Dynamics of resonant tunneling diode optoelectronic oscillators

Tese de dout., Física, Faculdade de Ciências e Tecnologia, Univ. do Algarve, 2012The 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

Synchronization of chaotic systems by using occasional coupling

Ankara : The Department of Electrical and Electronics Engineering and Institute of Engineering and Sciences, Bilkent Univ., 1997.Thesis (Master's) -- Bilkent University, 1997.Includes bibliographical references leaves 84-88.Nonlinear and chaotic systems are difficult to control due to their unstable and unpredictable nature. Although, much work has been done in this area, synchronization of chaotic systems still remains a worthwhile endeavor. In this thesis, a method to synchronize systems, inherently operating in a chaotic mode, by using occasional coupling is presented. We assume that a masterslave synchronizing scheme is available. This approach consists of coupling and uncoupling the drive and response systems during some alternated intervals. It is then shown how this synchronization method can be used to transmit information on a chaotic carrier. The applicability of this method will be illustrated using Lorenz system as the chaotic oscillator.Feki, MoezM.S

18th IEEE Workshop on Nonlinear Dynamics of Electronic Systems: Proceedings

Proceedings of the 18th IEEE Workshop on Nonlinear Dynamics of Electronic Systems, which took place in Dresden, Germany, 26 – 28 May 2010.:Welcome Address ........................ Page I Table of Contents ........................ Page III Symposium Committees .............. Page IV Special Thanks ............................. Page V Conference program (incl. page numbers of papers) ................... Page VI Conference papers Invited talks ................................ Page 1 Regular Papers ........................... Page 14 Wednesday, May 26th, 2010 ......... Page 15 Thursday, May 27th, 2010 .......... Page 110 Friday, May 28th, 2010 ............... Page 210 Author index ............................... Page XII

Nonlinear dynamics of two angles subtended by an angle

The work was based from previous analytical results that aims to facilitate rotations. It aims to initially use an elliptical track. However, from previous experimental observations, it was noted that addition of another pendulum, at an angle, instead of introducing a circular track, seemed more effective in inducing rotations. The idea of inducing rotations with a higher range of frequency is intriguing, with rotations being one of the centerpiece of energy generations or mechanical motion. Rotations are used because there is a continuous translational energy as compared to oscillations where it loses energy on it’s peak. If the experiment can induce rotations with impacts present and is still capable of rotating to generate electricity, it could lead to many more possibilities. Renewable energy using vibration is the main approach of this work, and investigating ways to achieve such energy with rotations using electromechanical device is one of the initial conditions that have been chosen to act as a motivation

Measurements, Models, Systems and Design

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Nonlinear dynamics of two angles subtended by an angle

The work was based from previous analytical results that aims to facilitate rotations. It aims to initially use an elliptical track. However, from previous experimental observations, it was noted that addition of another pendulum, at an angle, instead of introducing a circular track, seemed more effective in inducing rotations. The idea of inducing rotations with a higher range of frequency is intriguing, with rotations being one of the centerpiece of energy generations or mechanical motion. Rotations are used because there is a continuous translational energy as compared to oscillations where it loses energy on it’s peak. If the experiment can induce rotations with impacts present and is still capable of rotating to generate electricity, it could lead to many more possibilities. Renewable energy using vibration is the main approach of this work, and investigating ways to achieve such energy with rotations using electromechanical device is one of the initial conditions that have been chosen to act as a motivation

Subwavelength Sensing Using Nonlinear Feedback in a Wave-Chaotic Cavity

<p>Typical imaging systems rely on the interactions of matter with electromagnetic radiation, which can lead to scattered waves that are radiated away from the imaging area. The goal such an imaging device is to collect these radiated waves and focus them onto a measurement detector that is sensitive to the wave's properties such as wavelength (or color) and intensity. The detector's measurements of the scattered fields are then used to reconstruct spatial information about the original matter such as its shape or location. However, when a scattered wave is collected by the imaging device, it diffracts and inteferes with itself. The resulting interference pattern can blur spatial information of the reconstructed image. This leads to a so-called diffraction limit, which describes the minimum sizes of spatial features on a scatterer that can be resolved using conventional imaging techniques. The diffraction limit scales with the wavelength &lambda; of the illuminating field, where the limit for conventional imaging with visible light is approximately 200 nm. Investigating subwavelength objects (< &lambda;) requires more advanced measurement techniques, and improving the resolving capabilities of imaging devices continues to be an active area of research.</p><p>Here, I describe a new sensing technique for resolving the position of a subwavelength scatterer (< &lambda;) with vastly subwavelength resolution (<< &lambda;). My approach combines two separate fields of scientific inquiry: time-delayed nonlinear feedback and wave chaos. In typical time-delayed nonlinear feedback systems, the output of a nonlinear device is delayed and fed back to its input. In my experiment, the output of a radio-frequency (&lambda; ~ 15 cm) nonlinear circuit is injected into a complex scattering environment known as a wave-chaotic cavity. Inside the cavity, the field interacts with a subwavelength dielectric object from all sides, and a portion of the scattered waves are coupled out of the cavity, amplified, and fed back to the input of the nonlinear circuit. The resulting closed-feedback loop generates its own radio-frequency illumination field (> 1 GHz), which contains multiple wavelengths and is sensitive to location of the scattering object. Using the dynamical changes in the illumination field, I demonstrate subwavelength position-sensing of the scatterer's location in the cavity with a one-dimensional resolution of ~&lambda;/10,000 and a two-dimensional resolution of ~ &lambda;/300. </p><p>This novel method demonstrates that the dynamical changes of a feedback oscillator can be exploited for resolving subwavelength spatial features. Unlike conventional imaging techniques, it uses a single scalar measurement of the scattered field and takes advantage of a complex scattering environment. Furthermore, this work demonstrates the first application of quasiperiodic dynamics (oscillations with incommensurate frequencies) from a nonlinear system. Using the key ingredients from my radio-frequency system, I extend my method to an experiment that uses optical frequencies (&lambda; = 1550 nm) to demonstrate subwavelength sensing in two dimensions with a resolution of approximately 10 nm. Because this new sensing technique can be adapted to multiple experiments over vastly different length scales, it represents a potential platform for creating a new class subwavelength imaging devices.</p>Dissertatio