundamental physical and chemical processes. In this review, we examine the current state and prospects of ultrafast phenomena driven by plasmons both from a fundamental and applied point of view. This research area is referred to as ultrafast plasmonics and represents an outstanding playground to tailor and control fast optical and electronic processes at the nanoscale, such as ultrafast optical switching, single photon emission, and strong coupling interactions to tailor photochemical reactions. Here, we provide an overview of the field and describe the methodologies to monitor and control nanoscale phenomena with plasmons at ultrafast timescales in terms of both modeling and experimental characterization. Various directions are showcased, among others recent advances in ultrafast plasmon-driven chemistry and multi-functional plasmonics, in which charge, spin, and lattice degrees of freedom are exploited to provide active control of the optical and electronic properties of nanoscale materials. As the focus shifts to the development of practical devices, such as all-optical transistors, we also emphasize new materials and applications in ultrafast plasmonics and highlight recent development in the relativistic realm. The latter is a promising research field with potential applications in fusion research or particle and light sources providing properties such as attosecond duration.

The unique property of a charge transfer plasmon (CTP) that emerges in conductively bridged plasmonic nanoparticles makes linked nanosystems suitable candidates for building artificial molecules, nanomotors, sensors, and other optoelectronic devices. In this focused review, we present recent theoretical and experimental developments in fundamentals and applications of CTPs in conductively coupled metallic nanoparticles of various sizes and shapes. The underlying physics of charge transfer in linked nanoparticles with nanometer- and atomic-scale inter-particle gap is described from both classical and quantum mechanical perspectives. In addition, we present a detailed discussion of mechanisms of controlling charge transfer and tuning the corresponding CTP spectra in bridged nanoparticles as functions of junction conductance and nanoparticle parameters. Furthermore, the active control of reversible switching between capacitive and conductive coupling in plasmonic nanoshell particles and dynamic evolution of related plasmon modes are emphasized. Finally, after highlighting the implication of the CTP resonance shift for surface-based sensing applications, we end up with the current challenges and future outlooks of the topic that need to be addressed.

Coupling effect of chemical composition and physical structure is a key factor to construct superaerophobic electrodes. Almost all reports about superaerophobic electrodes were aimed at precisely controlling morphology of loaded materials (constructing specific structure) and ignored the due role of substrate. Nevertheless, in this work, by using high precision and controllable femtosecond laser, hierarchical micro-nano structures with superaerophobic properties were constructed on the surface of silicon substrate (fs-Si), and such special super-wettability could be successfully inherited to subsequent self-supporting electrodes through chemical synthesis. Femtosecond laser processing endowed electrodes with high electrochemical surface area, strong physical structure, and remarkable superaerophobic efficacy. As an unconventional processing method, the reconstructed morphology of substrate surface bears the responsibility of superaerophobicity, thus liberating the structural constraints on loaded materials. Since this key of coupling effect is transferred from the loaded materials to substrate, we provided a new general scheme for synthesizing superaerophobic electrodes. The successful introduction of femtosecond laser will open a new idea to synthesize self-supporting electrodes for gas-involving reactions.

Generation of a high spectral power supercontinuum (SC) is reported from controlled multifilamentation of femtosecond pulses in fused silica. The use of a microlens array allows the manipulation of the filamentation pattern under very high-incident laser pulse energy without sample damage and, consequently, compared with using a single focusing lens, higher power of SC generation with a similar spectral broadening can be obtained. Moreover, the role of the interplay between diffraction pattern and proximity to the focus of the microlens array in SC generation is discussed.