GDR Nanoteramir 24-25 November 2016

ABSTRACT BOOKLET

(ORAL PRESENTATIONS)

GDR NanoTeraMIR 24-25 Nov 2016

Towards 300 GHz 100 Gbit/s THz

communications P. Latzel1, F. Pavanello1,*, S. Bretin1, M. Billet1, E. Peytavit1, M. Zaknoune1, P. Szriftgiser2, JF Lampin1, G.

Ducournau1 1IEMN UMR CNRS 8520, University of Lille, Avenue Poincaré, Cité scientifique, 59652 Villeneuve d’Ascq

CEDEX, France 2Laboratoire de physique des Lasers, atomes et Molécules-PhLAM, UMR CNRS 8523, Université Lille 1, F-

59655 Villeneuve d’Ascq Cedex, France

guillaume.ducournau@iemn.univ-lille1.fr

*F.P. is now at IMEC, Belgium

Due to an increasing demand of data transmissions capability, especially for nomadic users, the

evolution of wireless communications data rates has become a key point for future networks. In this

context, the THz band, precisely beyond 200 GHz, has been shown to be very interesting to reach

these new services [1]. Even if the THz range is associated with many technical challenges, it is now

considered that the lower THz frequencies (200-500 GHz) could target wireless communications

applications within the next 10 years. In addition, the expected standard for these future systems is

now going towards 100 Gbps [2]. Among several approaches considered, the photonics-based THz

emitters (photomixers), featuring high bandwidth lead to highest reported data rates using both

direct real-time [3] and off-line [4], and have also the big advantage to be compatible with fiber optic

core networks.

Moreover, as the evolution of optical communications

leads to the massive use of light vectorial signaling

(high efficiency modulations), photomixers have to be

developed accordingly for THz communication

purposes. In this work, a high-efficiency and high

power photomixer based on unitravelling carrier

(UTC) photodiode is presented, along its application

for the realization of a vectorial THz link in the 300

GHz band.

In this talk, initial developments of THz com links using UTC-PD will be presented and the actual

investigated way with 32 Gbit/s transmission performance. Last results towards 100 Gbit/s at 300

GHz will also be discussed.

[1] T. Nagatsuma, G. Ducournau & C.C. Renaud, “Advances in terahertz communications accelerated by photonics”,

Nature Photonics 10, 371–379 (2016) doi:10.1038/nphoton.2016.65.

[2] Task Group 3d 100 Gbit/s Wireless (TG 3d (100G)); http://www.ieee802.org/15/pub/index_TG3d.html

[3] Nagatsuma, T. & Carpintero, G. Recent progress and future prospect of photonics-enabled terahertz communications

research. IEICE Trans. Electron. E98-C, 1060–1070 (2015).

[4] Koenig, S. et al. Wireless sub-THz communication system with high data rate. Nature Photon. 7, 977–981 (2013).

We gratefully acknowledge the Agence Nationale de la Recherche (ANR) for funding the COM’TONIQ ‘Infra’ 2013

program on THz communications, through the grant ANR-13-INFR-0011-01, and the support from several French

research programs and institutes — Lille University, IEMN institute (RF/MEMS Characterization Center, Nanofab and

Telecom platform), IRCICA institute (USR CNRS 3380), the CNRS and by the French RENATECH network. This

work was also supported in part by the French Programmes d’investissement d’avenir Equipex FLUX 0017,

ExCELSiOR project and the Nord-Pas de Calais Regional council, and the FEDER through the CPER Photonics for

Society.

Figure 1. QAM-16 / 8 Gbaud / 32

Gbit/s signal at 280 GHz carrier frequency

using high-efficiency UTC-PD.

Coherent & Tunable THz Source

R. Paquet1, S. Blin@1, M. Myara1, L. Le Gratiet2, M. Sellahi2, B. Chomet2, P. Latzel2, G. Ducournau2, J.F. Lampin2, G. Beaudoin3,

I. Sagnes3, A. Garnache1

@Stephane.Blin@umontpellier.fr

1IES, CNRS UMR 5214—University of Montpellier, France 2IEMN, CNRS UMR 8520, University of Lille, France

3LPN, CNRS UPR 20, Marcoussis, France

We report a continuous-wave highly-coherent and tunable dual-frequency laser emitting at two frequencies separated by 30 GHz to 700 GHz, based on compact III–V diode-pumped quantum-well surface-emitting semiconductor laser technology. The concept is based on the stable simultaneous operation of two Laguerre–Gauss transverse modes in a single-axis short cavity, using an integrated sub-wavelength-thick metallic mask. To this aim, we realized a vertical-external-cavity-emitting laser (VeCSEL) whose cavity is about 1-cm long. We demonstrated a >80 mW output power around 1064 nm, diffraction-limited beam, narrow linewidth of <300 kHz, linear polarization state (>45 dB), and low intensity noise class-A dynamics of <0.3% rms. The beat frequency was tuned by steps of ~15 GHz (free spectral range) by controlling the pump power. THz continuous-wave emission is demonstrated by excitation of a commercial uni-travelling-carrier photodiode. Spectra at THz frequencies are measured using a 220–325 GHz calibrated heterodyne receiver head, showing a tunable and coherent THz signal whose maximum power (<–40 dBm) is limited by the photodiode. The physical concepts that ensure the stable and robust dual-frequency operation, along with the pump-driven beat frequency tunability will be discussed. Perspectives to increase the THz power and thus overpass the photodiode limitation will also be discussed.

Figure 1: Dual-frequency VeCSEL emission characterization:

(a) Dual-frequency optical spectra showing a 300 GHz and a 650 GHz beat frequency at different pumping rates, (b) Optical beat frequency as a function of pump power for LG00/LG02, LG00/LG03 or LG00/LG04 couples,

( c ) THz spectra at different pumping rates.

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NEW OPTICALLY PUMPED THZ MOLECULAR LASERS

Martin Mičica@,$, Mathias Vanwolleghem@, Kamil Postava$, Jaromír Pištora, Jean-François Lampin$

@Institut d'Electronique de Microélectronique et de Nanotechnologie, Université de Lille 1, France $Nanotechnology centre and IT4Innovations, VŠB – Technical University of Ostrava, Czech Republic

Development of new robust and reliable THz lasers is important for commercial applications of THz technology. Current state of art of THz lasers consists mostly of optically pumped molecular gas lasers and quantum cascade lasers. Terahertz quantum cascade lasers (THz QCLs) show as perspective source of coherent radiation, however, required cryogenic cooling limits applications outside laboratory. THz molecular gas lasers are usually optically pumped by mid infrared CO2 laser. These lasers are big and because of required line coincidence of CO2 and THz active molecular gas, they have low power and lasing frequency is limited to several lines. Mid infrared quantum cascade lasers (MIR QCLs) are becoming widely available and compared to THz QCLs can operate at room temperature. High tunability of MIR QCLs allows to access sharp lines of THz active molecular gases which are not coincident with standard optical pumping. Thanks to this we are able to reach new THz lasing frequencies and obtain more efficiency. THz molecular gas lasers pumped by MIR QCL could allow construction of smaller and portable THz laser compared to its predecessors. In the first part of this contribution we present measurement of THz gain in gaseous ammonia. Evaluated will be new lines with frequency around 1 THz with pumping frequency close to 10.3 μm, which are accessible only with fine tuned MIR QCL. Results show high gain and efficiency in comparison with CO2 pumped THz laser. In the second part we propose new approach for optically pumped solid state THz lasers where potential lasing media are molecular crystals. By optical pumping of C-O bonds (or other bonds in MIR region) of these crystals with MIR QCL we could change population in weak molecular bonds (located mostly in THz region) of crystal and possibly create population inversion. If we will be successful, it can lead to very compact and portable THz solid state laser. Theory, current status of work and preliminary results from spectroscopic measurements will be presented.

Figure 1: Obtained intensity of THz radiation in ammonia gas pumped by QCL (tuned to 966 cm-1) at different pressure.

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Sub-Nanometrically Resolved Chemical Maps and Their Benefits for Quantum Cascade Laser

Design and Fabrication K. Pantzas@, G. Beaudoin@, G. Patriarche@, A. Vasanelli$, C. Sirtori$, and I. Sagnes@

@Centre de Nanosciences et de Nanotechnologies, CNRS, Univ. Paris-Sud, Université Paris-Saclay, C2N – Marcoussis, 91460 Marcoussis, France

$Université Paris Diderot, Sorbonne Paris Cité, Laboratoire Matériaux et Phénoménes Quantiques, UMR 7162, F-75013, Paris, France

Quantum cascade lasers (QCL) are devices with an unparalleled potential for laser emission with an emission energy fine-tuned down to the meV. These devices are, however, complex to model and manufacture: they often comprise 30 or more stages, each stage itself containing about 20 wells and barriers, some of which are only a few Angstrom thick. Precisely controlling the composition and thickness of each individual well and barrier in every stage is crucial in attaining the desired emission in the final device. In this context, sub-nanometrically resolved chemical mappings are instrumental in the fabrication of a QCL. Such mappings provide both modelling and epitaxial teams the necessary feedback to identify deviations from a nominal structure, optimize both the design and the fabrication process, and, finally, demonstrate a QCL with the desired emission. However, even with the latest generation of transmission electron microscopes, equipped with state of the art EDX systems it is not possible to measure the composition of the finest wells. Thus, the quantification of the HAADF signal provides the only means to obtain chemical mappings with the desired resolution. In the present contribution, the key role of chemical mappings is illustrated within the specific case of In53Ga47As/In52Al48As QCL structures, grown on lattice-matched on InP using metal-organic chemical vapor deposition (MOCVD). In this specific case, the challenge lies in optimizing the switching between gallium and aluminum precursors in a way that enables one to obtain the targeted composition and thickness, while avoiding memory effects that mollify the interfaces between InGaAs and InAlAs and both broaden and shift the emission line. The QCLs under investigation are based on a two-phonon resonance design. The injector active region in this design consists of 36 stages of the following sequence of InGaAs and InAlAs layers, starting with the injection barrier 40/19/7/58/9/57/9/50/22/34/14/33/13/32/15/31/19/30/23/ 29/25/29A. The InAlAs barriers are in bold and the underlined layers are Si-doped injector layers with a nominal doping level of 3.3e16cm-3. The injector/active region is placed between InGaAs waveguiding layers, 400nm thick and Si-doped to 1.5e16cm-3. The structure is clad with lightly n-doped InP layers. All QCLs were grown lattice-matched on n-doped (100)-oriented InP substrates in a Veeco D180 reactor. Two structures are considered here: the first is a reference structure, obtained in conditions that are commonly used for the growth of QCLs. The second has been obtained from an optimization of this process based on results from the chemical mappings detailed below. Sub-nanometrically resolved chemical mappings of one stage of each structure were computed by quantifying the chemical contrast in HAADF-STEM images. The chemical mappings revealed that InAlAs barriers thinner than 20A do not reach the nominal 48% of aluminum and are in fact InAlGaAs quaternaries. This lack of aluminum is compensated for in the second structure. This

Please submit to: gdr.nanoteramir.2016@gmail.com results in a 20% improvement of the dynamic range of a laser fabricated from the second structure with respect to the first. Furthermore, numerical simulations that take into account the compositions and thicknesses from the chemical mappings produce LIV curves that are in excellent agreement with experimental data collected on both structures, indicating that it is possible to better model and further fine-tune future structures.

Figure 1: HAADF-STEM images of the QCL structure (a) without and (b) with overshoots. The corresponding mappings of the aluminum content in the structure, computed using the algorithm described in the text, are shown in (c) and (d), respectively. The mappings show that there is net increase in the aluminum content of the optimized QCL.

Photonique intégrée à base de guides d'ondes Silicium-Germanium à forte concentration en

Germanium pour le moyen infra rouge

Delphine Marris-Morini,1 Vladyslav Vakarin,1 Joan Manel Ramírez,1 Clément Gilles,2 Jacopo Frigerio,3 Andrea Ballabio,3 Qiankun Liu, 1 Papichaya Chaisakul,1

Carlos Alonso-Ramos1, Daniel Chrastina, 3 Xavier Le Roux,1 Laurent Vivien,1 Grégory Maisons,2 Mathieu Carras,2 Giovanni Isella 3

1Centre de Nanosciences et Nanotechnologies, Univ. Paris-Sud, CNRS, UMR 9100, Université Paris Saclay,

Bâtiment 220, 91405 Orsay Cedex, France; 2MirSense, 86 Rue de Paris, 91400 Orsay, France.

3L-NESS, Dipartimento di Fisica, Politecnico di Milano, Polo di Como, Via Anzani 42, I 22100 Como, Italy

La réalisation de circuits intégrés photoniques dans le moyen infra rouge (2-20 µm) est un enjeu majeur pour la réalisation de capteurs pour de nombreuses applications nécessitant des systèmes portables de détection spectroscopiques. L’utilisation de la photonique silicium (Si) pour réaliser ces circuits intégrés photoniques permettra à terme d’offrir des composants compacts, bas coûts, à faible poids et à faible consommation énergétique, pour des applications portant sur des systèmes de détection portables. Parmi les différents matériaux disponibles dans la filière silicium, le germanium (Ge) et les alliages silicium germanium (SiGe) à forte concentration en Ge présentent un intérêt majeur, car la fenêtre de transparence du Ge s’étend de 1.5 à 15 µm. Ces matériaux ont été largement utilisés dans le proche infra-rouge(1.3-1.5µm). Un lien optique intégrant modulateur et photodétecteur a ainsi pu être démontré, les composants actifs utilisant des structures à base de puits quantiques Ge/SiGe et les guides d’onde étant formés dans le substrat virtuel SiGe riche en Ge. L’extension de cette plateforme du proche vers le moyen infra rouge présente des intérêts majeurs, notamment grâce à la possibilité d’étendre la longueur d’onde de fonctionnement jusque 15 µm. De plus le coefficient non linéaire d’ordre 3 dans le Ge étant plus grand que celui du Si, permet d’envisager des fonctions actives à base d’effets non linéaires optiques efficaces.

Les premières étapes vers le développement de cette nouvelle plateforme ont porté sur la conception, la réalisation et la caractérisation des premiers dispositifs (passifs) pour démontrer la possibilité de guider la lumière avec de faibles pertes optiques dans le moyen infra rouge. Des guides en arêtes en Si0.2Ge0.8 sur substrat graduel Si1-xGex (x variant de 0 à 0.79) ont été fabriqués et caractérisés à la longueur d’onde de 4.6 µm. Les pertes de propagation ont été mesurées par la technique « cut-back ». Des pertes de respectivement 1.5 ± 0.5 dB/cm et 2 ± 0.5 dB/cm ont été mesurées pour les modes quasi-TE et quasi-TM.

Les travaux présentés bénéficient du soutien du projet Européen ERC INsPIRE (grant agreement N°639107).

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Silicon Carbide Microdisk on Silicon Pillar Probed

by Evanescent Coupling David Allioux1, Ali Belarouci1, Darren Hudson2, Eric Mägi2 Guillaume Beaudin3,

Adrien Michon4, Regis Orobtchouk1, Christian Grillet1

1Université de Lyon, Institut des Nanotechnologies de Lyon (INL), 69131, Ecully, France 2Nanotechnology & Nanosystems Laboratory LN2, Université de Sherbrooke, Sherbrooke Canada

3CUDOS, School of Physics, University of Sydney, NSW 2006, Australia 4CRHEA Centre de Recherche sur l'Hétéroépitaxie et ses Applications, CNRS, Valbonne 06560, France

Silicon carbide (SiC) is a well-known material in the field of high temperature electronics and

astrophysics. Yet, due to complicated fabrication processes it has long been disregarded for

integrated optic despite its promising optical properties. It is a high index material (n=2.6) allowing a

good confinement and its wide transparency window (from UV up to 12 µm) makes it suitable for

applications up to the mid-infrared. In addition SiC displays good nonlinear properties, high χ3 and

very low multi-photon absorption [1]. The non-linear loss associated with two photon absorption,

which often limits non-linear efficiency, vanishes beyond 1.1 µm owing to the SiC wide-bandgap.

This makes SiC an ideal candidate for nonlinear applications in the near-infrared (near-IR) up to the

mid-infrared (Mid-IR) [2,3] potentially well suited for the realization of Kerr-based broadband

sources like frequency combs or supercontinuum. Improved manufacturing technics have recently

led to a renewed interest in SiC photonics with structures ranging from photonic crystals [1] to

waveguides [4] or microdisks [5] demonstrated.

In this work, we present structures aiming at non-linear operation from near-IR to mid-IR and

designed to present high-Q whispering gallery modes with low radial mode number at λ= 4 µm. We

report preliminary experimental results in the linear regime around 1.55 µm via an evanescent

coupling technique exploiting a silica tapered fibre with loaded measured Q factor to be around ≈

5000, supported by theoretical calculation.

[1] S. Yamada & al., “Suppression of multiple photon absorption in a SiC photonic crystal nanocavity

operating at 1.55 um,” Opt. Express 20, 14789-14796 (2012).

[2] Richard Soref, “Mid-infrared photonics in silicon and germanium”, Nature Photonics 4, 495 - 497 (2010).

[3] L. Carletti & al. , `”Mid-infrared nonlinear optical response of Si-Ge waveguides with ultra-short optical

pulses”, Opt. Express 23, 32202-32214 (2015).

[4] J. Cardenas & al., “Optical Nonlinearities in High Confinement SiC Waveguides,” in CLEO: 2014, OSA

Technical Digest, paper SW3I.4.

[5] X. Lu, J.Y. Lee, P. X. Feng, and Q. Lin, “Silicon carbide microdisk resonator,” Opt. Lett. 38, 1304-1306

(2013).

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VERRES DE CHALCOGENURES ET FIBRES OPTIQUES : APPLICATIONS POUR

L’INFRAROUGE MOYEN J.Troles@, V. Nazabal@, C. Boussard-Plédel@, L. Calvez@, D. Le Coq@, B. Bureau,

X.H. Zhang@, J.L. Adam@ @ Equipe Verres et Céramiques, UMR CNRS 6226 Institut des sciences chimiques de Rennes, Université de Rennes 1,

Rennes

Les verres de chalcogènures sont des matériaux transparents dans l’infrarouge comprenant les fenêtres 3-5 et 8-12 µm. Ces verres non conventionnels sont le résultat de combinaisons entre éléments ayant des électronégativités proches dont la majorité appartient à la famille des chalcogènes Soufre S, Sélénium Se, Tellure Te, le plus souvent associés à des voisins de la classification périodique comme le Germanium Ge, Gallium Ga, Arsenic As, Antimoine Sb… Ces verres sont des matériaux originaux tant par leur aspect que par leurs propriétés physico-chimiques. La plupart se présente sous forme de blocs opaques à la lumière visible qui rappellent davantage l'aspect d'un métal que celui d'un verre classique à base de silice. Les applications potentielles de ces verres sont toutes liées d’une part à leur transparence optique, et d’autre part à la possibilité de les mettre sous forme d’objets fonctionnels tels que des lentilles optiques par pressage, des couches minces ou des fibres optiques par étirage. Les applications de ces verres concernent alors l’imagerie infrarouge (de défense ou civile), mais aussi la spectroscopie infrarouge car en effet la fenêtre transmission des verres et des fibres de chalcogénures (Fig1) contient les signatures infrarouges de la plupart des espèces chimiques. Figure 1: Courbes d’atténuation de fibres de chalcogénures de différentes compositions en comparaison à une fibre de silice classique

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Optomechanical detection of THz waves Yanko Todorov@, Cherif Belacel@, Djamal Gacemi@, Stefano Barbieri@,

Ivan Favero@ and Carlo Sirtori@ @Université Paris Diderot, Sorbonne Paris Cité, Laboratoire Matériaux et Phénomènes Quantiques

The THz spectral domain (1-20 THz) has numerous applications in spectroscopy, gas sensing,

security screening, and imaging, and is even seen as the next frontier for wireless communications [1,

2]. Compact and powerful sources of THz radiations, such as quantum cascade lasers are now

available, and they deliver more than 10mW in continuous wave, even if they are constrained to

operate at cryogenic temperatures (< 50 K). On the other hand, the detection in the THz domain is a

notoriously difficult problem, owe to the large photon wavelengths involved. Indeed, neither of the

existing commercial THz detectors, such as bolometers or Golay cells, are altogether sensitive, fast

and room temperature [3]. These issues can be tackled by adopting completely novel approaches for

the electromagnetic confinement in the detector, inspired from the recent progress of

electromagnetic metamaterials [4]. In this approach, engineered metamaterial resonators are used to

provide highly sub-wavelength confinement of the electromagnetic field, and direct THz photons

into detector absorbers with high efficiency.

We will report on a THz metamaterial resonator that has been upgraded with a mechanical element

(Fig. 1), enabling thus a nanoscale optomechanical coupling. This system has two mechanism of

operation: photo-thermal, based on the THz Eddy currents induced in the resonator, and an electro-

mechanical coupling, that exploits the highly sub-wavelength confinement in the resonator. Both

these approaches allow detection at room temperature with high speed and sensitivities that can

potentially reach those of commercial semiconductor bolometers operating at cryogenic

temperatures [5].

Figure 1(a) SEM image of the THz optomechanical resonator (b) Measurements of the mechanical movement with (red) and

without (blue) incident THz beam from a QCL laser.

[1] M. Tonouchi, Nature Phot. 1, 97 - 105 (2007)

[2] I. F. Akyildiz, J. M. Jornet, C. Han, , Phys. Comm. 12, 16 (2014)

[3] A. Rogalski and F. Sizov, Opto-Electron. Rev. 19, 346-404 (2011)

[4] Cai and Shalaev, Optical Metamaterials: Fundamentals and Applications (Springer, 2009).

[5] “Optomechanical transducer for terahertz electromagnetic waves”, EP16305288

Mid Infrared (~5m) Quantum Cascade

Detectors Operating at Room Temperature

Z. Asgharia, A. Mottaghizadeha, M. Amantia, A. Evirgenb, A. Delgab, C. Sirtoria aUniversité Paris Diderot, Laboratoire Matériaux et Phénomènes Quantiques, 75013 Paris, France

bAlcatel Thales III V Lab,, 91767 Palaiseau, France

Mid-infrared (MIR) detection has wide range of applications in spectroscopy and has recently attracted a

wealth of attention in the field of optical communications.

Mercury Cadmium Telluride (MCT) detectors are widely used for application in the MIR because of their

high responsivity (~ 1010 cm. Hz1/2 /W). However, their frequency bandwidth is limited to less than 1GHz.

For some time now, research has focused on a new type of device which is based on intersubband

transition as the QCL and QWIP, the Quantum Cascade Detectors (QCDs). The last are supposed to

operate at room temperature, particularly in the 3-5 m atmospheric window. As a matter of fact, QCDs

are unipolar detectors and their electronic response is limited by electron scattering time (τ≃ps) leading to

cut off frequencies on the order of 100 GHz [H.C.Liu, APL 1995].

The working principle of QCDs is based on a vertical intersubband transition followed by an extraction in

a cascade shape thanks to LO-phonons. Their specific design enables detection at zero bias which leads to

a minimal dark current hence a higher detectivity.

The QCD used in our research is based on GaInAs/AlInAs quantum wells grown at III-V Lab Thales. The

results we are presenting are promising as we have reached room temperature detection at the expected

wavelength (≃5μm) (Figure 1). The measured dark current for different size of QCDs structures shows a

really low current value (~10-5A/cm2). A high frequency study of these devices is our next goal.

Ultimately, we are planning to develop high frequency QCDs for free space optical communication at

around 5m.

Figure 1: Responsivity of a QCD operating at 5μm for different value of the temperature

Ultra-fast THz meta-atom quantum well photo-detector B. Paulillo1, S. Pirotta1, H. Nong2, L. Li3, E.H. Linfield3, G.A. Davies3,

P.Crozat1, S. Dhillon2, R. Colombelli1

1Centre for Nanoscience and Nanotechnology (C2N Orsay), CNRS UMR9001, Univ. Paris Sud, Univ. Paris Saclay, 91405 Orsay, France 2Laboratoire Pierre Aigrain, Ecole Normale Superieure, UMR 8551 CNRS, UPMC, Univ. Paris 6 ,75005 Paris, France

3School of Electronic and Electrical Engineering, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, United Kingdom

Most of the available THz detectors (thermal, FETs, …) are currently limited in response time and/or operating temperature by slow thermal processes (≈ms) and/or by the read-out electronics. In the THz range, the quantum well infrared photodetector (QWIP) architecture is promising when an efficient photon detector featuring an ultra-fast response is needed. This stems from the intrinsic short lifetime of ISB transitions (≈ps) [1-2]. However, the operating regime of THz QWIPs is currently limited at cryogenic temperatures (typical background limited infrared temperatures (Tblip) are ≈15 K) which hampers practical applications. An effective strategy to improve the performance of a QWIP, especially in terms of device speed, is to reduce its volume.

In this contribution, the key idea is to exploit a miniaturized RF antenna as a coupler element to efficiently feed THz radiation (λ=100-200 µm) into an ultra-subwavelength (4-µm-side) QWIP active core. To this scope, we exploit the 3D THz meta-atom geometry recently developed in our team [3] to demonstrate QWIP detectors with extremely sub-wavelength dimensions of the order of λeff/10 (corresponding to λ0/25 in the detector active core). These objects are topologically equivalent to planar split-ring resonators, behaving as sub-wavelength THz antennas. The active core of the device hosts a GaAs/AlGaAs multiple-quantum-well structure designed to detect radiation at ~3 THz [4] and the active volume is about 20 µm3 only, as shown in Figure 1(a). The LC resonance of the device has been centered on the QWIP structure response band by carefully selecting both the capacitor and inductor sizes.

Photocurrent spectra show a clear response around 3 THz at 4.5K, for devices consisting of a single element, or a 2D array (≈300 single devices), as reported in Figure 1(c). Moreover, electrical measurements support our claim of very low dark currents related to the extremely sub-wavelength active volume: less than 2 nA and 20 nA for single device and array configuration, respectively at 4.5K for the typical operational bias. This complete analysis permits estimating the Tblip≈8K for both configurations.

On the other hand, the effect of this architecture on the device speed is dramatic. Experimentally measured electrical S-parameters show a -3dB cutoff beyond 40 GHz and 10 GHz, for the single object and array respectively. This finding suggests that these detectors have an ultra-fast response. In order to measure the optical response, we have illuminated the detector with a continuous-wave THz QC laser that was intensity-modulated using a RF generator. The output of the detector was then fed to a spectrum analyzer to detect the laser modulation frequency. Our latest results, that will be thoroughly discussed during the talk, prove a clear optical response up to 2.5 GHz for the array geometry, currently limited only by the experimental setup.

Figure 1 (a) Scheme of the sub-wavelength 3D THz micro-resonator. (b) SEM picture of a typical fabricated LC micro-resonators on a ground plane. (c) Photocurrent spectrum for the QWIP array with 50mV bias applied. Inset: photocurrent from the single QWIP device with 100mV bias applied.

[1] H. Schneider, H.C. Liu, Quantum Well Infrared Photodetectors. Physics and Applications, Springer Series in Optical Sciences, Springer Verlag Berlin Heidelberg (2007) [2] D. Palaferri, Y. Todorov, Y.N. Chen, J. Madeo, A. Vasanelli, L.H. Li, A.G. Davies, E.H. Linfield and C. Sirtori, “Patch antenna terahertz photodetectors “, Applied Physics Letters, 106, 161102 (2015) [3] B. Paulillo, J. Manceau, A. Degiron, N. Zerounian, G. Beaudoin, I. Sagnes, and R. Colombelli, "Circuit-tunable sub-wavelength THz resonators: hybridizing optical cavities and loop antennas," Opt. Express 22, 21302-21312 (2014) [4] H. Luo, H. C. Liu, C. Y. Song, and Z. R. Wasilewski, “Background-limited THz quantum-well photodetector,” Appl. Phys. Lett., 86, 1 (2005)..

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Antenna-coupled two photon quantum well infrared photodetector

Daniele Palaferri1, Yanko Todorov1, Lianhe Li2, Chen Li2, Edmund H. Linfield2, Carlo Sirtori1 1Laboratoire Matériaux et Phénomènes Quantiques, Université Paris Diderot – CNRS UMR 7162,

75205 Paris Cedex 13, France 2School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom

Quantum well photodetectors (QWIP) are optoelectronic devices which use intersubband (ISB) transitions in semiconductor heterostructures (mainly n-type doped GaAs/AlGaAs) to generate photocurrent signal in the infrared and far-infrared spectral region (5µm < λ < 200µm). [1, 3] Recently, the concept of antenna-coupled microcavity has been demonstrated as a functional photonic architecture to enhance performances of mid-infrared and terahertz QWIP [4, 5]: the use of array of metallic patch antennas allows to collect photons from an area larger than the device itself, allowing a reduction in the dark current and a consequent increase of BLIP (background-limited performance) detectivity and temperature. In this configuration the active region (the quantum wells) is sandwiched between two metal layers and light-coupling occurs with normal incident radiation: such a geometry can be seen as an array of microcavities, where the external electromagnetic field is squeezed and confined as a standing wave between the two metallic mirrors. The antenna-coupled microcavity as light-coupling enhancement method can be applied to other types of detectors. In the last fifteen years optical nonlinearities involving intersubband transitions have received growing attention [6]; in particular Schneider et al. have demonstrated a quadratic detector based on a three level configuration, two bound states and one continuum resonance. Such a detector, which depends quadratically on the input power, allows the characterization of ultrashort infrared pulses, by performing interferometric autocorrelation techniques (at the subpicosecond time resolution). [7, 8] In the following work it is investigated the combination of a quadratic quantum well photodetector with the geometry of nano-antennas arrays, by exploiting the non-linear electromagnetic field enhancement.

The two photon-detector under study is a GaAs/AlGaAs multiple quantum wells structure The active region consists of 4 periods of 7.4 nm wide QWs separated by 45 nm wide barriers, with n-type contact layers at the top and the bottom of the structure. The central 5 nm of each QW are Si doped Nd = 2.0x1018 cm-3. The first device is processed in standard mesa with 200µm diameter and 45 degree facet. Figure 1(left) shows the photocurrent spectra taken at 78K, with a globar source: it is

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possible to observe the different linear photo-responses of the electronic transitions: the broad absorption bound to continuum 1->3 (which should be forbidden) is always present (between 220 and 450 meV) for different applied voltages due to residual asymmetric doping into the well; the sharp response peak bound-to-bound 1->2 (around 137 meV) is activated only at a specific high voltage, due to the tunneling through the barrier. Looking at the non-linear response with a 9µm quantum cascade laser, cooling the QWIP at 50K, it is evident the quadratic regime at low voltage (50mV), the black dots in Fig. 1(right), and the linear regime at high voltages (250mV), red points.

Figure 1(left): Photocurrent Spectra of the mesa device, using a globar source, at 77K, for different applied voltages. Figure 1(right): Photoresponse as function of the optical power, using a quantum cascade laser at 9μm as source, qwip at 50K

The antenna-coupled two photon detector is currently under exploration. As the electromagnetic density energy compression inside a microcavity is defined by the focusing factor F ~ |Ein|²/|Eout|² , considering Eout the electric field amplitude of the incident radiation and Ein the amplitude of the electric field stored inside the photonic resonator, we expect the antenna-coupled quadratic detector to show an enhancement of the non-linear response proportional to F², with a particular impact on the power-limited performances of the device. [9]

[1] B. F. Levine et al., “New 10 μm infrared detector using intersubband absorption in resonant tunneling GaAlAs superlattices”, Appl. Phys.Lett. 50, 1092 (1987).[2] H. Luo, H.C. Liu, Song, C.Y., and Z.R Wasilewski, “Background-limited terahertz quantum-well photodetector” Appl. Phys. Lett. Vol.86 (2005).[3] H.C. Liu, “Intersubband Transitions in Quantum Wells”, edited by H. C. Liu and F. Capasso, Academic Press,San Diego (2000).[4] Y.N. Chen, Y. Todorov, B. Askenazi, A. Vasanelli, G. Biasiol and C. Sirtori, “Antenna-coupled microcavities for enhanced infrared photo-detection”, Appl. Phys. Lett. Vol.104 (2014).[5] D. Palaferri, Y. Todorov, Y.N. Chen, J. Madeo, A. Vasanelli, L. H. Li, A. G. Davies, E.H. Linfield and C. Sirtori “Patch antenna terahertz photodetectors”. Applied Physics Letters, 106(16), 161102 (2015).[6] H. C. Liu, E. Dupont, and M. Ershov, “Nonlinear quantum well infrared photodetector” J. Nonlinear Optic. Phys. Mat. 11, 433 (2002)[7] H. Schneider, T. Maier, H. C. Liu, M. Walther, and P. Koidl, ”Ultra-sensitive femtosecond two-photon detector with resonantly enhanced nonlinear absorption,” Opt. Lett. 30, 287-289 (2005).[8] T. Maier, H. Schneider, H. C. Liu, M. Walther, and P. Koidl, ”Two-photon QWIPs for quadratic detection of weak mid-infrared pulsed lasers,” Infrared Phys. Technol. 47, 182-187 (2005)[9] D. Palaferri, Y. Todorov, G. Frucci, G. Biasiol and C. Sirtori ”Ultra-subwavelength resonators for high temperature high performance quantum infrared detectors.,” New Journal of Physics, in press (2016)

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L’électronique THz au service de l’astronomie : l’instrument hétérodyne submillimétrique de la

sonde planétaire JUICE Alain Maestrini@

@LERMA, Observatoire de Paris & Université Pierre et Marie Curie

Abstract : JUICE, pour JUpiter ICy moons Explorer, est la première mission de grande envergure du programme Cosmic Vision 2015-2025 de l'Agence Spatiale Européenne. Prévu pour être lancée en 2022 et arriver au voisinage de Jupiter en 2030, cette sonde planétaire passera au moins trois ans à faire des observations détaillées de Jupiter et de trois de ses plus grandes lunes, Ganymede, Callisto et Europa. La charge utile est composée de dix instruments dont SWI, acronyme anglais de Submillimeter Wave Instrument, qui étudiera la structure, la composition et la dynamique des températures de la stratosphère et de la troposphère de Jupiter ainsi que les exosphères et les surfaces des lunes glacées. SWI est un spectromètre hétérodyne offrant une résolution spectrale de ~107 et une précision de fréquence de ~108, utilisant une antenne parabolique de diamètre effectif 30 cm et fonctionnant dans deux gammes spectrales 1080-1275 GHz et 530-625 GHz. Le LERMA, en partenariat avec le LPN (désormais C2N), a développé un procédé de fabrication de diodes Schottky sur membrane de GaAs qui a abouti - après près de dix ans de misse au point - à la réalisation en 2015 du récepteur Schottky à 530-625GHz le plus sensible au monde, et, en 2016, à la réalisation du premier récepteur à 1080-1275 GHz européen aux spécifications de SWI. Suite à ces résultats, le LERMA a été chargé par le groupe allemand PI de l’instrument, le Max-Planck-Institut für Sonnensystemforschung, de réaliser la partie haute fréquence du canal à 1080-1275GHz, incluant le mélangeur et deux étages de multiplication de fréquence. Cette présentation sera centrée sur les aspects conception et réalisation du mélangeur à 1080-1275 GHz.

Figure 1: diodes Schottky en configuration antiparallèle du mélangeur à 1080-1275GHz de SWI

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LARGE ARRAYS OF KINETIC

INDUCTANCE DETECTORS FOR MILLIMETRE AND SUB-MILLIMETRE

IMAGING A. Monfardini

Institut NEEL, Grenoble (FRANCE)

We are since 2009 developing in Grenoble arrays of Kinetic Inductance Detectors (KID) mainly devoted to millimetre astronomy. Our instrument, NIKA (New IRAM KID Arrays), has been the very first based on this technology to be open open to the larger astronomical community via competitive proposals. This camera has been recently replaced, at the 30-meteres radiotelescope at Sierra Nevada, by NIKA2, ten times bigger. I will describe the development of such instruments and give some quick examples of the scientific results achieved. Besides astronomical applications, we have studied the interaction of high-energy particles and photons in arrays of KID and applied this technology to other domains like superfluid hydrodynamics and solid state physics.

SINGLE PHOTON SUPERRADIANCE AND COOPERATIVE LAMB SHIFT IN AN

OPTOELECTRONIC DEVICE G. Frucci@, S. Huppert@, A. Vasanelli@, B. Dailly@, Y. Todorov@, G. Beadoin$, I.

Sagnes$, and C. Sirtori@ @Université Paris Diderot, Sorbonne Paris Cité, Laboratoire Matériaux et Phénomènes Quantiques

$Laboratoire de Photonique et de Nanostructures, CNRS, 91460 Marcoussis, France

When a single photon excitation is shared between a large number of emitters, quantum electrodynamics predicts an enhanced spontaneous emission phenomenon, the superradiance [1-2], accompanied by a shift of the emission frequency, the cooperative Lamb shift [3-4]. The last is a real effect, though it is issued from an exchange of virtual photons between the emitters. In this work we present a semiconductor optoelectronic device allowing the observation of these two phenomena at room temperature [5]. The two samples used in this study are based on GaInAs/AlInAs highly doped QWs. The first one consists of a single 45 nm GaInAs layer, n-doped with a surface density Ns = 7.5×1013 cm−2, sandwiched between two AlInAs barriers. The second sample is designed such that six QWs, identical to that of single quantum well sample, are distributed within one wavelength and separated one another by a sufficiently thick barrier to avoid tunneling. We show experimentally and theoretically that single photon superradiance and cooperative Lamb shift are engineered in our semiconductor device by spatially separating plasma optical resonances arising from the collective motion of confined electrons in the QWs [6]. These resonances have no mutual Coulomb coupling and interact only through absorption and re-emission of real and virtual free space photons, similarly to macro-atoms that can be localized on different positions along the axis perpendicular to the sample surface, with their dipole oriented along the same axis. Our semiconductor quantum system is therefore very valuable to simulate, in a solid state system, the low excitation regime of phenomena typical of quantum electrodynamics.

Figure 1: Linewidth (a) and energy shift with respect to 6◦ (b) of the main plasmon peak as a function of θ and its comparison to the theoretical model (black line). Inset: schematic representation of the two samples used in this study. [1] R. H. Dicke, Phys. Rev. 93, 99 (1954). [2] M. Gross and S. Haroche, Physics Reports 93, 301 (1982). [3] M. O. Scully and A. A. Svidzinsky, Science 325, 1510 (2009). [4] R. Friedberg and J. T. Manassah, Phys. Rev. A 81, 043845 (2010). [5] G. Frucci, et al. arXiv:1610.06391 [cond-mat.mes-hall] (2016). [6] T. Laurent, et al., Phys. Rev. Lett. 115, 187402 (2015).

ULTRA-STRONG COUPLING WITH THE FREE SPACE: THE SUPERRADIANCE

S. Huppert1, A. Vasanelli1, T. Laurent1, Y. Todorov1, G. Beaudoin2, I. Sagnes2 and C. Sirtori1

1Paris Diderot, Sorbonne Paris Cité, Laboratoire Matériaux et Phénomènes Quantiques, UMR7162, 75013 Paris, France 2Laboratoire de Photonique et de Nanostructures, CNRS, 91460 Marcoussis, France

Light-matter interaction, usually considered only as a weak probe, becomes the dominant energy relaxation mechanism for collective excitations in a two-dimensional electron gas. Indeed, when the concentration is sufficiently high, electrons respond to the solicitation of photons as a whole, with an absorption spectrum presenting a single resonance at a completely different energy with respect to that of the electronic transitions [1]. This resonance corresponds to a many-body excitation of the system that ties together all dipoles, thus presenting a huge interaction with light. The spontaneous emission rate is proportional to the number of particles taking part in the collective excitation, a phenomenon known as superradiance [2]. For high electronic densities, spontaneous emission is therefore the dominant relaxation mechanism and the associated broadening can even become a sizable fraction of the resonance frequency. This physical situation is reminiscent of the ultra-strong coupling regime in micro-cavities [3]. In recent experiments we showed that the collective excitation can reach the regime of strong coupling with free space radiation, where the radiative broadening dominates the non-radiative one [4,5]. We also show that this superradiant behavior is associated with a cooperative Lamb shift of the resonance frequency, arising from emission and absorption of virtual photons. This work opens exciting perspectives, as it enables achieving ultra-strong coupling [6] and paves the way to the observation of novel quantum effects in open systems, without any light confinement.

Figure 1: Normalized incandescent emission spectra, for three quantum wells with three different electronic densities Ns. Note the

increased width due to enhanced radiative decay. [1] A. Delteil, et al. Phys. Rev. Lett. 109, 246808 (2012). [2] R. H. Dicke, Phys. Rev. 93, 99 (1954). [3] C. Ciuti, G. Bastard, and I. Carusotto, Phys. Rev. B 72, 115303 (2005). [4] T. Laurent, et al. Phys. Rev. Lett., 115, 187402 (2015). [5] S. Huppert, et al., ACS Photonics 2, 1663 (2015). [6] S. Huppert, A. Vasanelli, G. Pegolotti, Y. Todorov,C. Sirtori, Phys. Rev. B 94, 155418 (2016).

*Corresp. author: arnaud.grisard@thalesgroup.com, Phone: +33-1-6941-5546, Fax: +33-1-6941-5552

Quasi-phase-matched semiconductors for versatile long wavelength conversion

A. Grisard*,1, E. Lallier1, and B. Gérard2

1Thales Research and Technology, Campus Polytechnique, 1 av. Augustin Fresnel, 91767 Palaiseau cedex, France 2III-V Lab, Campus Polytechnique, 1 av. Augustin Fresnel, 91767 Palaiseau cedex, France

Orientation-Patterned gallium arsenide (OP-GaAs) has recently emerged as a key enabling non-linear optical material for demanding infrared applications. For efficient frequency conversion from various laser sources, it combines the advantages of the Quasi-Phase Matching (QPM) capability and the extremely large transmission range of undoped GaAs. Taking advantage of a number of additional properties (small dependance on polarization, large thermal conductivity, etc.), it enables versatile non-linear interactions without the wavelength or power restrictions of former QPM crystals such as Periodically Poled Lithium Niobate (PPLN) and similar ferroelectric oxides. Following a short tutorial on the fabrication of bulk OP-GaAs samples and their characteristics relevant to various pumping formats, this review will present the state-of-the-art in experiments and devices based on this material and focus on recent developments such as:

- Multi-watts multi-wavelength sources for optical infrared counter-measures. - Compact single frequency Optical Parametric Oscillators for gas detection. - Fiber laser pumped amplifiers of tunable Quantum Cascade Lasers for remote

spectroscopic applications. - Efficient up-conversion by sum-frequency generation for easier detection - QPM interactions in low loss semiconductor waveguides

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Diode à transfert électronique distribuée GaN au THz Christophe Dalle, François Dessenne, Jean-Luc Thobel

Institut d’Electronique, de Microélectronique et de Nanotechnologies, UMR

CNRS 8520, Cité Scientifique, Avenue Poincaré, BS 60069, 59652Villeneuve d’Ascq cedex, France

La réalisation de sources RF à l’état solide aisément utilisables, c’est-à-dire suffisamment puissantes et

fonctionnant à température ambiante sans assistance thermique, demeure un challenge aux

fréquences THz. Une solution est peut-être la diode à transfert électronique distribuée au nitrure de

gallium (GaN). Sa structure, ici de type N+NN+, s’apparente à celle d’une ligne microstrip

multicouche ou plutôt d’un guide plan parallèle multicouche dans le cadre d’une modélisation

bidimensionnelle (2D) (figure1). Son principe de fonctionnement RF repose sur l’amplification

d’une onde électromagnétique transverse se propageant parallèlement aux couches épitaxiées au sein

de la zone active N se comportant comme un milieu à résistance négative. Cette propriété résulte du

mouvement des électrons, perpendiculaire aux couches N+NN+, s’effectuant suivant le mode dit à

couche d’accumulation et temps de transit. Elle repose fondamentalement sur l’existence d’une zone

de mobilité différentielle négative dans la caractéristique champ/vitesse du GaN.

Le simulateur physique 2D temporel permet la résolution des équations de l’électromagnétisme de

Maxwell ainsi que celles de l’électrostatique pour la détermination des conditions de polarisation

continue et la distribution initiale des électrons. Le modèle de transport des charges électriques est de

type énergie-moment. La résolution numérique repose sur la méthode des différences finies. Dans un

premier temps, la structure géométrique et technologique du composant est optimisée en mode

purement sinusoïdal à 1 THz à l’aide d’un modèle énergie-moment quasi-électrostatique. Le

simulateur électromagnétique 2D permet l’étude exhaustive du fonctionnement de la diode, du

régime transitoire de mise en oscillations jusqu’au régime établi, le calcul de grandeurs

caractéristiques (figures 2,3,4) ainsi que l’analyse spatio-temporelle des grandeurs physiques internes.

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Terahertz imaging systems developed in LIA-TERAMIR

W. Knap, N. Dyakonova, F. Teppe, D.But, D.Coquillat L2C CNRS University of Montpellier, France

M. Sypek, J.Suszek

Optical Information Processing Laboratory Warsaw University of Technology, and ORTEH Warsaw, Poland

B. Moulin, M.Triki, C.Archier,T. Antonini T-Waves Technologies Montpellier -France

We present an overview of some recent results concerning THz detection related to plasma nonlinearities in nanometer field effect transistors [1, 2]. The subjects were selected in a way to show physics related limitations and advantages rather than purely technological or engineering improvements of nanometer Field Effect transistors (FETs) working as Terahertz detectors. We address the basic physics related problems like temperature dependence of the response [3], helicity sensitive detection [4] and nonlinear/saturation response at high incident power [5]. The results will be discussed in view of the physical and technical limitations of Field Effect Transistors based THz detectors in view of their application for terahertz imagers [6,7].

ACKNOWLEDGEMENTS

This work was partially supported by the National Centre for Research and Development in Poland (grant no. PBS1/A9/11/2012), by the National Science Centre in Poland (DEC-2013/10/M/ST3/00705) and by CNRS France via LIA –TERAMIR projects.

REFERENCES

[1] W. Knap and M. Dyakonov, in Handbook of Terahertz Technology edited by D. Saeedkia (Woodhead Publishing, Waterloo, Canada, 2013), pp. 121-155.

[2] W. Knap, S. Rumyantsev, M. Vitiello, D. Coquillat, S. Blin, N. Dyakonova, M. Shur, F. Teppe, A. Tredicucci and T. Nagatsuma, Nanotechnology 24 (21), 214002-214002 (2013).

[3] O. A. Klimenko, W. Knap, B. Iniguez, D. Coquillat, Y. A. Mityagin, F. Teppe, N. Dyakonova, H. Videlier, D. But, F. Lime, J. Marczewski and K. Kucharski, J. Appl. Phys. 112 (1), 014506-014505 (2012).

[4] C. Drexler, N. Dyakonova, P. Olbrich, J. Karch, M. Schafberger, K. Karpierz, Y. Mityagin, M. B. Lifshits, F. Teppe, O. Klimenko, Y. M. Meziani, W. Knap and S. D. Ganichev, J. Appl. Phys. 111 (12), 124504-124506 (2012).

[5] D. B. But, C. Drexler, M. V. Sakhno, N. Dyakonova, O. Drachenko, F. F. Sizov, A. Gutin, S. D. Ganichev and W. Knap, J. Appl. Phys. 115 (16), 164514 (2014).

[6] J. Suszek, A. Siemion, M. S. Bieda, N. Blocki, D. Coquillat, G. Cywinski, E. Czerwinska, M. Doch, A. Kowalczyk, N. Palka, A. Sobczyk, P. Zagrajek, M. Zaremba, A. Kolodziejczyk, W. Knap and M. Sypek, Terahertz Science and Technology, IEEE Transactions on 5 (2), 314-316 (2015).

[7] Mail scanner: http://www.orteh.pl/page/22/research-development [8] 2D Imaging system: http://www.t-waves-technologies.com/en

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Topological Phase Transition in

Pb1-xSnxSe Topological Crystalline Insulator T. Phuphachong1, B.A. Assaf1, V.V. Volobuev2,3, G. Bauer2, G. Springholz2,

L.A. de Vaulchier1, Y. Guldner1 1Laboratoire Pierre Aigrain et Département de Physique, Ecole Normale Supérieure,

CNRS, PSL Research University, Université Pierre et Marie Curie, 24 rue Lhomond, 75005 Paris, France 2Institut für Halbleiter und Festkörperphysik, Johannes Kepler Universität, Altenberger Straße 69, 4040 Linz, Austria

3National Technical University ‘‘Kharkiv Polytechnic Institute’’, Frunze Str. 21, 61002 Kharkiv, Ukraine

Recently, the study of topological states of matter beyond the existing Z2 topological insulators (TIs)

protected by time-reversal symmetry has attracted great attention in the field of condensed matter

physics. A novel topological state called topological crystalline insulator (TCI) protected by mirror

symmetry of the crystal has been discovered in narrow gap rocksalt IV-VI semiconductors such as

Pb1-xSnxSe and Pb1-xSnxTe alloys [1]. Such materials were shown to exhibit semiconducting bulk states

accompanied by gapless surface states when a band inversion occurs. Interestingly, a band inversion

occurs at four equivalent L-points in the three-dimensional Brillouin zone when the Sn content x is above a critical value xc. Therefore, this results in the emergence of an even number of massless

topological surface Dirac cones at points, on the corresponding two-dimensional Brillouin zone,

which are mirror symmetric with respect to six equivalent {110} planes. As a consequence, such

surface states can only exist on (001), (110) or (111) surfaces of the material.

In this work, we present far- and mid-infrared magneto-optical investigation in high-mobility Bi-

doped (111)-oriented Pb1-xSnxSe films grown on BaF2 substrates by molecular beam epitaxy (MBE)

for 0≤x≤0.30. The absorption measurements were performed at T=4.5K and in magnetic fields

B=0-17T. Massive and massless Dirac fermion models including far-band contributions are used to

analyze transmission spectra. We are able to determine the band parameters (energy gap, Fermi

velocity, effective mass) of the bulk and the topological surface states (TSS) of such material. The

observation of the cyclotron resonance of the TSS confirms that this compound goes from trivial to

nontrivial regime at a critical value xc≈0.16. Such a topological phase transition can also be verified

by studying the variation of bulk Fermi velocity through all examined samples. Moreover, we find

that the energy gap changes sign when the system is in the nontrivial regime. Finally, our

experimental findings [2] show that the Fermi velocity of massive Dirac fermions can be used as a

universal measure of the topological character of all material classes hosting a topological phase

transition, including 3D-Dirac and Weyl semimetals.

References

[1] Y. Ando and L. Fu. Topological crystalline insulators and topological superconductors: from concepts to materials. Annu. Rev. Condens. Matter Phys. 6, 361-381 (2015). [2] B.A. Assaf, T. Phuphachong, V.V. Volobuev, G. Bauer, G. Springholz, L.A. de Vaulchier, and Y.

Guldner. Universal relation between velocity and topological character of Dirac fermions through a

topological phase transition. arXiv:1608.08912.

Stabilisation de lasers à cascade quantique pour les mesures de précision

Rosa Santagata, Bérengère Argence, Dang Bao An Tran, Olivier Lopez, Andrei Goncharov, Sean Tokunaga, Daniele Nicolodi, Michel Abgrall, Rodolphe Le Targat, Paul-Eric Pottie, Christian Chardonnet, Christophe Daussy, Yann Le Coq, Benoit Darquié, Anne Amy-Klein 1 Laboratoire de Physique des Lasers, Université Paris 13, Sorbonne Paris Cité, CNRS, 93430 Villetaneuse,France 2 Laboratoire National de Métrologie et d’Essais-Systèmes de Références Temps-Espace, Observatoire de Paris, CNRS, UPMC, 61 Avenue de l’Observatoire, 75014 Paris, France

De par la richesse de leur structure interne, les molécules peuvent jouer un rôle déterminant pour des tests de physique fondamentale, comme par exemple les tests de variation dans le temps des constantes fondamentales ou de non conservation de la parité. La plupart de ces expériences repose sur la stabilité et l’exactitude de la source laser utilisée pour sonder les transitions moléculaires, en général dans le moyen infrarouge (MIR). Dans ce but, nous avons développé un dispositif de stabilisation de fréquence d’un laser à cascade quantique (QCL), émettant dans le moyen IR, à un niveau inférieur au Hz. Ce dispositif repose sur le transfert de stabilité et d’exactitude à partir d’un laser ultrastable émettant à 1.5 µm, par l’intermédiaire du peigne de fréquence d’un laser femtoseconde et d’un lien optique fibré de 43 km reliant le LNE-SYRTE au LPL. Nous avons ainsi asservi en phase un laser à cascade quantique émettant à 10 µm avec une stabilité relative de fréquence meilleure que 2x10-15 à 1 s. La largeur de raie obtenue est de l’ordre de 0.2 Hz. Ce dispositif nous a permis de mesurer des raies de la molécule OsO4 avec une incertitude de 8x10-13. Nous développons actuellement un système de balayage de la QCL afin de sonder une large bande spectrale d’absorption. Ce schéma de stabilisation de fréquence présente des performances équivalentes à celles accessibles dans le proche IR et le visible et constitue une étape clé pour étendre toutes les expériences de spectroscopie à haute résolution des atomes vers les molécules.

Spectroscopie rotationnel de molécule faiblement polaire CH3D et non-polaire CH4 utilisant une source THz accordable et verrouillée sur un

peigne de fréquence Cédric Bray1, Arnaud Cuisset1, Francis Hindle1, Gael Mouret1, Robin Bocquet1,

1Laboratoire de Physico-Chimie de l’Atmosphère, Université du Littoral Côte d’Opale, Dunkerque, France, cedric.bray@univ-littoral.fr,

Le Laboratoire de Physico Chimie de l'Atmosphère a développé durant près d’une décennie un spectromètre THz exploitant une technique de photomélange. L’ensemble est accordable entre 0,3 et 3,3 THz, tout en bénéficiant d’une excellente métrologie de fréquence (quelques de kHz) en tirant profit d’un peigne de fréquence produit par un laser femtoseconde.1 Les performances de cet instrument unique contribuent à améliorer les bases de données internationales telles que HITRAN ou JPL par des études de spectroscopie rotationnel (positions et profils de raie) sur des espèces stables et instables. Ces dernières jouent un rôle clé dans la photochimie de l’atmosphère terrestre ou planétaire.2,3 Récemment, le seuil de sensibilité a été amélioré permettant d’obtenir le spectre du méthane deutérée (CH3D), une cible principale pour déterminer l'origine de certains gaz atmosphériques, notamment du méthane (CH4), gaz d’importance pour de nombreuses atmosphères planétaires. Des mesures d'absorption directes entre 1 et 2,5 THz ont été réalisées avec un trajet optique de 20 m permettant d’observer des transitions de rotation d’intensités inférieures à 10-25 cm-1 / (molecules.cm-2). Le spectromètre développé se révèle également capable d’enregistrer des transitions de rotation pure de molécules non polaires telles que CH4, possible du fait d’un moment dipolaire induit par la distorsion centrifuge. Afin d’atteindre des niveaux de performances plus importants, notamment en terme de sensibilité, une expérience de « MicroWave Chirped Pulse Fourier Transform Spectroscopy » est en cours de développement. A ce jour, ce spectromètre permet une acquisition extrêmement rapide sur un domaine de fréquence allant de 190 à 210 GHz. Les performances du spectromètre optoélectroniques seront présentées ainsi que les résultats préliminaires concernant nos derniers développements encore inédites en France. Références : [1] Hindle, F., et al., Appl. Phys. B, 2011. 104: p. 763-768. [2] Martin-Drumel, M. A., et al., Ap. J. , 2015. 799: 115. [3] Guinet, M., et al., J. Quant. Spectrosc. Radiat. Transfer, 2012. 113: p. 1113-1126. [4] Drouin, B. J., et al., J. Quant. Spectrosc. Radiat. Transfer, 2009. 110: p. 2077-2081.

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Improved Mid Infrared Detector for High Spectral or Spatial Resolution Measurements

Mbaye Faye, Jean Blaise Brubach, Pascale Roy, Laurent Manceron

Synchrotron SOLEIL, Beamline AILES, Saint Aubin, F91192

When using bright, small effective size sources, such as synchrotron radiation light beam, for broadband spectroscopy at spectral or spatial high resolution for mid-IR FTIR measurements, a marked detectivity improvement can be achieved by setting up a device matching the detector optical étendue to that of the source. Further improvement can be achieved by reducing the background unmodulated flux and other intrinsic noise sources using a lower temperature cryogen such as liquid helium. By the combined use of cooled apertures, cold reimaging optics, filters and adapted detector polarization and preamplification electronics, the sensitivity of a HgCdTe photoconductive IR detector can be improved by a significant factor (more than one order of magnitude on average over the 6 to 20 µm region) and the usable spectral range extended to longer wavelengths. This development, intended first for high resolution spectroscopy, can be applied to other cases where the sample or setup size severely limits the signal-to-noise ratio of the measurements. The performances of the detector developed on the AILES Beamline at SOLEIL will be presented.

Figure 1: Performance comparison between the infrared detector developed at SOLEIL and the standard available detector. Example of the CO2 absorption recorded using the two types of detectors under the same conditions.

Nancristaux colloidaux infrarouges

Emmanuel Lhuillier

INSP

Les nanocristaux colloidaux sont des nanoparticules de semi-conducteur dont la croissance est faite en solution. C’est en particulier leurs propriétés de luminescence à température ambiante et ajustable avec la taille qui a suscité l’intérêt pour ces nanoparticules. Au début des années 90, ces matériaux ont été synthétisés dans des matériaux à grand gaps (CdSe) avec des propriétés optiques dans le visible. Ce n’est que depuis une dizaine d’année que des matériaux à plus petit gap (PbS) ont pu être synthétisés par voie colloidale, d’abord dans le proche infrarouge avec pour objectif le design de cellule solaire. Dans ce talk je vais parler de développement encore plus récent que sont les nanocristaux à base de chalcogénures de mercure(HgTe et HgSe) et dont les propriétés infrarouges permettent de balayer le moyen et même maintenant le lointain infrarouge jusqu’à 20µm.

Mon talk se divisera en trois parties. La première partie sera une longue introduction aux nanocristaux colloidaux et à leur première application grand public que sont les fluorophores pour les écrans. Puis je parlerais des nanocristaux de HgTe qui sont un exemple de system à transition interbande de faible énergie. J’aborderais les phénomènes de photoconduction et évoquerais les premiers dévellopment de caméra IR utilisant les nanocristaux colloïdaux comme matériaux actifs. Pour finir la dernière partie de mon talk sera dédiée à l’observation de processus intrabande dans les nanocristaux de HgSe autodopés

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Emission thermique de lumière avec des

nanoantennes métalliques

Patrick Bouchon

ONERA Palaiseau (FRANCE)

On peut manipuler efficacement la lumière avec des nanoantennes métalliques, et en particulier on peut contrôler (spectralement, spatialement, en polarisation) son absorption. En vertu de l'équivalence entre émissivité et absorptivité (loi de Kirchhoff), les nanoantennes peuvent ainsi devenir des sources de lumière fonctionnant par émission thermique. Dans cet exposé, je montrerai qu'il est possible de développer une métasurface à base d'ensemble de nanoantennes métal-isolant-métal, où chaque nanoantenne, de dimensions petites devant la longueur d'onde, se comporte comme un émetteur à une polarisation et une longueur d'onde données, indépendamment des antennes voisines. Il est ainsi possible d'obtenir un contrôle spatial, spectral et en polarisation de la lumière, et d'encoder des images. J'évoquerai également l'intérêt du résonateur de Helmholtz optique, qui permet de contrôler la finesse spectrale de l'émission thermique.

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Harnessing blackbody radiation with metasurfaces

E. Sakat, L. Wojszwzyk, J-P. Hugonin, F. Marquier, J.-J. Greffet E-mail: emilie.sakat@institutoptique.fr

Laboratoire Charles Fabry, Institut d'Optique Graduate School, CNRS, Université Paris Saclay,

France The goal of this work is to discuss how blackbody radiation can be tailored using nanoantennas. In the last 15 years, many ideas have completely changed our perspective on what can be done with incandescent sources. Taking advantage of the existence of the spatial coherence of surface waves, highly directional sources have been demonstrated [1]. Taking advantage of the spectral resonances of plasmonic structures, quasimonochromatic sources have been fabricated [2]. Electrical modulation of the absorptivity has allowed modulating the thermal emission at a rate of 600 kHz by a stack of quantum wells [3]. We present here a novel approach. We start by introducing a generalized Kirchhoff law valid for anisothermal bodies. The idea is simple: Kirchhoff’s law can be extended to objects such as a hot nanoemitter in the gap of a cold nanoantenna.To illustrate the concept, we will take the example of a metasurface consisting in an array of half-wavelength nanoantennas. By inserting a small volume of absorber in the gap of a dimer antenna, it is possible to enhance the power extracted from the small hot volume by more than three orders of magnitude. This can be achieved provided that the absorber has been properly designed in order to verify a critical coupling condition with the antenna.

A key feature of this type of source is the small size of the heated volume. While usual incandescent sources cannot be modulated at high frequency due to their thermal inertia, nanovolumes can be cooled in a few tens of ns offering a new opportunity for high speed modulation. In order to produce a practical emitter, a periodic array of antennas can be fabricated which results in a metasurface for IR emission. Finally, by tuning the properties of the antennas, the metasurface can control the frequency, polarization and direction of emission.

References

1. J.J. Greffet et al. Nature 416, 61 (2002). 2. X. Liu et al. Phys.Rev.Lett. 107, 045901 (2011). 3. T. Inoue et al., Nature Mat. 13, 928 (2014).

Figure 1: Near field enhancement of a hot nanoemitter inserted in the gap of a dimer plasmonic antenna

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RANDOM METAMATERIAL ABSORBERS N.Fernez1, F. Garet2, C. Boyaval1, E. Lheurette1, J. L. Coutaz2, and D. Lippens1

1Univ. Lille, UMR 8520 - IEMN, F-59000 Lille, France 2 Université de Savoie, UMR 5130 , IMEP-LAHC F-73376 Le Bourget du Lac cedex

Metamaterial-based nearly-total absorbers are narrowband in essence owing to their surface to free space impedance matching that results from a magnetic resonance. Many efforts are now paid for improving their bandwidth capability notably through multisize pattern periodic array that resonate at various frequencies. Despite the existence of an optimal period that satisfies the so-called critical coupling criterion, the enhancement in the absorption is local and not related to an array effect. On this basis, some disorder can also be introduced in the position of resonators notably with a Poisson distribution function. Also for absorbers operating in the optical regime such random metamaterial structures pave the way of a great simplification in the fabrication of large area absorbers. In this communication, we illustrate the potentiality of random metamaterial in terms of overall performance and technological challenges for some metasurfaces operating at Terahertz frequencies. To this aim, micrometer-size ( fig. 1(b) –(c)) regular and random arrays of aluminum patches deposited onto a kapton dielectric grounded substrate ( Fig. 1(a) were fabricated and experimentally assessed by Time Domain Spectroscopy. From the physics side, full wave simulations ( CST code ) of the field maps show antiparallel configurations of the conduction currents in the metal sheet and displacement currents within the dielectric layer. In-plane magnetic dipoles are thus created with significant dipole –dipole inteplay when two resonators are in close proximity. These coupling effects yield some splitting in the resonance frequency that explains a broader band for random structure whereas a narrow band still hold for a regular arrangement. ( Fig 1 e-f )

(a) (b) (c)

(d ) (e )

(f)

Figure 1 ( a ) Optical view of an absorbing metasurface made of 400 magnetic resonators randomly positioned onto a 50µm-thick kapton film grounded with a 100 µm-thick aluminum uniform plate (b) Scanning Electron Microphotograph of

hexagonal shaped Aluminum ~60µm-thick ~500µm wide metallic plates (c) (d) schematic of this prototype modeled by Full wave analysis (e ) numerical absorbance and (f) experimental reflectance

Acknowledgments: N. Fernez would like to thank DGA (Délégation Générale à l’Armement) and the University of Lille for his PhD scholarship. This work was partly supported by the CNRS RENATECH network

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Réseau de plots hexagonals métalliques sur Kapton(05-10-2016)

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Compact THz Isolator Using Nonreciprocal Magnetoplasmonic Mirror

T. Horák@$, M. Vanwolleghem@, G. Ducournau@, O. Stepanenko@, K. Postava$ and J.-F. Lampin@ @ Univ. Lille, CNRS, Centrale Lille, ISEN, Univ. Valenciennes, UMR 8520 - IEMN, F-59000 Lille, France

$Department of Physics and Nanotechnology Center, Technical University of Ostrava, 17. listopadu 15, 708 33 Ostrava, Czech Republic

A key element for protecting of coherent sources and achieving of desired power stability and spectral purity for certain applications is an isolator, which in THz range has still no effective solution. Our concept of a novel THz isolating device builds on the recently demonstrated proof-of-principle design based on a one-way reflecting surface for NIR and visible wavelengths, combining gyrotropy nearby plasmon resonances. A first crucial requirement to realize this is a sufficiently strong THz gyrotropic material. In the last decade new fabricating and material processing methods have enabled creating a new type of ferrite material with hexagonal magnetoplumbite structure (e.g. SrFe12O19). They are formed by iron, oxygen and one or more other elements, which could be barium, strontium, cobalt, or a combination of these. Gyrotropy in this material is created by gyromagnetic effects when saturation magnetization precesses nonreciprocally at Larmor frequency ω0 = µ0γHint around internal magnetic field Hint. Permeability of hexaferrites acquires in THz range a tensorial form: and its unequal off-diagonal elements are responsible for nonreciprocal (NR) behavior.

First important step for development of the device is complete material characterization of used hexaferrites. In a first instance the diagonal permittivity and permeability elements have been characterized using both standard Time-Domain Spectrometry (TDS) and time-windowed Vector Network Analyzer (VNA) characterization. In a second step, the off-diagonal tensorial contributions are characterized in a Faraday configuration by measuring the magnetized samples with magnetization co-aligned with the beam path. This was done both on the TDS and the VNA setup. The resulting NR rotation of the polarization of the incident linearly-polarized wave is the result of the broken degeneracy of the propagation index of the two counter-rotating circularly polarized waves that form the linearly polarization. Because the VNA’s head-units emit and receive only linearly-polarized beam-modes in vertical direction, we placed for maximum sensitivity the polarizer P1 at 45° and measured transmittances at several angles of P2 in order to completely characterize the rotation of polarization in the sample. The NR of the polarization rotation is directly obtained by the asymmetry of the 2x2 S-matrix elements of the sample, as illustrated in Fig. 1Left for one generic (P1, P2) setting. The obtained strong THz gyrotropy of hexaferrites proves their unique potential for THz isolator applications, as will be shown by first designs of a NR magnetoplasmonic mirror using the fitted material parameters (Fig. 1Center). Our design combines strong gyromagnetic properties of hexaferrites in THz range with surface plasmon resonances formed due to the presence of a metallic grating at the hexaferrite surface. Close to these SPP resonances there can appear frequency ranges where the device acts as a one-way mirror (Fig. 1Right).

Figure 1: Left: Forward (S21) and backward (S12) transmittance of magnetized Sr-hexaferrite (FB6N) measured in free-space (75-110 GHz) with angles of polarizers P1 = -45°, P2 = 30° from vertical axis. Center: design of the isolator. Right: simulation results showing a shift of reflection dip according the direction of substrate magnetization (or incidence).