4:00pm - 4:30pmInvited
Nanowires and Metamaterials as a Platform for Functional Devices
1University of California, Los Angeles, United States; 2Cardiff University, UK
In this presentation, we discuss two active devices platforms, lasers and detectors, based on integrated nanowires and metamaterials directly formed on silicon-on-insulator (SOI). First, the direct integration of compact and efficient light sources on silicon or silicon-on-insulator (SOI) platforms is a crucial requirement in the field of chip-scale optical interconnects. Direct growth of III-V semiconductor nanowires on silicon is considered as a promising alternative, as nanoscale interface between the nanowire and silicon effectively reduces the strain and enables the growth of high-quality nanowires despite a huge lattice mismatch. Plasmonic slot couplers transfer energy from waveguide to nanoscale detectors.
We will also discuss our single photon avalanche diodes (SPADs) as an integral component of light detection and ranging (LiDAR) systems used in imaging technologies such as acquisition, tracking, and pointing for autonomous vehicles. These devices are formed using patterned nanoepitaxy with self-aligned 3D plasmonic antennae for effective light coupling.
4:30pm - 5:00pmInvited
Semiconductor Nanowires for Optoelectronics Applications
Australian National University, Australia
In this talk, I will introduce III-V compound semiconductor nanowires and discuss about the ways to control their size, shape and composition and optical properties of the nanowires. Results from both nanowires grown by vapour liquid solid (VLS) growth mechanism and selective area epitaxy will be discussed. I will present results on GaAs nanowires, role of surface passivation and how plasmonic cavities improve the light emission efficiency from these nanowires. I will also present the results on both GaAs and InP nanowire lasers and role of impurities such as zinc on GaAs nanowire lasers. I will present the results from quantum confined nanowire lasers and discuss their performance.
5:00pm - 5:15pmOral
Recent Advances in AFM Based Nanoscale Infrared Spectroscopy and Photonics
Anasys Instruments, United States
This talk will focus on the recent advances in measuring the chemical and optical properties of materials with nanometer scale spatial resolution. Conventional infrared spectroscopy is one of the most widely used tools for chemical analysis, but optical diffraction limits its spatial resolution to the scale of many microns. Atomic force microscopy (AFM) enjoys excellent spatial resolution, but has historically lacked the ability to perform robust chemical analysis. This presentation will discuss the advances in two techniques (1) AFM-based infrared spectroscopy (AFM-IR) and (2) scattering scanning near field optical microscopy (s-SNOM). Both of these techniques overcome the diffraction limit, providing the ability to measure and map chemical and optical properties with 10 nanometer spatial resolution. Recent advances including Tapping AFM-IR and increases in laser sweep rates have significantly improved the resolution and sensitivity of AFM-IR, allowing for the capability to collect hyperspectral images. As complementary techniques, AFM-IR and s-SNOM together provide an unrivaled capability to perform nanoscale chemical analysis on a diverse range of organic, inorganic, photonic and electronic materials. This technical talk will focus on the techniques and applications of AFM-IR and s-SNOM including novel 2D materials, nanoantennas and polymers.
5:15pm - 5:45pmInvited
Artificial Photosynthesis of Glucose using Microfluidic Reactors
Hong Kong Polytechnic University, Hong Kong S.A.R. (China)
Solar energy is the fundamental energy source of human being. Recent years have witnessed a rapid increase of research interest in the conversion of the solar energy into chemical energy, such as the degradation of organic pollutant, the splitting of water into hydrogen and the capture of CO2 into energy-rich carbohydrates. Optofluidics may play a unique role in overcoming some of the fundamental limits of traditional photocatalysis technology such as mass transfer limit, photon transfer limit, electron/hole recombination, oxygen deficiency/removal and many others. Our group first proposed the planar reactor design based on the optofluidic principle in 2010 and found a significant increase of the photocatalytic efficiency, and since then we have explored various reactor designs and have also attempted to generate glucose using CO2 and sunlight. This talk will summarize the recent development of the niche area of optofluidic photocatalysis, and hopefully will take an outlook of the progress in near future.
National Natural Science Foundation of China (61377068), Research Grants Council of Hong Kong (N_PolyU505/13, 5334/12E, 152184/15E), and Hong Kong Polytechnic University (G-YN07, G-YBBE, G-YBPR, 4-BCAL, 1-ZVAW, 1-ZE14, A-PM21, 1-ZE27, 1-ZVGH).
5:45pm - 6:00pmOral
Microfluidic Metasurface for Dispersion Compensated Flat Lens and Beam Tracking
Nanyang Technological University, Singapore
Metasurfaces are two-dimensional artificial material composed of miniaturized sub-wavelength optical scatterers, which perform extraordinary electromagnetic properties. Metasurfaces serve as a new platform to tailor the properties of electromagnetic wave through the entire electromagnetic spectrum, enabling plenty of new planar optical components such as beam steering device, flat lens, and so on. However, the tuning potential of metasurfaces are generally suppressed because of the solid structure, which limits the realization of multi-function within an identical sample of metasurface. Here, we present a microfluidic metasurface with high tunability, showing its potential of realizing multi-function by demonstrating dispersion-compensated focusing and beam tracking. In the metasurface, each optical scatter is formed by microfluidic ring-shaped cavities partially filled with liquid metal (Galinstan) and controlled with pneumatic control system. This freedom of tuning of the microfluidic metasurface paves the way of realizing multi-function, which is promising for practical applications including dispersion-controllable beam steering, tunable flat lens and three-dimensional beam tracking and so forth.
6:00pm - 6:15pmOral
Perfect Absorber for Organic Solar Cells
Tokyo University of Agriculture and Technology, Japan
Metamaterial perfect absorber is the structure confines light into a thin film. Here, we propose to apply the perfect absorber to organic solar cells for the purpose of light absorption enhancement of the photoelectric conversion materials.
The problems limit low conversion efficiency of organic solar cells mainly are short exciton migration lengths and weak light absorption of the active materials. That indicates solar cells should be physically thinness and optically thickness.
We fabricated perfect absorber with Ag nanogrids and Al planar film, and put photoelectric conversion materials between them. PC61BM:P3HT was used as the photoelectric conversion material.
From reflection spectra, we found reflectivity of the perfect absorber was suppressed compared to the sample without Ag nanogrids, indicating perfect absorber confine sun light into the active layer, resulting in light absorption enhancement of the layer.
6:15pm - 6:30pmOral
Correlation between Localized SPP Modes and Circular Dichroism of Basic Planar Nanostructures
1Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore; 2National University of Singapore, Singapore
A correlation is observed between localised SPP modes with the circular dichroism (CD) signature of nanoparticles excited by circularly polarised waves. These localized SPP modes give rise to different mode profiles depending on the polarization of the externally excited light. This correlation can be observed by deriving the mode profile of excited polarised modes in elementary metal nanoparticles under the influence of circularly polarised waves. From this study, we are able to predict the SPP mode profiles of different fundamental circular, triangular, square and rectangular nanoparticles excited by circularly polarised light sources. This in turn allows us to determine their respective CD signature. A positive or negative CD signature will mean a stronger dominance of absorption by either left or right handed circularly polarised waves respectively. Nanostructures with strong CD signatures are especially desired for sensing of chiral biomolecules as well as to aid in photochemical catalysis. We also found out that CD signatures can even be induced via angular rotation. This is true for elementary nanostructures which do not possess a CD signature. The use of elementary nanoparticles poses a huge advantage over complex nanostructures due to the ease of fabrication. The observed CD signature can be validated in accordance to theory and simulation results, which may be contrary to what is predicted based on intuition. By using this correlation, we are able to generate and utilise the CD signature even in elementary nanoparticles.