High efficiency bias stabilisation for resonant tunneling diode oscillators

We report on high-efficiency, high-power, and low-phase-noise resonant tunneling diode (RTD) oscillators operating at around 30 GHz. By employing a bias stabilization network, which does not draw any direct current (dc), the oscillators exhibit over a tenfold improvement in the dc-to-RF conversion efficiency (of up to 14.7%) compared to conventional designs (~0.9%). The oscillators provide a high maximum output power of around 2 dBm, and low phase noise of -100 and -113 dBc/Hz at 100 kHz and 1 MHz offset frequencies, respectively. The proposed approach will be invaluable for realizing very high efficiency, low phase noise, and high-power millimeter-wave (mm-wave) and terahertz (THz) RTD-based sources

Accurate small-signal equivalent circuit modelling of resonant tunneling diodes to 110 GHz

This article presents a novel, on-wafer deembedding technique for the accurate small-signal equivalent circuit modeling of resonant tunneling diodes (RTDs). The approach is applicable to stabilized RTDs, and so enables the modeling of the negative differential resistance (NDR) region of the device's current-voltage (I-V) characteristics. Furthermore, a novel quasi-analytical procedure to determine all the equivalent circuit elements from the deembedded S-parameter data is developed. Extraction results of a 10 μm × 10 μm stabilized, low-current density RTD at different bias points show excellent fits between modeled and measured S-parameters up to 110 GHz

Brain-inspired nanophotonic spike computing:challenges and prospects

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.</p

A História da Alimentação: balizas historiográficas

Os M. pretenderam traçar um quadro da História da Alimentação, não como um novo ramo epistemológico da disciplina, mas como um campo em desenvolvimento de práticas e atividades especializadas, incluindo pesquisa, formação, publicações, associações, encontros acadêmicos, etc. Um breve relato das condições em que tal campo se assentou faz-se preceder de um panorama dos estudos de alimentação e temas correia tos, em geral, segundo cinco abardagens Ia biológica, a econômica, a social, a cultural e a filosófica!, assim como da identificação das contribuições mais relevantes da Antropologia, Arqueologia, Sociologia e Geografia. A fim de comentar a multiforme e volumosa bibliografia histórica, foi ela organizada segundo critérios morfológicos. A seguir, alguns tópicos importantes mereceram tratamento à parte: a fome, o alimento e o domínio religioso, as descobertas européias e a difusão mundial de alimentos, gosto e gastronomia. O artigo se encerra com um rápido balanço crítico da historiografia brasileira sobre o tema

Broadband Chaotic Signals and Breather Oscillations in an Optoelectronic Oscillator Incorporating a Microwave Photonic Filter

We propose a technique to generate broadband chaotic and breather signals employing an optoelectronic oscillator (OEO) comprising a phase modulator (PM) and a linearly chirped fiber Bragg grating (LCFBG). The joint operation of the PM and the LCFBG forms a broadband microwave photonic filter (MPF), which allows the OEO to generate chaotic signals and breathers taking advantage of the interplay between the broadband MPF and the time-delayed feedback loop provided by a long optical fiber delay line. The breather excitations are characterized by nanosecond chaotic oscillations breathing periodically at a significantly lower time-scale determined by the OEO large delay time. A theoretical analysis based on a modified Ikeda time-delayed model to include the effect of the broadband filtering process is provided. The analysis is verified by an experiment. The proposed LCFBG-based OEO and the possibility to control in the optical domain its broadband bandpass characteristics considering the flexibility, accuracy, and precision in FBG fabrication can find applications in chaos-based communications and in fast optical processing systems, such as random number generation, or optical processing in reservoir computing taking advantage of the intrinsic multiple time scales of the LCFBG-based OEO. © 2012 IEEE.Peer Reviewe

Broadband Chaotic Signals and Breather Oscillations in an Optoelectronic Oscillator Incorporating a Microwave Photonic Filter

We propose a technique to generate broadband chaotic and breather signals employing an optoelectronic oscillator (OEO) comprising a phase modulator (PM) and a linearly chirped fiber Bragg grating (LCFBG). The joint operation of the PM and the LCFBG forms a broadband microwave photonic filter (MPF), which allows the OEO to generate chaotic signals and breathers taking advantage of the interplay between the broadband MPF and the time-delayed feedback loop provided by a long optical fiber delay line. The breather excitations are characterized by nanosecond chaotic oscillations breathing periodically at a significantly lower time-scale determined by the OEO large delay time. A theoretical analysis based on a modified Ikeda time-delayed model to include the effect of the broadband filtering process is provided. The analysis is verified by an experiment. The proposed LCFBG-based OEO and the possibility to control in the optical domain its broadband bandpass characteristics considering the flexibility, accuracy, and precision in FBG fabrication can find applications in chaos-based communications and in fast optical processing systems, such as random number generation, or optical processing in reservoir computing taking advantage of the intrinsic multiple time scales of the LCFBG-based OEO. © 2012 IEEE.Peer Reviewe

Stochastic induced dynamics in neuromorphic optoelectronic oscillators

© Springer Science+Business Media New York 2013. We investigate the dynamics of optoelectronic oscillator (OEO) systems based on resonant tunneling diode photodetector (RTD-PD) and laser diode hybrid integrated circuits. We demonstrate that RTD-based OEOs can be noise-activated in either monostable or bistable operating conditions, providing a rich variety of signal outputs—spiking, square pulses, bursting—and behaviours—stochastic and coherence resonances—that are similar to that of biological systems such as neurons. The potential for fully monolithic integration of our OEO confers them a great potential in novel neuromorphic optoelectronic circuits for signal processing tasks including re-timing and re-shaping of pulsed signals exploiting either the monostable or the bistable operating conditions.J.J. acknowledges financial support from the Ramon y Cajal fellowship. B.R. thanks FCT Portugal for a Postdoctoral Fellowship (Grant FRH/BPD/84466/2012). J.J. and S.B. acknowledge financial support from project RANGER (TEC2012-38864-C03-01) and from the Direcció General de Recerca del Govern de les Illes Balears and the FEDER fundsPeer Reviewe