Stage

  • (en anglais) Integrated Mid-IR photonics: High quality factor resonators

    A partir de mars 2024

    Adel Bousseksou

    adel.bousseksou@c2n.upsaclay.fr - +33 1 70 27 06 22

    Département Photonique

    Stage

    Scientific project:  Applications relying on mid-infrared radiation (MIR, l = 3-12 μm) have progressed at a rapid pace recently, stimulated by scientific and technological breakthroughs. For instance MIR cameras have enabled thermal imaging and the invention of the quantum cascade laser (QCL) has enabled a vast range of applications in spectroscopy, metrology, medicine. In addition to the generation and detection of light, a key functionality for most photonic systems is the possibility to electrically control the amplitude, phase, and polarization of a laser beam up to ultrashort time scales. Contrary to the visible and near-IR range, in the MIR range passive or active integrated components such as modulators and directional couplers do not exist, but recent experiments [1] have revealed propagation losses less that 1dB/cm at l=5.2µm. In this context, the host team has recently developed passive integrated waveguides on III-V semicondutor plaforms (InGaAs/InP and AlGaAs/GaAs), and identified the opportunity of greatly improving the propagation losses at longer wavelengths.

    But du stage/internship objectives: The goal of the internship is to develop mid-infrared integrated optical resonators based on a low loss integrated waveguide geometry. The perspective student will perform the design of the optical cavities such as ring or racetrack resonators. The material systems that will be investigated are GaAs/AlGaAs-on-GaAs and InGaAs/InP-on-InP. The subtle design of optical waveguide features such as optical refractive index contrast, free carrier absorption and geometric parameters will be a primordial element that will be taken into account. Operation will be optimized for the 8-9 mm wavelength range, in the center of an atmospheric transparency region. The sample characterizations will take place with a dedicated end fire coupling setup equipped with a variety of mid-IR laser sources (allowing to control the injected wavelength, power and polarization) and detectors. She/he will benefit from the experience of the host team (https://odin.c2n.universite-paris-saclay.fr/en/activities/mir-thz-devices/) in quantum and electromagnetic design of opto-electronic devices, of cleanroom fabrication, and device opto-electronic characterizations [2].

     

    Qualités du candidat(e) requises/ required skills: Basic knowledge in optics and electromagnetics, semiconductor physics, optoelectronics, ability to work in groups, interest for experimental work.

    Relevant References:[1]  Kevin Zhang, Gerhard Böhm, Mikhail A. Belkin; Mid-infrared microring resonators and optical waveguides on an InP platform. Appl. Phys. Lett. 7 February 2022; 120 (6): 061106. https://doi.org/10.1063/5.0077394 

    [2]    S. Pirotta et al., "Fast amplitude modulation up to 1.5 GHz of mid-IR free-space beams at room-temperature", Nat. Commun. 12, 799 (2021).   https://www.nature.com/articles/s41467-020-20710-2 

    poursuite en thèse envisageable

  • (en anglais) Ultra-Low power semiconductor saturable absorber mirrors in the mid-IR

    A partir de mars 2024

    Raffaele Colombelli

    raffaele.colombelli@universite-paris-saclay.fr - +33 1 70 27 06 29

    Département Photonique

    Stage

    Scientific project: Saturation of the light-matter interaction is a general nonlinear feature of material systems, be they atoms or semiconductors [1]. A saturable absorber exhibits an absorption coefficient that depends on the incident intensity. In semiconductors, the possibility of judiciously controlling saturation phenomena is of great importance for fundamental physics as well as applications. A seminal example is the development of the semiconductor saturable absorption mirror (SESAM) [2] based on interband transitions in quantum wells, that revolutionized the field of ultra-fast lasers in the vis/near-IR spectral range, allowing ultra-fast lasers pulses (see picture). Ultra-fast lasers based on SESAMs find applications in several domains, and even in quantum phenomena.

    In the mid-IR (λ~10 µm), the intensity required to reach saturation is very high, about 1 MW/cm2. This very high value explains why saturable absorbers, SESAM mirrors, bistable systems are missing from the current toolbox of mid-IR opto-electronic devices: they could only be used with extremely high power laser sources and are incompatible with the output power levels of typical mid-IR semiconductor lasers such as quantum cascade lasers (QCLs).

    The host team has recently proposed that absorption saturation can be engineered if the system operates in the so called strong light-matter coupling regime [3], and has also provided its experimental proof [4]. In this regime, the response is governed by coupled light-matter states called polaritons. In particular, they designed a SESAM with ultra-low saturation intensities, that are compatible – for the first time – with table-top QCLs.

    The goal of this internship is to demonstrate ultra-low power nonlinear mirrors in the mid-IR, supported by the recent results obtained by the host team [4]. The experiments will be performed by optical pumping with a tunable, commercial QCL. Two experiments will be performed.

    In the first, already implemented experimental configuration, the device reflectivity spectrum will be measured using the tunable QCL at different incident powers. The theoretical outcome of the experiment is shown panel (a): the low intensity spectrum (blue) shows two polariton resonances. Increasing the laser intensity leads to the collapse of the light-matter coupling towards the purple curv: this is the manifestation of saturation. In a second experiment, the QCL power is varied while the wavelength is fixed: a typical outcome is in panel (b). This experiment permits to gauge the saturation threshold to be compared with simulations, for further device optimization. If time permits, charac-terizations in the time domain will be performed too. This project, that evolves in the context of a running ANR grant,  opens up exciting perspectives in the realization of ultrafast, mode-locked mid-IR fiber and semiconductor lasers.

    [1] R. W. Boyd, Nonlinear Optics, 3rd ed. (Elsevier, Amsterdam, 2008).

    [2] U. Keller, et al., Opt. Lett. 17, 505 (1992) and U. Keller, Nature 424, 831 (2003)

    [3] M. Jeannin, JM Manceau, R. Colombelli, Phys. Rev. Lett 127, 187401 (2021)

    [4] M. Jeannin, E. Cosentino, et al., Appl. Phys. Lett. 122, 241107 (2023)

    poursuite en thèse envisageable

  • (en anglais) All-Dielectric Metamaterials for Zero-Index-Photonic  : Negative Index and Near-Zero Index Materials at Terahertz

    A partir de février 2024

    Éric Akmansoy

    eric.akmansoy@universite-paris-saclay.fr - ‭01 70 27 05 29‬

    Département Photonique

    Stage

    M2 internship research proposal

    All-Dielectric Metamaterials for Zero-Index-Photonic  :

    Negative Index and Near-Zero Index Materials at Terahertz

    Éric Akmansoy

    Département Photonique - C2N

    __________________

    General framework

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

    We consider All-Dielectric Metamaterials (ADM) which are the promising alternative to metallic metamaterials, because they undergo no ohmic losses and consequently benefit of low energy dissipation and because they are of simple geometry [3]. They consist of high permittivity dielectric resonators involving Mie resonances. We have experimentally demonstrated negative effective permeability and/or permittivity by the means of all-dielectric metamaterials [4]. Previously, we have also demonstrated a negative index all-dielectric metamaterial [5].

    Metamaterials that exhibit Near-Zero Index metamaterials (NZI) have a large number of applications including wavefront engineering, directivity and gain enhancement of antennas, electromagnetic cloaking, phase matching for nonlinear applications, unidirectional transmission, defect waveguides, Zero-index Materials (ZIM) cavities, . . . [6]

    The main feature of Zero Index Materials is that the phase distribution of the EM field is nearly constant, because of the decoupling of the electric and the magnetic fields, that results in the “decoupling of the “spatial” (wavelength) and the “temporal” (frequency)”. [1] Zero Index Photonics has consequently fundamental and technological implications on different subfields of optics and nanophotonics. Antennas systems and optical components operating in the terahertz range are the targeted devices.

    Recently, we have numerically demonstrated a metadevice, namely, a metalens that focuses an incident plane wave and is less than one and a half wavelength thick. Its focal length is only a few wavelengths and the spot in the focal plane is diffraction-limited. [7]. We have also addressed the role of the coupling of the modes of Mie resonances in an all-dielectric metamaterial so as to achieve negative index and Near-Zero Index at terahertz frequencies [8].

    Work Plan

    During this M2 interbship, All-Dielectric Metamaterials will be numerically designed ; Negative Index and Near-Zero Index will be addressed. The All-Dielectric Metamaterials will also be characterized in the THz frequency range. In the first instance, our aim is to demonstrate near-zero index and negative index. Then antennas systems and various photonics components will be considered.

    This work takes place within the framework of the DisPonT ANR project. It gathers a group of scientists of different disciplines (chemists, material scientists and physicists) [9] which deals with All-Dielectric Metamaterials design, hight dielectric material fabrication, structuration and characterization [9, 10].

    ________________________

    Bibliography

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

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

    [3]  S. Jahani and Z. Jacob, “All-dielectric metamaterials,” Nature Nanotechnology, vol. 11, pp. 23 EP –, 01 2016.

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

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

    [6]  N. Shankhwar, Y. Kalra, Q. Li, and R. K. Sinha, “Zero-index metamaterial based all-dielectric nanoantenna,” AIP Advances, vol. 9, no. 3, p. 035115, 2019.

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

    [8]  Akmansoy, Eric and Marcellin, Simon, “Negative index and mode coupling in all-dielectric metamaterials at terahertz frequencies,” EPJ Appl. Metamat., vol. 5, p. 10, 2018.

    [9]  C. Dupas, S. Guillemet-Fritsch, P.-M. Geffroy, T. Chartier, M. Baillergeau, J. Mangeney, J.-F. Roux, J.-P. Ganne, S. Marcellin, A. Degiron, and É. Akmansoy, “High permittivity processed SrTiO3 for metamaterials applications at terahertz frequencies,” Scientific Reports, vol. 8, no. 1, p. 15275, 2018

    [10] Djemmah, Djihad Amina and Geffroy, Pierre-Marie and Chartier, Thierry and Roux, Jean-François and Bouamrane, Fayçal and Akmansoy, Éric. "Processing High Permittivity TiO2 for All-Dielectric Metamaterials Applications at Terahertz Frequencies" , Proceedings of the Sixth International Symposium on Dielectric Materials and Applications (ISyDMA’6), pp. 177–183, 2022

     

    poursuite en thèse envisageable

  • SNOM development for guided wave near-field characterization

    A partir de janvier 2024

    Béatrice Dagens

    beatrice.dagens@c2n.upsaclay.fr - 01 70 27 04 86

    Département Photonique

    Stage

    consult the offer in attached file

  • (en anglais) Silicon optomechanics for microwave-photonic transduction

    A partir de novembre 2023

    Carlos RAMOS

    carlos.ramos@c2n.upsaclay.fr - 01 70 27 40 53

    Département Photonique

    Stage

    Conversion between electrical and optical signals enabled the use of near-infrared (near-IR) photons for high data rate transmission through optical fibre networks. Likewise, coherent conversion between microwave and optical photons stands as a promising solution to transfer quantum states between remote quantum processors, thus enabling the development of large-scale quantum networks. However, the vast frequency difference between microwave (GHz) and near-IR (200 THz) optical photons hampers direct coherent conversion. The Silicon photonics team at C2N leads a new ERC project, SPRING, that aims at demonstrating phonon-mediated transduction between microwave and near-IR signals at the quantum regime.

  • (en anglais) Neuromorphic silicon photonic circuits for smart gas sensors

    A partir de novembre 2023

    Carlos RAMOS

    carlos.ramos@c2n.upsaclay.fr - 01 70 27 40 53

    Département Photonique

    Stage

    Air pollution poses a great environmental risk to health, accounting for nearly half a million premature deaths each year in Europe. Ubiquitous, real-time air quality monitoring could reduce the negative impact of pollution. However, air pollution monitoring generally relies on costly (k€ range), complex stationary equipment, that limits its widespread deployment. The Silicon Photonics team at C2N leads a new European project, SYMPHONY that aims at developing a new technology combining different silicon photonics platforms and silicon microelectronics to enable the implementation of dense networks of cloud-connected, low-cost (< 100 €), and portable (5-80 cm3 size) easy-to-use smart sensors, capable of multi-target detection in air pollution monitoring.

  • (en anglais) Photonic neuromorphic computing with coupled microlaser spiking neurons

    A partir de novembre 2023

    Sylvain Barbay

    sylvain.barbay@c2n.upsaclay.fr - 0170270451

    Département Photonique

    Stage

    Neuromorphic photonics is an expanding field of research at the heart of recent progresses in analog computation and machine learning. Its goal is to investigate new ways to process optical information or to compute using brain-inspired physical concepts.

    We propose to investigate the physics and applications of coupled spiking photonic nodes implementing artificial spiking neural networks. Each node (optical neuron) is materialized by a micropillar laser with integrated saturable absorber, whose neuromimetic properties have already been explored in the team. In neurons, information is coded with spikes (electrical pulses) which are excited in an all-or-none fashion provided input stimuli to the neuron soma exceed a given threshold. This generic property is called excitability and has been demonstrated in micropillar lasers with optical spikes [1]. Though, the optical spikes emitted by these latter are more than one millions times shorter in duration than biological action potentials. Hence, photonic neurons could in principle be interesting to build ultrafast artificial neural networks with low power consumption.

    The objective of the internship will be to take part to the projects developed in the group to fabricate and study neuromorphic architectures, understand the physics involved in the dynamics of these coupled microlasers and demonstrate ultrafast analog computation. The work will mainly involve experimental and modeling activities, with nanofabrication aspects. The internship will take place at the C2N (Palaiseau) which hosts a first-class nanofabrication facility.

    The applicant should have a background in physics, optics, laser physics, semiconductor physics. Background in semiconductor lasers and/or nonlinear dynamics and/or machine learning is appreciated but not compulsory.

    Website: https://toniq.c2n.universite-paris-saclay.fr/fr/activites/smila/

    Reference

    [1] Micro-lasers for neuromorphic computing V. A. Pammi, S. Barbay, Photoniques 104, 26-29 (2020) https://doi.org/10.1051/photon/202010426

    poursuite en thèse envisageable

  • (en anglais) Mid-infrared ultrafast pump-probe spectroscopy of the saturation process in bound-to-continuum polaritons

    A partir de novembre 2023

    Jean-Michel Manceau

    jean-michel.manceau@c2n.upsaclay.fr - 0170270673

    Département Photonique

    Stage

    Non-equilibrium Bose-Einstein condensation of exciton-polaritons have become a vast playground for fascinating phenomena previously reserved to ultracold atomic gases. In particular, it has led to the demonstration of superfluidity, topological lasing and non-Hermitian effects. In these polaritonic systems the fundamental energy scale is intrinsically fixed by the interband transition of the underlying material, limiting flexibility and also the magnitude of the Rabi splitting. Conversely, the transition energy of intersubband (ISB) polaritons in doped semiconductor quantum well (QW) structures can be freely tuned by varying the QW width and doping to reach the mid-IR and Far-IR range of the electromagnetic spectrum. As their excitonic counter-part, it has been predicted that they can show exotic quantum behavior such as final state stimulation and condensation. This would open interesting perspectives of a condensate operating at much lower energy scale and interacting with a 2D gas of electrons to form Fermi-Bose mixtures. Our team has made major progresses towards that goal in the recent years. Starting with dispersion engineering [1], we developed a clear roadmap towards condensation [2] and confirmed the existence of a spontaneous process based on ISB polariton - LO phonon scattering [3]. More recently, in the frame of an international collaboration, we demonstrated for the first time polariton-polariton interaction in the regime of final state stimulation (see figure) [4]. In this pump-probe experiment, we have shown an amplification process occurring on an ultrafast time scale; this is the key ingredient towards condensation.
    In this continuity, this internship aims at exploring the nonlinearities of a novel polaritonic scheme based on the strong coupling regime of bound-to-continuum transition and a microcavity [5]. Such novel polaritonic scheme has been demonstrated recently by our team and hold great promises for the demonstration of condensation with polaritons issued from a 2D gas of electrons. The main task of the candidate will be the exploration of the saturation process in such systems, using already existing samples. The candidate will have to use the optical MIR pump-probe setup recently built in the team and characterized the reflectance of the system as a function of the pump fluence. The candidate will then record the dynamic of the system on an ultrafast time scale to fully capture the nonlinearities at play. Finally, she/he will use an in-house numerical code to simulate the polaritons scattering dynamic and amplification process within the novel polaritonic architectures that was characterized earlier on.
    Furthermore, and if time allows, the candidate will also be invited to follow the different steps of the fabrication process of the samples in clean room. The project offers a global view of the different activities led in our team from the numerical design, the fabrication in cleanroom and the optical characterization.
    [1] J.-M. Manceau et al., Mid-Infrared Intersubband Polaritons in Dispersive Metal-Insulator-Metal Resonators, Appl. Phys. Lett. 105, 8 (2014).
    [2] R. Colombelli and J.-M. Manceau, Perspectives for Intersubband Polariton Lasers, Phys. Rev. X 5, 1 (2015).
    [3] J.-M. Manceau et al., Resonant Intersubband Polariton-LO Phonon Scattering in an Optically Pumped Polaritonic Device, APL. 112, 19 (2018).
    [4] M. Knorr, J.-M. Manceau et al., Intersubband Polariton-Polariton Scattering in a Dispersive Microcavity, Phys. Rev. Lett. 128, 247401 (2022).
    [5] E. Cortese, et al., “Excitons bound by photon exchange,” Nat. Phys., (2020)

    poursuite en thèse envisageable

  • (en anglais) Development of selective wet etching for seeded epitaxy of SiGe-2H

    A partir de octobre 2023

    Laetitia Vincent

    laetitia.vincent@c2n.upsaclay.fr - 01 70 27 03 81

    Département Materiaux

    Stage

    General framework

    SEEDs team has long standing know-how in synthesis and characterisation of group-IV semiconductor. At the moment we are especially investigating different ways to synthesize the very promising hexagonal SiGe-2H phase (an allotrope of the standard diamond cubic 3C structure) which exhibits a direct band gap and excellent light emission capabilities [1] with a tuneable emission wavelength in the mid infrared between 1.8-3.5 μm by a concentration range of 0-40% of Si. This material may therefore provide additional photonic functionality to the silicon technology and fill the gap between electronics and photonics industry. We aim at
    integrating SiGe-2H light sources on silicon on insulator in a CMOS compatible way.
    We have pioneered an original method to achieve a shear induced phase transformation in Ge and Si nanowires NWs resulting in unprecedented heterostructures with quasi periodic embedded 2H domains distributed all along the nanowire (fig). The process is described in refs [2,3]. Using Si/Ge/Si heterostructures enables promoting and localising the transformed domain in the Ge section.
    We propose to combine this strain-induced process with selective epitaxial growth on the transformed SiGe-2H seed. We aim at developing a highly selective etching method to remove the cubic untransformed top part and uncover the 2H transformed domain which is expected to serve as a seed for further epitaxy in order to subsequently increase the volume of the 2H segment.

    Objectives and work plan
    The student is expected to contribute to :
    - participate to the realization of Ge thin layers in Si using UHV-CVD
    - selective etching of the cubic Si top part to uncover the Ge-2H surface
    - develop the seeded epitaxial regrowth on the Ge-2H

    More information in the attached file

    Contact :

    Laetitia Vincent, C2N, CNRS / Université Paris-Saclay, Département Matériaux / Equipe SEEDs