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SUMMARY:Nano-optics of complex media - R. Sapienza\, King's College London
DTSTART:20130215T140000Z
DTEND:20130215T150000Z
UID:TALK43516@talks.cam.ac.uk
CONTACT:Alessio Zaccone
DESCRIPTION:Central to modern nanophotonics is spontaneous emission contro
 l which can be attained by local density of states (LDOS) engineering in d
 ielectric and metallic nano structures. I will discuss our recent studies 
 of fluorescence from a nano-sized emitter embedded in complex photonic med
 ia\, such as photonic crystals and random powders.\nI will report nanoscal
 e mapping of the local density of states by\ncathodo-luminescence microsco
 py\, a combination of electron-beam scanning and optical spectroscopy [1]\
 ; it relies on scanning a transient dipolar emitter induced by electron be
 am bombardment with respect to its photonic environment while measuring th
 e total emitted power. Each individual electron traversing the photonic st
 ructure generates a nanoscale transient dipole by the accelerated charge w
 hich we exploit as a local probe of the LDOS.\n\nWith unprecedented resolu
 tion (∼10 nm) we image localized photonics crystal cavity modes in a nan
 o-structured silicon nitride membrane\, over the visible spectrum into the
  near-IR. We identify individual cavity modes that are spatially different
  and we map their  LDOS. Also\, our measurements reveal extended Bloch mod
 es which are delocalized over the crystal and periodically modulated. More
 over\, by momentum spectroscopy\, we resolve the angular emission pattern 
 of the radiation emitted\, which exhibits complex diffraction patterns [1]
 .\n\nIn addition\, by fluorescence dynamics we measure LDOS distributions 
 in 3D disordered dielectric powders. We observe a surprisingly long-tailed
  distribution of the LDOS with Purcell factor up to ~10 [2]. I will discus
 s how our experimental results contribute to shed light onto the controver
 sial\ndependence of the C0 correlation function on macroscopic disorder pa
 rameters.\n\n[1] R. Sapienza\, et al. Deep-subwavelength imaging of the mo
 dal dispersion of light\, Nature Materials 11\, 781–787 (2012).\n[2] R. 
 Sapienza\, et al. Long-Tail Statistics of the Purcell Factor in\n Disorder
 ed Media Driven by Near-Field Interactions\, Phys. Rev. Lett. 106\, 163902
  (2011).
LOCATION:Small Lecture Theatre\, Cavendish Laboratory
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