Photonic approaches emulating the powerful computational capabilities of the brain are receiving increasing research interest for radically new paradigms in ultrafast neuromorphic (brain-like) information processing and Artificial Intelligence (AI). This talk will report our research on light-enabled neuromorphic systems built with artificial photonic spiking neurons and photonic spiking neural networks (SNN). We will review the properties and performance of the photonic devices employed for the implementation of optical spiking neurons, including semiconductor lasers (e.g. Vertical Cavity Surface Emitting Lasers) and resonant tunnelling diodes. We will also discuss the strategies for their network-connectivity into photonic SNN architectures, and the techniques and algorithms realised for their use in complex functional information processing tasks (e.g. pattern recognition, image processing, data classification). We will also showcase the potentials of these spike-based photonic processing systems for ultrafast, low-energy and high-accuracy performance, with a hardware-friendly implementation that benefits from spike-based learning protocols with highly-reduced complexity.
Semiconductor Nanowires (NWs) have revolutionized photonics by providing minimal footprint optoelectronic devices and coherent light sources. However, given their nanoscale dimensions, their integration with nanophotonic systems is a significant challenge. To overcome this issue, we have developed a hybrid nanofabrication technique, known as nanoscale transfer-printing, permitting the accurate integration of individually-selected NWs at target positions onto desired surfaces. Examples of nanophotonic systems enabled by our technique include 1D/2D NW laser arrays and on-chip waveguide-coupled NW laser systems. We have also recently demonstrated a nanophotonic circuit for THz signal detection formed by a 3D semiconductor NW network coupled with a metallic antenna structure.
Photonic techniques emulating the brain’s powerful computational capabilities are attracting considerable research interest as these offer promise for ultrafast operation speeds. In this talk we will review our approaches for ultrafast photonic neuronal models based upon Semiconductor Lasers, the very same devices used to transmit internet data traffic over fiber-optic telecommunication networks. We will show that a wide range of neuronal computational features, including spike activation, spiking inhibition, bursting, etc., can be optically reproduced with these devices in a controllable and reproducible way at sub-nanosecond time scales (up to 9 orders of magnitude faster than the millisecond timescales of biological neurons). Moreover, all our results are obtained using off-the-shelf, inexpensive Vertical-Cavity Surface Emitting Lasers (VCSELs) emitting at 1310 nm and 1550 nm; hence making our approach fully compatible with current optical communication technologies. Further, we will also introduce our recent work demonstrating the successful communication of sub-nanosecond spiking signals between interconnected artificial VCSEL-based photonic neurons and the potential of these systems for the ultrafast emulation of basic cortical neuronal circuits. These early results offer great prospects for novel neuromorphic (brain-like) photonic networks for brain-inspired ultrafast information processing systems going beyond traditional digital computing platforms.
Semiconductor nanowire lasers have revolutionized the field of photonics offering highly localised coherent light sources at the nanoscale. However, due to the ultra-small dimensions of nanowire lasers, their manipulation and accurate integration at desired locations on targeted surfaces and optoelectronic platforms is a fundamental challenge. This poses critical limitations for the development of complex and tailored nanophotonic circuits using nanowire lasers as building blocks. In this talk, I will present a novel nanoscale transfer printing technique enabling the controllable integration of individually-selected semiconductor nanowires onto multiple receiving substrates (e.g. polymer, silica, metals) and pre-patterned systems. We will show that this technique provides very high positioning accuracy (<1μm) and full control of the orientation angle of the printed nanowires. Hence, this new hybrid nanoscale transfer printing technique offers great potential for the fabrication of bespoke nanophotonic systems with ultra-small nanowire lasers at their core. During the talk we will also present our recent results demonstrating the precise formation of user-defined complex micrometric spatial patterns, such as 1- and 2-Dimensional arrays, using Indium Phosphide (InP) nanowires lasers as building blocks. Furthermore, we will introduce our work on the coupling of InP nanowire lasers onto waveguide systems (built on both planar and mechanically flexible substrates) for on-chip guiding of the nanowire’s emitted light and plasmonic nanoantennas for controlled light directionality. Finally, during the talk we will also review our ongoing activities towards new hybrid nanowire laser systems enabled by our nanoscale transfer printing technique.
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