Bruno Romeira

A LiÉnard Oscillator Resonant Tunnelling Diode-Laser Diode Hybrid Integrated Circuit: Model and Experiment

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 Lienards 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.

Excitability and optical pulse generation in semiconductor lasers driven by resonant tunneling diode photo-detectors

We 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.

Delayed Feedback Dynamics of Liénard-Type Resonant Tunneling-Photo-Detector Optoelectronic Oscillators

We use the nonlinear dynamics approach for studying delayed feedback optoelectronic oscillators (OEOs) formed by hybrid integration of resonant tunneling diode (RTD) photo-detectors with laser diodes, in both single and dual optical fiber feedback routes. In the single loop topology, the performance of the RTD-OEO free-running self-sustained oscillator is improved in terms of phase noise, with a compromise between the delay line and the strength of the optical re-injection. In the dual-loop configuration, superior performance is achieved due to the suppression of the side modes associated with the optical cavity length, resulting in a side mode suppression ratio of up to -60 dBc of the carrier frequency. We compare experimental results with numerical simulations based on a system of delay differential equations comprising a Liénard oscillator model driven by white Gaussian noise and coupled with laser rate equations. The delayed feedback Liénard oscillator model gives considerable insight into the RTD-OEO dynamical regimes predicting its main features in both single- and dual-loop configurations.

Optical Control of a Resonant Tunneling Diode Microwave-Photonic Oscillator

We report on optical injection-locking of a microwave-photonic oscillator based on the integration of a resonant tunneling diode optical waveguide photodetector with a communication laser diode. The oscillator locking was achieved with in-fiber optical powers as low as 0.2 mW, and locking ranges up to 23.8 MHz for in-fiber optical power of few milliwatts and with phase-noise suppression below -110 dBc/Hz at 10-kHz frequency offset from the center frequency. The circuits dynamics are well described as an optically controlled Liénard oscillator.

Nonlinear Dynamics of Resonant Tunneling Optoelectronic Circuits for Wireless/Optical Interfaces

We 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.

Regenerative memory in time-delayed neuromorphic photonic resonators

We 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 Diodes

We report on photo-detectors consisting of an optical waveguide that incorporates a resonant tunneling diode (RTD). Operating at wavelengths around 1.55 μm 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 RTDs 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 Diode

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.

A Dual-Wavelength Fiber Ring Laser Incorporating an Injection-Coupled Optoelectronic Oscillator and Its Application to Transverse Load Sensing

A novel configuration for a dual-wavelength fiber ring laser with improved lasing stability realized through the use of an injection-coupled optoelectronic oscillator (OEO) is proposed and demonstrated, and its application to transverse load sensing is studied. The OEO-coupled dual-wavelength laser has two mutually coupled loops: the fiber ring loop and the OEO loop. In the fiber ring loop, a polarization-maintaining phase-shifted fiber Bragg grating is incorporated to generate two optical wavelengths with the wavelength spacing determined by the birefringence of the polarization-maintaining (PM) fiber. In the OEO loop, a microwave signal with its frequency also determined by the birefringence of the PM fiber is generated, which is fed into the fiber ring loop to injection lock the dual wavelengths. Due to the injection locking, a very stable dual-wavelength operation is established. The use of the dual wavelengths for high-resolution and high-speed transverse load sensing is then implemented. The sensitivity of the transverse load sensor is measured as high as +9.7573 and -9.7350 GHz/(N/mm), along the fast and slow axes, respectively. The high frequency purity and stability of the generated microwave signal permits very reliable and high accuracy measurement and the microwave frequency interrogation allows the system to operate at an ultra-high speed.

Waveguide-coupled nanopillar metal-cavity light-emitting diodes on silicon

Nanoscale light sources using metal cavities have been proposed to enable high integration density, efficient operation at low energy per bit and ultra-fast modulation, which would make them attractive for future low-power optical interconnects. For this application, such devices are required to be efficient, waveguide-coupled and integrated on a silicon substrate. We demonstrate a metal-cavity light-emitting diode coupled to a waveguide on silicon. The cavity consists of a metal-coated III–V semiconductor nanopillar which funnels a large fraction of spontaneous emission into the fundamental mode of an InP waveguide bonded to a silicon wafer showing full compatibility with membrane-on-Si photonic integration platforms. The device was characterized through a grating coupler and shows on-chip external quantum efficiency in the 10−4–10−2 range at tens of microamp current injection levels, which greatly exceeds the performance of any waveguide-coupled nanoscale light source integrated on silicon in this current range. Furthermore, direct modulation experiments reveal sub-nanosecond electro-optical response with the potential for multi gigabit per second modulation speeds.