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VERSION:2.0
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UID:69f27c350be0e
DTSTART:20210324T140000Z
SEQUENCE:0
TRANSP:OPAQUE
DTEND:20210324T163000Z
LOCATION:Online (Teams) and ICFO Auditorium
SUMMARY:ICFO | NICOLA PALOMBO
CLASS:PUBLIC
DESCRIPTION:The study of light-matter interaction at the nanoscale is a ver
 y promising field of research\, providing the possibility to manipulate th
 e interaction with single quantum systems like single atoms\, molecules\, 
 atomic defects or quantum dots\, systems that can emit one photon at a tim
 e\, so-called single-photon emitters (SPEs). From the fundamental point of
  view\, light-matter interaction at the nanoscale allows the exploration o
 f the ultrasmall\, providing superresolution and decomposition of the ense
 mble. From the applied point of view\, it offers the possibility to manipu
 late SPEs and control their optical properties for important applications 
 in the field of ultrasensitive detectors development and quantum communica
 tions.\nYet\, the ultrasmall SPEs have a relatively small absorption cross
 -section\, making their interaction with light quite weak. In fact\, even 
 in a tight excitation focus at room temperature they only absorb one photo
 n over ten million. Additionally\, in many cases such emitters have a low 
 quantum efficiency\, making them hard to detect. Furthermore\, in many cas
 es\, they are optically quite fragile and tend to blink and bleach\, thus 
 no high illumination powers can be used in order to increase their emissio
 n of light.\nFortunately\, nanoantennas allow to confine light well below 
 the diffraction limit\, and through efficient coupling can increase the ef
 fective absorption cross-section of SPEs\, allowing effective excitation a
 nd high-resolution imaging. Moreover\, nanoantennas\ncoupled to SPEs modif
 y the local mode density\, shortening the emitters excited state lifetime\
 , increasing the internal quantum efficiency\, resulting in bright SPEs.\n
 In this thesis\, we study the interaction of light and matter at the nanos
 cale through deterministic coupling between a SPE and a nanoantenna\, usin
 g nanometer scale control. We use scanning probe technology to scan a sing
 le nanoantenna in close proximity to a single emitter. First\, we show a n
 ovel near-field probe based on a dipolar nanoantenna design that provides 
 a higher optical and topographical resolution compared to the state-of-the
 -art. Next\, we apply such novel antenna probes to the study of recently d
 iscovered single atomic defects in hBN\, ultrastable SPEs in an atomically
  thin layer\, ideal for nanoscale control. Despite the hBN high refractive
  index\, and the low absorption cross-section of the defect\, we provide h
 igh-resolution imaging of single hBN emission centers\, enhanced by the ho
 t-spot of our antenna probe. The controlled interaction is demonstrated by
  lifetime mapping\, showing a shorter lifetime for the coupled emitter-ant
 enna case. Finally\, we develop a novel light confinement mechanism based 
 on local subwavelength field suppression by near field interference: gener
 ating &ldquo\;cold&rdquo\; spots. We obtain such dark spots by antenna pha
 se engineering through length control. We image optically for the first ti
 me and with high resolution the cold spots\, and measure fluorescence life
 time reduction\, inhibition of emission for the coupled system\, despite t
 he losses of the metallic nanoantenna.\nSuch low-intensity sub-wavelength 
 dark spots provide novel tools for high-resolution imaging of SPEs with ul
 tralow intensity and a nanoscaling of advanced super-resolution techniques
  like MINFLUX.
DTSTAMP:20260429T214629Z
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