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Centre de Nanosciences
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  • ['Photonique']

    (en anglais) Time-resolved cathodoluminescence: multiscale characterization of photovoltaic materials


      Stéphane Collin.

    (en anglais)

    A unique cathodoluminescence (CL) tool has been installed at C2N in late 2015 with state-of-the-art capabilities (only three similar setups exist worldwide). Its basic principle is the following (see the figure): a material is excited with an electron beam in a scanning electron microscope (SEM), providing a spatial resolution of 10nm. Secondary electrons (SE), emitted photons (cathodoluminescence, CL) and even electron-beam-induced current (EBIC) are collected and recorded simultaneously in order to form 2D maps. For each spatial position, CL spectra provide information on the luminescence efficiency, band structure and defects. In our tool, laser-controlled bunches of electrons can also be used for excitation instead of a steady-state excitation beam, resulting in time-resolved CL measurements (TRCL) that provide valuable information on carrier dynamics and lifetime. Our CL/TRCL setup has state-of-the-art specifications and is extremely versatile: wide ranges of wavelengths (200nm-1600nm) and temperatures (10K-350K), time-resolved measurements (temporal resolution 10ps). In addition, its very high collection efficiency on a wide field of view is perfectly adapted to CL and TRCL mapping of a wide variety of photovoltaic (PV) materials.

    This project is focused on polycrystalline semiconductor materials (CdTe, CIGS, perovskites) for PV in the framework of internal and collaborative projects. The goal of the internship is to perform multiscale CL/TRCL mapping in order to investigate the impact of (large-scale) inhomogeneities, of localized defects (at the nanoscale), of the size and shape of grains, and of the passivation of grain boundaries. The results will be analyzed and correlated to the macroscopic properties and efficiency of PV devices.

    The candidate will be first trained on the CL/TRCL tool. Then, she/he will use this technique to perform and analyze multiscale CL/TRCL mapping of selected series of samples, with the goal to develop new methods to reveal the dynamics of carriers (lifetime, diffusion length, recombination velocities at interfaces...) and correlate these properties to the functional parameters of solar cells. In this context, she/he will work with several members of the sunlit team (C2N) and in close collaboration with the “Institut photovoltaïque d’Ile-de-France” (IPVF). A PhD position on CL/TRCL characterization of photovoltaic nanomaterials may be opened in 2019.

    poursuite en thèse envisageble

    fichier joint

    Stephane.Collin@c2n.upsaclay.fr - +33 1 7027 0630

  • ['Photonique', 'Materiaux']

    (en anglais) III-V nanowires on Si for high-efficiency tandem solar cells


      Stéphane Collin / Andrea Cattoni.

    (en anglais)

    To exceed the efficiency limit of Si single junction solar cells (current record: 26.7%), a possible pathway is to make tandem solar cells by combining a top III-V cell onto a Si bottom cell. Efficiencies exceeding 33% have been demonstrated by wafer bonding of III-V layers on Si, but this costly process can hardly be extended at an industrial level. The direct epitaxy of III-V semiconductors layers on Si is an appealing concept but it is impractical due to thermal- and lattice-mismatch. The direct growth of III-V nanowires (NWs) on Si is another elegant but challenging path, where the matching constraints can be relaxed with small NW diameters and lead to high quality III-V semiconductors with the optimum band gap.

    Recently, in the framework of the C2N/IPVF collaboration, we made several decisive steps along this path: we achieved high yield (>95%) of vertical nanowires uniformly arranged over large patterned areas (>1 cm²); we demonstrated the fabrication of GaAs NWs without stacking faults; we developed a method for the quantitative determination of the doping level (n and p) in single GaAs NWs by cathodoluminescence; and we developed a process to encapsulate and contact NW arrays that led to first-generation NW solar cells. We also introduced a core-shell heterostructure for further Voc improvements.

    In this context, the short-term objective of this work is to simulate (both optically and electronically) the first generation of nanowire solar cells fabricated in our labs, to contribute to the analysis of optoelectronic and luminescence characterizations, and to propose further improvements in the design of next-generation NW solar cells.

    This work will be done in close collaboration with the C2N, IPVF and EDF teams, in both C2N and IPVF buildings (close to each other on the Paris-Saclay campus in Palaiseau).

    poursuite en thèse envisageble

    fichier joint

    Stephane.Collin@c2n.upsaclay.fr - +33 1 7027 0630

  • ['Photonique']

    (en anglais) Hybrid III-V semiconductor on SOI optoelectronic devices


      Fabrice Raineri.

    (en anglais)

    Photonic devices play a crucial role in the domain of information and communication technology, due to their ability to bring efficient solutions to data transmission and processing.Tremendous development, through optical fibres backed by related devices and circuits composed of light sources, optical amplifiers, wavelength multiplexers, photodetectors, etc, have greatly revolutionized communication in general. As a necessary evolution, attention is now being directed to optical datacom and computercom with an emphasis on the conception of power efficient ultracompact optoelectronic components. In photonics, the challenges which we face today, swirls around providing together the necessary active and passive functionalities fully integrated into a chip. These functionalities are, among others, light emission and amplification, filtering, wavelength routing ((de)multiplexing), detection or switching. Because all of these functionalities have to comply with ultra-compactness and low-loss circuitry while maintaining low cost production in CMOS fabs, few materials can pretend to fit in. In this context, Silicon on insulator (SOI) photonics, enhanced by III-V semiconductors is a key technology combining the best of both materials leading to a highly versatile hybrid photonics platform which opens the way to large scale photonic integration. During the last years, in my research team, we have taken forward this domain to the nanophotonic world by demonstrating III-V on SOI active devices based on planar photonic crystals (PhCs) to address the issues of compactness and power efficiency. Indeed, planar PhCs which consist of wavelength scale arrangements of holes (typ. radius~100nm), drilled into a semiconductor thin slab enable a quasi-extensive control of the electromagnetic field confinement and propagation. They have demonstrated over the last decade their capacity to shelter extremely efficient nonlinear interactions exploitable for low threshold laser emission , all-optical switching , etc… The proposed project aims at building a new panel of hybrid III-V on SOI optical devices with performance beyond the state of the art in terms of footprint, power efficiency and speed, to meet the stringent requirements for on-chip optical interconnects. The targeted components will be electrically driven nanolaser, an optical amplifier and a memory.

    The student will be required to focus on the design, fabrication, and experimental aspects withcontinuous feedbacks “loops” between all these different aspects. This multi-task work is possible with the remarkable facilities and resources of C2N.

    The work can be pursued during a PhD thesis within the framework of the ERC project HYPNOTIC.


    fabrice.raineri@c2n.upsaclay.fr - 0170270461

  • ['Photonique']

    (en anglais) Analog computing with brain-inspired micropillar lasers


      Sylvain Barbay.

    (en anglais)

    Artificial neural networks, which are at the heart of recent progress in analog computation and machine learning, are becoming increasingly important for our future digital societies. We propose to study coupled spiking photonic nodes in order to implement simple photonic artificial neural networks. Each node is materialized by a micropillar laser with integrated saturable absorber, whose neuromimetic properties have already been explored in the team.

    In neurons, information is coded with spikes (electrical pulses) which are excited in an all-or-none fashion provided input stimuli to the neuron soma exceed a given threshold. This generic property is called excitability and has been demonstrated in micropillar lasers. Though, the optical spikes emitted by these latter are more than one millions times shorter in duration than biological action potentials. Hence, photonic neurons could in principle be interesting to build ultrafast artificial neural networks. The computing capability of optical neurons are enforced by the property of temporal summation also already demonstrated by us in micropillar lasers, and which provides universal computation capability.

    The internship will consist in participating to the research lead in the group on the implementation of brain-inspired, photonic analog computing. The work consists majorily of optical experiments, with modelling and technology in the C2N clean-room.

    References :

    Pulse train interaction and control in a microcavity laser with delayed optical feedback S. Terrien, B. Krauskopf, N. G. Broderick, R. Braive, G. Beaudoin, I. Sagnes, S. Barbay, Opt. Lett. 43, 3013 (2018)

    Spike latency and response properties of an excitable micropillar laser F. Selmi, R. Braive, G. Beaudoin, I. Sagnes, R. Kuszelewicz, T. Erneux, S. Barbay, Phys. Rev. E 94, 042219 (2016)

    Temporal summation in a neuromimetic micropillar laser F. Selmi, R. Braive, G. Beaudoin, I. Sagnes, R. Kuszelewicz, S. Barbay, Opt. Lett. 40, 5690 (2015)

    Relative Refractory Period in an Excitable Semiconductor Laser F. Selmi, R. Braive, G. Beaudoin, I. Sagnes, R. Kuszelewicz, S. Barbay, Phys. Rev. Lett. 112, 183902 (2014)

    F. Selmi, Thèse de doctorat, Réponse excitable et propriétés neuromimétiques de micropiliers lasers à absorbant saturable, 2015.

    website : https://toniq.c2n.universite-paris-saclay.fr/fr/activites/smila/neuromimetic-photonics/

    poursuite en thèse envisageble


    sylvain.barbay@c2n.upsaclay.fr - 0170270451

  • ['Photonique']

    (en anglais) Hybrid nanostructures for nonlinear parametric processes


      Fabrice Raineri.

    (en anglais)

    The control of light propagation at the nanoscale is one of the major subjects of present research. By enabling the confinement of the light in volumes as small as few cubic half-wavelength, photonic nanostructures allowed the demonstration of very interesting devices such as efficient single photon sources, low threshold nanolasers and low energy activation all optical gates.

    Since a few years, our team at LPN has been particularly interested in exploiting the enhancement of the light-matter interaction using photonic crystals in order to obtain large nonlinear effects with reduced powers. The nonlinear effects under study, such as Kerr effect or second harmonic generation, enable a range of possibilities such as the control of light by light, light amplification or the generation of new frequencies.

    In the proposed project, the candidate will focus her/his work on the study of second and third order nonlinear processes within semiconductor micro/nanostructures. The idea will be to use the unique dispersive properties of, e.g. photonic crystals, in order to obtain integrated parametric amplifier or frequency combs sources. As the use of only one type of material can be a limitation, heterogeneous integration of different materials will be implemented as a novel approach with the idea to exploit each class of material at its best.

    The candidate will be involved in the modelling and the simulation of the structures under investigation, in the nanofabrication of the samples and in the sophisticated optical experiments necessary to observe the nonlinear behaviours.

    The work can be pursued during a PhD thesis within the framework of the european Training Network H2020 - MOCCA.

     


    fabrice.raineri@c2n.upsaclay.fr - 0170270461

  • ['Photonique']

    Cristaux photoniques à gradient et dispositifs


      Eric Akmansoy.

    Cadre général

    D’une part, les cristaux photoniques à gradient permettent un réel contrôle de la propagation de la lumière par le profil de leur bandes photoniques[1]. De l’autre, l’optique à gradient d’indice (GRIN Optics) connaît un renouveau parce qu’elle offre de nouveaux degrés de liberté pour le « design» de dispositifs optiques [2]. Cependant, la fabrication du profil d’indice à gradient est difficile. Les nanotechnologies permettent de fabriquer facilement des cristaux photoniques, ce que nous considérerons en concevant des cristaux photoniques à gradient pour réaliser des dispositifs optiques à gradient d’indice. 

    Pour démontrer que les cristaux photoniques à gradient permettent de contrôler la propagation du champ électromagnétique, nous avons mis en en évidence expérimentalement un « mirage photonique» (cf. fig. 2)[1]. Nous concevons, simulons numériquement et caractérisons des cristaux photoniques à gradient pour des dispositifs à gradient d’indice (cf. fig. 1)[3, 4]). Par ex., nous avons conçu une lentille plate que nous avons caractérisée dans le domaine des micro-ondes [5]. Récemment, nous avons conçu et simulé une lentille de Luneburg [6] (cf. fig. 1). Pour concevoir ces dispositifs optiques, nous mettons en oeuvre une ingénierie des courbes iso-fréquences qui traduisent la relation de dispersion des cristaux photoniques. Notre but est de monter en fréquences vers le domaine optique. La démonstration expérimentale de tels composants est une fin en soi, car il y a un défi technologique à les fabriquer. Nous envisageons un grand nombre d’applications à ces cristaux photoniques à gradient pour la photonique intégrée, le laboratoire sur puce, la biophotonique, le pompage optique de matériaux organiques, etc. 

    Plan du stage

    Durant ce stage, des dispositifs à cristaux photoniques seront conçus et simulés numériquement. Ils fonctionneront dans différentes gammes de fréquences, de l’optique aux micro-ondes. Le but est de pouvoir les fabriquer et les caractériser par la suite. Ce stage pourra se poursuivre par une thèse.

    Bibliographie

    [1]    Éric Akmansoy, Emmanuel Centeno, Kevin Vynck, David Cassagne, and Jean-Michel Lourtioz, Graded photonic crystals curve the flow of light : An experimental demonstration by the mirage effect, Appl. Phys. Lett. 92, 133501 (2008) 

    [2]    Predrag Milojkovic, Stefanie Tompkins, Ravindra Athale, Gradient Index Optics, Optical Engineering, November 2013/Vol. 52(11), p. 112101-1 

    [3]    F. Gaufillet, É. Akmansoy, Graded photonic crystals for graded index lens, Optics Communications, Volume 285, 2638 (2012). 

    [4]    F. Gaufillet, É. Akmansoy, Design of flat graded index lenses using dielectric Graded Photonic Crystals, Optical Materials, Vol. 47, 555-560 (2015) 

    [5]    F. Gaufillet and E. Akmansoy. Design and experimental evidence of a flat graded-index photonic crystal lens. Journal of Applied Physics, 114(8) :083105, 2013. 

    [6]    F. Gaufillet and E. Akmansoy. Graded photonic crystals for Luneburg lens, IEEE Photonics Journal, vol. 8, 11 (2016) 

    [7]    CVI Melles Griot. Gradient-Index Lenses – http://pdf.directindustry.com/pdf/cvi-melles-griot/gradient-index-lenses/12567-66963.html. 

    [8]    Z. Han, X. Checoury, D. Néel, S. David, M. El Kurdi, P. Boucaud, Optimized design for ultra-high Q silicon photonic crystal cavities, Optics Communications 283 (21) (2010) 4387 – 4391.

    Bibliographie

    [1]    Éric Akmansoy, Emmanuel Centeno, Kevin Vynck, David Cassagne, and Jean-Michel Lourtioz, Graded photonic crystals curve the flow of light : An experimental demonstration by the mirage effect, Appl. Phys. Lett. 92, 133501 (2008) 

    [2]    Predrag Milojkovic, Stefanie Tompkins, Ravindra Athale, Gradient Index Optics, Optical Engineering, November 2013/Vol. 52(11), p. 112101-1 

    [3]    F. Gaufillet, É. Akmansoy, Graded photonic crystals for graded index lens, Optics Communications, Volume 285, 2638 (2012). 

    [4]    F. Gaufillet, É. Akmansoy, Design of flat graded index lenses using dielectric Graded Photonic Crystals, Optical Materials, Vol. 47, 555-560 (2015) 

    [5]    F. Gaufillet and E. Akmansoy. Design and experimental evidence of a flat graded-index photonic crystal lens. Journal of Applied Physics, 114(8) :083105, 2013. 

    [6]    F. Gaufillet and E. Akmansoy. Graded photonic crystals for Luneburg lens, IEEE Photonics Journal, vol. 8, 11 (2016) 

    [7]    CVI Melles Griot. Gradient-Index Lenses – http://pdf.directindustry.com/pdf/cvi-melles-griot/gradient-index-lenses/12567-66963.html. 

    [8]    Z. Han, X. Checoury, D. Néel, S. David, M. El Kurdi, P. Boucaud, Optimized design for ultra-high Q silicon photonic crystal cavities, Optics Communications 283 (21) (2010) 4387 – 4391.

    poursuite en thèse envisageble

    fichier joint

    eric.akmansoy@u-psud.fr - 01 69 15 41 43

  • ['Photonique']

    Métamatériaux « tout diélectrique» : indice nul et indice négatif


      Eric Akmansoy.

     

    Proposition de stage de master 2

    Métamatériaux « tout diélectrique» : 

     

    indice nul et indice négatif 

     Éric Akmansoy 

    Département Photonique

    Les métamatériaux ont ouvert un nouveau champ en physique et en ingénierie. En effet, ces matériaux artificiels structurés possèdent des propriétés électromagnétiques surprenantes, telles que l’indice de réfraction négatif ou nul. L’indice de réfraction négatif permet la la focalisation sub-longueur d’onde par la lentille parfaite, c-à-d, une lentille plate s’affranchissant du critère de Rayleigh. Un autre phénomène que permettent les métamatériaux est la cape d’invisiblité. Les métamatériaux se développent maintenant vers la mise en oeuvre de composants [1]. Les métamatériaux « tout diélectrique» sont prometteurs car ils subissent de faibles pertes et leur géométrie est simple [2]. 

    Nous concevons, fabriquons et caractérisons des métamatériaux « tout diélectrique» opérant des micro-ondes au térahertz. Ils fonctionnent à partir des résonances de Mie de résonateurs diélectriques à grande permittivité. Nous avons mis en évidence un indice de réfraction négatif à 10 GHz [3, 4]. Récemment, nous avons aussi conçu une « métalentille» i.e., une lentille plate à gradient d’indice fonctionnant au térahertz [5]. 

    Durant ce stage, le couplage entre les modes de résonance sera étudié de façon à mettre en évidence un indice de réfraction négatif et un indice de réfraction quasi-nul. Les métamatériaux « tout diélectrique» seront simulés numériquement au moyen d’un logiciel afin d’extraire les paramètres électromagnétiques et l’indice de réfraction (cf. figure 1). Ce travail pourra être poursuivi par une thèse. 

     

    Fig. 1: Couplage entre les deux modes de résonance d’un métamatériau « tout diélectrique»le domaine téraHertz. Les trois zones du couplage sont mises en évidence  ; la courbe a la forme d’un diapason  : couplage faible  : pas d’indice négatif  ; couplage optimal (zone en grisé)  : l’indice est négatif  ; couplage fort  : l’indice n’est plus défini et les modes sont dégénérés. 

     

    Références

    [1]    N. I. Zheludev and Y. S. Kivshar, “From metamaterials to metadevices,”  Nat Mater, vol. 11, pp. 917–924, 11 2012.

    [2]    S. Jahani and Z. Jacob, “All-dielectric metamaterials,” Nat Nano, vol. 11, pp. 23–36, 01 2016.

    [3]    T. Lepetit, E. Akmansoy, and J.-P. Ganne, “Experimental evidence of resonant effective permittivity in a dielectric metamaterial,” Journal of Applied Physics, vol. 109, no. 2, p. 023115, 2011.

    [4]    T. Lepetit, É. Akmansoy, and J.-P. Ganne, “Experimental measurement of negative index in an all-dielectric metamaterial,” Applied Physics Letters, vol. 95, no. 12, p. 121101, 2009.

    [5]    F. Gaufillet, S. Marcellin, and E. Akmansoy, “Dielectric metamaterial-based gradient index lens in the terahertz frequency range,” IEEE J Sel Top Quant, vol. 10. 1109/JSTQE. 2016. 2633825, 2017.

     

    poursuite en thèse envisageble

    fichier joint

    eric.akmansoy@u-psud.fr - 01 69 15 41 43

  • ['Photonique']

    (en anglais) Si photonic using direct band gap group IV elements


      Moustafa El Kurdi.

    (en anglais)

    The objective of the project is to explore the potential of merging direct band gap Ge-based material for developing new electro-optical application with group IV elements such as optical sources in the NIR and the MIR.

     

    poursuite en thèse envisageble

    fichier joint

    moustafa.el-kurdi@u-psud.fr - 0170270511

  • ['Photonique']

    (en anglais) Quantum nanolaser sources


      Alejandro Giacomotti.

    (en anglais)

    A PhD position is open at C2N (France). This project aims at realizing quantum photonic sources based on nonlinear interactions in optical nanocavities with few photons. Unlike conventional semiconductor quantum sources that require deterministic coupling of cavity modes to single nanoemitters (i.e. quantum dots) and operate at ultralow temperatures, this PhD thesis will focus on the realization of nanophotonic devices capable of achieving quantum correlations with few photons using material optical nonlinearities at room temperature, in coupled nanocavities. Such capabilities will rely on a few recent observations at C2N of highly nonlinear phenomena in laser nanocavities with moderate to low photon numbers [1,2]. Building blocks will be hybrid III-V semiconductor photonic crystal nanocavities and nanolasers, incorporating active materials such as InP-based quantum wells. The candidate will explore innovative technological developments that will ultimately enable room-temperature, single photon sources in the telecommunication C-band, with a high potential for integration. The PhD work will include design and modeling, clean room fabrication, and experimental characterization.

    The candidate should ideally have a strong background in physics, with particular emphasis on experimental skills. Previous experience in quantum optics and/or nanofabrication will be appreciated.

    The candidate may send a CV and/or request further information to:

    - Alejandro Giacomotti (C2N): alejandro.giacomotti@c2n.upsalcay.fr

    - Ariel Levenson: juan-ariel.levenson@c2n.upsaclay.fr

     

    [1] P. Hamel et al, Spontaneous mirror-symmetry breaking in coupled photonic-crystal nanolasers, Nat Photon. 9, 311 (2015).

    [2] M. Marconi, et al, Far-from-equilibrium route to superthermal light in bimodal nanolasers, Phys. Rev. X 8, 011013 (2018).

    poursuite en thèse envisageble

    fichier joint

    alejandro.giacomotti@c2n.upsaclay.fr - 0170270458

  • ['Photonique']

    (en anglais) Graded Photonic Crystals Devices for Graded Index Optics


      Eric Akmansoy.

    (en anglais)

      

    Centre de Nanosciences et nanotechnologies

    UMR 9001 du CNRS,

    université Paris-Sud, université Paris-Saclay

    91 405 Orsay – France

      

    PhD research proposal

    Graded Photonic Crystals Devices for Graded Index Optics

     Éric Akmansoy 

    Département Photonique

    __________________ 

     

    General framework

    On the one hand, Graded Photonic Crystals (GPC) allow to efficiently control the flow of light thanks to the shape of their photonic bands, which we verified by demonstrating a “photonic mirage” at wavelength scale[1]. In the other hand, GRaded INdex (GRIN) optics is undergoing a renewal because it allows to downsize optical systems, opening a new way to optical design[2]. But GRIN optics was limited by a lack of easy to implement fabrication techniques. Nanotechnology enables to efficiently fabricate photonic crystals, which we will implement to fabricate GPC for GRIN optics. 

    We are designing, numerically simulating and characterising GPC devices (see fig.1)[3, 4]. More specifically, we have conceived a GRIN flat lens which we have characterised in the microwave[5]. Recently, we have designed and simulated a Luneburg lens[6] (see fig.1). We conceive thin and thick flat GRIN lenses[7]. For the sake, we engineer the equi-frequency curves which convey the dispersion properties of photonic crystals. Our aim is to go further up to the optical domain. The experimental evidence of such devices is an end in itself because it is a technological challenge to fabricate such GPC. Nevertheless, we will investigate the great variety of applications of GPC flat lens, which concerns Photonic Integrated Circuits, Lab on Chip, optical pumping of organic materials, OLED, biophotonics, fluorescence of cells, etc.

    PhD work plan

    GPC devices will be designed, fabricated and characterised at the Centre de Nanosciences et Nanotechnologies (C2N). This work will concern numerical simulation and optical design, nanotechnological processes and optical characterisation. These devices will operate at telecommunication wavelengths (1,55 μm). The Silicium On Insulator (SOI) channel of the C2N will be involved, because “state of the art" photonic crystal -based devices have already been fabricated in its clean-room [8]. These devices require the technological mastery of the position, of the size and of the shape of the patterns, which is adapted for the realisation of GPC devices. The size of the patterns of these latter is of several tens of nanometers, which will be challenging. The devices will be also characterised at the C2N. GPC devices operating in the near infrared (NIR) spectrum will also investigated (from 1 to 20μm) because, in this domain, lies a lot of molecular signatures, which is fruitful for NIR spectroscopy, chemical sensing, polluant detection, etc. 

          

     

    Fig. 1: Right : Focusing by a GPC GRIN flat lens[3] ; left : focusing by a Luneburg lens[6] 

    Bibliography

    [1]    Éric Akmansoy, Emmanuel Centeno, Kevin Vynck, David Cassagne, and Jean-Michel Lourtioz, Appl. Phys. Lett. 92, 133501 (2008) 

    [2]    Predrag Milojkovic, Stefanie Tompkins, Ravindra Athale, Gradient Index Optics, Optical Engineering, November 2013/Vol. 52(11), p. 112101-1 

    [3]    F. Gaufillet, É. Akmansoy, Graded photonic crystals for graded index lens, Optics Communications, Volume 285, 2638 (2012). 

    [4]    F. Gaufillet, É. Akmansoy, Design of flat graded index lenses using dielectric Graded Photonic Crystals, Optical Materials, Vol. 47, 555-560 (2015) 

    [5]    F. Gaufillet and E. Akmansoy. Design and experimental evidence of a flat graded-index photonic crystal lens. Journal of Applied Physics, 114(8) :083105, 2013. 

    [6]    F. Gaufillet and E. Akmansoy. Graded photonic crystals for Luneburg lens, IEEE Photonics Journal, vol. 8, 11 (2016) 

    [7]    CVI Melles Griot. Gradient-Index Lenses – http://pdf.directindustry.com/pdf/cvi-melles-griot/gradient-index-lenses/12567-66963.html. 

    [8]    Z. Han, X. Checoury, D. Néel, S. David, M. El Kurdi, P. Boucaud, Optimized design for ultra-high Q silicon photonic crystal cavities, Optics Communications 283 (21) (2010) 4387 – 4391.

    fichier joint

    eric.akmansoy@u-psud.fr - 33-1-6915 4143

  • ['Photonique']

    (en anglais) All-Dielectric Metamaterials for Terahertz metadevices


      Eric Akmansoy.

    (en anglais)

    Centre de Nanosciences et nanotechnologies

     UMR 9001 du CNRS,

    université Paris-Sud, université Paris-Saclay

    91 405 Orsay – France

      

    PhD research proposal

    All-Dielectric Metamaterials for Terahertz metadevices

     Éric Akmansoy 

    Département Photonique

    __________________ 

     

    General framework

    Metamaterials have opened a new field in physics and engineering. Indeed, these artificial structured materials give rise to unnatural fascinating phenomena such as negative index, sub-wavelength focusing and cloaking. Metamaterials also exhibit near-zero refractive index [1]. These open a broad range of applications, from the microwave to the optical frequency domain. Metamaterials have now evolved towards the implementation of optical components[2]. 

    We consider All-Dielectric Metamaterials which are the promising alternative to metallic metamaterials, because they do not suffer from ohmic losses and consequently benefit of low energy dissipation and because they are of simple geometry. They consist of high permittivity dielectric resonators involving Mie resonances. We have experimentally demonstrated negative effective permeability and/or permittivity by the means of all-dielectric metamaterials [3]. Previously, we have also demonstrated a negative index all-dielectric metamaterial [4]. Recently, we have numerically demonstrated a metadevice, namely, a metalens that focuses an incident plane wave, is less than one and a half wavelength thick. Its focal length is only a few wavelength and the spot in the focal plane is diffraction - limited.[5]. We also study role of the coupling of the modes of Mie resonances in an all-dielectric metamaterial so as to achieve negative index at terahertz frequencies (see fig. 1)[6].

    Work Plan

    During this thesis, all dielectric metamaterials will be designed, fabricated and characterized for the terahertz range. Negative index will be studied in this frequency domain, which is a challenge. Various devices which will be investigated such as flat lens, gradient devices, etc. This work takes place within a group of scientists of different disciplines (chemists, material scientists, physicists). 

     

     

    Fig. 1: Spatial mode coupling : frequency of the first two modes of Mie resonances in function of the distance  between two resonators which is half the lattice period . The shaded area corresponds to negative value of the effective index . It evidences the mode degeneracy [6].

    Bibliography

    [1]    I. Liberal and N. Engheta, “Near-zero refractive index photonics,”  Nature Photonics, vol. 11, pp. 149 EP –, 03 2017.

    [2]    N. I. Zheludev and Y. S. Kivshar, “From metamaterials to metadevices,”  Nat Mater, vol. 11, pp. 917–924, 11 2012.

    [3]    T. Lepetit, E. Akmansoy, and J.-P. Ganne, “Experimental evidence of resonant effective permittivity in a dielectric metamaterial,” Journal of Applied Physics, vol. 109, no. 2, p. 023115, 2011.

    [4]    T. Lepetit, É. Akmansoy, and J.-P. Ganne, “Experimental measurement of negative index in an all-dielectric metamaterial,” Applied Physics Letters, vol. 95, no. 12, p. 121101 (, 2009.

    [5]    F. Gaufillet, S. Marcellin, and E. Akmansoy, “Dielectric metamaterial-based gradient index lens in the terahertz frequency range,” IEEE J Sel Top Quant, vol. 10. 1109/JSTQE. 2016. 2633825, 2017.

    [6]    S. Marcellin and É. Akmansoy, “Negative index and mode coupling in all-dielectric metamaterials at terahertz frequencies,” in 2015 9th International Congress on Advanced Electromagnetic Materials in Microwaves and Optics (Metamaterials), pp. 4–6, Sept 2015.

    fichier joint

    eric.akmansoy@u-psud.fr - 33-1-6915 4143

  • ['Photonique']

    (en anglais) Direct band gap Ge-based laser sources for silicon photonics


      Moustafa El Kurdi.

    (en anglais)

    The objective of the project is to develop direct band gap group IV laser sources operating at room temperature. This goal will rely on recent innovation and merging technologies allowing to reach direct band gap in Ge-based material.

    fichier joint

    moustafa.el-kurdi@u-psud.fr - 0170270511

  • ['Microsyst']

    Poste d'ingénieur CDD pour le développement d'une instrumentation spécifique pour la quantification et le dosage de petites séquences d’ADN en puce microfluidique


      Jean Gamby.

    Résumé:

    Le but du projet est l’optimisation d'une nouvelle méthode brevetée pour la capture et la

    détection de petites séquences d'ADN en puce microfluidique. Ce concept est très prometteur

    pour son application au diagnostic précoce du cancer. Le projet, cofinancé par le Labex

    Nanosaclay et le CNRS, vise à atteindre la miniaturisation du montage expérimental et le

    développement de nouvelles géométries de dispositifs microfluidiques pour la quantification et

    le dosage direct de brins d’ADN.

    Compétences souhaitées:

    i) Microfabrication de dispositifs microfluidiques en salles blanches

    ii) Modélisation par éléments finis (comsol) des électro-aimants (AC / DC)

    iii) Instrumentation électronique

    Profil: Ce projet fait appel à des compétences interdisciplinaires dans les domaines de la

    micro nanotechnologie, de l'excitation magnétique et de l'électrochimie. Le candidat doit avoir

    un intérêt marqué pour la micro nanotechnologie salles blanches (compétences attendues

    mais non obligatoires) et avoir une formation en génie électrique, et/ ou instrumentation.

    Lieux : C2N-CNRS, Equipe Biosys, Palaiseau, France.

    PHENIX-CNRS, Equipe Colloïdes Inorganiques, Paris, France.

    Informations supplémentaires: 1 an de CDD Ingénieur à partir de septembre 2018 avec

    une extension possible.

    Contact C2N: jean.gamby@c2n.upsaclay.fr

    Webpage : https://www.c2n.universite-paris-saclay.fr/fr/

    Contacts PHENIX: vincent.dupuis@sorbonne-universite.fr and jean-michel.siaugue@sorbonneuniversite.

    fr

    Webpage : http://www.phenix.cnrs.fr/

    fichier joint

    jean.gamby@c2n.upsaclay.fr - 01 69 63 60 60

  • ['Photonique']

    (en anglais) Non-linear dynamics of nano-optomechanical resonators


      Rémy Braive.

    (en anglais)

    Nonlinear dynamics in optomechanical resonator can cause both the optical and the mechanical modes to evolve from periodic to chaotic oscillations. Despite recent progress and growing interest on nonlinear dynamical effects occurring in Nano-OptoElectroMechanical systems (NOEMs), optomechanical chaos and stochastic resonance remain largely unexplored experimentally in such research field. Further experimental and theoretical studies will not only substantially deepen our understanding of noise-induced processes in non-linear NOEMs but also cast the bases for their use in noise-aided high-precision measurements and noise-assisted detection of weak signals.

    fichier joint

    remy.braive@c2n.upsaclay.fr - 01 69 63 60 49

  • ['Photonique']

    (en anglais) Nano-optomechanics for time-frequency metrology and microwave photonics


      Rémy Braive.

    (en anglais)

    The photonic clock architecture will rely on an integrated high-quality optomechanical resonator, namely a photonic crystal defect cavity, in order to achieve very stable oscillation in the GHz range, where the lack of good quality and miniaturized sources is a severe issue. Thanks to the strong reduction of the oscillator dimensions down to nanoscale, the resonator will sustain mechanical modes strongly coupled to light up to 3-5 GHz, directly at the operating frequency of interest for optoelectronic microwave oscillators and metrology applications.

    fichier joint

    remy.braive@c2n.upsaclay.fr - 01 69 63 60 49