Articles récents

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.

Next meeting : BCP Marseille Dec 03rd

22 Novembre 2007 , Rédigé par JW Publié dans #Nanophotonics pick

Scientific meeting of Marseille’s community of biologists, chemists and physicists. The webpage is somehow difficult to find so here a direct link :
 

http://www.fresnel.fr/mosaic/BCP/journee.html


Training periods and PhD positions in optics & biophotonics

29 Octobre 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 (read more about this topic in my previous post here). More information can be found on the MOSAIC website.

I would like to give a special emphasis to the subject I propose following this link:

http://www.fresnel.fr/mosaic/jobs/pdf_files/Nanoapertures%20JW.pdf


Summer 2007 article selection

27 Octobre 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 :

 

"Generation of optical Schrödinger cats from photon number states"; Alexei Ourjoumtsev, Hyunseok Jeong, Rosa Tualle-Brouri et Philippe Grangier, Nature 448, 784-786 (2007). 

Schrodinger’s cat is a Gedankenexperiment in quantum physics, in which an atomic decay triggers the death of the cat. Because quantum physics allow atoms to remain in superpositions of states, the classical cat would then be simultaneously dead and alive. By analogy, a ‘cat’ state of freely propagating light can be defined as a quantum superposition of well separated quasiclassical states—it is a classical light wave that simultaneously possesses two opposite phases. Such states play an important role in fundamental tests of quantum theory and in many quantum information processing tasks, including quantum computation, quantum teleportation and precision measurements. Recently, optical Schrodinger ‘kittens’ were prepared; however, they are too small for most of the aforementioned applications and increasing their size is experimentally challenging. Here we demonstrate, theoretically and experimentally, a protocol that allows the generation of arbitrarily large squeezed Schrodinger cat states, using homodyne detection and photon number states as resources. We implemented this protocol with light pulses containing two photons, producing a squeezed Schro¨dinger cat state with a negative Wigner function. This state clearly exhibits several quantum phase-space interference fringes between the ‘dead’ and ‘alive’ components, and is large enough to become useful for quantum information processing and experimental tests of quantum theory.


"Label-free single molecule detection with optical microcavities"; A. A. Armani, R. P. Kulkarni, S.E. Fraser, R. C. Flagan et K. J. Vahala, Science 317, 783-787 (2007). 

Current single-molecule detection techniques require labeling the target molecule. We report a highly specific and sensitive optical sensor based on an ultrahigh quality (Q) factor (Q > 1e8) whispering-gallery microcavity. The silica surface is functionalized to bind the target molecule; binding is detected by a resonant wavelength shift. Single-molecule detection is confirmed by observation of single-molecule binding events that shift the resonant frequency, as well as by the statistics for these shifts over many binding events. These shifts result from a thermo-optic mechanism. Additionally, label-free, single-molecule detection of interleukin-2 was demonstrated in serum. These experiments demonstrate a dynamic range of 1e12 in concentration, establishing the microcavity as a sensitive and versatile detector.
 

"Electromigrated nanoscale gaps for surface enhanced Raman spectroscopy"; D.R. Ward, N.K. Grady, C.S. Levin, N.J. Halas, Y. Wu, P. Nordlander et D. Nathelson, Nano Letters 7, 1396-1400 (2007).

Single-molecule detection with chemical specificity is a powerful and much desired tool for biology, chemistry, physics, and sensing technologies. Surface-enhanced spectroscopies enable single-molecule studies, yet reliable substrates of adequate sensitivity are in short supply. We present a simple, scaleable substrate for surface-enhanced Raman spectroscopy (SERS) incorporating nanometer-scale electromigrated gaps between extended electrodes. Molecules in the nanogap active regions exhibit hallmarks of very high Raman sensitivity, including blinking and spectral diffusion. Electrodynamic simulations show plasmonic focusing, giving electromagnetic enhancements approaching those needed for singlemolecule SERS.