BEGIN:VCALENDAR VERSION:2.0 PRODID:Icfo X-PUBLISHED-TTL:P1W BEGIN:VEVENT UID:69d8d1f6b4519 DTSTART:20221118T090000Z SEQUENCE:0 TRANSP:OPAQUE LOCATION:Auditorium SUMMARY:ICFO | EDUARDO DIAS CLASS:PUBLIC DESCRIPTION:Besides its relevant fundamental interest\, the in-depth unders tanding of light-matter interactions at the nanoscale has a profound impac t on modern technological applications in diverse areas including telecomm unications\, information processing\, sensing\, and energy harvesting. In this context\, surface polaritons provide us with the appealing ability to confine light down to subwavelength regions and produce strong near-field enhancements\, thus assuming a growing importance in Nanophotonics resear ch.\nIn this Thesis\, we explore the precise control of nanoscale optical fields enabled by strong light-matter interactions in different materials. We concentrate on noble metals\, due to their technological relevance and alluring near-infrared response\, and graphene\, due to its wide tunabili ty and exceptional optical and thermal properties.\nAfter an introductory revision of the necessary theoretical concepts in Chapter 1\, we address i n Chapters 2 and 3 the long-standing problem of efficiently coupling light into polaritons via scattering by small particles. Specifically\, in Chap ter 2\, we quantify the coupling strength between light and 2D polaritons using accurate rigorous analytical methods\, and find closed-form constrai nts that limit the maximum possible values of the corresponding coupling c ross-section. We further argue that resonant particles placed at an optimu m distance from the film can boost light-to-polariton coupling to order un ity.\nIn Chapter 3\, we address the poor light-to-polariton coupling probl em by demonstrating that\, indeed\, a small scatterer placed at a suitable distance from a planar surface can produce complete coupling of a focused light beam to surface polaritons. We formulate detailed general prescript ions on the beam profile and particle response that are required to achiev e maximum coupling.\nWe then turn our attention to the manipulation of the plasmonic response of nanostructures via the modulation of the thermal re sponse of graphene. In Chapter 4\, we demonstrate the ability of hybrid sy stems composed by graphene and thin metal films to undergo large photother mal optical modulation upon ultrafast pumping by laser pulses to raise the electron temperature of graphene. Furthermore\, we predict that ultrafast electron microscopy can be used to trace the rich out-of-equilibrium temp oral dynamics of plasmons in graphene samples.\nFinally\, in Chapter 5\, w e propose that a high-energy electron beam can be used to experimentally p robe the ultrafast nanoscale dynamics of dense charge-carrier plasmas. The interaction between the electron beam and the plasma results in a sizeabl e electron-beam energy variation as a signature that reveals information a bout the femtosecond and nanometer time- and length-scale dynamics of the electron cloud. We develop a comprehensive microscopic theory describing t his interaction and allowing us to explain recent experimental results. We further propose that the low-frequency and strongly localized electromagn etic fields generated by the electron cloud can be manipulated and optimiz ed via the geometrical characteristics of the system and the optical chara cteristics of the laser pump.\nIn summary\, in this Thesis we explore the modulation of the nanoscale optical fields that arise from resonant light- matter interactions in different nanostructures\, via the optimized shapin g of light pulses or the induction of thermal effects. We hope that the re sults presented in this Thesis contribute to deepen the fundamental unders tanding of optical excitations at the nanoscale.\n \;\nThesis Director : Prof Dr. Javier Garcí\;a de Abajo DTSTAMP:20260410T103326Z END:VEVENT END:VCALENDAR