News
-Special issue on Optical Antennas

This special issue features contributing and invited papers from leading groups in the field of optical antennas.
14 papers address some of the most challenging aspects of these photonic components aimed to increase at a nanometer scale and at room temperature the light/matter interaction.
The editorial letter can be downloaded here.
- Special session 'Molecular and Hybrid Plasmonics'
to be held in Montpellier during the 13th Journées de la Matière Condensée - JMC13 in Montpellier from August 27nd to 31st, 2012.

During the colloquium, emphasis will be placed on the photophysical
processes that govern the interaction between confined electromagnetic fields and molecular systems
or excitons. In particular, we will discuss how to optimize energy absorption, emission and funneling
at nanometer scales. Contributions are welcome on the following topics: nanofabrication (top-down
and bottom-up); linear and nonlinear optical properties of metallic nanostructures; (bio)chemical sensors
(LSPR and colorimetric sensing); nanoantennas; surface-enhanced spectroscopy (fluorescence,
SERS, SEIRA); exciton/plasmon coupling; plasmonic solar cells. . .
- Opening positions
- A master project on nano-optics, plasmonics and nano-antennas, will be available in spring 2012 for undergraduate students and it will be supported by a monthly grant of 436.05 €. Interested master students should contact me by email.

-A master project will be available in spring 2012 to develop diffraction gratings for the compression of ultrahigh power laser pulses. This master project will be followed by a PhD position which will open in september 2012 in the framework of a collaboration between Institut Fresnel/CNRS and CEA CESTA to design and characterize diffraction gratings for the PETawatt Aquitaine Laser project.

Research topics
Plasmonic
Nanoantennas
SPPs on nanostructured metals
Nano-optic
Light focusing with dielectric spheres
Light focusing with sub-wavelength holes
Photonic
Diffraction gratings for ultrashort pulse compression

Recently published papers

Digital Heterodyne Holography Reveals the Non-Quasi-Static Scattering Behaviour of Transversally Coupled Nanodisk Pairs
We reconstruct the full three-dimensional scattering pattern of longitudinal and transverse modes in pairs of coupled gold
nanodisks using digital heterodyne holography. Near-field simulations prove that, in our experimental conditions, the induced
dipoles in the longitudinal mode are in phase while they are nearly in opposite phase for the transverse mode. The scattering
efficiency of the two modes is of the same order of magnitude, which goes against the common belief that antisymmetric
transverse modes are “dark.” The analysis of the reconstructed hologram in the Fourier plane allows us to estimate the angular
scattering pattern for both excited modes. In particular, the antisymmetric transverse mode scatters light mostly into one halfplane,
demonstrating that the quasi-static approximation breaks down in nanodisk pairs even for an interparticle distance lower
than λ/4.

S. Y. Suck, S. Bidault, N. Bonod, S. Collin, N. Bardou, Y. De Wilde, G. Tessier, “Digital Heterodyne Holography Reveals the Non-Quasi-Static Scattering Behaviour of Transversally Coupled Nanodisk Pairs,” International Journal of Optics 2012, 532576 (2012) download

Optical and topological characterization of gold
nanoparticle dimers linked by a single DNA
double-strand
We demonstrate that symmetric or asymmetric gold nanoparticle dimers with substantial
scattering cross sections and plasmon coupling can be produced with a perfectly controlled
chemical environment and a high purity using a single DNA linker as short as 7 nm. A statistical
analysis of the optical properties and morphology of single dimers is performed using
darkfield and cryo-electron microscopies. These results, correlated to Mie theory calculations,
indicate that the particle dimers are stretched in water by electrostatic interactions.

M. P. Busson, B. Rolly, B. Stout, N. Bonod, E. Larquet, Albert Polman, S. Bidault, “Optical and topological characterization of gold nanoparticle dimers linked by a single DNA double-strand,” Nano Lett. 11, 5060-5065 (2011) link
Metallic dimers: When bonding transverse modes shine light
Optical properties of dimers of dipolar metallic particles of typical size 100 nm cannot be predicted
by the quasi-static approximation, even for nano-gap sizes much smaller than the illuminating
light, due to the strong inter-particle scattering. The derivation of non quasi-static expressions
for scattering cross sections show that the transverse bounding mode is the brightest mode for tiny
nanogap antennas and we demonstrate the fundamental role of the inter particle scattering term
in those unexpected optical properties.

B. Rolly, B. Stout, N. Bonod, “Metallic dimers: When bonding transverse modes shine light,” Phys. Rev. B. 84, 125420 (2011) download
Crucial role of the emitter–particle distance on the directivity of optical antennas
We demonstrate that the reflecting properties of a single particle nanoantenna can be extremely sensitive to its distance from a quantum emitter at frequencies lower than the plasmon resonance.
The phenomenon is shown to arise from rapid phase variations of the emitter field at short distances associated with a phase of the antenna particle polarizability lower than π/4.

B. Rolly, B. Stout, S. Bidault, N. Bonod, “Crucial role of the emitter–particle distance on the directivity of optical antennas,” Opt. Lett. 36, 3368-3370 (2011) download

The role of electric field polarization of the incident laser beam in the short pulse damage mechanism of pulse compression gratings

We investigate the short pulse laser induced damage initiation mechanism on multilayer dielectric
pulse compression gratings. We report that damages initiate at the edge of the grating pillars
opposite to the incoming wave. It demonstrates, at a nanometer scale, the role of the electric field
in the damage process coupled with periodic ripple pattern developing along the polarization
direction. We avoid the formation of ripples by illuminating the diffraction grating in TM
polarization and measure a significantly improved laser induced damage threshold associated with
a strong decrease of the electric field in the grating structure.

S. Hocquet, J. Neauport, N. Bonod, “The role of electric field polarization of the incident laser beam in the short pulse damage mechanism of pulse compression gratings,” Appl. Phys. Lett. 99, 061101 (2011) download

selected for the September 2011 issue of Virtual Journal of Ultrafast Science, published by the American Physical Society and the American Institute of Physics