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Our team consists of physicists and chemists skilled in optics, spectroscopy, crystal growth and material science aiming at understanding and optimizing the optical properties from the experimental and theoretical point of view.
The main research outcomes are nonlinear frequency conversion, generation of new quantum states, bio-imaging, lighting, applications as photodetectors and photocells.
Our strength is to master the whole chain of competence from the development of new materials, their characterizations and theoretical studies, to the optimization of optical properties.
We elaborate from solution chemistry a wide variety of materials from nm to the cm scale, highly crystalline or amorphous, inorganic, organic or hybrid for non linear frequency conversion, lighting, bio-sensing and bio-imaging, or photodetectors and photocells.
Thanks to our strong competence in laser and non linear optics, we evaluate single crystals for optical frequency synthesis, and we work at the generation of new quantum states of light. We also develop new spectroscopic tools.
Associated staff: Julien Zaccaro, Alexandra Peña Revellez and Alain Ibanez
Current PhD student: Vijaya Shanthi Paul Raj and Javier Mayen
The fine control of nucleation and growth mechanisms in solution close to room temperature and at high temperature, often involving original homemade reactors, constitutes a very strong activity of OPTIMA.
It enabled the preparation of high-quality crystals for demanding applications and fundamental research as in the case of NaI3O8 NLO crystals (see OPTIMA research axis Nonlinear optics for frequency conversion). Concerning bulk crystals, we transferred our patented process to CEA-Le Ripault, optimizing the rapid growth (1 cm per day) of deuterated KDP 20x20x10 cm3 crystals with ultimate optical homogeneity. Centimetric CsCuCl3 homochiral crystals (free from domains of the wrong handedness) are grown for studying new properties such as multiferroism under a high magnetic field, magnetic chiral dichroism and thermal Hall effect (Hiroshima, Osaka & Tokyo Univ.). We recently started the growth of hybrid perovskite single crystals [1] and polycrystalline thick films (MAPbBr3) for direct X-ray detection and associated radiography applications (CEA-LITEN & LETI, TRIXELL Company) supported by two E.C Grants [2].
The high temperature solution or flux method is a versatile crystal growth technique used to grow high quality bulk crystals that cannot be grown from melt.
In OPTIMA team, as well as in the technical group Bulk Crystal Growth, we are specialist in this growth method and we work in improving conditions or developing original approaches to obtain epitaxial layers or bulk nonlinear optical crystals, such as KTiOPO4 and RbTiOPO4, and bulk piezoelectric crystals, α-GeO2 [3, 4, 5]. The projects concerning nonlinear crystals is developed in collaboration with KTH in Sweden and the one concerning piezoelectric crystals with ICGM in Montpellier.
Our constant effort to control and understand nucleation and growth mechanisms to ensure optimal crystal quality and adequate morphology, of the crystals grown by solution and flux methods, is being increased nowadays.
For bulk crystals, in situ studies of growing interfaces by interferential microscopy (SIMaP) and the implementation of a numerical model to predict crystal shapes by Phase Field Modeling (LPMC) is being developed. This will improve our understanding of growth processes and defect formation, decreasing the time needed to optimize growth conditions (solvent, morphology, solution structure, hydrodynamics) that will be specified for homochiral crystals: α-GeO2, LiFe5O8, CsCuCl3 (Univ. Hiroshima & Tokyo).
Associated staff : Xavier Cattoën, Geraldine Dantelle, Fabien Dubois, Alain Ibanez
Post-docs: Ricardo Alvarado Meza
Current PhD students: Italia Vallerini-Barbosa; Andrea Montero-Oleas
Former Phd students: Shridevi Shenoi-Perdoor (2015-2018), Sylvain Regny (2016-2019), Alexandra Cantarano (2017-2020)
Our group is specialized in the synthesis of colloids of luminescent nanomaterials to be used for bio-imaging. These nanoparticles are made of organic, inorganic or organic-inorganic hybrid materials and their composites. In particular, we target the use of infrared light for both emission and excitation, to realize conventional imaging or nanothermometry.
Recent highlights include:
We developed microwave-assisted hydrothermal synthesis [1, 2, 3] of different lanthanum iodate polymorphs. This synthesis method helps promoting rapid nanocrystallisation and allows nanoparticle size control. We focus on non-centrosymmetric Yb3+,Er3+-codoped α-La(IO3)3 nanocrystals which present both Second Harmonic and up-conversion photoluminescence signals when excited with a single beam in the near-infrared range. It opens the door to multi-modal detection techniques: classical routinely-available fluorescence imaging and non-linear microscopy for in-depth analysis. Moreover, photoluminescence intensity ratio based on the two emission lines at 525 and 545 nm depends on temperature, which can be used for monitoring local temperature with a thermal sensitivity of 1.2 %.K-1. This project is in collaboration with Laboratoire SYMME, Annecy.
Left: TEM image of α-La(IO3)3 nanocrystals. Right: Emission spectra of Yb3+,Er3+-doped α-La(IO3)3 nanocrystal dispersions in ethylene glycol under a 800-nm excitation (red curve) and a 980-nm excitation (dark red curve). For sake of clarity, the spectra have been stacked. The arrows point out the SHS signals, whereas the up-conversion emission is evidenced at 525, 550, and 660 nm.
YAG:Nd3+ nanocrystals of controlled size have been developed [4, 5] by a modified solvothermal method, consisting in coupling high temperature (400°C) and high pressure (200 – 400 bars) to control nanocrystallisation procees. After functionalization by block copolymers, the nanocrystals are stabilized in physiological medium and can used for in vivo imaging. The high crystal quality of the nanocrystals leads to narrow emission lines from Nd3+ ions, which can be isolated from the autofluorescence of a mouse tissue, allowing in vivo imaging (Coll. Univ. Autonoma de Madrid, Prof. Jaque). Additionally, by monitoring two distinct emission lines of Nd3+ in the NIR, local temperature can be determined with a relative thermal sensitivity of 0.2%.K-1.
Left: TEM image of YAG and associated Fourier Transform pattern, showing the single crystal character of the nanoparticle. Right: Emission spectrum of YAG:Nd3+ nanoparticles (max. emission, λ2) and of whole body autofluorescence of a mouse (max. emission, λ1), Exc. 808 nm. Photography of an In vivo differential (λ2 − λ1) fluorescence of the mouse
We developed an original spray-drying pathway [6, 7] for the one-pot preparation of organic nanocrystals embedded in a hybrid silica matrix. These nanoparticles can be functionalized by PEG chains to form stable fluorescent colloids. Using tailor-made dyes prepared at the Laboratoire de Chimie (ENS Lyon), we could realize the two-photon imaging of the brain vasculature of mice (Collaboration INMG Lyon).
Left: SEM micrograph of organic nanocrystals obtained after dissolution of the organosilica shell. Right: Two-photon fluorescence In vivo Imaging of the brain vasculature of a mice expressing GFP in the microglia (green cells) using silica-coated organic nanoparticles (red)
[1] Regny et al. Inorganic Chemistry 58(2) (2019) 1647-1654
[2] Regny et al. Crystal Engineering Communications 22 (2020) 2517-2525
[3] Dantelle et al. Nanomaterials 11 (2021) 479
[4] Dantelle et al. Physical Chemistry Chemical Physics 21 (2019) 11132-11141
[5] Cantarano et al. ACS Applied Materials & Interfaces 12(46) (2020) 51273-51284
[6] S Shenoi-Perdoor et al, New J. Chem., 2018, 42, pp.15353-15360.
[7] S Shenoi Perdoor et al, ACS Applied Nano Mater, 2020, 3, pp. 11933-11944.
Associated staff: Véronique Boutou and Benoît Boulanger
Former PhD student: Augustin Vernay (2017-2021)
Triple photon generation (TPG: 3ω → ω + ω + ω) based on a third-order nonlinear optical interaction is the most direct way to produce pure quantum three-photon states. They can exhibit three-body quantum entanglement and their statistics go beyond the usual Gaussian statistics of twin- photons, offering new tools for quantum mechanics. This research field is a real challenge in both nonlinear and quantum optics, opening the door to the production of heralded two-photon entanglement: a revolution in quantum information. Our pioneer works of 2004 [1] on the first experimental demonstrations of pure TPG has inspired several groups of quantum optics over the world. We have developed classical as well quantum models for TPG [2], [3].
More recently in collaboration with Kamel Bencheikh and Ariel Levenson in C2N Paris-Saclay, we have shown theoretically that a robust and genuine triple-photon entanglement is expected in the Continuous-Variable description when TPG is seeded [4].
Our pioneer triple photon generator [1] is based on a double-seeded TPG phase-matched in a bulk KTP crystal. We also considered other nonlinear media with the goal of increasing the TPG efficiency so that a spontaneous optical parametric process could be achieved. We studied step index optical fibers and showed that the modal overlap would not be good enough to provide the generation of a triplet source usable for quantum optics [5]. Then we proposed to explore the feasibility of a new technology taking advantage of both birefringence of crystals and confinement of waveguides. The idea is to use a ridge waveguide where the direction of propagation is along a birefringence phase-matching direction of a nonlinear crystal [6]. Then the phase-matched pump and triplet waves can exhibit the same spatial modes so that the overlap will be optimal in the medium. This is at the heart of the ANR/FNS PRCI France-Switzerland project 2018-2023 that we coordinate: TRIQUI (Triple photons for quantum information) involving NÉEL in Grenoble, FEMTO-ST in Besançon (Mathieu Chauvet and Florent Bassignot), C2N in Paris-Saclay (Kamel Bencheikh and Ariel Levenson), and GAP in Geneva (Hugo Zbinden and Félix Bussières).
We also consider an alternative and new scheme using a cascade of two second-order nonlinear processes in the same nonlinear medium: 3ω → ω + 2ω and 2ω → ω + ω. It may also lead to three correlated photons at ω, but it requires to simultaneously phase-match the two steps in a specific poling configuration of KTP. We started a fruitful collaboration with Ady Arie that developed this new technology at Tel Aviv University.
The occurrence of triplets will be certified using a protocol of coincidence requiring at least three detectors. We are using superconducting nanowire single photon detectors (SNSPD) from GAP and ID Quantique.
Associated staff: Patricia Segonds, Alexandra Peña Revellez and Benoît Boulanger
Current PhD students: Baptiste Bruneteau, Théodore Remark
There are many applications through this research axes such as: Terahertz, phase matching and cylindrical optical parametric oscillators.
We study the potentiality of new nonlinear crystals for the generation of parametric light in the infrared and Terahertz ranges, from phase-matched second-order processes. The full characterization of their optical properties is performed in a unique platform using a crystal shaped as a sphere or a cylinder that is polished to optical quality. Euler or Kappa circles allow the studied sample to be rotated on itself while it is pumped by a parametric source tunable between 0.4 μm and 12 μm. It is then possible to access directly to the angular distribution of the phase-matching directions, and the associated frequency conversion efficiencies or the angular and spectral acceptances over the whole transparency domain, from ultraviolet to TeraHertz ranges [1]. That can be done for Sum-Frequency Generation (SFG), including Second-Harmonic Generation (SHG), as well as for Difference-Frequency Generation (DFG). We studied numerous nonlinear crystals, as KTP, KTA, RTP, RTA, YCOB, GdCOB, LGT, LGN, CSP, CdSe, BGSe and GeO2 [2], thanks to many collaborations with leader groups in crystal growth over the world as for example BAE Systems, Shandong & Tianjin Universities, Kuban State University, Riken, Chimie ParisTech.
The interpolation and analysis of all these measurements lead to the determination of accurate Sellmeier equations, as well as to the magnitudes and relative signs of the second-order nonlinear tensor coefficients, over the full transparency range of the crystal. This corpus of data allows us to perform calculations of optimized frequency conversion parametric processes for the generation of tunable beams or supercontinua for example. In the case of Terahertz generation, we complete our phase-matching measurements with studies of Time-Domain Spectroscopy in collaboration with IMEP-LAHC in Chambéry [3].
Quasi-Phase Matching (QPM) is usually achieved in periodically poled (PP) ferroelectric crystals, i.e. exhibiting a periodic modulation of the sign of the second-order nonlinear coefficient. The improvement of the poling process led to large-aperture periodically poled crystals like PP-LiNbO3 and PP-KTiOPO4. These large crystals give the possibility to perform frequency conversion with interacting waves propagating at any angle to the grating vector. We called Angular Quasi Phase Matching (AQPM) this generalization of QPM.
We experimentally validated AQPM by the study of a 5%MgO doped PP-LiNbO3 crystal (uniaxial optical class) in collaboration with IMS in Japan, and of a Rb doped PP-KTiOPO4 crystal (biaxial optical class) in collaboration with KTH in Sweden [4]. We showed that AQPM can provide an enlargement of the phase-matching range as well as giant spectral acceptances.
We built several homemade Cylindrical Optical Parametric Oscillators (Cyl-OPOs) pumped by a commercial nanosecond pulsed Nd:YAG laser. They are based on a rotating nonlinear crystal shaped as a cylinder or a partial cylinder providing a continuous and wide wavelength tunability. They were implemented in the case of birefringence phase-matching with KTP, as well as AQPM with PP-KTiOPO4 and PP-LiNbO3. We also built a Dual-OPO based on two identical Cyl-OPOs pumped by the same Nd:YAG laser [5]. The two emitted beams are independently tunable between 1.4 µm and 4.4 µm, and their tunability can be extended down to 0.7 µm thanks to SHG stages.
We are also working at developing new OPO’s architectures in the picosecond regime with the company TEEM PHOTONICS in Meylan in France. The goal is to get a continuous tunability between 0.4 µm and 0.9 µm. Their packaging must be compact, and their reliability compatible with the targeted applications, mostly in medicine.
Associated staff: Alain Ibanez, Isabelle Gautier-Luneau, Geraldine Dantelle and Mathieu Salaün
PhD students: Jeremy Cathalan
Former PhD students: Vinicius Guimaraes (2009-2012), Pauline Burner (2014-2017), Alexandra Cantarano (2017-2020), Pierre Gaffuri (2017-2021)
Devices based on light emitting diodes (LEDs) are a major disruptive technology saving more than 50 % of energy consumption due to lighting with respect to conventional lighting. Today, commercialy available white LEDs (wLEDs) combine blue semi-conductors with yellow micron-sized Ce3+-doped Y3Al5O12 (YAG:Ce) phosphors to produce white light. However, these wLEDs present some limitations (light losses by re-absorption due to the micron size of phosphors, “cold white” emission, use of costly lanthanide elements) that we aim at overcome in our team through the research of new phosphors.
Optimas strategies to adress the new lighting challenges
We develop: (1) Yellow phosphors at the nanoscale in order to control light propagation inside wLED devices, thus limiting light losses, and to get a better coupling with nanostructured blue diodes. (2) Lanthanide-free emitters, presenting broad emission over the whole visible spectrum, allowing, when coupled to a near-UV diode, to give a “warm white” emission without any expensive chemical elements.
The challenge of this research, funded through the NanophosforLED ANR project, is to produce YAG:Ce nanoparticles with a controlled size (in the 50 to 100 nm range), a high crystal quality and optical properties as good as their micron-sized equivalents, in terms of photostability and internal quantum yield (iQY). A modified solvothermal route, coupling high pressure (up to 500 bars) and high temperature (up to 400 °C) conditions was developed. We showed that the chemical (nature of the solvent, of the precursors, water content, etc) and physical (temperature, pressure, synthesis duration, etc) conditions strongly influence the nanoparticle morphology and size. TEM observations and in situ photoluminescence allow for the determination of the best experimental conditions to control the nucleation and growth mechanisms. As a result, YAG:Ce nanoparticles can be produced with a controlled size between 30 nm and 200 nm, with a narrow size dispersity (± 10 %).[1]
X-Ray Absorption spectroscopy performed on the Fame-UHD beamline on the ESRF Synchrotron to determine the Ce3+/Ce4+ ratio in YAG:Ce nanophosphors. Inset: TEM image of YAG:Ce nanoparticles.
In situ X-Ray absorption experiments, performed during YAG formation on the Fame-UHD beamline (ESRF Synchrotron), enable us to follow, for the first time, Ce3+ oxidation into photoluminescent-silent Ce4+ upon reaction. We demonstrate that there is a trade-off between the high crystal quality, requiring high synthesis temperature and the preservation of cerium ions in their 3+ oxidation state, requiring a lower synthesis temperature.[1] Our best results lie in the synthesis of 80-nm sized YAG:Ce nanoparticles presenting with a iQY of 60 %, about twice higher to that of YAG:Ce nanoparticles already reported in the literature. No additional thermal treatment is required, allowing for a high dispersibitity of the particles in ethanol. This is a strong asset for further controlled particle shaping as thin films or nanoceramics to be coupled with blue diodes or directly dispersed on nanostructured ones.
We have worked on a new type of phosphors based on amorphous yttrium aluminum borate (YAB) powders, constituted of non-toxic and abundant elements without lanthanide. These powders are prepared from wet chemical routes using the Pechinni or sol-gel methods.
Descriptive scheme of the obtention of YAB powders by the modified Pechini method
The innovation of these phosphors is their broad and intense PL emission in the whole visible range (400-800 nm) when excited by a near UV-LED. Syntheses optimizations (organic and metal precursors, metal/ligand ratio, reflux time…) and thermal treatments (temperature, heating rate, atmosphere…) have been realized to enhance the PL properties and to better understand the role of the different parameters in the PL broadening. The best powders emit warm white light with a correlated color temperature adjustable between 2800K and 5300K, a very good color rendering (90-93) with an iQY of around 50%.
Correlation between photoluminescence evolution and apparition of polycyclic carbonic species (EPR, NMR). Hypothetic scheme of the structure is presented on the right.
We have successfully specified the nature of emitting centers and understood the photoluminescence mechanisms, thanks to complementary spectroscopic studies, structural and thermal analyses, PL spectroscopy including time-resolved and thermo-luminescence; involving the complementary skills of the different LUMINOPHORLED ANR project partners. Furthermore, we have understood the indirect role of yttrium atom in PL luminescence properties in YAB and similar materials, allowing now the yttrium atom substitution by other abundant metal elements.
White emission from YAB powder in a transparent matrix.
This is the first time to our knowledge that PL of lanthanide-free phosphors is clearly attributed to organic molecules (small polyaromatic hydrocarbons formed during the thermal treatments) confined and stabilized in an inorganic matrix.
We believe that this result is of the highest importance to understand the photoluminescence mechanisms of this emerging kind of white phosphors, to rationalize their design and to improve their performances for future lighting applications.[2],[3]
[1] G. Dantelle et al. RSC Advances 8 (2018) 26857-26870
[2] V. F. Guimaraes et al. J. Mater. Chem. C. 2015, 3, 5795.
[3] P.Burner, et al., Angew. Chem. Int. Ed., 2017, 56, 13995.
The tools and methods developed and used for the OPTIMA team are related to the growth/synthesis/study of new materials for:
In OPTIMA team we grow or synthesize inorganic, organic and hybrid compounds in the form of:
rt from “X’press“.Techniques such as X-ray diffraction & Topography, dynamic light scattering, fluorescence and Raman correlations spectroscopies, Electron microscopies (TEM, SEM), Atomic Force Microscopy (AFM), thermal analyses (DSC, DTA-TGA-MS) are indispensable to characterize the obtained materials. All of these techniques are available at Institut Néel.
In the OPTIMA team we have several commercial laser sources CW (@532 nm and @800 nm) or with pulses duration ranging from nanosecond to femtosecond. These sources are tunable from visible to mid-infrared. For the femtosecond laser, a APE autocorrelator is available in order to get the pulse duration in the near and mid infrared range.
A large panel of detectors is used for parametric generation detection : silicium photodiodes, joulemeters and PMT, APD InGas in the visible and the near IR range, an Helium cooled Bolometer for Terahertz generation. For specific pair or triplet generation experiments, we also have photon counting facilities in the IR : SNSPD nanowires installed in a Helium cooled cryostat and a time controler electronics for coincidence measurements.
A platform based on gonometric methods (kappa and Euler circles) is available to measure the angular distribution of linear and nonlinear optical properties of new crystals (shaped as sphere or cylinders) for infra-red. This technique is really powerful for the direct determination of phase-matching angles of any uniaxial and biaxial crystals. The use of this technique allows us to experimentally prove new phase-matching configurations such as Angular Quasi Phase Matching (see Nonlinear optics for frequency conversion). This activity is done with support and collaboration of the technical groups “Cristaux Massifs” and “Optique & Microscopie”.
Since 2016, in order to generate and study new quantum states of light such as Triple Photons (see New quantum state of light), we explore the use of optical ridge waveguides diced from bulk in a KTP crystal. The goal is to take benefit of the confinement in such waveguides to increase the efficiency of third order driven processes. Special care has to be bring to the optomechanical setup in order to:
This activity is done with support and collaboration of the technical group “Optique & Microscopie”.
Position type: Master 2 internships and theses
Contact: Boulanger Benoît - | Boutou Véronique -
This position concerns Triple Photons Generation (TPG). It is based on a third order nonlinear optical interaction is the most direct way to produce pure quantum states of light, called three-photons states. These states exhibit three-body quantum entanglement and their statistics go beyond the usual Gaussian statistics relevant to coherent sources and optical parametric twin-photon generators, offering thus outstanding potential applications in the field of quantum information. Undoubtedly, three-photons states are new quantum tools to study the non-intuitive properties of quantum mechanics
Person in charge: Véronique BOUTOU
Permanents
Students & Post-docs & CDD
Aude BARBARA
Personnel Chercheur - CNRS
Aude.Barbara [at] neel.cnrs.fr
Phone: 04 76 88 10 85
Office: D-311
Benoit BOULANGER
Personnel Chercheur - UGA
benoit.boulanger [at] neel.cnrs.fr
Phone: 04 76 88 78 07
Office: F-414
Véronique BOUTOU
Personnel Chercheur - CNRS
veronique.boutou [at] neel.cnrs.fr
Phone: 04 76 88 74 10
Office: F-306
Xavier CATTOEN
Personnel Chercheur - CNRS
xavier.cattoen [at] neel.cnrs.fr
Phone: 04 76 88 10 42
Office: F-211
Fabien DUBOIS
Personnel Chercheur - UGA
fabien.dubois [at] neel.cnrs.fr
Phone: 04 76 88 74 10
Office: F-306
Isabelle GAUTIER-LUNEAU
Personnel Chercheur - UGA
Isabelle.Gautier-Luneau [at] neel.cnrs.fr
Phone: 04 76 88 78 04
Office: F-308
Alain IBANEZ
Personnel Chercheur - CNRS
Alain.Ibanez [at] neel.cnrs.fr
Didier MAYOU
Personnel Chercheur - CNRS
Didier.Mayou [at] neel.cnrs.fr
Phone: 04 76 88 74 66
Office: M-109
Alexandra PENA
Personnel Chercheur - CNRS
alexandra.pena [at] neel.cnrs.fr
Phone: 04 76 88 79 41
Office: F-420
Pascal QUEMERAIS
Personnel Chercheur - CNRS
pascal.quemerais [at] neel.cnrs.fr
Phone: 04 76 88 10 82
Office: M-210
Mathieu SALAUN
Personnel Chercheur - UGA
mathieu.salaun [at] neel.cnrs.fr
Phone: 04 76 88 90 16
Office: F-409
Patricia SEGONDS
Personnel Chercheur - UGA
patricia.segonds [at] neel.cnrs.fr
Phone: 04 76 88 78 07
Office: F-414
Julien ZACCARO
Personnel Chercheur - CNRS
Julien.Zaccaro [at] neel.cnrs.fr
Phone: 04 76 88 78 04
Office: F-308
Sireen AL-KHAWAND
Personnel Chercheur - UGA
sireen.al-khawand [at] neel.cnrs.fr
Phone: 04 76 88 11 40
Office: F-209
Referent: Xavier CATTOEN
Julien BERTRAND
Personnel Chercheur - UGA
julien.bertrand [at] neel.cnrs.fr
Phone: 04 56 38 70 52
Office: F-401
Referent: Benoit BOULANGER
Clara Lana BISPO FIDELIS
Personnel Chercheur - CNPEM - Brésil
clara-lana.bispo-fidelis [at] neel.cnrs.fr
Phone: 04 76 88 78 13
Office: F-422
Referent: Xavier CATTOEN
Adrien CLAVEL
Personnel Chercheur - G-INP
adrien.clavel [at] neel.cnrs.fr
Phone: 04 56 38 70 52
Office: F-401
Referent: Mathieu SALAUN
Mathis GANDIN
Personnel Chercheur - CNRS
mathis.gandin [at] neel.cnrs.fr
Phone: 04 56 38 70 52
Office: F-401
Referent: Alexandra PENA
José TRUJILLO-GALARZA
Personnel Chercheur - UGA
jose.trujillo-galarza [at] neel.cnrs.fr
Phone: 04 76 88 11 40
Office: F-209
Referent: Xavier CATTOEN
