Metallic nanoparticles and more recently dielectric nanoparticles are receiving tremendous attention due to their ability to concentrate light energy into volumes at the nanometer scale. Optimizing the absorption of light by suitably designed nanoparticles is of crucial importance for a wide range of applications including optical antennas, light harvesting, thermoplasmonics and local surface plasmon resonance sensing.
In an article recently published in ACS Photonics, we develop a new conceptual framework to achieve ideal absorption of light by metallic and dielectric particles. Our main results:
- We provide analytical formulations Eq.(16) describing the conditions to reach ideal absorption up to nanoparticle sizes of several hundreds of nanometer.
- Being analytical, these formulas are of immediate use for other researchers to optimize absorption in nanoparticles.
- The approach covers the important experimental case of core-shell nanoparticles which can satisfy the ideal light absorption condition over the full visible spectrum.
- We also address the problem of light absorption by dielectric and lossy particles, like silicon, that can exhibit both electric and magnetic Mie resonances.
- Our method enables the calculation of non-fundamental ideal absorption modes.
With the transfer to the new kiwi platform, Overblog almost killed the blog. The transfer was a real mess and all articles in 2006-2012 period have been lost...
I seriously considered shutting down this site and going elsewhere, but at the end, I like the blog concept. It's about... being different.
I hope you'll enjoy the new version.
Congratulations to Deep Punj for his successful PhD defence and his cum laude award!
Committee: Philip Tinnefeld (president), Sebastien Bidault (reviewer), Cyriaque Genet (reviewer), Sophie Brasselet (member), Herve Rigneault (co-supervisor), Jerome Wenger (supervisor)
Where is Niek? I want Niek!
Paper submission is open to join the next CLEO/Europe-EQEC conference at Munich in June 2015. The CLEO/Europe-EQEC conference series has a strong tradition as a comprehensive and prestigious gathering of optics and photonics researchers and engineers in Europe.
Plasmonics and metamaterials are specially highlighted by a dedicated topical meeting, see EQEC 2015 topic EH Plasmonics and Metamaterials. Metal nanophotonics from fundamentals towards applications and including all spectral regimes: plasmonic nanostructures, antennas, cavities and waveguides; metamaterials; hybrid materials; nonlinear structures and effects; active systems, systems with gain.
Theodor W. Hänsch, Ludwig-Maximilians-Universität München, Munich, Germany
Serge Haroche, Collège de France & Ecole Normale Supérieure, Paris, France
Federico Capasso, University of Harvard, Cambridge, MA, USA
Aydogan Ozcan, University of California, Los Angeles (UCLA), USA
Niek van Hulst, ICFO - The Institute of Photonic Sciences, Castelldefels (Barcelona), Spain
Thomas Ebbesen, Université de Strasbourg, France
Yuri S. Kivshar, Australian National University, Australia
The committee EH Plasmonics and Metamaterials is composed of:
Chair: Jérôme Wenger, Institut Fresnel, Aix-Marseille University, Marseille, France
Javier Aizpurua, Center for Material Physics (CSIC - UPV/EHU and DIPC), Donostia - San Sebastian, Spain
Andrea Alù, University of Texas at Austin, Austin, USA
Alexandre Bouhelier, CNRS, Laboratoire Interdisciplinaire Carnot de Bourgogne, Dijon, France
Sol Carretero Palacios, Instituto de Cienca de Materiales de Sevilla, Sevilla, Spain
Luca Dal Negro, Boston University, Boston, USA
Vassili Fedotov, University of Southampton, Southampton, United Kingdom
Femius Koenderink, FOM Institute AMOLF, Amsterdam, The Netherlands
Kristjan Leosson, Innovation Center Iceland, Reykjavik, Iceland
Din Ping Tsai, National Taiwan University, Taipei, Taiwan
Ralf Vogelgesang, University of Oldenburg, Oldenburg, Germany
Our article “Multi-focus parallel detection of fluorescent molecules at picomolar concentration with photonic nanojets arrays” has just been released in Applied Physics Letters. We replace the complex microscope objective commonly used in fluorescence sensing by an array of latex microspheres. This realizes a novel regime where several focal spots are illuminated to detect the possible presence of a fluorescent molecule in one of them. A detailed theoretical description of the phenomen is provided along with experimental demonstration.
This work describes an efficient disposable lens element that enables single molecule sensitivity at low picomolar concentration. The simplicity of the design makes it perfect for integration in portable microfluidic readers.
Deep Punj is giving a talk at the 13th international conference of Near-field Optics and Nanophotonics NFO13 on nanoantennas for enhanced single molecule fluorescence detection at high concentrations. Our group will also have two posters:
- Plasmonic enhanced fluorescence energy transfer
- Enhanced fluorescence from resonant DNA assembled plasmonic nanoantennas loaded with single dye molecules
Energy transfer between molecules is promoted when they are set in an environment that confines light
The energy transfer between molecules is an essential phenomenon for photosynthesis, photovoltaics and biotechnology. Now, thanks to the work of the Institut Fresnel Institute, energy transfer between molecules can be controlled and enhanced with optical structures etched at the nanoscale.
Researchers prepared pairs of energy donor and acceptor molecules linked by rigid double stranded DNA. These pairs were then inserted into apertures milled in a gold film with nanoscale dimensions. By accurately measuring the radiation properties of pairs of molecules, the researchers were able to demonstrate that the rate of energy transfer between molecules is 6 times greater when placed in a nanoaperture.
These promising results are clearing a new path to improve the energy transfer process widely used in life sciences and biotechnology. Optical nanostructures open up many potential applications for biosensors, light sources or photovoltaics.
This work has been supported by the European Research Council under ERC Grant 278242.
Wenger praises the team for 'being mentally strong' after they responded to criticism with an emphatic publication in Nano Letters: Nanophotonic Enhancement of the Förster Resonance Energy-Transfer Rate with Single Nanoapertures.
What is cool with football media is that it gives a never-ending list of fun pompous sentences...
The ability to design metamaterials with the prescribed properties is a key to their numerous applications and a focus of intense studies in the photonics community. As metamaterials are engineered at a scale which is much smaller than the wavelength of light, it is possible to treat them as a homogeneous medium with the effective values of permittivity and permeability. Nevertheless, there is no common approach to extract these effective parameters despite the significant efforts of the research community over the last years.
In a recent paper published in Phys Rev B, we propose a novel approach to extract the homogenized parameters by analyzing the reflection and transmission spectra. We show that this generalization preserves the physical meaning of the effective parameters at high frequencies and in the vicinity of resonances, where the nonlocal contributions cannot be neglected. It is also shown the decomposition of scattering spectra into even and odd modes helps to separate various contributions and to derive the explicit formulas for the effective permittivity and permeability which always satisfy the passivity and causality constraints.
There is currently one opening position for an Attaché Temporaire d'Enseignement et de Recherche ATER (one-year non-renewable assistant professor contract) associated to Aix Marseille University. The research program will be done in one the groups at the Fresnel Institute under the supervision of a statutory researcher.
Deadline for application April 30th
Contract start September 1st
See the application procedure: http://drh.univ-amu.fr/public_content/recrutement-ater-2014-2015-modalites-liste-postes-section
Some new elements about the debate whether Förster resonance energy transfer can be tuned (or not) with the photonic environment have been recently published in Nature Communications.The authors use a model system of LaPO4 nanocrystals co-doped with Ce3+ donors and Tb3+ acceptors.To tune the photonic environment and the local density of optical states (LDOS), the authors change the refractive index n of the solvent. The experiments conclude that the donor emission rate increases linearly with the refractive index n, while the energy transfer rate does not.This brings the authors to the general conclusion that "FRET rates are independent of the photonic environment". I feel this conclusion so abrupt that it deserves at least a comment here.
First, let's look back at Förster theory as derived in the late 40s. On wikipedia, one can readily find that the rate of spontaneous emission can be described by Fermi's golden rule, and that under the dipole approximation the radiative rate is given by:
which directly shows that the emission rate scales linearly with the refractive index n of the environment. This is what the authors observe for their donor emission. Turning to FRET, the well-established Förster theory states that the energy transfer rate scales as the product of the donor emission rate in absence of the acceptor time the sixth power of the Förster radius Ro, which is given by:
Here, the Förster formalism indicates that Ro scales with the refractive index as (1/n4)1/6 so 1/n2/3, which is almost constant for most refractive indexes of common solvents. So the Förster radius is not expected to vary noticeably as the refractive index is changed, which is again what the authors observe.
The expected evolution of the energy transfer rate ΓFRET = Γ rad (R0/r)6 can be deduced from the two equations above as function of the refractive index. The FRET rate then evolves as n/n4 = 1/n3, so the energy transfer rate actually decreases when the refractive index is increased. Nothing really special here, just the standard Förster theory from 1948.
Based on the above observations, how can one conclude that FRET rates are independent of the photonic environment? What is true (and well within the Förster theory) is that increasing the refractive index increases the radiative decay rate and reduces the energy transfer rate. However, the authors skip that the refractive index comes as some sort of prefactor in the porportionality relationship between the emission rate and the LDOS. There are actually two ways to tune the LDOS and the photonic environment. The obvious way is to change the medium refractive index (or the emission wavelength). The second (and physically relevant) way is to play with the secondary local field Es that is back-scattered by the (inhomogeneous) environment onto the emitter (equivalent to Green's dydadic approach). This is the only way to enhance the LDOS by more a hundred times, and requires photonic crystals or plasmonic antennas.
This is not simply a pure theory debate, FRET has huge applications in bioimaging, lighting sources and photovoltaics, and plays a key role in photosynthesis. Only complex photonic environments can assess the relationship of FRET with the LDOS and unlock the application of the nanophotonics toolbox to enhance FRET.
Do not get me wrong: I don't say/think the paper is wrong, I don't say/think the reviewers or editors took a bad decision, I don't go into personal debate. I simply discuss the scientific conclusion that one can draw from this study, they are far away from "settling the debate about conversion of light".
See our new preprint released on ArXiv 1403.2222: Nanophotonic enhancement of the Förster resonance energy transfer rate on single DNA molecules
Nanophotonics achieves accurate control over the luminescence properties of a single quantum emitter by tailoring the light-matter interaction at the nanoscale and modifying the local density of optical states (LDOS). This paradigm could also benefit to Förster resonance energy transfer (FRET) by enhancing the near-field electromagnetic interaction between two fluorescent emitters. Despite the wide applications of FRET in nanosciences, using nanophotonics to enhance FRET remains a debated and complex challenge. Here, we demonstrate enhanced energy transfer within single donor-acceptor fluorophore pairs confined in gold nanoapertures. Experiments monitoring both the donor and the acceptor emission photodynamics at the single molecule level clearly establish a linear dependence of the FRET rate on the LDOS in nanoapertures. These findings are applied to enhance the FRET rate in nanoapertures up to six times, demonstrating that nanophotonics can be used to intensify the near-field energy transfer and improve the biophotonic applications of FRET.
Jerome will attend SPIE Photonics Europe 2014 conference in Brussels on April 14-17. He will present four contributions from the group:
- Paper 9126-57 Plasmonic nanoantennas for enhanced single molecule analysis at high concentrations (invited paper)
- Paper 9126-62 Enhanced fluorescence emission from resonant DNA assembled plasmonic nanoantennas loaded with single dye molecules
- Paper 9129-91 Hollow core photonic crystal fiber probes for Raman and fluorescence spectroscopy with photonic nanojet focusing
- Paper 9125-62 Homogenization of metamaterials through the singular analysis of scattering spectra
We have recently published a review paper about plasmonic antennas and zero mode waveguides (nanoapertures) to enhance the detection and analysis of fluorescent molecules. Single molecule spectroscopy techniques, FRET and FCS can greatly benefit from zero mode waveguides and plasmonic antennas to enter a new dimension of molecular concentration reaching physiological conditions. You can find the review on WIREs Nanomedicine and Nanobiotechnology, or alternatively, we posted an unedited version on arXiv.
Petru, Juan and Jerome will attend the NanoLight 2014 conference in Benasque during the first week of March. They will give one talk and three poster contributions:
- Plasmonic enhanced fluorescence energy transfer
- Enhanced fluorescence emission from resonant DNA assembled plasmonic nanoantennas loaded with single dye molecules
- Homogenization of metamaterials through the singular analysis of scattering spectra
- Optical ﬁber probe for remote single molecule fluorescence sensing
Got the guts? Get the glory: only a few days are left before the application deadline for the PhD grants offered by the Erasmus Mundus Europhotonics doctorate program. There are several PhD positions at the Fresnel Institute in Marseille France. Get this opportunity now, next year will likely see no call.
The Institut Fresnel at Marseille is seeking to recruit talented, enthusiastic young scientists who are highly motivated to boost their research career in the areas of nanophotonics and biophotonics and join the prestigious European Erasmus Mundus Doctorate program Europhotonics.
Check out the five open PhD positions in nanophotonics and biophotonics and enjoy the living in the South of France:
- Photonic antennas for super-resolution imaging and dynamic sensing on cell membranes, Jérome Wenger (FRESNEL - équipe MOSAIC) et Maria Garcia-Parajo (ICFO, Barcelona)
- Silicon photonics : engineering the optical properties of Si-based photonic devices, Nicolas Bonod (FRESNEL - équipe CLARTE) et Massimo Gurioli (LENS, Florence)
- The role of coherence in energy efficiency uncovered by fs single molecule detection, Hervé Rigneault (FRESNEL - équipe MOSAIC) et Niek van Hulst (ICFO, Barcelona)
- Super-resolution imaging using unknown illuminations, Hugues Giovannini, Anne Sentenac (FRESNEL - équipe SEMOX) et Pablo Loza , David Artigas (ICFO, Barcelona)
- Modelling and first observation of plasmon-soliton waves, Gilles Renversez (FRESNEL - équipe CLARTE) et Romain Quidant (ICFO, Barcelona)
As the ACS ads puts it, it is no longer sufficient to publish not to perish, your paper needs to be found. The good news is that scientific editors come to maximize the benefit we (and they) can get from search engine optimization for scientific papers.Check the links, your abstract will never look the same...
SEO for authors by Wiley
Optimizing your article for search engines by Wiley-Blackwell
Be found or perish by ACS
Interestingly, I didn't find any of these speaking about getting your research article freely accessible via open access or redeposition websites. Business is business