Synthesis of Silver Nanoparticle Thin-Film Lasing SPASERs

Surface plasmon amplification by stimulated emission of radiation (SPASER) is a mechanism first theoretically proposed by Bergman and Stockman in 2003, and the first metal nanoparticle lasing SPASERs were demonstrated by Noginov et al. in 2009 using dye-doped gold nanospheres. Lasing SPASERs can be far smaller than the wavelength of light they emit, which is impossible in conventional lasers due to the diffraction limit of light. This project seeks to develop a metal nanoparticle SPASER-based laser in a thin-film structure, using silver nanoparticles in a poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO) organic polymer gain medium, expanding on the work of Tracey et al. in 2018. The device consists of 50 nm diameter silver nanoparticles spin-coated onto a glass substrate, onto which PFO is spin-coated to surround the particles (~50 nm layer thickness). After attaching a cover slide to the device, it is excited with a 355 nm laser and the resulting photoluminescence is measured at varying settings of laser power. The devices demonstrated spectral narrowing as the laser power increased, a strong indicator of laser behavior. Upon examination under a visible microscope under UV illumination, the excitation appears to occur inhomogeneously in the film, with certain regions producing much more gain than the rest of the device. Possible further investigation of this device includes measuring single particle photoluminescence (and its coherence) and developing a single-step synthesis method for the device instead of two separate spin-coating steps.