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Single particle nanophotonic switching - bridging electron microscopy and photonics

Final Report Summary - SPANS (Single particle nanophotonic switching - bridging electron microscopy and photonics)

The main scientific objective of this Specific Target Research Project (STREP) was to study underlying physical mechanisms of optical switching based upon single-particle phase transitions triggered by light or electron beam excitation and to investigate feasibility of constructing new types of nanophotonics switches based on this principle. If successful this project was supposed to provide a new paradigm for optical data processing with potential impact in telecommunications and computation technologies by large-scale assembly of such switches in new photonic circuits and will play key roles in other technologies such intelligent high-resolution imaging systems and new artificially engineered metamaterials with properties not available in nature.

The second equally important objective of this STREP was to develop new techniques to study nanophotonic structures by combining nano-photonic with electron microscopy. Alongside with simple scanning electron imaging providing resolution below the nanometre (far better than conventional scanning near-field optical microscopy), we intended to employ techniques such as cathodeluminescence (CL, equivalently designed as electron induced radiation emission (EIRE)) and electron energy loss spectroscopy (EELS) to determine optical properties of photonic and plasmonic structures.

The consortium of SPANS has demonstrated a blossoming effort in the field of electron-beam nanophotonics, leading to additional unexpected applications of the SPANS project's electron microscopy and numerical simulation tools.

Experimental activities have resulted in:
(1) Demonstration of new concepts for nanoparticle optical switch / memory
(2) Design of new instrumentation, including new forms of detectors and ad-hoc scanning electronic, with capabilities for independent or simultaneous EIRE, EELS, and EEGS recording. This has lead to pioneering works, for example, in plasmons mapping with EIRE and EELS.
(3) Demonstration of the use of EIRE for optical switching measurement
(4) Development of several simulation tools for EIRE, EELS and EEGS modelling
(5) A theoretical proof of concept of the EEGS spectroscopy plus the development of the related experimental set-up.

Building substantially on the techniques and concepts developed within SPANS, the consortium has performed several EELS and EIRE mapping (on different types of plasmonic nanoparticles) with unrivalled spatial resolution. Combined EELS and EIRE experiments have been performed for the first time. Also, the spectral mapping techniques have been extended to additional systems such as metamaterials, novel electron-beam-pumped nanoscale light sources and quantum semi-conducting nanowires.