Chipping in to transform Artificial Intelligence

An international project aimed at increasing the efficiency and portability of artificial intelligence (AI) technology has been launched with the University of Strathclyde as a partner.

The ChipAI Project is developing a nanoscale photonics-enabled technology capable of delivering compact, high-bandwidth and energy efficient neuromorphic (brain-like) central processing units (CPUs).

Nanostructures

This is to be achieved through the use of low-dimensional semiconductor nanostructures embedded in ultra-small cavities, 100 times smaller than conventional devices, for efficient light confinement, emission and detection of spiking neuron-like signals, similar to the signalling found in the brain. It will develop proof-of-principle of nanophotonic components and chips for AI applications.

The three-year academic and industrial partnership project has secured funding of nearly €3.9 million (£3.354 million) from Horizon 2020, the EU framework programme for research and innovation. It is led at INL – International Iberian Nanotechnology Laboratory, in Braga, Portugal.

Dr Antonio Hurtado, a Senior Lecturer in Strathclyde’s Institute of Photonics, is the University’s lead on the project. He said: “In the same way that the internet has revolutionised our society, the rise of Artificial Intelligence that can learn without the need of explicit instructions is transforming our lives.

“AI uses brain inspired neural network algorithms powered by computers. However, current central processing units are extremely energy-inefficient in implementing these tasks; this represents a major bottleneck for scalable and portable AI systems.

“Reducing the energy consumption needed to emulate complex brain functions is a major challenge that ChipAI is now addressing using photonics-based technologies.

“ChipAI will not only lay the foundations for the new field of neuromorphic optical computing but will also enable new non-AI functional applications in biosensing, imaging and many other fields where masses of cheap miniaturised pulsed sources and detectors are opening up disruptive innovations.”

Key components to be developed in ChipAI include non-linear nanoscale lasers, LEDs (Light-Emitting Diodes), detectors and synaptic optical links on silicon substrates, all of which will be used to make ChipAI an economically viable technology.

This radically new architecture will be tested for neuron-like information processing, towards validation for use in artificial neural networks. This will enable the development of real-time and offline portable AI and neuromorphic, or brain-like, CPUs.

Other partners in the project are the University of Glasgow, Eindhoven University of  Technology, the Faculty of Sciences (FCiencias.id)  at the University of Lisbon, the University of the Balearic Islands, IQE plc and IBM Research Gmbh.

ChipAI forms part of FET Open, a Horizon 2020 programme which supports the early-stages of the science and technology research and innovation around new ideas towards radically new future technologies.

The Institute of Photonics is based in Strathclyde’s Technology and Innovation Centre. This is sited in the Glasgow City Innovation District, which is transforming the way academia, business and industry collaborate to bring competitive advantage to Scotland. The model – which is recognised for improving productivity, creating jobs and attracting inward investment in several cities around the globe – brings together researchers and high-growth firms with technology and creative start-ups, to work side-by-side in vibrant, walkable innovation communities.

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Post-Doctoral Position Available in “Semiconductor Laser Networks for Neuro-Inspired Information Processing functionalities”

Post-doctoral Research Associate Position Available in Dr Hurtado’s Lab at the Institute of Photonics of the University of Strathclyde (Glasgow, Scotland, UK) to work on “Semiconductor Laser Networks for Neuro-Inspired Information Processing”. The successful candidate for this position will join the Optoelectronics and Nanophotonics Group, part of the wider Photonic Materials and Devices Group at Strathclyde’s Institute of Photonics.

The post holder will work on the ‘BRAIN LASER’ project, funded by the US Office of Naval Research Global (ONRG), to develop cutting-edge research in photonic technologies for neuromorphic (brain-like) information processing.

Applicants should have a PhD in Photonic Technologies or in Laser Physics/Engineering and have experience with semiconductor lasers and/or optoelectronic systems. Experience with the characterisation of nonlinear dynamics in laser systems and/or photonic (integrated) circuits would also be an advantage. Additionally, relevant student supervision experience would be desirable.

Brief Outline of Job:

To undertake research as part of the ONRG ‘Brain Laser’ project and as part of the wider Photonic Materials and Devices Group, working specifically on the experimental development and characterisation of semiconductor laser systems and networks for neuromorphic (brain-like) information processing applications; to progress the work of the project towards high quality publications and presentation of research results in scientific conferences, working with the wider team in a self-motivated but coordinated and organised manner; to work with the principal investigator and colleagues within the team to engender and pursue opportunities to obtain further funding for this work; to engage where required in relevant teaching, professional and knowledge exchange activities; and input to administrative activities, especially in assisting the principal investigator with the administration of the grant.

This post is offered for 6 months and is subject to a review at the end of that period. It is highly expected that further funding will be provided to extend the post up to a period of 24 months.

Click here for full details

Informal enquiries about the post can be directed to Dr Antonio Hurtado, Senior Lecturer (antonio.hurtado@strath.ac.uk; +0141 548 4668).

Paper on Vertically Emitting Nanowire Lasers published in Nano Letters

Our work on vertically-emitting nanowire lasers has been accepted for publication in Nano Letters. The paper can be accessed here.

This paper demonstrates for the first time nanowire lasers with vertically directed light emission, reduced threshold for lasing, operation at room temperature and highly reduced footprint. The structure of this device is based on a nanowire laser integrated with a Cat’s Eye metallic nanoantenna. Moreover, this paper describes in detail the different novel strategies developed to enable the fabrication of the ultrasmall nanoantenna-nanowire laser structures of this work.

This work is the result of a collaboration between the Institute of Photonics at the University of Strathclyde (Glasgow, UK), Nanjing University (China) and the Australian National University at Canberra.

The full paper details are as follows:

Title: Vertically Emitting Indium Phosphide Nanowire Lasers

Authors: W.-Z. Xu, F.F. Ren, D. Jevtics, A. Hurtado, L. Li, Q. Gao, J. Ye, F. Wang, B. Guilhabert, L. Fu, H. Lu, R. Zhang, H.H. Tan, M. Dawson and C. Jagadish

Abstract: Semiconductor nanowire (NW) lasers have attracted considerable research effort given their excellent promise for nanoscale photonic sources. However, NW lasers currently exhibit poor directionality and high threshold gain, issues critically limiting their prospects for on-chip light sources with extremely reduced footprint and efficient power consumption. Here, we propose a new design and experimentally demonstrate a vertically emitting indium phosphide (InP) NW laser structure showing high emission directionality and reduced energy requirements for operation. The structure of the laser combines an InP NW integrated in a cat’s eye (CE) antenna. Thanks to the antenna guidance with broken asymmetry, strong focusing ability, and high Q-factor, the designed InP CE-NW lasers exhibit a higher degree of polarization, narrower emission angle, enhanced internal quantum efficiency, and reduced lasing threshold. Hence, this NW laser–antenna system provides a very promising approach toward the achievement of high-performance nanoscale lasers, with excellent prospects for use as highly localized light sources in present and future integrated nanophotonics systems for applications in advanced sensing, high-resolution imaging, and quantum communications.

 

 

Invited Paper published in IET Optoelectronics

An invited article has been published in IET Optoelectronics. This paper reviews our recent activities on the hybrid integration of semiconductor nanowire lasers onto heterogeneous photonic platforms by means of nanoscale Transfer Printing techniques.

This work is the result of an ongoing collaboration between our group at the Institute of Photonics at the University of Strathlyde (UK) and our colleagues at the Australian National University (Canberra, Australia).

The paper details are as follows:

Title: Transfer Printing of Semiconductor Nanowire Lasers
Authors: Antonio Hurtado, Dimitars Jevtics, Benoit Guilhabert, Qian Gao, Hark Hoe Tan, Chennupati Jagadish and Martin D. Dawson
Abstract: The authors review their work on the accurate positioning of semiconductor nanowire (NW) lasers by means of nanoscale Transfer Printing (nano-TP). Using this hybrid nanofabrication technique, indium phosphide NWs are successfully integrated at selected locations onto heterogeneous surfaces with high positioning accuracy. Moreover, they show that NW lasers can also be organised to form bespoke spatial patterns, including (one-dimensional) 1D or 2D arrays, or complex configurations with a defined number of NWs and controlled separation between them. Besides, their nano-TP technique also permits the integration of NWs with different dimensions in a single system. Notably, the nano-TP fabrication protocols do not affect the optical or structural properties of the NWs and they retain their room-temperature lasing emission after their positioning onto all investigated receiving surfaces. This developed nano-TP technique offers therefore new exciting prospects for the fabrication of hybrid bespoke nanophotonic systems using NW lasers as building blocks.

The paper can be accessed in the following link.

Paper on hybrid integration of nanowire lasers in waveguide elements accepted in Nano Letters

Our work on the hybrid integration of nanowire lasers in waveguide devices has been accepted for publication in Nano Letters. The paper can be accessed here.

This work uses a hybrid nanofabrication technique, referred as nanoscale Transfer Printing (nano-TP), to precisely integrate individually selected semiconductor nanowire lasers in on-chip waveguide elements. Two coupling configurations are demonstrated: from nanowires printed at a waveguide’s facet and from nanowires directly printed on top of a waveguide. Basic photonic circuits with these nanoscale laser sources are also demonstrated including power splitting and coupling and multiple wavelength operation. We also report on the integration of nanowire lasers in systems fabricated in mechanically flexible substrates allowing the on-chip guiding of the nanowires’ light even for large substrate’s deformation.

This work is the result of a collaboration between the Institute of Photonics at the University of Strathclyde (Glasgow, UK) and the Australian National University (Canberra).

The full paper details are as follows:

Title: Integration of Semiconductor Nanowire Lasers with Polymeric Waveguide Devices on a Mechanically Flexible Substrate

Authors: D. Jevtics, A. Hurtado, B. Guilhabert, J. McPhillimy, G. Cantarella, Q. Gao, H.H. Tan, C. Jagadish, M.J. Strain, and M. Dawson

Abstract: Nanowire lasers are integrated with planar waveguide devices using a high positional accuracy micro-transfer printing technique. Direct nanowire to waveguide coupling is demonstrated, with coupling losses as low as -17 dB, dominated by mode mismatch between the structures. Coupling is achieved using both end-fire coupling into a waveguide facet, and from nanowire lasers printed directly onto the top surface of the waveguide. In-waveguide peak powers up to 11.8 μW are demonstrated. Basic photonic integrated circuit functions such as power splitting and wavelength multiplexing are presented. Finally, devices are fabricated on a mechanically flexible substrate to demonstrate robust coupling between the on-chip laser source and waveguides under significant deformation of the system.

Research on neuromorphic photonics highlighted in Laser Focus World

Our group’s recent work on Neuromorphic Photonics has been highlighted in an article in the latest issue of Laser Focus World (LFW). The article, included in the ‘World News’ section of the magazine can be accessed in the following link. The magazine can also be read online in its website.

This article in LFW highlights our recent work on the use of Vertical-Cavity Surface Emitting Lasers (VCSELs) for ultrafast photonic neurons. Specifically, this article reviews our recent paper describing an all-optical VCSEL inhibitory optical neuron able to operate at sub-nanosecond speeds. The article in LFW also collects opinions from the group leader at Strathclyde (Dr Antonio Hurtado) and from colleagues at Princeton (USA) regarding the future propsects of the emerging field of neuromorphic photonics.

 

Citation: J. Robertson, T. Deng, J. Javaloyes, A. Hurtado, “Controlled inhibition of spiking dynamics in VCSELs for neuromorphic photonics: theory and experiments,” Opt. Lett.
42, 1560-1563 (2017).

Invited talk at the Workshop on “Computational Neuroscience and Optical Dynamics”

Antonio Hurtado attended the Workshop in “Computational Dynamics and Optical Dynamics” (cnod.info) to give an invited talk reviewing his group’s recent work on neuromorphic photonics with semiconductor lasers. The event took place at the CNRS’s Institute Non Lineaire de Nice (France) last May.

In this talk he reviewed the group’s latest reports on neuromorphic photonics research. In particular, he presented our recent developments on the use of Vertical-Cavity Surface Emitting Lasers (VCSELs) for the generation, inhibition and propagation of multiple spiking regimes at sub-nanosecond speeds.

The details of the talk are as follows:

Title: Activation, Inhibition and Propagation of Spiking Regimes in Vertical Cavity Surface Emitting Lasers

Abstract: Photonic techniques emulating the brain powerful computational capabilities are the subject of increasing research interest as these offer excellent prospects for ultrafast neuro-inspired information processing systems going beyond classical digital modules. One of these approaches considers the use of semiconductor lasers, as these devices can undergo a rich variety of dynamical responses similar to those observed in neurons; yet, remarkably these are obtained at speeds up to 9 orders of magnitude faster than the millisecond timescales of biological neurons. Amongst semiconductor lasers, Vertical Cavity Surface Emitting Lasers (VCSELs) are ideal for use in neuromorphic photonics as they possess important inherent advantages, e.g. low fabrication costs, ease to integrate in 2- and 3-Dimensional arrays, high coupling efficiency to optical fibres, etc.

In this talk, we will review our recent progress on the achievement of controllable and reproducible spiking patterns in VCSELs with ultrafast speed resolution. Specifically, we will show that a wide variety of spiking regimes, e.g. single and multiple spiking and bursting patterns can be controllably activated and inhibited in these devices in response to external perturbations. Additionally, we will introduce our recent results demonstrating the successful communication of spiking photonic signals between two interconnected VCSELs. Moreover, the activation, inhibition and propagation of the aforementioned spiking regimes are all obtained at sub-nanosecond speeds, thus offering high potentials for novel ultrafast non-traditional information processing capabilities with these laser sources. Also, our results, obtained with off-the-shelf inexpensive components operating at the most relevant wavelengths in present optical fibre networks (1300 and 1550 nm), make our approach fully compatible with optical communication technologies.

In summary, the reproducible and controllable activation, suppression and propagation of spiking photonic signals at high speeds in VCSELs operating at telecom wavelengths offer great potential for the use of these devices in excitatory and inhibitory photonic neuronal models for future neuromorphic photonic information processing systems.

Paper published in Optics Letters

Our paper ‘High frequency continuous birefringence-induced oscillations in spin-polarized vertical-cavity surface-emitting lasers”, has been published in Optics Letters.

This work is the result of a collaboration between the Institute of Photonics at the University of Strathclyde (Glasgow, UK), the University of Essex (UK) and the Institute de Fisica Arroyo Seco (Tandil, Argentina).

Paper details are as follows:

Title: ‘High frequency continuous birefringence-induced oscillations in spin-polarized vertical-cavity surface-emitting lasers’

Authors: M. S. Torre, H. Susanto, Nianqiang Li, K. Schires, M. F. Salvide, I. D. Henning, M. J. Adams and A. Hurtado

Abstract: Sustained, large amplitude and tuneable birefringenceinduced oscillations are obtained in a spin-Vertical Cavity Surface Emitting Laser (spin-VCSEL). Experimental evidence is provided using a spin-VCSEL operating at 1300 nm, under continuous wave optical pumping and at room temperature. Numerical and stability analyses are performed to interpret the experiments and to identify the combined effects of pump ellipticity, spin relaxation rate and cavity birefringence. Importantly, the frequency of the induced oscillations is determined by the device’s birefringence rate which can be tuned to very large values. This opens the path for ultrafast spin-lasers operating at record frequencies exceeding those possible in traditional semiconductor lasers and with ample expected impact in disparate disciplines (e.g. datacomms, spectroscopy).

Journal: Optics Letters (Vol. 42, Issue 8, pp. 1628-1631, 2017)

Invited talk at the European Semiconductor Laser Workshop 2016 (24th Sept 2016)

Antonio Hurtado will be giving an invited talk in the upcoming edition of the European Semiconductor Laser Workshop (ESLW). This event will be taking place from the 23nd to the 24th of September at the Technical University of Darmstadt (Germany).

In this talk he will be reviewing our recent progress on the nanoscale transfer printing technology developed at Strathclyde’s Institute of Photonics allowing the accurate manipulation and organization of semiconductor nanowire lasers.

The details of the talk are as follows:

Title: Transfer Printing of Semiconductor Nanowire Lasers for Nanophotonic Device Fabrication

Time, Date and Place: 11.15am, 24th of September 2016, S208 Building, TU Darmstadt (Darmstadt, Germany)

Abstract: Precise positioning of semiconductor nanowires with lasing emission at room temperature at desired locations, onto diverse substrates and forming complex patterns is demonstrated using a novel nanoscale Transfer Printing technique.

Paper accepted for publication in ACS Nano

Our paper ‘Transfer Printing of Semiconductor Nanowires with Lasing Emission for Controllable Nanophotonic Device Fabrication’ has been accepted for publication in ACS Nano.

In this work we report a nanoscale Transfer Printing platform enabling the precise and controllable manipulation and positioning of semiconductor nanowires onto targeted locations and onto multiple receiving substrates. Specifically, in this work we demonstrate the possibility to transfer and print Indium Phosphide (InP) nanowires with lasing emission at room temperature onto different substrates with high positioning accuracy (e.g. polymers, glass, gold). Moreover, we show that this technique enables the formation of bespoke patterns with controlled dimensions and number of nanowires. Finally, the transfer printing techique reported did not affect the properties of the nanowires and these retained their lasing emission after the transfer printing experiments onto multiple surfaces. These results open exciting new routes for the integration of nanowire lasers and other semiconductor nanowire devices onto bespoke nanophotonic integrated systems.

This work is the result of a collaboration between the Institute of Photonics at the University of Strathclyde (Glasgow) and The Australian National University (Canberra).

Paper details are as follows:

Title: ‘Transfer Printing of Semiconductor Nanowires with Lasing Emission for Controllable Nanophotonic Device Fabrication’

Authors: B. Guilhabert, A. Hurtado, D. Jevtics, Q. Gao, H. Tan, C. Jagadish and M. Dawson

Abstract: Accurate positioning and organization of Indium Phosphide (InP) Nanowires (NW) with lasing emission at room temperature is achieved using a nanoscale Transfer Printing (TP) technique. The NWs retained their lasing emission after their transfer to targeted locations on different receiving substrates (e.g. polymers, silica and metal surfaces). The NWs were also organized into complex spatial patterns, including 1D and 2D arrays, with a controlled number of elements and dimensions. The developed TP technique enables the fabrication of bespoke nanophotonic systems using NW lasers and other NW devices as building blocks.

Figure. (Top) Images of one of the µ-stamps used in this work. Enlarged images show respectively flat tip and (left) the elongated pyramid tipped (right) µ-stamps. (Bottom) Image of the pattern ‘IOP’, initials of the University of Strathclyde’s Institute of Photonics formed with InP NWs (diameter Ø 435 nm) onto a PDMS substrate. The image shows a collage merging independently captured micrographs of the individual elements on the ‘IOP’ pattern. The dashed lines connecting the NWs are plotted as a guide to the eye.