Crossover from Nonthermal to Thermal Photoluminescence from Metals Excited by Ultrashort Light Pulses

Abstract

Photoluminescence from metal nanostructures following intense ultrashort illumination is a fundamental aspect of light–matter interactions. Surprisingly, many of its basic characteristics are under ongoing debate. Here, we resolve many of these debates by providing a comprehensive theoretical framework that describes this phenomenon and support it by an experimental confirmation. Specifically, we identify aspects of the emission that are characteristic to either nonthermal or thermal emission, in particular, differences in the spectral and electric field dependence of these two contributions to the emission. Overall, nonthermal emission is characteristic of the early stages of light emission, while the later stages show thermal characteristics. The former dominate only for moderately high illumination intensities for which the electron temperature reached after thermalization remains close to room temperature.

Compact Implementation of a 1-Bit Adder by Coherent 2-Beam Excitation of a Single Plasmonic Cavity

“…While the assumptions of the phenomenological description of the plasmon-to-photon transduction and some standard approximations in the near-field simulation model may partially account for these differences, they underline the still lacunary knowledge of the mechanism of the remote generation of NPL photons in spite of recent theoretical advances. 25,26 Generalization of Holistic Arithmetic and Logic Units. The design, identification, and location of ALU functions with increasing Boolean complexity implemented within plasmonic cavities is a tedious and time-consuming task.…”

“…Nevertheless, in contrast to confocal map simulations, , some minor differences are visible in the relative intensities at the apexes. While the assumptions of the phenomenological description of the plasmon-to-photon transduction and some standard approximations in the near-field simulation model may partially account for these differences, they underline the still lacunary knowledge of the mechanism of the remote generation of NPL photons in spite of recent theoretical advances. , …”

Non-thermal emission in gap-mode plasmon photoluminescence

“…1 d 12 , 50 . To the best of our knowledge, precise numerical modeling of the PLE lineshape for such non-Fermi distributions has not yet been attempted, although several studies have investigated the spectral character of emission with a non-Fermi term 22 , 30 .…”

“…An isolated single nanostructure avoids ensemble averaging that can obscure the intrinsic mechanisms of NPL, which has motivated the studies of broadband emission from single nanoparticles, dimers, and few-particle aggregates 13 – 22 . These studies showed that the hot-electron intraband model, while accounting for the PL emission from rough films, may not provide a good approximation for isolated nanostructures.…”

Memristive Control of Plasmon-Mediated Nonlinear Photoluminescence in Au Nanowires

“…The illumination of metallic nanostructures by ultrashort laser pulses at near-IR wavelengths induces a broadband upconverted emission spanning the visible spectral regime. Under high-intensity femtosecond excitation, this nonlinear signal has been shown to be dominated by a thermal luminescence continuum emitted by out-of-equilibrium surface electrons with transiently elevated temperatures. − Indeed, following the absorption of the light pulse, the temperature of the electron gas at the surface of the metal can reach thousands of kelvins for about a picosecond , and radiates before equilibrating with the phonons. − This nonlinear photoluminescence (N-PL) has been studied on a wide range of plasmonic geometries and materials. ,− An important feature is the dramatic signal enhancement observed from hot-spots favored by the presence of localized resonances (e.g., at nanoparticles , ). Such local signal enhancements are observed because the luminescence emanates from hot thermal electrons generated at the surface of the metal. ,, Further, in structures sustaining surface plasmon propagation (e.g., nanowires, cavities), N-PL has been shown to be spatially distributed throughout the modal landscape. , Hence, N-PL has been a key observable to unlock ultrafast light–matter interactions, and this response has found numerous usages.…”