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- Optical modulation at around 1550 nm in an InGaAlAs optical waveguide containing an InGaAs/AlAs resonant tunneling diodePublication . Figueiredo, J. M. L.; Boyd, A. R.; Stanley, C. R.; Ironside, C. N.; McMeekin, S. G.; Leite, A. M. P.We report electroabsorption modulation of light at around 1550 nm in a unipolar InGaAlAs optical waveguide containing an InGaAs/AlAs double-barrier resonant tunneling diode ~RTD!. The RTD peak-to-valley transition increases the electric field across the waveguide, which shifts the core material absorption band edge to longer wavelengths via the Franz–Keldysh effect, thus changing the light-guiding characteristics of the waveguide. Low-frequency characterization of a device shows modulation up to 28 dB at 1565 nm. When dc biased close to the negative differential conductance region, the RTD optical waveguide behaves as an electroabsorption modulator integrated with a wide bandwidth electrical amplifier, offering a potential advantage over conventional pn modulators.
- Modelling of optoelectronic circuits based on resonant tunneling diodesPublication . Rei, João F. M.; Foot, James A.; Rodrigues, Gil; Figueiredo, José; Costa, M. F. M.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 response. We will present and discuss the models, and evaluate the simulation packages.
- 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).
- 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
- Superhigh-frequency characteristics of optical modulators on the basis of InGaAlAs resonance-tunnel heterostructuresPublication . Aleshkin, V. Ya; Lyubchenko, V. E.; Figueiredo, J. M. L.; Ironside, C. N.; Stanley, C. R.The impedance of InGaAlAs resonance-tunnel heterostructures used for modulation of optical radiation is experimentally studied in the frequency range from 45 to 18 MHz. The dependence of their equivalent circuit on the bias voltage is determined. The spectrum of the harmonics of the current in the resistive frequency multiplication in such structures is calculated. The results confirm that these structures are promising as applied to the frequency multiplication. The effect of frequency multiplication is demonstrated experimentally at low frequencies.
- Analysis of Resonant Tunnelling Diode Oscillators under Optical ModulationPublication . Tavares, J. S.; Pessoa, L. M.; Figueiredo, José; Salgado, H. M.In this paper, we investigate the optical modulation characteristics of a resonant tunnelling diode (RTD) oscillator. This preliminary work on the first RTD-PD oscillators with an optical window available from the iBROW project demonstrate that this device can effectively be used to accomplish amplitude and frequency modulation with light injection.
- Coherent approach to transport and noise in double-barrier resonant diodesPublication . Aleshkin, V. Ya; Reggiani, L.; Alkeev, N. V.; Lyubchenko, V. E.; Ironside, C. N.; Figueiredo, J. M. L.; Stanley, C. R.We implement a quantum approach which includes long range Coulomb interaction and investigate current voltage characteristics and shot noise in double-barrier resonant diodes. The theory applies to the region of low applied voltages up to the region of the current peak and considers the wide temperature range from zero to room temperature. The shape of the current voltage characteristic is well reproduced and we confirm that even in the presence of Coulomb interaction the shot noise can be suppressed with a Fano factor well below the value of 0.5. This feature can be an indication of coherent tunneling since the standard sequential tunneling predicts in general a Fano factor equal to or greater than the value 0.5. This giant suppression is a consequence of Pauli principle as well as long range Coulomb interaction. The theory generalizes previous findings and is compared with experiments.
- Ultralow voltage resonant tunnelling diode electroabsorption modulatorPublication . Figueiredo, J. M. L.; Ironside, C. N.; Stanley, C. R.Embedding a double barrier resonant tunnelling diode (RTD) in a unipolar InGaAlAs optical waveguide gives rise to a very low driving voltage electroabsorption modulator (EAM) at optical wavelengths around 1550 nm. The presence of the RTD within the waveguide core introduces high non- linearity and negative di erential resistance in the current±voltage (I±V) characteristic of the waveguide. This makes the electric ®eld distribution across the waveguide core strongly dependent on the bias voltage: when the current decreases from the peak to the valley, there is an increase of the electric ®eld across the depleted core. The electric ®eld enhancement in the core-depleted layer causes the Franz±Keldysh absorption band-edge to red shift, which is responsible for the electroabsorption e ect. High-frequency ac signals as low as 100mV can induce electric ®eld high-speed switching, producing substantial light modulation (up to 15 dB) at photon energies slightly lower than the waveguide core band-gap energy. The key di erence between this device and conventional p-i-n EAMs is that the tunnelling characteristics of the RTD are employed to switch the electric ®eld across the core-depleted region; the RTD- EAM has in essence an integrated electronic ampli®er and, therefore, requires considerably less switching power.
- Reply to comment on 'Giant suppression of shot-noise in double barrier resonant diode: a signature of coherent transport'Publication . Aleshkin, V. Ya; Reggiani, L.; Alkeev, N. V.; Lyubchenko, V. E.; Ironside, C. N.; Figueiredo, J. M. L.; Stanley, C. R.Shot noise suppression below 1/2 of the full Poisson value in double barrier resonant diodes is confirmed to be a signature of coherent rather than sequential tunnelling transport. We reply to the arguments of the previous comment which dispute the above claim. We anticipate the development of a rigorous theory that improves previous approaches without contradicting the essential findings we recently reported (Aleshkin et al 2003 Semicond. Sci. Technol. 18 L35).
- 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