Spasers (Surface Plasmon Amplification by Stimulated Emission of Radiation) are the nanoscale counterpart to a laser. These are important because they are coherent light sources with physical dimensions below the diffraction limit of light, leading to a multitude of potential applications. Only a few demonstrations of spasers have been realized to date, each of which required high input energy for spasing. These demonstrations used gold nanoparticles for the resonator and either laser dyes or inorganic semiconductors as the active gain medium. Due to gold’s interband electronic absorption at wavelengths below 550 nm, blue wavelengths are inaccessible. Alternative spaser materials and designs are necessary to improve the efficiency of spasers, and allow for a wider range of spaser emission wavelengths to be accessed. For example, silver has a surface plasmon resonance which is tunable across the entire visible spectrum, allowing for the implementation of different gain media such as organic semiconducting conjugated polymers which have higher chromophore densities, superior synthetic tuneability, strong room-temperature excitonic emission, biocompatibility, and more facile processing compared to inorganic semiconductors.<br/><br/>The goal of this research project is to develop thin film silver nanoparticle/conjugated polymer composites to demonstrate functioning spasers. To verify spasing is occurring two tests are performed, first, utilizing high-excitation-pump-power photoluminescence spectroscopy to observe emission spectral narrowing, and, second, excitation-pump-power dependent spectroscopy, to observe nonlinear (specifically; linear to superlinear) emission intensity behavior. Both of these tests are used to observe signatures of stimulated emission, which is a characteristic of spasing. This presentation will focus on the fabrication and characterization of planar, thin-film array configurations of spasers. Many variables are investigated to achieve functioning spasers, including silver nanoparticle size, silver nanoparticle density, and conjugated polymer layer thickness. Our results indicate that spasing is achievable using 60 nm diameter silver nanoparticles and poly(9,9-di-n-octylfluorenyl-2,7-diyl) as the gain media. However all three of these variables (nanoparticle size, nanoparticle density, conjugated polymer layer thickness) play a key role in the functionality of the thin-film spasers, as will be discussed in this presentation.

Utilizing novel configurations of silver nanoparticles and poly(9,9-di-n-octylfluorenyl-2,7-diyl) polymer films to achieve array spasing

254th National Meeting (2017)

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