This PDF file contains the front matter associated with SPIE Proceedings Volume 10521, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

Monolayers of transition-metal dichalcogenides (TMDCs) are recently isolated materials combining strong light-matter interactions and high charge mobilities. Many TMDCs possess direct bandgap - a necessary property for optoelectronic and photonic applications. On the other hand, colloidal semiconductor nanocrystals (NQDs) exhibit high emission efficiency, chemical lability and excellent bandgap tunability via size quantization. Joining the two classes of materials in hybrid structures aims to utilize their respective strengths. Among those, hybrids where two constituents are coupled via non-radiative energy transfer (NRET) present a particular interest. In the NRET process, exciton energy is transferred from NQD donor to TMDC acceptor via near-field, dipole-dipole energy coupling. This process plays an important role in photosynthetic plants and has been recently considered for energy harvesting in NQD/semiconductor architectures. Its efficiency depends on the distance, spectral overlap and dielectric screening properties of the acceptor material and its dimensionality. With the emergence of 2D materials, there is strong motivation, both for fundamental reasons and for the new applications, to study NRET in these novel systems. We have studied NRET coupling between several types of NQDs and MoS2 monolayers using photoluminescence (PL) and femtosecond transient absorption (TA) spectroscopies. Both methods indicate very efficient NRET into the MoS2 acceptor, with donor PL intensity quenching concurrent with energy influx into acceptor as observed by TA. These effects are facilitated by reduced dielectric screening inherent to strongly polarizable TMDC materials as described by classical electromagnetic model. We envision energy coupling in 0D-2D hybrids enabling applications in photosensing, photovoltaics and light emission.

Two-dimensional (2D) materials such as graphene, transition metal dichalcogenides (TMDs), and hexagonal boron nitride (hBN) have attracted a large amount of interests due to their extraordinary electrical, optical, and mechanical properties comparing with their bulk counterparts. Recently, black phosphorus (BP) has emerged as a new 2D material with demonstrated high hole mobility, showing great potential in electronic applications such as field-effect transistors (FETs). In this talk we will first review our recent works on the electric, photo-electrical, mechanical, and thermal behaviors of few-layer black phosphorus [1-4]. We will then discuss the photonics applications of black phosphorus. 2D black phosphorus is an excellent candidate for use in photodetection devices due to its direct and thickness-dependent bandgap [1]. However, light absorptions in these 2D materials are often very low due to its ultra- thin nature. For example, the visible light absorption in single layer graphene is only 2.3%. Making plasmonic structures, such as nano disks and rods, on top of the 2D material can be a possible way to enhance the absorption. In our work, a new bowtie-like plasmonic structure was proposed, and numerical simulations were used to design and optimize the plasmonic structures that are used to enhance both absorption and polarization selectivity in black phosphorus photodetection devices. The optimized structure devices were then fabricated on black phosphorus on transparent substrate. Photocurrent measurements showed strong light polarization dependence/selectivity in the fabricated device as well as much stronger photo responsivity compared with devices without plasmonic enhancement. Our study demonstrated the potentials of black phosphorus for photodetection and other light harvesting applications. [1] Liu, H., Neal, A., Zhu, Z., Luo, Z., Xu, X., Tomanek, D., Ye, P.D., 2014, “Phosphorene: An Unexplored 2D Semiconductor with a High Hole Mobility,” ACS Nano, 8(4), pp. 4033–4041. [2] Deng, Y., Luo, Z., Conrad, N. J., Liu, H., Gon,g Y., Najmaei, S., Ajayan, P. M., Lou, J., Xu, X., and Ye, P. D., 2014, “Black Phosphorus-Monolayer MoS2 van der Waals Heterojunction P-N Diode.,” ACS Nano, 8(8), pp. 8292–8299. [3] Luo, Z., Maassen, J., Deng, Y., Du, Y., Garrelts, R. P., Lundstrom, M. S., Ye, P. D., and Xu, X., 2015, "Anisotropic in-plane thermal conductivity observed in few-layer black phosphorus", Nat. Commun. 6:8572, pp. 9572-1-8. [4] Du, Y., Maassen, J., Wu, W., Luo, Z., Xu, X., and Ye, P., 2016, "Auxetic Black Phosphorus: A 2D Material with Negative Poisson’s Ratio", Nano Lett., DOI: 10.1021/acs.nanolett.6b03607.

Over the recent years, van der Waals (vdW) materials, a class of materials composed of weakly bound two-dimensional (2D), atomically thin, crystalline layers, have attracted great interest due to their ability to deeply confine light and therefore significantly enhance its interaction with matter. This interaction is embodied in coupled states between light and the polarization of the media, polaritons. The most studied type of polaritons, plasmon polariton, stems from the collective oscillations of conduction electrons. These, however, suffer great losses and therefore offer limited applications. Recently, among the several other types of polaritons supported by vdW materials, the exciton polariton (EP) has stimulated intense research efforts because it can sustain both strong light– matter interactions and long-distance propagation that is necessary for applications associated with energy harvesting or information manipulation and transfer. In this context, WSe2 is of particular interest for integrated applications since it supports EP modes in the Visible- Near Infrared (VIS-NIR) spectral region at room temperature due to its tightly bond excitonic state. In the quest to unravel the underlying physics, scanning near field optical microscope (SNOM) has provided valuable insights on the nature of the steady state EP modes sustained in vdW and in WSe2 in particular. However the dynamics of the EP formation, happening in the first few hundreds of femtoseconds subsequent to light absorption, remains largely unexplored. Here we employ a unique broadband ultrafast near-field pump-probe imaging method and observe for the first time, at femtosecond and nanometric spatiotemporal scale, the dynamics of the EP waves generation and propagation in WSe2 waveguides. Our observations suggest an important interplay between the waveguide EP mode and the tip-supported plasmon. Morever, we observe an intriguing ultrafast change in the EP waveguiding properties of the WSe2 waveguides happening in the first few hundreds of femtoseconds of the EP wave formation. Our method paves the way to in-situ ultrafast coherent control of EPs modes in vdW materials.

Electrochemical nanoimpacts monitoring, developed within the last decade, is based on the time-resolved detection of stochastic collisions of individual NanoParticles (NPs) in micro/nano-confined electrochemical cells[1]. Although electrochemical techniques are now able to measure electron transfer processes associated to single NP impacts, they are not spatially resolved and fail to characterize complex multiple chemical events. Superlocalization optical microscopies have recently allowed a complementary visualization of the transformation of NPs during electrochemical reactions. We proposed the coupling of holographic microscopy to electrochemistry[2] to record scattering by individual NPs. Real-time holograms are reconstructed in order to superlocalize and track several individual NPs in 3D with 3x3x10 nm3 accuracy. During Ag electrodissolution experiments, it allowed the 3D monitoring of Brownian or phoretic motion and individual dissolution. In situations where chemical transformations occur, spectroscopy associated to finite element or FDTD modelling can provide additional information on individual NPs during electrochemical processes. We will illustrate the possibilities of this coupled characterization in several systems, where 3D particle tracking can provide a NP size estimate during the Brownian approach of the particle. During chemical reactions on the metal interface, we will show that holography, spectroscopy, associated to an optical model of the scattering, gives access to relevant information on the size, position, and composition of the NPs. [1]Y.Zhou et al, Angew. Chem. 2011, X.Xiao et al. J. Am. Chem. Soc. 2007 [2] V.Brasiliense et al., Acc. Chem. Res., 2016 V.Brasiliense et al. J. Am. Chem. Soc., 2016 A.N Patel et al. Nano Lett., 2015

We investigate conditions of excitation and properties of Plasmonic Surface Lattice Resonances (PSLR) over glass substrate-supported Au nanoparticle dimers (~100-200 nm) arranged in a periodic metamaterial lattice, in Attenuated Total Reflection (ATR) optical excitation geometry, and assess their sensitivities to variations of refractive index (RI) of the adjacent sample dielectric medium. We show that spectral sensitivity of PSLR to RI variations is determined by the lattice periodicity (~ 320 nm per RIU change in our case), while ultranarrow resonance lineshapes (down to a few nm full-widthat-half-maximum) provide very high figure-of-merit values evidencing the possibility of ultrasensitive biosensing measurements. Combining advantages of nanoscale architectures, including a strong concentration of electric field, the possibility of manipulation at the nanoscale etc, and high phase and spectral sensitivities, PSLRs promise a drastic advancement of current state-of-the-art plasmonic biosensing technology.

Methods of femtosecond laser ablation were used to fabricate bare (ligand-free) silicon (Si) nanoparticles in deionized water. The nanoparticles were round in shape, crystalline, free of any impurities, and water-dissolvable, while the dissolution rate depended on the concentration of oxygen defects in their composition. The nanoparticles were then eletrospun with chitosan to form nanoparticle decorated nanofibrous matrices. We found that the functionalization of nanofibers by the nanoparticles can affect the morphology and physico-chemical characteristics of resulting nanostructures. In particular, the presence of Si nanoparticles led to the reduction of fibers thickness, suggesting a potential improvement of fiber’s surface reactivity. We also observed the improvement of thermal stability of hybrid nanofibers. We believe that the incorporated Si nanoparticles can serve as functional elements to improve characteristics of chitosan-based matrices for cellular growth, as well as to enable novel imaging or therapeutic functionalities for tissue engineering applications.

Glioma accounts for the majority of brain cancer and is the most common and aggressive human cerebral disease with low survival rates, which have received much attention on how the cancer cells can be controlled. The aim of this report is to investigate the controlling of C6 glioma cells on 3D micro/nano silicon structures with different surface energy. The silicon surface topography was formed by femtosecond laser and adjusted through changing the processing parameter. The transformation of surface energy was realized by covering a layer of organosilane with low surface tention--1H,1H,2H,2H-perfluorodecyltrichlorosilane (PFDTS). The results showed that the fewest C6 cells adhered onto hierarchical micro-mountain structures with organosilane, which exhibited the anti-cell property, while the most C6 cells adhered onto nano-grain particle structures without any modification. For the same 3D structure, the adhesion force between cells and silicon surface with various structure was weaker while lowering the surface energy. Based on the analysis of fluorescence and scanning electron microscopy images, we proposed an underlining mechanism on how C6 cell morphology and adhesion is controlled by silicon 3D structure and surface energy. In addition, the formation of arbitrary cell patterns was achieved successfully. The findings may provide a conception for the preparation of cell detector and implantable biological scaffold.

In metal nanoparticles (NP), localized surface plasmon resonances induce enhanced light absorption and scattering. In ohmic metals, however, this charge oscillation induces Joule heating. The study of temperature generated by plasmonic nanostructures is an emerging field with promising applications in photothermal therapeutics or imaging1,2. The optical properties of these NP strongly depend on the morphology of the nanostructure and its dielectric environment, allowing a control of their optical and thermal properties at the nanoscale. Here, we aim at modelling, characterizing and optimizing the thermal properties of metallic nanostructures. Simple geometries such as ellipsoids and disks have been investigated. For any NP shape, FDTD and FEM models were used to determine the influence of NP morphology on the steady-state temperature inside a nano-object immersed in a homogeneous medium. We will present numerical optimizations of the thermal properties of these structures, showing a maximum in the achievable temperature. The corresponding gold nanostructures have been fabricated by 20 nm-resolution e-beam lithography. The heat generation in these nanostructures was probed by photothermal digital heterodyne holography3. In the presence of kHz-modulated heating, the refractive index is modified, inducing a modulation of the scattering, detected by interference with a reference wave on a CCD camera. Quantitative temperature measurements obtained on an array of nano-ellipsoids of varying size and aspect ratios are compared to opto-thermal modelling. [1] A. Lalisse, et al. Scientific Reports (2016) [2] A. Lalisse, et al. J. Phys. Chem. C (2015) [3] E. Absil, et al. Optics Express (2010).

Materials showing special extreme wettability are particularly captivating. Until now, a very large number of superhydrophobic surfaces have been fabricated, and these artificial materials have a wide range of applications. Different with superhydrophobic surfaces, superoleophobic surfaces that repel organic liquids are difficult to achieve because of the low surface tension of organic liquids. Superoleophobic surfaces have also gained more and more attention recently for their remarkable potential applications in oil-repellent coatings, self-cleaning, oil/water separation, oil droplet manipulation, chemical shielding, anti-blocking, oil capture, bioadhesion, and so on. The realization of more complicated and subtle superoleophobic surfaces has many opportunities and challenges. Herein, we systematically summarize the recent developments of superoleophobic surfaces. This talk will focus on the design, fabrication, characteristics, functions, and important applications of various superoleophobic surfaces. Although many significant advances have been achieved, superoleophobic surfaces are still in their “toddler stage” of development. Therefore, the current challenges and future prospects of this fast-growing field of superoleophobicity are finally discussed.

Self-organization is a principle found everywhere in nature, for example in the growth of organisms and phase transitions. An interesting system used to study the nonlinear governing equations giving rise to this behaviour are electrochemically anodized titania nanotubes. The physics of this system is complex, involving electrodynamics, chemical diffusion, reaction kinetics, and material stresses. By patterning the surface of titanium with Laser Induced Periodic Surface Structures (LIPSS) prior to growth, we manipulate the subsequent electrochemical growth of the nanotubes. This is, a double-self-organized growth process, as both the nanotubes and LIPSS grow in a self-organized manner to create the LIPSS-NT structure. We, in effect, changed the ‘initial condition’ of the nonlinear growth equations, which allows us to study the titania nanotubes, and compare them to numerical predictions of the morphology. We investigated how LIPSS structures of varying periodicity affect the nanostructure of the anodized nanotubes. The surface was patterned with a Ti:sapphire femtosecond pulsed laser (800 nm, 110 fs, 1kHz), and characterized with scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, UV-Visible spectroscopy, transmission electron microscopy, and X-ray diffraction. Finally, we fabricated structures for photonic applications such as Surface Enhanced Raman Spectroscopy substrates, and photocatalysts in pollutant degradation. The grating-like structure of the LIPSS-NT enhances the trapping of visible light and increases the rate of photocatalytic degradation under solar irradiation.

This paper reports for, the first time, the influence of silicon nanocrystals on the photoluminescence and optical gain of Yb³⁺/Er³⁺ codoped Bi₂O₃−GeO₂ waveguides for amplification at 1542 nm. Pedestal waveguides were fabricated by RF- sputtering followed by optical lithography and reactive ion etching. RF-sputtering followed by heat treatment produced silicon nanocrystals with average size of 8 nm and resulted in a photoluminescence enhancement of about 10 times for the 520 nm and 1530 nm emission bands. The resulting internal gain was 5.5 dB/cm at 1542 nm, which represents and enhancement of ∼50%, demonstrating potential for applications in integrated optics.