Articles récents

Training periods and PhD positions in optics & biophotonics

21 Janvier 2007 , Rédigé par JW Publié dans #Recent research work

The Mosaic group at the Institut Fresnel offers training periods for graduate students in optics and photonics. PhD positions are also available based on the different internship subjects, depending on the applicant’s profile and fundings. More information can be found on the MOSAIC website.

I would like to give a special emphasis to the subject I propose (in French) : 

L'interaction entre la lumière et une structure métallique de taille nanométrique donne accès à des effets impossibles à obtenir avec des systèmes de taille supérieure. Notre équipe s'intéresse à des trous nanométriques percés dans des films métalliques. Ces structures possèdent des propriétés remarquables, notamment leur capacité d'exaltation locale du champ lumineux. De nombreuses propriétés restent encore à défricher, de la compréhension des phénomènes fondamentaux au développement d'applications en nanophotonique et biophotonique.

Le sujet de stage proposé vise à s'intégrer dans le groupe de recherche pour participer aux développements et aux expériences en cours. Une orientation plutôt optique ou plutôt biologie sera possible suivant la sensibilité du candidat, avec toujours une forte composante expérimentale.

Latest (collaboration) article published

18 Janvier 2007 , Rédigé par JW Publié dans #Recent research work

Title : Single-scattering theory of light diffraction by a circular subwavelength aperture in a finitely conducting screen

Authors : Evgeny Popov, Michel Nevière, Anne Sentenac, Nicolas Bonod, Anne-Laure Fehrembach, Jérome Wenger, Pierre-François Lenne, and Hervé Rigneault 

It has been released in the February edition of the journal of the optical society of JOSA A, vol. 24, pp. 339-358 (2007). Click here to read the abstract and download the paper (subscribers only). 

This theoretical paper provides analytical formulas for the electromagnetic field diffracted by a subwavelength aperture in an opaque screen (metallic or dielectric). My contribution to these findings is very small, my name was put on the paper mostly because of the ongoing collaboration between the theoretical and experimental groups at the Fresnel Institute.

In my opinion, the main application concerns the far-field directivity from a nanoaperture (part 6, figures 8 to 11). The theory predicts a directivity of the radiation pattern that increases for small permittivities. Surprisingly, this holds for metals AND dielectrics, thus independently of surface plasmon excitation.

Dark Side of the Lab

12 Janvier 2007 , Rédigé par JW Publié dans #Fancy lab

Some other views of the experimental setup, but in the dark !

Laser powers are about 10mW, camera integration time is 3s.


New article submitted

11 Janvier 2007 , Rédigé par JW Publié dans #Recent research work

Aaaarrrrgggghhhhh…. I finally submitted that doomed paper to this high-impact factor physics journal. Took me a too long time to write it down, and to get it into the limited article length :o((

For those interested, here is the abstract : 

We resolve the photokinetic rates enhancement of Rhodamine 6G molecules in single nanometric apertures milled in an opaque aluminum film. Combining fluorescence correlation spectroscopy and lifetime measurements, we detail the relative influence of excitation, radiative and non-radiative decay on the emission process, and describe the physics underneath the overall 15 fold fluorescence enhancement. This procedure is broadly adaptable to a wide range of nanostructures.



Autumn 2006 article selection

9 Janvier 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 :

 

"Creating hot nanoparticle pairs for surface enhanced Raman spectroscopy through optical manipulation"; Fredrik Svedberg, Zhipeng Li, Hongxing Xu, Mikael Käll, Nano Letters 6, 2639-2641 (2006).

Abstract : We use optical tweezers to move single silver nanoparticles into near-field contact with immobilized particles, forming isolated surfaceenhanced Raman spectroscopy (SERS) active Ag particle dimers. The surface-averaged SERS intensity increases by a factor 20 upon dimerization. Electrodynamics calculations indicate that the final approach between the particles is due to “optical binding”. The described methodology may facilitate controlled single molecule SERS analysis.

 

"Enhancing sensitivity of a whispering gallery mode biosensor by subwavelength confinement"; O. Gaathon, J. Cullic-Viskota, M. Mihnev, I. Terakoa, S. Arnold, Applied Physics Letters 89, 223901 (2006).

Abstract : the authors demonstrate enhanced sensitivity of a spherical whispering gallery mode biosensor WGMB by confining orbiting light near the surface using a subwavelength high refractive index layer on a fluorine doped silica microsphere. Their experiments at a free space wavelength of 1310 nm show that the frequency shift sensitivity by changing the external refractive index is increased by more than 700% by adding a 340 nm thick polystyrene layer. This advance is expected to move the WGMB well into the lead as the most sensitive method for unlabeled biosensing.

 

"Shining new light on neural circuits"; Greg Miller, Science 314, 1674-1676 (2006).

Abstract : Emerging methods that combine genetics and optics have neuroscientists glowing about the possibilities

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