Examinando por Autor "Ortega-Piwonka, Ignacio"

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Artificial optoelectronic spiking neuron based on a resonant tunnelling diode coupled to a vertical cavity surface emitting laser
(De Gruyter, 2022-11-11) Hejda, Matěj; Malysheva, Ekaterina; Owen-Newns, Dafydd; Al-Taai, Qusay Raghib Ali; Zhang, Weikang; Ortega-Piwonka, Ignacio; Javaloyes, Julien J. P.; Wasige, Edward; Dolores-Calzadilla, Victor; Figueiredo, José; Romeira, Bruno; hurt, Antonio
Excitable optoelectronic devices represent one of the key building blocks for implementation of artificial spiking neurons in neuromorphic (brain-inspired) photonic systems. This work introduces and experimentally investigates an opto-electro-optical (O/E/O) artificial neuron built with a resonant tunnelling diode (RTD) coupled to a photodetector as a receiver and a vertical cavity surface emitting laser as a transmitter. We demonstrate a well-defined excitability threshold, above which the neuron produces optical spiking responses with characteristic neural-like refractory period. We utilise its fan-in capability to perform in-device coincidence detection (logical AND) and exclusive logical OR (XOR) tasks. These results provide first experimental validation of deterministic triggering and tasks in an RTD-based spiking optoelectronic neuron with both input and output optical (I/O) terminals. Furthermore, we also investigate in simulation the prospects of the proposed system for nanophotonic implementation in a monolithic design combining a nanoscale RTD element and a nanolaser; therefore demonstrating the potential of integrated RTD-based excitable nodes for low footprint, high-speed optoelectronic spiking neurons in future neuromorphic photonic hardware.
Brain-inspired nanophotonic spike computing: challenges and prospects
(IOP Publishing, 2023-07-14) Romeira, Bruno; Adão, Ricardo; Nieder, Jana B.; Al-Taai, Qusay Raghib Ali; Zhang, Weikang; Hadfield, Robert H.; Wasige, Edward; Hejda, Matěj; Hurtado, Antonio; Malysheva, Ekaterina; Dolores-Calzadilla, Victor; Lourenço, João; Alves, David Castro; Figueiredo, José; Ortega-Piwonka, Ignacio; Javaloyes, Julien J. P.; Edwards, Stuart; Davies, J. Iwan; Horst, Folkert; Offrein, Bert J.
Nanophotonic spiking neural networks (SNNs) based on neuron-like excitable subwavelength (submicrometre) devices are of key importance for realizing brain-inspired, power-efficient artificial intelligence (AI) systems with high degree of parallelism and energy efficiency. Despite significant advances in neuromorphic photonics, compact and efficient nanophotonic elements for spiking signal emission and detection, as required for spike-based computation, remain largely unexplored. In this invited perspective, we outline the main challenges, early achievements, and opportunities toward a key-enabling photonic neuro-architecture using III–V/Si integrated spiking nodes based on nanoscale resonant tunnelling diodes (nanoRTDs) with folded negative differential resistance. We utilize nanoRTDs as nonlinear artificial neurons capable of spiking at high-speeds. We discuss the prospects for monolithic integration of nanoRTDs with nanoscale light-emitting diodes and nanolaser diodes, and nanophotodetectors to realize neuron emitter and receiver spiking nodes, respectively. Such layout would have a small footprint, fast operation, and low power consumption, all key requirements for efficient nano-optoelectronic spiking operation. We discuss how silicon photonics interconnects, integrated photorefractive interconnects, and 3D waveguide polymeric interconnections can be used for interconnecting the emitter-receiver spiking photonic neural nodes. Finally, using numerical simulations of artificial neuron models, we present spike-based spatio-temporal learning methods for applications in relevant AI-based functional tasks, such as image pattern recognition, edge detection, and SNNs for inference and learning. Future developments in neuromorphic spiking photonic nanocircuits, as outlined here, will significantly boost the processing and transmission capabilities of next-generation nanophotonic spike-based neuromorphic architectures for energy-efficient AI applications. This perspective paper is a result of the European Union funded research project ChipAI in the frame of the Horizon 2020 Future and Emerging Technologies Open programme.
Breather Bound States in a Parametrically Driven Magnetic Wire
(MDPI, 2024-11-22) Castro, Camilo José; Ortega-Piwonka, Ignacio; Malomed, Boris A.; Urzagasti, Deterlino; Pedraja-Rejas, Liliana; Díaz, Pablo; Laroze, David
We report the results of a systematic investigation of localized dynamical states in the model of a one-dimensional magnetic wire, which is based on the Landau-Lifshitz-Gilbert (LLG) equation. The dissipative term in the LLG equation is compensated by the parametric drive imposed by the external AC magnetic field, which is uniformly applied perpendicular to the rectilinear wire. The existence and stability of the localized states is studied in the plane of the relevant control parameters, namely, the amplitude of the driving term and the detuning of its frequency from the parametric resonance. With the help of systematically performed simulations of the LLG equation, the existence and stability areas are identified in the parameter plane for several species of the localized states: stationary single- and two-soliton modes, single and double breathers, drifting double breathers with spontaneously broken inner symmetry, and multisoliton complexes. Multistability occurs in this system. The breathers emit radiation waves (which explains their drift caused by the spontaneous symmetry breaking, as it breaks the balance between the recoil from the waves emitted to left and right), while the multisoliton complexes exhibit cycles of periodic transitions between three-, five-, and seven-soliton configurations. Dynamical characteristics of the localized states are systematically calculated too. These include, in particular, the average velocity of the asymmetric drifting modes, and the largest Lyapunov exponent, whose negative and positive values imply that the intrinsic dynamics of the respective modes is regular or chaotic, respectively.
Bursting and Excitability in Neuromorphic Resonant Tunneling Diodes
(American Physical Society, 2021-03-05) Ortega-Piwonka, Ignacio; Piro, Oreste; Figueiredo, José; Romeira, Bruno; Javaloyes, Julien J. P.
We study in this paper the dynamics of quantum nanoelectronic resonant tunneling diodes (RTDs) as excitable neuromorphic spike generators. We disclose the mechanisms by which the RTD creates excitable all-or-nothing spikes and we identify a regime of bursting in which the RTD emits a random number of closely packed spikes. The control of the latter is paramount for applications in event-activated neuromorphic sensing and computing. Finally, we discuss a regime of multistability in which the RTD behaves as a memory. Our results can be extended to other devices exhibiting negative differential conductance.
Emergence of spatiotemporal dislocation chains in drifting patterns
(American Institute of Physics, 2014-06-16) Clerc, Marcel G.; Falcón, Claudio; García-Ñustes, Mónica A.; Odent, Vincent; Ortega-Piwonka, Ignacio
One-dimensional patterns subjected to counter-propagative flows or speed jumps exhibit a rich and complex spatiotemporal dynamics, which is characterized by the perpetual emergence of spatiotemporal dislocation chains. Using a universal amplitude equation of drifting patterns, we show that this behavior is a result of a combination of a phase instability and an advection process caused by an inhomogeneous drift force. The emergence of spatiotemporal dislocation chains is verified in numerical simulations on an optical feedback system with a non-uniform intensity pump. Experimentally this phenomenon is also observed in a tilted quasi-one-dimensional fluidized shallow granular bed mechanically driven by a harmonic vertical vibration.
Generalized master equations and fractional Fokker-Planck equations from continuous time random walks with arbitrary initial conditions
(Elsevier, 2017-03-15) Angstmann, Christopher N.; Henry, Bruce I.; Ortega-Piwonka, Ignacio
n the standard continuous time random walk the initial state is taken as a non-equilibrium state, in which the random walking particle has just arrived at a given site. Here we consider generalizations of the continuous time random walk to accommodate arbitrary initial states. One such generalization provides information about the initial state through the introduction of a first waiting time density that is taken to be different from subsequent waiting time densities. Another generalization provides information about the initial state through the prior history of the arrival flux density. The master equations have been derived for each of these generalizations. They are different in general but they are shown to limit to the same master equation in the case of an equilibrium initial state. Under appropriate conditions they also reduce to the master equation for the standard continuous time random walk with the non-equilibrium initial state. The diffusion limit of the generalized master equations is also considered, with Mittag-Leffler waiting time densities, resulting in the same fractional Fokker–Planck equation for different initial conditions.
Noise induced aperiodic rotations of particles trapped by a non-conservative force
(American Institute of Physics, 2018-04-03) Ortega-Piwonka, Ignacio; Angstmann, Christopher N.; Henry, Bruce I.; Reece, Peter J.
We describe a mechanism whereby random noise can play a constructive role in the manifestation of a pattern, aperiodic rotations, that would otherwise be damped by internal dynamics. The mechanism is described physically in a theoretical model of overdamped particle motion in two dimensions with symmetric damping and a non-conservative force field driven by noise. Cyclic motion only occurs as a result of stochastic noise in this system. However, the persistence of the cyclic motion is quantified by parameters associated with the non-conservative forcing. Unlike stochastic resonance or coherence resonance, where noise can play a constructive role in amplifying a signal that is otherwise below the threshold for detection, in the mechanism considered here, the signal that is detected does not exist without the noise. Moreover, the system described here is a linear system.
Nonconservative dynamics of optically trapped high-aspect-ratio nanowires
(American Physical Society, 2016-02-24) Toe, Wen Jun; Ortega-Piwonka, Ignacio; Angstmann, Christopher N.; Gao, Qiang; ta, Hark Hoe; Jagadish, Chennupati; Henry, Bruce I.; re, Peter J.
We investigate the dynamics of high-aspect-ratio nanowires trapped axially in a single gradient force optical tweezers. A power spectrum analysis of the dynamics reveals a broad spectral resonance of the order of kHz with peak properties that are strongly dependent on the input trapping power. A dynamical model incorporating linear restoring optical forces, a nonconservative asymmetric coupling between translational and rotational degrees of freedom, viscous drag, and white noise provides an excellent fit to experimental observations. A persistent low-frequency cyclical motion around the equilibrium trapping position, with a frequency distinct from the spectral resonance, is observed from the time series data.
Resonant Tunneling Diode Nano-Optoelectronic Excitable Nodes for Neuromorphic Spike-Based Information Processing
(American Physical Society, 2022-02-02) Hejda, Matěj; Alanis, Juan Arturo; Ortega-Piwonka, Ignacio; Lourenço, João; Figueiredo, José; Javaloyes, Julien J. P.; Romeira, Bruno; Hurtado, Antonio
n this work, we introduce an interconnected nano-optoelectronic spiking artificial neuron emitter-receiver system capable of operating at ultrafast rates (about 100 ps/optical spike) and with low-energy consumption (< pJ/spike). The proposed system combines an excitable resonant tunneling diode (RTD) element exhibiting negative differential conductance, coupled to a nanoscale light source (forming a master node) or a photodetector (forming a receiver node). We study numerically the spiking dynamical responses and information propagation functionality of an interconnected master-receiver RTD node system. Using the key functionality of pulse thresholding and integration, we utilize a single node to classify sequential pulse patterns and perform convolutional functionality for image feature (edge) recognition. We also demonstrate an optically interconnected spiking neural network model for processing of spatiotemporal data at over 10 Gbit/s with high inference accuracy. Finally, we demonstrate an off-chip supervised learning approach utilizing spike-timing-dependent plasticity for the RTD-enabled photonic spiking neural network. These results demonstrate the potential and viability of RTD spiking nodes for low footprint, low-energy, high-speed optoelectronic realization of spike-based neuromorphic hardware.
Scientific production in Latin American physics: a bibliometric analysis
(Springer, 2024-06-14) Pedraja-Rejas, Liliana; Garrido-Tamayo, Miguel Ángel; Ortega-Piwonka, Ignacio; Rodríguez-Ponce, Emilio; Laroze, David
In this article, a bibliometric analysis of the authors, journals, research institutions, coun- tries and keywords found in 27,750 documents from the Web of Science written by Latin American authors or co-authors in Physics between the years 2013 and 2022, is carried out. The results show that the last ten years have seen increasing numbers in the scientific production and that the more outstanding authors of the region are mainly from Brazil, Mexico, Argentina, Chile and Colombia, with the United States being the non-Latin Amer- ican country involved in the largest number of collaborations. Brazil is the most productive country in the region and the areas that draw most interest are Optics, Materials Science, Physics Applied, Nanotechnology and Chemistry Physical. Given that collaborations with the European Organization for Nuclear Research (CERN) involve more than 1000 authors per document or other large similar collaborations, works associated with high energy physics have been excluded from this study.
Simplified description of dynamics in neuromorphic resonant tunneling diodes
(American Institute of Physics, 2021-11-15) Ortega-Piwonka, Ignacio; Teruel, Antonio E.; Prohens, Rafel; Vich, Catalina; Javaloyes, Julien J. P.
In this article, the standard theoretical model accounting for a double barrier quantum well resonant tunneling diode (RTD) connected to a direct current source of voltage is simplified by representing its current–voltage characteristic with an analytically approachable, anti-symmetric N-shaped function. The time and variables involved are also transformed to reduce the number of parameters in the model. Responses observed in previous, more physically accurate studies are reproduced, including slow–fast dynamics, excitability, and bistability, relevant for spiking signal processing. A simple expression for the refractory time of the excitable response is derived and shown to be in good agreement with numerical simulations. In particular, the refractory time is found to be directly proportional to the circuit’s intrinsic inductance. The presence or absence of bistability in the dependence of the parameters is also discussed thoroughly. The results of this work can serve as a guideline in prospective endeavors to design and fabricate RTD-based neuromorphic circuits for power and time-efficient execution of neural network algorithms.
Spike propagation in a nanolaser-based optoelectronic neuron
(Optica Publishing Group, 2022-07-01) Ortega-Piwonka, Ignacio; Hejda, Matěj; Alanis, Juan Arturo; Lourenço, João; Hurtado, Antonio; Figueiredo, José; Romeira, Bruno; Javaloyes, Julien J. P.
With the recent development of artificial intelligence and deep neural networks, alternatives to the Von Neumann architecture are in demand to run these algorithms efficiently in terms of speed, power and component size. In this theoretical study, a neuromorphic, optoelectronic nanopillar metal-cavity consisting of a resonant tunneling diode (RTD) and a nanolaser diode (LD) is demonstrated as an excitable pulse generator. With the proper configuration, the RTD behaves as an excitable system while the LD translates its electronic output into optical pulses, which can be interpreted as bits of information. The optical pulses are characterized in terms of their width, amplitude, response delay, distortion and jitter times. Finally, two RTD-LD units are integrated via a photodetector and their feasibility to generate and propagate optical pulses is demonstrated. Given its low energy consumption per pulse and high spiking rate, this device has potential applications as building blocks in neuromorphic processors and spiking neural networks. © 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
Subharmonic wave transition in a quasi-one-dimensional noisy fluidized shallow granular bed
(American Physical Society, 2010-04-19) Ortega-Piwonka, Ignacio; Clerc, Marcel G.; Falcón, Claudio; Nicolás, Mujica
We present an experimental and theoretical study of the pattern formation process of standing subharmonic waves in a fluidized quasi-one-dimensional shallow granular bed. The fluidization process is driven by means of a time-periodic air flow, analogous to a tapping type of forcing. Measurements of the amplitude of the critical mode close to the transition are in quite good agreement with those inferred from a universal stochastic amplitude equation. This allows us to determine both the bifurcation point of the deterministic system and the corresponding noise intensity. We also show that the probability density distribution is well described by a generalized Rayleigh distribution, which is the stationary solution of the corresponding Fokker-Planck equation of the universal stochastic amplitude equation that describes our system.
Symmetry-induced pinning-depinning transition of a subharmonic wave pattern
(American Physical Society, 2012-03-05) Garay, Jeremías; Ortega-Piwonka, Ignacio; Clerc, Marcel G.; Falcón, Claudio
The stationary to drifting transition of a subharmonic wave pattern is studied in the presence of inhomogeneities and drift forces as the pattern wavelength is comparable with the system size. We consider a pinning-depinning transition of stationary subharmonic waves in a tilted quasi-one-dimensional fluidized shallow granular bed driven by a periodic air flow in a small cell. The transition is mediated by the competition of the inherent periodicity of the subharmonic pattern, the asymmetry of the system, and the finite size of the cell. Measurements of the mean phase velocity of the subharmonic pattern are in good agreement with those inferred from an amplitude equation, which takes into account asymmetry and finite-size effects of the system, emphasizing the main ingredients and mechanism of the transition.