Colloidal Silver Nanoparticle Plasmonic Arrays for Versatile Lasing Architectures via Template‐Assisted Self‐Assembly

Abstract

The characteristic narrow spectral features of surface lattice resonances emerge as great candidates for the rational design of optical nanocavities targeting enhanced light‐matter interaction, ultrasensitive detection, or efficient light‐energy conversion. Traditional fabrication of metal arrays involves thermal evaporation and annealing steps, limiting scalability and adaptability. In contrast, template‐assisted self‐assembly provides a high‐throughput all‐around approach for implementing colloidal plasmonic metasurfaces on a variety of different materials. Here, the use of pre‐synthesized silver nanoparticles is designed and tested for the construction of versatile lasing architectures. Plasmonic arrays are prepared directly on top of the gain media (a photoresist thin film doped with Rhodamine B), creating optical nanocavities with quality factors as high as 85. The proposed architecture circumvents the need for an index‐matching superstrate to promote the generation of collective resonances, leaving the plasmonic surface accessible for post‐assembly modification. Additionally, the angular dispersion of the metasurfaces is used to modify the angle of the lasing emission, achieving both normal and off‐normal lasing upon modification of the lattice parameter of the array. The results demonstrate how state‐of‐the‐art colloidal self‐assembly techniques offer a scalable and versatile alternative for the fabrication of plasmonic and photonic devices targeting advanced and non‐linear optical phenomena.

Colloidal Plasmonic Metasurfaces for the Enhancement of Non‐Linear Optical Processes and Molecular Spectroscopies

“…Indeed, the templates are often designed to engineer specific interactions with nanoparticles based on size, shape, and chemistry, [92] ensuring quality factors > 60 and enough efficiency to promote NL phenomena such as lasing emission. [115] This feature offers the possibility of engineering three different plasmonic responses within the same metasurfaces (i. e., the single colloidal response, the localized response of the repeating unit, and the collective response of the lattice), opening fascinating possibilities for the promotion of SE-NLOS. Another significant advantage of TASA is the possibility of performing the assembly directly on the substrate of choice without needing a mask or any other alignment tool.…”

“…In 2023, Conti et al reported lasing of a one-photon excited gain medium stimulated by silver colloidal plasmonic metasurfaces fabricated via TASA (Figure 6a-c), achieving on-and offnormal emission with thresholds as low as 0.3 mJ/mm 2 . [115] The reported system holds interesting characteristics in the direction of chemically active metamaterials, featuring an optical cavity that remains exposed to the surrounding environment, as the silver nanoparticle arrays were fabricated on top of a waveguiding material layer hosting the gain medium. In this way, they were able to support the outcoupling of plasmonic lattice resonances without using index matching layers, leaving at the same time the cavity accessible for further chemical functionalization.…”