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DTSTART:20250321T100000Z
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TRANSP:OPAQUE
LOCATION:ICFO Auditorium
SUMMARY:ICFO | SAURABH ISHWAR BORKAR
CLASS:PUBLIC
DESCRIPTION:This thesis investigates light-matter interactions within plasm
 onic nanocavities\, using ultraconfined optical environments to observe an
 d control molecular dynamics at the nanoscale. Plasmonic cavities\, formed
  by metallic nanoparticles in close proximity to metal films\, generate hi
 ghly localized optical fields within nanometer gaps. Such intense confinem
 ent allows molecules in these gaps to interact strongly with light at room
  temperature\, producing hybrid states that blend characteristics of both 
 photons and molecules- a phenomenon known as strong coupling. By focusing 
 light into such small volumes\, these cavities enable a platform to probe 
 both strong and weak coupling regimes. Various experimental setups were de
 veloped to explore these interactions\, enabling simultaneous Rayleigh and
  Raman scattering measurements from individual nanocavities and introducin
 g new methods for tracking polariton dynamics with femtosecond pulses. Und
 er strong coupling conditions\, plasmonic nanoparticles on mirror cavities
  paired with Methylene Blue molecules demonstrated hybrid light-matter sta
 tes. Through extensive quantitative measurements\, this study identified k
 ey parameters that drive strong coupling and distinguished it from the mec
 hanisms underlying Surface-Enhanced Raman Scattering\, offering a new unde
 rstanding of light-molecule interactions. The study also delves into dynam
 ic phenomena like spectral diffusion\, observed in host-guest molecular sy
 stems within plasmonic nanocavities\, revealing time-dependent spectral sh
 ifts that shed light on molecular behavior in confined fields. Control ove
 r these nanoscale interactions was achieved by tuning the cavity resonance
  through refractive index means and femtosecond optical pulses\, enabling 
 targeted shifts in the plasmonic resonance. Additionally\, using femtoseco
 nd pulses allowed the investigatio of decay dynamics in strongly coupled s
 ystems\, advancing optical control methods for polaritons and capturing pr
 eviously unobserved spectral evolutions in hybrid light-matter states. Fin
 ally\, a broadband white-light interferometric technique was employed to d
 irectly measure the spectral phase of polaritons. This revealed phase shif
 ts across hybrid light-matter states and added to understanding spectral p
 hase dynamics in strongly coupled plasmonic systems.\nThis thesis contribu
 tes a holistic view of light-matter interactions at the nanoscale by bridg
 ing the themes of understanding and control. It sets the stage for future 
 advancements in plasmonic nanocavities and their potential applications in
  chemical sensing and nanoscale spectroscopy.\nFriday March 21\, 11:00 h. 
 ICFO Auditorium\nThesis Director: Prof. Dr. Niek van Hulst
DTSTAMP:20260407T073405Z
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