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Nano-optics

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Photon Bunching in Cathodoluminescence

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We have measured the second order correlation function g(2)(t) of the cathodoluminescence intensity resulting from the excitation by fast electrons of defect centers in wide band-gap semiconductor nanocrystals of diamond and hexagonal boron nitride. We show that the cathodoluminescence second order correlation function g(2)(t) of multiple defect centers is dominated by a large, nanosecond zero-delay bunching (g(2)(0)>30), in stark contrast to their flat photoluminescence g(2)(t) function. We have developed a model showing that this bunching can be attributed to the synchronized emission from several defect centers excited by the same electron through the deexcitation of a bulk plasmon into few electron-hole pairs.

Recently published in S. Meuret et al Phys. Rev. Lett. 114 197401 (2015)

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Random surface plasmon eigenmodes revealed

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Surface Plasmon (SP) eigenmodes of single metallic nanoparticles have spatial and spectral features which depend on the shape of the nanoparticle. For simple shapes, these properties follow clear trends with the size, constitutive material and dielectric environment of the nanoparticle which are now well-known. However, the situation is far more complex in disordered, or random metal-dielectric systems. A simple example of disordered medium is a semicontinuous metal film, obtained naturally when depositing some metal onto a dielectric substrate. Very broadband strong absorption features have been reported in semicontinuous metal films around the percolation threshold. Simple theoretical models related them to light induced randomly dispersed very intense electric fields named Hot Spots (HS). These HS were predicted to show peculiar properties, namely, a strong confinement, a random position over the substrate, and a strongly broadband character. Read more »

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