He who seeks shall find.

-- Italian Proverb

Our research embraces key areas of nanoelectronics and nanophotonics, including organic semiconductors, nanowires, plasmonics, and new ideas in quantum and “cognitive” optical networks. We are particularly interested in fundamental properties of materials emerging from small dimensionality, large interface area, hybridization and artificial nanostructuring.

The main topics are:

Light Emission and Detection at the Nanoscale

Low dimensional material structures, like quantum dots and nanowires, offer immense possibilities for tailoring the optoelectronic response of heterogeneous nanoscale devices. We study the fundamental mechanisms of charge carrier photogeneration, transport and recombination in these nanostructures at extremely broad time and energy scales, and implement prototype devices such as nanowire lasers, quantum dot solar cells, and nanowire photodetectors.

These studies will push scaling limits and efficiency of photodetectors and nanoscale light sources for future integrated photonic circuits.

Ongoing project:

• Superconducting nanowire single photon detectors (NRF-QEP)

Relevant publications:

• Topological insulator metamaterial with giant circular photogalvanic effect, X. Sun, G. Adamo, M. Eginligil, H.N.S. Krishnamoorthy, N.I. Zheludev, C. Soci, arXiv:2008.08772
• Intrinsic lead ion emissions in zero-dimensional Cs4PbBr6 nanocrystals, J. Yin, Y. Zhang, A. Bruno, C. Soci, O. Bakr, J.-L. Bredas, O. Mohammed, ACS Energy Lett. 2, 2805 (2017)
• Hot exciton cooling and multiple exciton generation in PbSe quantum dots, M. Kumar, S. Vezzoli, Z. Wang, V. Chaudhary, R.V. Ramanujan, G.G. Gurzadyan, A. Bruno, C. Soci, Phys. Chem. Chem. Phys. 18, 31107 (2016)
• Small-size effects on electron transfer in P3HT/InP quantum dots, J. Yin, M. Kumar, Q. Lei, L. Ma, R.S.S. Kumar, G. Gurzadyan, C. Soci, J. Phys. Chem. C, 119, 26783 (2015)
• GaAs/AlGaAs nanowire photodetector, X. Dai, S. Zhang, Z. Wang, G. Adamo, H. Liu, Y.Z. Huang, C. Couteau, C. Soci, Nano Lett. 14, 2688 (2014)
• Monolithic integration of III-V nanowire with photonic crystal microcavity for vertical light emission, A. Larrue, C. Wilhelm, G. Vest, S. Combrié, A. De Rossi, C. Soci, Optics Expr. 20, 7758 (2012)
• Tailoring the Vapor-Liquid-Solid growth toward the self-assembly of GaAs nanowire junctions, X. Dai, S.A. Dayeh, V. Veeramuthu, A. Larrue, J. Wang, H. Su, C. Soci, Nano Lett. 11, 4947 (2011)
• Nanowire photodetectors, C. Soci, A. Zhang, X.-Y. Bao, H. Kim, Y. Lo, D. Wang, J. Nanosci. Nanotechnol. 10, 1430 (2010)

New Materials & Structures for Metamaterials

Electromagnetic metamaterials are artificial structures engineered to have optical properties that do not occur in natural materials. We employ unconventional material platforms such as hybrid perovskites, phase-change chalcogenide and topological insulators to demonstrate new metamaterial concepts and to control light-matter interaction.

Functional metamaterials obtained by hybridization and nanostructuring of emerging material platforms, with unique electronic, optical and magnetic properties, enable reconfiguration, spectral tunability, and new ways to interact with electrons and other quasiparticles.

Ongoing projects:

• Perovskites for tunable nanoantennas at visible and infra-red frequencies (A*STAR-AME)
• Quantum and topological nanophotonics (MOE-Tier 3)

Relevant publications:

• Metamaterial enhancement of metal-halide perovskite luminescence, G. Adamo, H. Krishnamoorthy, D. Cortecchia, B. Chaudhary, V. Nalla, N. Zheludev, C. Soci, Nano Lett., accepted (2020)           
• Infrared dielectric metamaterials from high refractive index chalcogenides, H.N.S. Krishnamoorthy, G. Adamo, J. Yin, V. Savinov, N.I. Zheludev, C. Soci, Nat. Commun. 11, 1692 (2020)
• Engineering the emission of broadband 2D perovskites by polymer distributed Bragg reflectors, P. Lova, D. Cortecchia, H.N.S. Krishnamoorthy, P. Giusto, C. Bastianini, A. Bruno, D. Comoretto, C. Soci, ACS Photonics 5, 867 (2018)
• A non-volatile chalcogenide switchable hyperbolic metamaterial, H.N.S. Krishnamoorthy, B. Gholipour, N.I. Zheludev, C. Soci, Adv. Optical Mater. 1800332 (2018)
• Plasmonics of topological insulators at optical frequencies, J. Yin, H.N.S. Krishnamoorthy, G. Adamo, A.M. Dubrovkin, Y.D. Chong, N.I. Zheludev, C. Soci, NPG Asia Materials 9, e425 (2017)
• Organometallic perovskite metasurfaces, B. Gholipour, G. Adamo, D. Cortecchia, H.N.S. Krishnamoorthy, M.D. Birowosuto, N.I. Zheludev, C. Soci, Adv. Mat. 29, 1604268 (2017)
• Plasmon-polaron coupling in conjugated polymer on infrared nanoantennas, Z. .Wang, J. Zhao, B. Frank, Q. Ran, G. Adamo, H. Giessen, C. Soci, Nano Lett.15, 5382 (2015)
• Plasmonic nanoclocks, H. Liu, Z. Wang, .J. Huang, H.J. Fan, N.I. Zheludev, C. Soci, Nano Lett. 14, 5162 (2014)

Organic Optoelectronics

Organic semiconductors (conjugated polymers, molecular crystals, small molecules) and organic-inorganic hybrids (organo-metal halide perovskites, heterostructures) are widely considered for applications in low-cost organic solar cells, light-emitting diodes, field-effect transistors and sensors. Lying at the boundary between conventional semiconductor crystals and disordered materials, these systems have extremely rich photophysical properties.

By advancing the understanding of fundamental optical and transport properties of these systems, we aim at finding new ways to optimize efficiency and extend functionality of organic photovoltaic, photo/chemo/bio-sensors, and light emitting devices.

Ongoing projects:

• Perovskite optoelectronics: multidimensional perovskites for high performance solution-processed light-emitting devices (NRF-CRP)
• Probing the biotic/abiotic interface of living cells on metasurfaces (MOE-Tier 1)

Relevant publications:

• Large polaron self-trapped states in three-dimensional metal-halide perovskites, W.P.D. Wong, J. Yin, B. Chaudhary, X.-Y. Chin, D. Cortecchia, S-Z.A. Lo, A.C. Grimsdale, G. Lanzani, C. Soci, ACS Materials Lett. 2, 20 (2020)
• White light emission in low-dimensional perovskites, D. Cortecchia, J. Yin, A. Petrozza, C. Soci, J. Mat. Chem. C 7, 4956 (2019)
• Brightness enhancement in pulsed-operated perovskite light-emitting transistors, F. Maddalena, X.Y. Chin, D. Cortecchia, A. Bruno, C. Soci, ACS Appl. Mater. Interfaces 10, 37316 (2018)
• Structure-controlled optical thermoresponse in Ruddlesden-Popper layered perovskites, D. Cortecchia, S. Neutzner, J. Yin, T. Salim, A.R.S. Kandada, A. Bruno, Y.M. Lam, J. Martí-Rujas, A. Petrozza, C. Soci, APL Materials 6, 114207 (2018)
• Polaron self-localization in white-light emitting hybrid perovskites, D. Cortecchia, J. Yin, A. Bruno, S.-Z. A. Lo, G.G. Gurzadyan, S. Mhaisalkar, J.L. Bredas, C. Soci, J. Mater. Chem. C 5, 2771 (2017)
• X-ray scintillation in lead halide perovskite crystals, M.D. Birowosuto, D. Cortecchia, W. Drozdowski, K. Brylew, W. Lachmanski, A. Bruno, C. Soci, Scientific Reports, 6, 37254 (2016)
• Lead iodide perovskite light-emitting transistor, X.Y. Chin, D. Cortecchia, J. Yin, A. Bruno, C. Soci, Nat. Commun. 6, 7383 (2015)
• Interfacial charge transfer anisotropy in polycrystalline lead iodide perovskite films, J. Yin, D. Cortecchia, A. Krishna, S. Chen, N. Mathews, A.C. Grimsdale, C. Soci, J. Phys. Chem. Lett. 6, 1396 (2015)
• Mapping polarons in polymer FETs by charge modulation microscopy in the mid-infrared, X.Y. Chin, J. Yin, Z. Wang, M. Caironi, C. Soci, Scientific Reports 4, 3626 (2014)

Specialty Optical Fibers and Photonic Networks

Optical fibers provide a mature, mass-manufacturable technology that has given rise to complex networks of interconnected computing nodes, transferring information around the planet. Our research in this area involves four layers of activity: 1. the integration of functional materials and devices within optical fibres, 2. the development of quantum technologies on the fibre platform, 3. the exploration of network architectures for optical neuromorphic computing, and 4. the application of deep-learning methods for optical fibre imaging and signal transmission.

“Cognitive” and quantum photonic networks may drastically increase efficiency and functionality of existing approaches for imaging, signal processing, and optical telecommunications.

Ongoing projects:

• Nanophotonic quantum toolkit on the fibre platform (A*STAR-QTE)
• Application of machine learning to complex photonics (MOE-Tier 1)

Relevant publications:

• Image reconstruction through a multimode fiber with a simple neural network architecture, C. Zhu, E.A. Chan, Y. Wang, W. Peng, R. Guo, B. Zhang,* C. Soci,* Y. Chong,* arXiv:2006.05708
• Coherent perfect absorption of single photons in a fibre network, A. Vetlugin,* R. Guo, A. Xomalis, S. Yanikgonul, G. Adamo, C. Soci,* N.I. Zheludev, Appl. Phys. Lett. 115, 191101 (2019)
• Optical NP problem solver on laser-written waveguide platform, M.R. Vazquez, V. Bharadwaj, B. Sotillo, S.-Z.A. Lo, R. Ramponi, N.I. Zheludev, G. Lanzani, S.M. Eaton, C. Soci, Opt. Expr. 26, 702 (2018)
• All-optical implementation of the ant colony optimization algorithm, W. Hu, K. Wu, P.P. Shum, N. Zheludev, C. Soci, Scientific Reports 6, 26283 (2016)
• Lithography assisted fiber-drawing nanomanufacturing, B. Gholipour, P. Bastock, L. Cui, C. Craig, K. Khan, D.W. Hewak, C. Soci, Scientific Reports 6, 35409 (2016)
• Amorphous metal-sulphide microfibers enable photonic synapses for brain-like computing, B. Gholipour, P. Bastock, C. Craig, K. Khan, D. Hewak, C. Soci, Adv. Opt. Mat. 3, 635 (2015)
• Computing matrix inversion with optical networks, K. Wu, C. Soci,* P.P. Shum, N.I. Zheludev, Optics Expr. 22, 295 (2014)
• An optical fibre network oracle for NP-complete problems, K. Wu, J. García de Abajo, C. Soci,* P.P. Shum, N.I. Zheludev, Light: Science & Applications 3, e147 (2014)