BEGIN:VCALENDAR VERSION:2.0 PRODID:Icfo X-PUBLISHED-TTL:P1W BEGIN:VEVENT UID:69e22ce0bcd05 DTSTART:20260319T100000Z SEQUENCE:0 TRANSP:OPAQUE LOCATION:Elements Room SUMMARY:ICFO | SAAD ABDULLAH CLASS:PUBLIC DESCRIPTION:Technological progress in the twenty first century increasingly relies on the ability to control light and electromagnetic fields across multiple spatial and spectral scales. As device dimensions shrink\, strong confinement becomes essential\, and plasmons\, the collective oscillation s of conduction electrons in metals\, provide an efficient route to concen trate optical fields far below the diffraction limit and enhance light mat ter interactions. In this thesis\, we engineer and study strongly confined optical fields in nanoengineered metallic systems\, where plasmonic reson ances play a central role in shaping both linear response and nonlinear em ission.\nIn the first part\, we study scatterer assisted coupling of free space radiation into surface supported plasmonic modes\, which cannot be e fficiently excited by direct illumination due to strong momentum mismatch. We show that metallic nanodisks placed near a plasmon supporting interfac e can launch surface plasmons\, with coupling governed by disk position an d distance from the surface. By tuning the nanodisk size\, we control its resonance wavelength and access a wide near infrared to infrared spectral region. We further investigate periodic nanodisk arrays\, where lattice re sonances reshape the scattering response and shift the optimal scatterer t o substrate distance. By tuning the array geometry\, we identify configura tions that maximize coupling and determine optimal launching conditions. R esults are supported by analytical modelling and numerical simulations.\nT he second part focuses on ultrathin epitaxial crystalline silver films wit h thicknesses of only a few tens of monolayers\, approaching the monolayer limit. These films provide strong intrinsic confinement and support high quality resonances over a broad spectral range spanning the visible and ne ar infrared. We investigate patterned geometries including ribbons\, nanot riangles\, bow tie antennas\, and rods\, and demonstrate robust tunability with quality factors approaching\, and for optimal configurations reachin g\, values on the order of 11. We compare pre patterned and post patterned fabrication approaches and show that suitable capping layers suppress dew etting and ensure long term stability. Despite their reduced thickness\, w e show that their optical response can be described using a modified Drude model with increased damping to account for confinement and fabrication r elated losses.\nFinally\, we investigate the nonlinear optical response of these ultrathin metal systems with emphasis on second harmonic generation . In ultrathin crystalline films\, strong interfacial symmetry breaking an d vertical confinement enable a measurable nonlinear response. We show tha t decreasing film thickness enhances the second harmonic signal\, and that resonant nanopatterning\, particularly using stable capped silver nanorib bon arrays\, yields broad tunability and strong plasmon enhanced near fiel ds\, producing conversion efficiencies a few orders of magnitude higher th an planar films under resonant excitation.\nOverall\, this work highlights plasmon enabled nanoengineering as a powerful route to control and concen trate light beyond the diffraction limit\, enabling compact nonlinear phot onic architectures\, silicon compatible frequency conversion\, and emergin g quantum photonic technologies.\nThursday March 19\, 11:00 h. Elements Ro om\nThesis Director: Prof. Dr. Javier Garcí\;a de Abajo and Dr. Vaha gn Mkhitaryan DTSTAMP:20260417T125144Z END:VEVENT END:VCALENDAR