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- Excitability and optical pulse generation in semiconductor lasers driven by resonant tunneling diode photo-detectorsPublication . Romeira, Bruno; Javaloyes, Julien; Ironside, James; Figueiredo, José; Balle, Salvador; Piro, OresteWe demonstrate, experimentally and theoretically, excitable nanosecond optical pulses in optoelectronic integrated circuits operating at telecommunication wavelengths (1550 nm) comprising a nanoscale double barrier quantum well resonant tunneling diode (RTD) photo-detector driving a laser diode (LD). When perturbed either electrically or optically by an input signal above a certain threshold, the optoelectronic circuit generates short electrical and optical excitable pulses mimicking the spiking behavior of biological neurons. Interestingly, the asymmetric nonlinear characteristic of the RTD-LD allows for two different regimes where one obtain either single pulses or a burst of multiple pulses. The high-speed excitable response capabilities are promising for neurally inspired information applications in photonics. (C) 2013 Optical Society of America
- Wireless interrogation of an optically modulated resonant tunnelling diode oscillatorPublication . Cantu, Horacio I.; Salgado, H. M.; Romeira, Bruno; Kelly, Anthony E.; Ironside, C. N.; Figueiredo, Jose M. L.In this work, a resonant tunnelling diode-photo-detector based microwave oscillator is amplitude modulated using an optical signal. The modulated free running oscillator is coupled to an antenna and phase locked by a wireless carrier that allows remote extraction of the information contained in the modulation. An off-the-shelf demodulator has been used to recover the envelope of the baseband data originally contained in the optical signal. Data were successfully transmitted at a rate of 1 MSym/s with a bit error rate below 10-6. (c) 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1728-1730, 2013
- Dynamics of resonant tunneling diode optoelectronic oscillatorsPublication . Romeira, Bruno; Figueiredo, J. M. L.; Ironside, C. N.; Quintana, J. M.The nonlinear dynamics of optoelectronic integrated circuit (OEIC) oscillators comprising semiconductor resonant tunneling diode (RTD) nanoelectronic quantum devices has been investigated. The RTD devices used in this study oscillate in the microwave band frequency due to the negative di erential conductance (NDC) of their nonlinear current voltage characteristics, which is preserved in the optoelectronic circuit. The aim was to study RTD circuits incorporating laser diodes and photo-detectors to obtain novel dynamical operation regimes in both electrical and optical domains taking advantage of RTD's NDC characteristic. Experimental implementation and characterization of RTD-OEICs was realized in parallel with the development of computational numerical models. The numerical models were based on ordinary and delay di erential equations consisting of a Li enard's RTD oscillator and laser diode single mode rate equations that allowed the analysis of the dynamics of RTD-OEICs. In this work, several regimes of operation are demonstrated, both experimentally and numerically, including generation of voltage controlled microwave oscillations and synchronization to optical and electrical external signals providing stable and low phase noise output signals, and generation of complex oscillations that are characteristic of high-dimensional chaos. Optoelectronic integrated circuits using RTD oscillators are interesting alternatives for more e cient synchronization, generation of stable and low phase noise microwave signals, electrical/optical conversion, and for new ways of optoelectronic chaos generation. This can lead to simpli cation of communication systems by boosting circuits speed while reducing the power and number of components. The applications of RTD-OEICs include operation as optoelectronic voltage controlled oscillators in clock recovery circuit systems, in wireless-photonics communication systems, or in secure communication systems using chaotic waveforms.
- Regenerative memory in time-delayed neuromorphic photonic resonatorsPublication . Romeira, Bruno; Avó, R.; Figueiredo, José; Barland, S.; Javaloyes, JulienWe investigate a photonic regenerative memory based upon a neuromorphic oscillator with a delayed self-feedback (autaptic) connection. We disclose the existence of a unique temporal response characteristic of localized structures enabling an ideal support for bits in an optical buffer memory for storage and reshaping of data information. We link our experimental implementation, based upon a nanoscale nonlinear resonant tunneling diode driving a laser, to the paradigm of neuronal activity, the FitzHugh-Nagumo model with delayed feedback. This proof-of-concept photonic regenerative memory might constitute a building block for a new class of neuron-inspired photonic memories that can handle high bit-rate optical signals.
- Photo-detectors integrated with resonant tunneling diodesPublication . Romeira, Bruno; Pessoa, Luis M.; Salgado, Henrique M.; Ironside, C. N.; Figueiredo, Jose M. L.We report on photo-detectors consisting of an optical waveguide that incorporates a resonant tunneling diode (RTD). Operating at wavelengths around 1.55 m in the optical communications C band we achieve maximum sensitivities of around 0.29 A/W which is dependent on the bias voltage. This is due to the nature of RTD nonlinear current-voltage characteristic that has a negative differential resistance (NDR) region. The resonant tunneling diode photo-detector (RTD-PD) can be operated in either non-oscillating or oscillating regimes depending on the bias voltage quiescent point. The oscillating regime is apparent when the RTD-PD is biased in the NDR region giving rise to electrical gain and microwave self-sustained oscillations Taking advantage of the RTD's NDR distinctive characteristics, we demonstrate efficient detection of gigahertz (GHz) modulated optical carriers and optical control of a RTD GHz oscillator. RTD-PD based devices can have applications in generation and optical control of GHz low-phase noise oscillators, clock recovery systems, and fiber optic enabled radio frequency communication systems.
- A self-synchronized optoelectronic oscillator based on an RTD photodetector and a laser diodePublication . Romeira, Bruno; Seunarine, Kris; Ironside, C. N.; Kelly, Anthony E.; Figueiredo, J. M. L.We propose and demonstrate a simple and stable low-phase noise optoelectronic oscillator (OEO) that uses a laser diode, an optical fiber delay line, and a resonant tunneling diode(RTD) free-running oscillator that is monolithic integrated with a waveguide photodetector. The RTD-OEO exhibits single-side band phase noise power below 100 dBc/Hz with more than 30-dB noise suppression at 10 kHz from the center free-running frequency for fiber loop lengths around 1.2 km. The RTD-OEO can be controlled either by the injected optical power or the fiber delay line and its power consumption is below 0.55 W. The RTD-OEO stability is achieved without using other high-speed optical/optoelectronic components and amplification.
- Nonlinear dynamics of resonant tunneling optoelectronic circuits for wireless/optical interfacesPublication . Romeira, Bruno; Figueiredo, J. M. L.; Slight, Thomas James; Wang, Liquan; Wasige, Edward; Ironside, C. N.; Kelly, Anthony E.; Green, RichardWe report on experimental and modeling results on the nonlinear dynamics of a resonant-tunneling-diode-based(RTD) optoelectronic circuits that can be used as the basis of a wireless/optical interface for wireless access networks. The RTD-based circuits are optoelectronic integrated circuits that have negative differential resistance and act as optoelectronic voltage-controlled oscillators. These circuits display many of the features of classic nonlinear dynamics, including chaos and synchronization. These highly nonlinear oscillators behaves as injection-locked oscillators that can be synchronized by a small injection signal of either wireless or optical origin, and thus, can transfer phase encoded information from wireless to the optical domain or the optical to the wireless domain.
- A liénard oscillator resonant tunnelling diode-laser diode hybrid integrated circuit: model and experimentPublication . Slight, Thomas James; Romeira, Bruno; Wang, Liquan; Figueiredo, J. M. L.; Wasige, Edward; Ironside, C. N.We report on a hybrid optoelectronic integrated circuit based on a resonant tunnelling diode driving an optical communications laser diode. This circuit can act as a voltage controlled oscillator with optical and electrical outputs. We show that the oscillator operation can be described by Liénard’s equation, a second order nonlinear differential equation, which is a generalization of the Van der Pol equation. This treatment gives considerable insight into the potential of a monolithic version of the circuit for optical communication functions including clock recovery and chaotic source applications.
- Optoelectronic oscillators for communication systemsPublication . Romeira, Bruno; Figueiredo, J. M. L.We introduce and report recent developments on a novel five port optoelectronic voltage controlled oscillator consisting of a resonant tunneling diode (RTD) optical-waveguide integrated with a laser diode. The RTD-based optoelectronic oscillator (OEO) has both optical and electrical input and output ports, with the fifth port allowing voltage control. The RTD-OEO locks to reference radio-frequency (RF) sources by either optical or electrical injection locking techniques allowing remote synchronization, eliminating the need of impedance matching between traditional RF oscillators. RTD-OEO functions include generation, amplification and distribution of RF carriers, clock recovery, carrier recovery, modulation and demodulation and frequency synthesis. Self-injection locking operation modes, where small portions of the output electrical/ optical signals are fed back into the electrical/optical input ports, are also proposed. The self-phase locked loop configuration can give rise to low-noise high-stable oscillations, not limited by the RF source performance and with no need of external optoelectronic conversion.
- Delay dynamics of neuromorphic optoelectronic nanoscale resonators: Perspectives and applicationsPublication . Romeira, B.; Figueiredo, José; Javaloyes, JulienWith the recent exponential growth of applications using artificial intelligence (AI), the development of efficient and ultrafast brain-like (neuromorphic) systems is crucial for future information and communication technologies. While the implementation of AI systems using computer algorithms of neural networks is emerging rapidly, scientists are just taking the very first steps in the development of the hardware elements of an artificial brain, specifically neuromorphic microchips. In this review article, we present the current state of the art of neuromorphic photonic circuits based on solid-state optoelectronic oscillators formed by nanoscale double barrier quantum well resonant tunneling diodes. We address, both experimentally and theoretically, the key dynamic properties of recently developed artificial solid-state neuron microchips with delayed perturbations and describe their role in the study of neural activity and regenerative memory. This review covers our recent research work on excitable and delay dynamic characteristics of both single and autaptic (delayed) artificial neurons including all-or-none response, spike-based data encoding, storage, signal regeneration and signal healing. Furthermore, the neural responses of these neuromorphic microchips display all the signatures of extended spatio-temporal localized structures (LSs) of light, which are reviewed here in detail. By taking advantage of the dissipative nature of LSs, we demonstrate potential applications in optical data reconfiguration and clock and timing at high-speeds and with short transients. The results reviewed in this article are a key enabler for the development of high-performance optoelectronic devices in future high-speed brain-inspired optical memories and neuromorphic computing. (C) 2017 Author(s).