Articles récents

Latest paper published

21 Janvier 2008 , Rédigé par JW Publié dans #Recent research work

Now it’s made available online : D. Gerard et al, Phys Rev B 77, 045413 (2008)

Briefly, we experimentally compare the properties of circular nanoapertures milled in gold and aluminium to enhance the fluorescence of dyes diffusing within the nanoapertures. Our main result is that nanoapertures in gold exhibit much higher fluorescence enhancement. We discuss the influence of a noble metal holding plasmonic resonances in the visible range such as gold. Altogether, these results provide crucial knowledge for the design of nanoapertures towards high-efficiency single-molecule analysis.


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Demonstration microscope and Fourier optics

16 Janvier 2008 , Rédigé par JW Publié dans #Recent research work

As an interdisciplinary project for students of the Ecole Centrale Marseille, a joint team with my lab developed a demonstration version of a trinocular microscope. The aim is to introduce students to the principles of image formation, Fourier optics, and basic contrast filtering techniques in microscopy.  This work follows a pioneering demonstration by Peter Evenett (Leeds, UK).

Two USB video cameras are used: the first one observes the image of the sample, the second is conjugated to the microscope objective’s back focal plane (Fourier plane). This allows a simultaneous monitoring of both direct and Fourier images.

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As an example, the following picture shows the direct (left) and Fourier (right) images of gratings with two different pitches. Smaller pitches yield farer diffracted orders in Fourier space.

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Different kind of filters can be set into the Fourier plane, direct observation on their influence on image formation can be inferred. In the following, a black mask is set in the back focal plane to suppress the central (non-diffracted) order. Only the first (plus and minus) diffracted orders are transmitted and contribute to the final image, giving a crisper contrast.

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First book on diffraction

7 Janvier 2008 , Rédigé par JW Publié dans #Nanophotonics pick

World’s first published studies on optical diffraction dating back to 1664, where the word “diffraction” itself was introduced for the first time. The original text is downloadable for free at the French National Library website http://gallica.bnf.fr/


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Happy winter break

26 Décembre 2007 , Rédigé par JW Publié dans #Recent research work


Best wishes

Winter 2007 article selection

26 Décembre 2007 , Rédigé par JW Publié dans #Nanophotonics pick

As member of the OMNT “materials and components for optics” committee, I regularly give a selection and a brief description of articles, that I found particularly relevant to the field. Here is my latest selection :

" Nano-optics from sensing to waveguiding"; Surbhi Lal, Stephan Link et Naomi J. Halas, Nature Photonics 1, 641-648 (2007). 

The design and realization of metallic nanostructures with tunable plasmon resonances has been greatly advanced by combining a wealth of nanofabrication techniques with advances in computational electromagnetic design. Plasmonics — a rapidly emerging subdiscipline of nanophotonics — is aimed at exploiting both localized and propagating surface plasmons for technologically important applications, specifically in sensing and waveguiding. Here we present a brief overview of this rapidly growing research field.

"Label-free optical imaging of mitochondria in live cells"; David Lasne, Gerhard. A. Blab, Francesca De Giorgi, François Ichas, Brahim Lounis et Laurent Cognet, Optics Express 15, 14184-14193 (2007). 

The far-field optical imaging of mitochondria of live cells without the use of any label is demonstrated. It uses a highly sensitive photothermal method and has a resolution comparable to confocal fluorescence setups. The morphological states of mitochondria were followed under different physiological treatments, and the role of cytochrome c was ruled out as the main origin of the photothermal signas. This label free optical method provides a high contrast imaging of live mitochondria and should find many applications in biosciences.

"Generation of single optical plasmons in metallic nanowires coupled to quantum dots"; A. V. Akimov, A. Mukherjee, C. L. Yu, D. E. Chang, A. S. Zibrov, P. R. Hemmer, H. Park & M. D. Lukin, Nature 450, 402-406 (2007). 

Control over the interaction between single photons and individual optical emitters is an outstanding problem in quantum science and engineering. It is of interest for ultimate control over light quanta1, as well as for potential applications such as efficient photon collection2, single-photon switching3 and transistors4, and long-range optical coupling of quantum bits5,6. Recently, substantial advances have been made towards these goals, based on modifying photon fields around an emitter using high-finesse optical cavities2,3,5–8. Here we demonstrate a cavity-free, broadband approach for engineering photon–emitter interactions4,9 via subwavelength confinement of optical fields near metallic nanostructures10– 13. When a single CdSe quantum dot is optically excited in close proximity to a silver nanowire, emission from the quantum dot couples directly to guided surface plasmons in the nanowire, causing the wire’s ends to light up. Non-classical photon correlations between the emission from the quantum dot and the ends of the nanowire demonstrate that the latter stems from the generation of single, quantized plasmons. Results from a large number of devices show that efficient coupling is accompanied by more than 2.5-fold enhancement of the quantum dot spontaneous emission, in good agreement with theoretical predictions.