Metasurfaces control optical wavefronts via arrays of nanoscale resonators laid out across a surface. When combined with III-V semiconductors with strong optical nonlinearities, a variety of nonlinear effects such as harmonic generation and all optical modulation can be enabled and enhanced at the nanoscale. This review presents our research on engineering and boosting nonlinear effects in ultrafast and nonlinear semiconductor metasurfaces fabricated at the Center for Integrated Nanotechnologies (CINT). We cover our recent works on parametric generation of harmonic light via direct and cascaded processes in GaAs-metasurfaces using Mie-like optical resonances or symmetric-protected Bound State in the Continuum, and then describe the recent advances on harmonic generation in all-dielectric metasurfaces coupled to intersubband transitions in III-V semiconductor heterostructures. The review concludes on the potential of metasurfaces to serve as the next platform for on-chip quantum light generation.
Optical metasurfaces have come into the spotlight as a promising platform for light manipulation at the nanoscale, including ultrafast all-optical control via excitation with femtosecond laser pulses. Recently, dichroic metasurfaces have been exploited to modulate the polarization state of light with unprecedented speed. Here, we theoretically predict and experimentally demonstrate by pump-probe spectroscopy the capability to reconfigure the ultrafast dichroic signal of a gold metasurface by simply acting on the polarization of the pump pulse, which is shown to reshape the spatio-temporal dist…
Ultrafast nanophotonics is an emerging research field aimed at the development of nanodevices capable of light modulation with unprecedented speed. A promising approach exploits the optical nonlinearity of nanostructured materials (either metallic or dielectric) to modulate their effective permittivity via interaction with intense ultrashort laser pulses. While the ultrafast temporal dynamics of such nanostructures following photoexcitation has been studied in depth, sub-ps transient spatial inhomogeneities taking place at the nanoscale have been so far almost ignored. Here we theoretically pr…
Optical Control of Chirality by Ultrafast Symmetry Breaking in Membrane Metasurfaces
École Polytechnique Fédérale de Lausanne (EPFL)（洛桑联邦理工学院）；Shubnikov Institute of Crystallography, NRC “Kurchatov Institute”（库尔恰托夫国家研究中心舒比尼科夫晶体学研究所）；School of Physics and Engineering, ITMO University（ITMO大学物理与工程学院）；University of Brescia（布雷西亚大学）；Qingdao Innovation and Development Center, Harbin Engineering University（哈尔滨工程大学青岛创新发展基地）；Theoretical Physics and Quantum Technologies Department, National University of Science and Technology ‘MISIS’（莫斯科国立科学技术大学“MISIS”理论与量子技术系）
Optically resonant dielectric metasurfaces offer unique capability to fully control the wavefront, polarisation, intensity or spectral content of light based on the excitation and interference of different electric and magnetic Mie multipolar resonances. Recent advances of the wide accessibility in the nanofabrication and nanotechnologies have led to a surge in the research field of high-quality functional optical metasurfaces which can potentially replace or even outperform conventional optical components with ultra-thin feature. Replacing conventional optical filtering components with metasu…
The ability to dynamically steer fs pulses from a monolithically integrated source is a critical milestone for the fields of nanophotonics and ultrafast optics. The nascent field of reconfigurable metasurfaces -- made of optically resonant meta-atoms -- has shown great promise in manipulating light-matter interactions through subwavelength control of the phase, amplitude, and polarization of light. These active metasurfaces arbitrarily transform an incident wavefront using a reconfigurable spatial phase profile and thus have been limited to manipulating coherent external sources. Light emittin…
Plasmonic metasurfaces based on the extraordinary optical transmission effect (EOT) can be designed to efficiently transmit specific spectral bands from the visible to the far-infrared regimes, offering numerous applications in im-portant technological fields such as compact multispectral imaging, biological and chemical sensing, or color displays. However, due to their subwavelength nature, EOT metasurfaces are nowadays fabricated with nano- and micro-lithographic techniques, requiring many processing steps and carried out in expensive cleanroom environments. In this work, we propose and expe…
In-line Dispersion Control of Femtosecond Laser Pulses by Multilayer Huygens' Metasurfaces
Friedrich-Schiller-University Jena（耶拿弗里德里希·席勒大学）；Australian National University（澳大利亚国立大学）；Fraunhofer Institute for Applied Optics and Precision Engineering IOF（弗劳恩霍夫应用光学和精密工程研究所）
Dynamic optical metasurfaces with ultrafast temporal response, i.e., spatiotemporal optical metasurfaces, provide attractive solutions and open fascinating perspectives for modern highly integrated optics and photonics. In this work, electro-optically controlled optical metasurfaces operating in reflection and utilizing resonant waveguide mode excitation are demonstrated from the viewpoint of free-space propagating light modulation. The modulation of reflected light power with superior characteristics in comparison with prior research is achieved by identifying a suitable low-loss waveguide mo…
Active Control of Topological Exceptional Points in Non-Hermitian Metasurfaces
Indian Institute of Technology Bombay (IITB)（印度理工学院孟买分校）；Nanyang Technological University（南洋理工大学）；University of Notre Dame（圣母大学）；Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR)（贾瓦哈拉尔·尼赫鲁高级科学研究中心）
Metafibers expand the functionalities of conventional optical fibers to unprecedented nanoscale light manipulations by integrating metasurfaces on the fiber tips, becoming an emerging light-coupling platform for both nanoscience and fiber optics communities. Mostly exploring the isolated bare fibers, current metafibers remain as proof-of-concept demonstrations due to a lack of standard interfaces with the universal fiber networks. Here, we develop new methodologies to fabricate well-defined plasmonic metasurfaces directly on the end facets of commercial single mode fiber jumpers using standard…
Nonreciprocity is important for optical information processing, full-duplex communications, and protection of sensitive laser equipment from unwanted reflections. However, it is very challenging to obtain strong nonreciprocal response in optical frequencies, especially when nanoscale configurations are considered. In this work, we solve this problem by demonstrating a compact bifacial plasmonic metasurface that acts as a new ultrathin nonreciprocal transmission filter at near-infrared frequencies. The proposed nanostructure is simple to be practically implemented, since it is composed of two s…
Localized plasmons formed in ultrathin metallic nanogaps can lead to robust absorption of incident light. Plasmonic metasurfaces based on this effect can efficiently generate energetic charge carriers, also known as hot electrons, owing to their ability to squeeze and enhance electromagnetic fields in confined subwavelength spaces. However, it is very challenging to accurately identify and quantify the dynamics of hot carriers, mainly due to their ultrafast time decay. Their non-equilibrium temperature response is one of the key factors missing to understand the short time decay and overall tr…
Tailoring optical nonlinear effects (e.g. harmonic generation, sum-frequency mixing, etc.) in the recently emerging all-dielectric platform is important for both the fundamental science and industrial development of high-efficiency, ultrafast, and miniaturized photonic devices. In this work, we propose a novel paradigm for dynamically switchable high-harmonic generation in Silicon nanodimer metasurfaces by exploiting polarization-controlled dual bound states in the continuum (BIC). Owing to the high-quality factor of BIC resonances, efficient harmonic signals including the third-harmonic gener…
Laser-Scrawled Random Plasmonic Metasurface in Nanoseconds for Physical Unclonable Functions
Dalian University of Technology（大连理工大学）；Dalian Institute of Chemical Physics, Chinese Academy of Sciences（中国科学院大连化学物理研究所）；China Jiliang University（中国计量大学）
Analog computing has emerged as a promising candidate for real-time and parallel continuous data processing. This paper presents a reciprocal way for realizing asymmetric optical transfer functions (OTFs) in the reflection side of the on-axis processing channels. It is rigorously demonstrated that the presence of Cross-polarization Exciting Normal Polarizabilities (CPENP) of a reciprocal metasurface circumvents the famous challenge of Green's function approach in implementation of on-axis reflective optical signal processing while providing dual computing channels under orthogonal polarization…
Freed from phase-matching constraints, plasmonic metasurfaces have contributed significantly to the control of the optical nonlinearity and enhancing the nonlinear generation efficiency by engineering subwavelength meta-atoms. However, the high dissipative losses and the inevitable thermal heating limit their applicability in nonlinear nanophotonics. All-dielectric metasurfaces, supporting both electric and magnetic Mie-type resonances in their nanostructures, have appeared as a promising alternative to nonlinear plasmonics. High-index dielectric nanostructures, allowing additional magnetic re…
All-dielectric nanophotonics has become one of the most active fields of research in modern optics, largely due to the opportunities offered by the simultaneous resonant control of electric and magnetic components of light at the nanoscale. In this rapidly evolving scenario, the possibility to design artificial Huygens sources by overlapping electric and magnetic resonances has established a new paradigm in flat optics, bringing devices closer to efficient wavefront shaping with a direct phase engineering at the level of the individual meta-atoms. However, their efficiency is fundamentally lim…
Ultrafast All-Optical Polarization Control in a Plasmonic Metasurface by Selective Hot-Electron Heating of Orthogonal Gold Nanorods
Institute of Nanoscience and Nanotechnology, National Center for Scientific Research “Demokritos”（纳米科学与技术研究所，国家科学研究中心“德莫克里斯”）；Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, NHRF（理论与物理化学研究所，希腊国家研究基金会）
Nanophotonic platforms such as metasurfaces, achieving arbitrary phase profiles within ultrathin thickness, emerge as miniaturized, ultracompact and kaleidoscopic optical vortex generators. However, it is often required to segment or interleave independent subarray metasurfaces to multiplex optical vortices in a single nano device, which in turn affects the compactness and channel capacity of the device. Here, inspired by phyllotaxis patterns in pine cones and sunflowers, we theoretically prove and experimentally report that multiple optical vortices can be produced in a single compact phyllot…
Polarization-Sensitive Third Harmonic Generation in resonant silicon nitride Metasurfaces for deep-UV Emission
Universitat Politècnica de Catalunya（加泰罗尼亚理工大学）；Università degli Studi di Brescia（布雷西亚大学）；DTU Nanolab, National Center for Nanofabrication and Characterization（丹麦技术大学纳米实验室，国家纳米加工与表征中心）；DTU Electro, Department of Electrical and Photonics Engineering（丹麦技术大学电气与光子工程系）
Selective control of light is essential for optical science and technology with numerous applications. Nanophotonic waveguides and integrated couplers have been developed to achieve selective coupling and spatial control of an optical beam according to its multiple degrees of freedom. However, previous coupling devices remain passive with an inherently linear response to the power of incident light limiting their maximal optical selectivity. Here, we demonstrate nonlinear optical selectivity through selective excitation of individual single-mode nanolasers based on the spin and orbital angular…
Nonlinear Self-Action across Temporal Regimes in Resonant Dielectric Metasurfaces
Politecnico di Milano（米兰理工大学）；Institute of Photonic and Nanotechnology (IFN) - Consiglio Nazionale delle Ricerche (CNR)（光子与纳米技术研究所（IFN）- 意大利国家研究委员会（CNR））；Institute of Photonics and Quantum Sciences, Heriot-Watt University（赫瑞-瓦特大学光子与量子科学研究所）；ICFO - Institut de Ciències Fotòniques, the Barcelona Institute of Science and Technology（ICFO - 巴塞罗那科学和技术理工学院光子科学研究所）；Università degli Studi di Brescia（布雷西亚大学）
A novel ultrafast all-optical switching mechanism is demonstrated theoretically and experimentally based on a plasmonic analog of the effect of \textit{Enhancement of Index of Refraction}(EIR) in quantum optics. In the quantum optical EIR the atomic systems are rendered by coherence and quantum interference to exhibit orders of magnitude higher index of refraction with vanishing or even negative absorption near their resonances. Similarly, in the plasmon-induced EIR, a probe signal can experience positive, zero or negative extinction while strongly interacting with a metallic nanorod in a meta…
