4:00pm - 4:30pmInvited
Active and Nonlinear Chiral Metamaterials
Georgia Institute of Technology, United States
The past few years have witnessed an explosive development of chiral photonic metamaterials that exhibit circular dichroism and optical rotation orders of magnitude larger than conventional materials. Though chirality is most commonly applied in linear optical regime, opposing circularly polarized waves can also display parity as a property of higher order optics. In this talk, we present a set of photonic metamaterials that possess pronounced chiroptical features in the nonlinear regime.
In addition to gigantic linear chiroptical responses, including the circular dichroism and optical activity that are many times stronger than those found in naturally occurring media, the metamaterials demonstrates a 20x contrast between second harmonic responses from the two circular polarizations. Linear and nonlinear response images probed with circularly polarized lights show strongly defined contrast, and the second-harmonic circular-dichroism images are produced to reveal the chiral characteristics of a metamaterial pattern consisting of opposite meta-enantiomers.
The chiral hotspots created at the center of the chiral meta-atoms can be made accessible to nanoscale probes. By both exposing the resonant near field of the chiral nanostructure via plasma etching and inserting quantum dots as indicators of localized chiral hotspots, we observed substantially enhanced and chiral-selective two-photon luminescence from the hybrid meta-system. The giant chiral response in the metamaterial facilitates circular dichroic manipulation of the far-field intensity of locally emitted nonlinear signals, and the strength of the two-photon signal is directly correlated to the chiral resonance in the linear regime.
In the end, we report a chiral metamaterial based on topologically continuous metallic layers, which supports a photon-drag effect with helicity-sensitive generation of photocurrent. The structure is further exploited under varying illumination intensity, with which we observe an intensity-dependent modulation of optically active signals, including the circular dichroism and polarization rotation, under a modest level of excitation power.
4:30pm - 5:00pmInvited
Controlling Light by Multispectral and Nonlinear Metasurfaces
Tel Aviv University, Israel
Recent years have shown a major progress in light manipulation capabilities offered by metasurfaces. Different configurations of linear and nonlinear metasurfaces were studied, based on metallic inclusions or all-dielectric, working in transmission or in reflection. Various linear and nonlinear optical components based on metasurfaces were demonstrated, including numerous types of lenses, beam shapers, optical switches, and holograms. Some of these metasurfaces function differently at different polarizations or different frequencies, but the degree of functional multiplexing in a single metasurfaces was rather limited. In this talk I will present a configuration of vertically stacked metasurfaces where each layer is constructed from a different optimal building block, e.g. different inclusion material and geometry, and is designed to a perform a different functionality with minimal crosstalk between the layers. This scalable approach allows us to demonstrate experimentally functional spectral multiplexing of visible light. We specifically show an aberration corrected metasurface-based triplet lens for RGB colors in the visible, integrated elements for STED microscopy, and elements with anomalous dispersive focusing. In the second part of the talk, I will describe also nonlinear quadratic effects in metasurfaces. I will show how nonlinear metasurfaces open the door to a variety of light generation and manipulation schemes and to new fundamental studies in the realm of nonlinear optics. Specifically I will present a new study on quadratic nonlinear coherent coupling between the building blocks of the metasurface. I will show that in this condition strong enhancement of the nonlinear polarizability of each of the particles in the array is obtained which leads to significantly enhanced second harmonic generation.
5:00pm - 5:30pmInvited
Engineering Ultrafast Nonlinearities with Metamaterials and Metasurfaces
King's College London, United Kingdom
We will discuss second- and third-order nonlinear optical processes in metamaterials and metasurfaces. They can be engineered at a required operation wavelength throughout visible and near-infrared spectral range by tuning solely geometrical parameters of a composite based on the same material constituents. The sign of nonlinearity (focusing or defocusing nonlinearity), the enhancement and dynamics of a nonlinear response can be controlled. Some of the examples to be discussed include ultrashort pulse propagation in waveguides and metamaterials, nonlinear polarisation control, and nonlinear metamaterial components integrated in silicon photonic circuitry. Nonlinear plasmonic metasurfaces combining strong Kerr-type and coherent second-order nonlinearities for efficient all-optical control of second-harmonic generation will also be discussed. Plasmonic and dielectric metamaterials and metasurfaces enable engineering of resonant optical response of meta-atoms and coupling between them and establish a new platform for free-space and integrated nonlinear photonics applications.
5:30pm - 5:45pmOral
Two-Photon Absorption and Subband Photodetection in Monolayer Transition-Metal Dichalcogenides
National University of Singapore, Singapore
Materials capable of simultaneously absorbing two photons and subsequently generating photoluminescence or photocurrents have great potential for applications in two-photon microscopy and light frequency up-conversion. Two-photon absorption (2PA) in semiconductors can also be applied to autocorrelation, optical signal processing, sub-band photodetectors, quantum detectors, coherent control, and others. Therefore, understanding 2PA of materials is of direct relevance to the above-mentioned applications. However, there is a lack of theoretical understanding on 2PA in recently-emerged, two-dimensional (2D) semiconductors. 2PA phenomena have been utilized for probing dark excitons in monolayer transition-metal dichalcogenides (TMDCs) . Large yet varied 2PA coefficients (103~105 cm/GW at 800 or 1040 nm) have been observed experimentally for monolayer MoS2  and WS2 [3, 4] made by chemical vapor deposition (CVD) methods. Notably, a high amount of defects/impurities could present in these CVD-made samples, and hence, the observed 2PA might not directly associate with the intrinsic nature of monolayer TMDCs. To the best of our knowledge, there is no report on the magnitude and spectrum of 2PA in highly-crystalline monolayer TMDCs. Herein, for the first time, we report a theoretical model to quantitatively predict the 2PA magnitude and spectrum in monolayer MoS2. Our model is also verified by our measurements of 2PA-induced photocurrents on an exfoliated monolayer MoS2 subband photodetector. Our theoretical and experimental findings pave the way to develop sensitive infrared MoS2-based two-photon detectors.
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 N. Dong, et al., Opt. Lett. 41, 3936-3939 (2016).
 X. Zheng, et al., Opt. Express 23, 15616-15623 (2015).
5:45pm - 6:00pmOral
Fast-Slow Red Up-Conversion Fluorescence Modulation from Ho3+-doped Glass Ceramics upon Two-Wavelength Excitation
1State Key Laboratory of Luminescent Materials and Devices, and Guangdong Provincial Key Laboratory of Fiber Laser Materials and Applied Techniques, South China University of Technology, China; 2State Key Laboratory of Advanced Optical Communication Systems and Network, Shanghai Jiao Tong University, China; 3College of Optical Science and Engineering, State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, China
The control of one light field by another, ultimately at manipulating efficiently photon-photon interactions obsoleting traditional electronic interconnection approach, is an attractive area of research in the development of all-optical network information science. Herein, we introduce an exquisite physical strategy to realize fast-slow optical modulation of red up-conversion (UC) fluorescence from Ho3+:LaF3 nanocrystals embedded glass ceramics (GCs) tailoring by simultaneous two-wavelength excitation at 980 and 1870 nm laser. We show an optical modulation of more than 2500% of the red UC fluorescence intensity and a fast response with rise time of 230 μs and decay time of 66 μs as well as a slow response with rise time of 23 ms and decay time of 6.65 ms in the red UC fluorescence signal. The dynamic evolution analysis and theoretical simulations suggest that this fast-slow optical modulation of red UC fluorescence is rooting from the presence of differentiation of the speed of electrons fully populated in the excited state 5I7 regulated by various pumping tactics. The fast-slow optical modulation of red UC fluorescence from Ho3+-doped GCs, manipulating through two-wavelength excitation at 980 and 1870 nm laser, may find novel application in future all-optical fiber data processing in various optoelectronic fields.
 Z. Chen, W. Cui, S. Kang, H. Zhang, G. Dong, C. Jiang, S. Zhou, and J. Qiu, Adv. Opt. Mater., 2016, DOI: 10.1002/adom.201600554.
 M. Geiselmann, R. Marty, F. J. G. de Abajo, and R. Quidant, Nat. Phys.,2013, 9, 785-789.
 Z. Sun, A. Martinez, F. Wang, Nat. Photonics, 2016, 10, 227-238.
 X. Fang, K. F. MacDonald, N. I. Zheludev, Light: Sci. Appli. 2015, 4, e292.
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6:00pm - 6:15pmOral
Hermitian Description of Localized Plasmons in Dispersive Dissipative Subwavelength Spherical Nanostructures
1Dukhov Research Institute of Automatics (VNIIA), Russian Federation; 2Moscow Institute of Physics and Technology, Russian Federation; 3Russian Academy of Sciences, Russian Federation
The canonical quantization procedure in dispersive and lossy media assumes the eigenstates of the system to be collective excitations of the electromagnetic field and reservoir degrees of freedom. In this paper, we show that in low loss limit, the collective plasmonic modes in a quasistatic approximation separate from the reservoir. As an example, we consider the localized surface plasmon on a spherical metallic nanoparticle in a vacuum and find the macroscopic longitudinal electric near field per plasmon in the cases of gold and silver. Using our canonical approach, we calculate the correction to the electric near field per plasmon obtained from phenomenological quantization. The canonical conjugated variable to the electric near field is determined.