Coherent Interference Fringes of Two-Photon Photoluminescence in Individual Au Nanoparticles: The Critical Role of the Intermediate State

Abstract

The interaction between light and metal nanoparticles enables investigations of microscopic phenomena on nanometer length and ultrashort time scales, benefiting from strong confinement and enhancement of the optical field. However, the ultrafast dynamics of these nanoparticles are primarily investigated by multiphoton photoluminescence on picoseconds or photoemission on femtoseconds independently.Here, we presented two-photon photoluminescence (TPPL) measurements on individual Au nanobipyramids (AuNP) to reveal their ultrafast dynamics by two-pulse excitation on a global time scale ranging from sub-femtosecond to tens of picoseconds.Two-orders-of-magnitude photoluminescence enhancement, namely super interference fringes, has been demonstrated on tens of femtoseconds. Power-dependent measurements uncovered the transform of the nonlinearity from 1 to 2 when the interpulse delay varied from tens of femtoseconds to tens of picoseconds. We proved that the real intermediate state plays a critical role in the observed phenomena, supported by numerical simulations with a three eigenstates model and further experiments on Au nanospheres with different diameters. The crucial parameters, including the dephasing time, the radiative rate, and the coupling between different states, have been estimated using numerical simulations. Our results provide insight into the role of intermediate states in the ultrafast dynamics of noble metal nanoparticles.

Quantum Coherence Effect in the Interaction of Light and Molecules

“…This result further demonstrates the promise of QCME-SMIM in molecular diagnostics and precision medicine. Using coherent control as a fundamental principle, luminescent particles, including a variety of nanoparticles (such as quantum dots, [112] gold nanoparticles, [113] and silver nanoclusters, [114] ) and organic fluorescent molecules, have made a lot of progress in super-resolution imaging and other areas. Coherent control performed in imaging is only a minor manifestation of its capabilities.…”

Plasmon-induced hot carrier dynamics and utilization

“…Thus, the enhanced luminescence can be regarded as the evidence of enhanced hot electron generation. Li et al performed a detailed ITR two-photon photoluminescence study on the sequential excitation of hot electrons [44] . They tuned the generated hot electron distribution by changing pulse widths, light power and time delay.…”

“…Therefore, the electron injection process should occur faster than electron thermalization. After electron thermalization, electron-phonon scattering can further contribute to the electron cooling and lattice heating until thermal equilibrium between electrons and lattice is established, which is usually completed within several picoseconds for noble metal NPs [43,44] . Finally, the heated lattice transfers the heat into an environment where the heat dissipation rate is dependent on the medium [45] .…”

The Geometry of Nanoparticle-on-Mirror Plasmonic Nanocavities Impacts Surface-Enhanced Raman Scattering Backgrounds

“…Metallic nanostructures possess the ability to confine light below the diffraction limit via the excitation of localized surface plasmons, which provides effective strategies for increasing the light–matter interaction. Extreme confinement of light allows for a dramatically enhanced electromagnetic field in the gap region between metallic nanostructures, making coupled metallic nanostructures a promising platform for nonlinear nano-optics [ 1 , 2 ], sensitive biosensing [ 3 ], and photocatalysis [ 4 ]. Among these nanostructures, the nanoparticle-on-mirror (NPoM) geometry [ 5 ], where a metal nanoparticle is separated from a metal film via a self-assembled molecular monolayer or a thin layer of 2D material, has attracted great attention due to its ease of fabrication but strong light–matter coupling.…”