Browsing by Author "Wasige, Edward"
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- DC characterization of tunnel diodes under stable non-oscillatory circuit conditionsPublication . Wang, Liquan; Figueiredo, J. M. L.; Ironside, C. N.; Wasige, EdwardA common problem in designing with Esaki tunneling diodes in circuits is parasitic oscillations, which occur when these devices are biased in their negative differential resistance(NDR) region. Because of this, the measured current–voltage(I–V )characteristics in the NDR region are usually incorrect, with sudden changes in current with voltage and a plateaulike waveform in this region. Using a full nonlinear analysis of the shunt-resistor-stabilized tunnel diode circuit, we have established the criteria for the range of element values that give stable operation. On this basis, I–V measurement circuits can be designedto be free from both low-frequency bias oscillations and highfrequency oscillations. The design equations lead to a direct I–V measurement setup in which the stabilization resistor in series with a capacitor can be employed. Experimental results validate the approach, and this is confirmed by second-derivative analysis (d2I/dV 2) of the measured I–V characteristics.
- 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.
- 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.
- Resonant tunneling diode oscillators for optical communicationsPublication . Watson, Scott; Zhang, Weikang; Wang, Jue; Al-Khalidi, Abdullah; Cantu, Horacio; Figueiredo, José; Wasige, Edward; Kelly, Anthony E.; Costa, M. F. M.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 diode photodetectors for optical communicationsPublication . Rodrigues, Gil C.; Rei, João F.; Foot, James A.; Alharbi, Khalid H.; Al-Khalidi, Abdullah; Wang, Jue; Wasige, Edward; Figueiredo, José; Costa, M. F. M.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 lambda = 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 tunnelling diode based high speed optoelectronic transmittersPublication . Wang, Jue; Rodrigues, G. C.; Al-Khalidi, Abdullah; Figueiredo, José; Wasige, Edward; Costa, M. F. M.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.
- Resonant tunnelling diode terahertz sources for broadband wireless communicationsPublication . Wasige, Edward; Alharbi, Khalid H.; Al-Khalidi, Abdullah; Wang, Jue; Khalid, Ata; Rodrigues, Gil; Figueiredo, José; Sadwick, L. P.; Yang, T.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).
- Self-oscillation and period adding from resonant tunnelling diode–laser diode circuitPublication . Figueiredo, J. M. L.; Romeira, Bruno; Slight, Thomas James; Wang, Liquan; Wasige, Edward; Ironside, C. N.A hybrid optoelectronic integrated circuit comprising a laser diode driven by a resonant tunnelling diode can output various optical and electrical signal patterns that include self-sustained oscillations, subharmonic and harmonic locking and unlocked signals, with potential applications in optical communication systems.
- Synchronisation and chaos in a laser diode driven by a resonant tunnelling diodePublication . Romeira, Bruno; Figueiredo, J. M. L.; Slight, Thomas James; Wang, Liquan; Wasige, Edward; Ironside, C. N.; Quintana, J. M.; Avedillo, M. J.The authors report on a hybrid integration of a resonant tunnelling diode laser diode driver configuration that can operate as a self-oscillating circuit, and when externally perturbed shows regions of frequency division and frequency multiplication, quasi-periodic and chaotic oscillations, both in the optical and electrical outputs. The authors also demonstrate that this optoelectronic circuit is well described as a Lie´nard’s oscillator. The synchronisation capabilities of the circuit have potentially novel functions for optical communications systems including clock recovery, clock division and data encryption.