Event-activated biological-inspired subwavelength (sub-λ) optical neural networks are of paramount importance for energy-efficient and high-bandwidth artificial intelligence (AI) systems. Despite the significant advances to build active optical artificial neurons using for example phase-change materials, lasers, photodetectors, and modulators, miniaturized integrated sources and detectors suited for few-photon spike-based operation and of interest for neuromorphic optical computing are still lacking. In this invited paper we outline the main challenges, opportunities, and recent results towards the development of interconnected neuromorphic nanoscale light-emitting diodes (nanoLEDs) as key-enabling artificial spiking neuron circuits in photonic neural networks. This method of spike generation in neuromorphic nanoLEDs paves the way for sub-λ incoherent neural circuits for fast and efficient asynchronous brain-inspired computation.
The ability to use resonant tunneling diodes (RTDs) as both transmitters and receivers is an emerging topic, especially with regards to wireless communications. Successful data transmission has been achieved using electronic RTDs with carrier frequencies exceeding 0.3 THz. Specific optical-based RTDs, which act as photodetectors, have been developed by adjusting the device structure to include a light absorption layer and small optical windows on top of the device to allow direct optical access. This also allows the optical signal to directly modulate the RTD oscillation. Both types of RTD oscillators will allow for seamless integration of high frequency radio and optical fiber networks.
Resonant tunneling diodes (RTDs) are the fastest pure electronic semiconductor devices at room temperature. When integrated with optoelectronic devices they can give rise to new devices with novel functionalities due to their highly nonlinear properties and electrical gain, with potential applications in future ultra-wide-band communication systems (see e.g. EU H2020 iBROW Project). The recent coverage on these devices led to the need to have appropriated simulation tools. In this work, we present RTD based optoelectronic circuits simulation packages to provide circuit signal level analysis such as transient and frequency responses. We will present and discuss the models, and evaluate the simulation packages.
Resonant tunneling diodes (RTDs) have been extensively studied due to their potential applications in very high speed electronics, optical communications, and terahertz generation. In this work, we report the latest results on the characterization of the resonant tunneling diode photo-detectors (RTD-PDs), incorporating InGaAlAs light sensitive layers for sensing at the telecommunication wavelength of λ = 1310 nm. We have measured responsivities up to 28.8 A/W and light induced voltage shift of 204.8 V/W for light injection powers around 0.25 mW.
Resonant tunneling diode (RTD) integration with photo detector (PD) from epi-layer design shows great potential for combining terahertz (THz) RTD electronic source with high speed optical modulation. With an optimized layer structure, the RTD-PD presented in the paper shows high stationary responsivity of 5 A/W at 1310 nm wavelength. High power microwave/mm-wave RTD-PD optoelectronic oscillators are proposed. The circuitry employs two RTD-PD devices in parallel. The oscillation frequencies range from 20-44 GHz with maximum attainable power about 1 mW at 34/37/44GHz.
This paper will discuss resonant tunnelling diode (RTD) sources being developed on a European project iBROW (ibrow.project.eu) to enable short-range multi-gigabit wireless links and microwave-photonic interfaces for seamless links to the optical fibre backbone network. The practically relevant output powers are at least 10 mW at 90 GHz, 5 mW at 160 GHz and 1 mW at 300 GHz and simulation and some experimental results show that these are feasible in RTD technology. To date, 75 - 315 GHz indium phosphide (InP) based RTD oscillators with relatively high output powers in the 0.5 – 1.1 mW range have been demonstrated on the project. They are realised in various circuit topologies including those that use a single RTD device, 2 RTD devices and up to 4 RTD devices for increasingly higher output power. The oscillators are realised using only photolithography by taking advantage of the large micron-sized but broadband RTD devices. The paper will also describe properties of RTD devices as photo-detectors which makes this a unified technology that can be integrated into both ends of a wireless link, namely consumer portable devices and fibre-optic supported base-stations (since integration with laser diodes is also possible).
The ability to produce narrow optical pulses has been extensively investigated in laser systems with promising applications in photonics such as clock recovery, pulse reshaping, and recently in photonics artificial neural networks using spiking signal processing. Here, we investigate a neuromorphic opto-electronic integrated circuit (NOEIC) comprising a semiconductor laser driven by a resonant tunneling diode (RTD) photo-detector operating at telecommunication (1550 nm) wavelengths capable of excitable spiking signal generation in response to optical and electrical control signals. The RTD-NOEIC mimics biologically inspired neuronal phenomena and possesses high-speed response and potential for monolithic integration for optical signal processing applications.
We experimentally investigate the synchronous response of two fiber-optic coupled optoelectronic circuit oscillators based on resonant tunneling diodes (RTDs). The fiber-optic synchronization link employs injection of a periodic oscillating optical modulated signal generated by a master RTD-laser diode (LD) oscillator to a slave RTD-photodetector (PD) oscillator. The synchronous regimes were evaluated as a function of frequency detuning and optical injection strength. The results show the slave RTD-PD oscillator follows the frequency and noise characteristics of the master RTD-LD oscillator resulting in two oscillators with similar phase noise characteristics exhibiting single side band phase noise levels below -100 dBc/Hz at 1 MHz offset from the carrier frequency. Optical synchronization of RTD-based optoelectronic circuit oscillators have many applications spanning from sensing, to microwave generation, and data transmission.
We investigate optoelectronic oscillator (OEO) configurations based on a laser diode driven by resonant tunnelling diode
(RTD) optical waveguide photo-detector (PD) oscillators, with an optical fiber feedback loop carrying a fraction of the
laser diode optical output that is re-injected into the OEO through the optical waveguide of the RTD-PD. In the
configurations reported here, we take advantage of the RTD negative differential resistance to provide electrical highbandwidth.
The optical fiber loop acts as a high quality optical energy storage element with low transmission loss. The
RTD based OEO can produces stable and low-phase noise microwave signals with attractive applications in photonics
and communication systems, mainly in fiber-optic based communication links since the RTD-OEO can be accessed both
optically and electrically.
Optoelectronic oscillators can provide low noise oscillators at radio frequencies in the 0.5-40 GHz range and in this
paper we review two recently introduced approaches to optoelectronic oscillators. Both approaches use an optical fibre
feedback loop. One approach is based on passively modelocked laser diodes and in a 40 GHz oscillator achieves up to 30
dB noise reduction. The other approach is based on resonant tunneling diode optoelectronic devices and in a 1.4 GHz
oscillator can achieve up to 30 dB noise reduction.
We present a review of Resonant Tunneling Diode (RTD) OptoElectronic Integrated Circuits (OEICs). Resonant
tunneling diodes (RTDs) can be relatively easily integrated on the same chip as optoelectronic components and in this
paper we discuss the integration of RTDs with laser diodes, electroabsorption modulators and photodiodes. The RTD
provides the OEIC with negative differential resistance over a wide bandwidth. RTDs are highly nonlinear devices and
by applying nonlinear dynamics we have recently gained considerable insight into the operation of the RTD OEICS and
that has allowed us to design, fabricate and characterize OEICs for wireless/photonic interfaces.
Recent work on an OptoElectronic Integrated Circuit (OEIC), the resonant tunneling diode-laser diode (RTD-LD) has
shown that it can act as an optoelectronic voltage controlled oscillator (OVCO). The RTD-LD oscillates because of the
negative differential resistance of the RTD and simply providing the RTD-LD with a dc voltage will cause it to oscillate
at frequencies determined by both the external components of the circuit and the value of the dc voltage. It has been
observed to oscillate at frequencies as high as 2.2GHz and be tunable from 1.8-2.2GHz as the dc voltage is tuned by
0.5V. Both monolithic and hybrid (separate RTD and LD chips) have been investigated. The hybrid RTD-LD has been
accurately modeled as a Liénard's oscillator - closely related to the Van der Pol oscillator. The model is a classic of
nonlinear systems theory and explains all of the observed operating features that include synchronization and chaotic
output. Applications include wireless to optical signal conversion where phase synchronization has been demonstrated to
transfer phase modulated signals from the wireless to the optical domain by modulating the RTD-LD OVCO to produce
a phase modulated optical sub-carrier.
The objective of this work is to analyse the dependence of the frequency response of Laterally Coupled Diode Lasers (LCDL) focusing on the separation between the laser ridges. A detailed study of the integrated optical spectra and frequency response is presented for LCDLs with 300 μm cavity length and separation between the ridges of 2, 4, 6, 8 and 10 μm. This study is of major importance as it defines the range of frequency locking for each ridge spacing and
also its dependence on the bias conditions applied.
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