Investigation of the parameters affecting the stimulated emission properties of a plasmonic lattice laser.

Plasmonic lattice lasers have emerged as a cutting-edge technology in the field of nanophotonics, offering a promising and innovative approach to the miniaturization of coherent light sources. Thanks to the coupling of light to charge oscillations in metals, these devices can overcome the limitation of physical confinement of light, which is the main drawback of commercial devices nowadays. The distinctive advantage of plasmonic lattice lasers lies in their capacity to sustain hybrid photonic-plasmonic modes, providing optical feedback for directional lasing emission at room temperature. This technology represents a significant advancement in the development of ultra-compact, tunable, and efficient light sources with applications ranging from sensing to quantum optics and on-chip optical communication. The aim of this work is the investigation of the main parameters that can affect the lasing properties of a plasmonic lattice laser, specifically, the study of the geometrical and temporal effect of the pumping system, the emitter-structure distances, and the emitter concentration. The study focuses on two distinct metallic nanostructures: Al nanocones triangular arrays and Au nanodisks square arrays. The morphological and optical properties of both the periodic arrays are investigated to obtain information about the supported optical modes. To have a complete comprehension of the array optical response, finite element simulations by COMSOL Multiphysics are performed to support the experimental results. Based on the acquired optical information, the gain emitter is carefully selected and characterized. The impact of the pumping conditions is investigated in triangular array of Al nanocones coupled to an organic emitter (Lumogen F305 Red) which emits at λ=603nm embedded in a polymeric matrix (PMMA). The emission properties are explored in both the linear regime, where enhanced fluorescence is observed, and nonlinear regime (stimulated emission). In the latter, a narrow and directional lasing emission is observed at the Γ point of the first Brillouin zone. The coherence properties of the emitted beam are investigated, revealing an ultra-long temporal coherence that is an order of magnitude longer than the values reported in existing literature. In this regime, the angular and temporal conditions of the pumping system are investigated. When the incident photons are coupled to the lattice mode of the array, the lasing intensity can be increased by an order of magnitude. The shorter pump pulse duration explored (ps) is demonstrated to induce a reduction of the lasing threshold, as a result of a preferred dynamic regime necessary for the system to attain the population inversion condition. In the same system, the dye concentration effect is studied. Different polymeric films with different concentrations are deposited on the array by spin coating. At lower concentration, the sample shows a single-mode emission, whereas at higher concentration, a second lasing peak appears at a longer wavelength, enabling a multimode lasing. The emitter-structure distance effect is investigated in the square arrays of Au nanodisks coupled with a solution of IR-140 in DMSO. This system presents a stimulated emission in the near-infrared region (875 nm) at Γ point characterized by low divergence and low threshold. Then, a thick film of silica (SiO2) is deposited on top of the structure to create a spacer between the lattice and the emitter. The emission characteristics of the new sample are investigated, revealing an increase in the lasing threshold. The obtained results demonstrate the high tunability of these systems, not only through parameters internal to the structure (optical band structure) but also with external parameters like the pumping conditions (geometry, temporal dynamics, polarization). This makes this device very promising for the development of tunable and highly coherent sources that can operate at room temperature.