No abstract

The integration of optical and electronic devices to achieve lower costs and higher functionality is attractive for a wide variety of opto-electronic applications. The key to innovation at the design level for these circuits is the availability of highly skilled personnel able to take advantage of sophisticated computer aided design (CAD) platforms. These tools enable them to undertake quick iterations of the design and simulation loop. The creation of such tools will need two interrelated initiatives: 1) The development of novel simulation and modelling techniques that will enable a robust and efficient simulation capability. These capabilities will include distributed thermal effects; modeling of non-linear optical devices; and the development of robust models for simulating circuits containing resonant devices.2) The simulation and analysis of general, large and complex mixed electro-optic circuits.An important part of the development of these tools is physically based, fast and flexible compact models for devices such as integrated lasers. In this paper we will present the integration of a travelling wave based laser model into a time-domain SPICE compatible optoelectronic circuit/system simulator (OptiSPICE) [1, 2] and its application to a mixed domain circuit containing an optical ring switch and driver and detector circuits.Previously, rate equation models (REM) were used to model the laser dynamics for optical circuit simulation [2] such as:where η is the injection efficiency, I d the diode current, V l the laser volume, N the electron carrier density, τ n and τ p are the electron and hole lifetimes, G 0 the gain coefficient , P the photon density, Γ the mode confinement factor, β the spontaneous emission coefficient and ε the gain compression coefficient. The equations for such a model are well suited to a SPICE-like circuit simulator providing a small (3 variables for single mode) description which captures the laser dynamics. However, it is desirable to have more accurate models that can model effects such as: 1) multi-mode gain dispersion, 2) distributed effects due to the longitudinal variation of carrier and photon density and temperature, 3) coupling in distributed feedback laser between the forward and backward propagating photons.A well establish laser model that is physically based and provides a significant improvement in sophistication is the travelling wave model(TWM) [3,4]. This model is derived directly from Maxwell's Equations and produces two 1D 1st order wave equations for the propagating forward and backward waves:Where E + and E − indicate forward and backward propagating complex envelopes, P is the local photon density and N the carrier density, n g the group velocity, c 0 the speed of light, κ a coupling coefficient, α the loss and F represents noise sources. The implementation of the model is simply to use a finite difference approach for both partial derivatives, use an up-wind formation for the spatial derivative and a simple explicit time-stepping of the solution [5]. However, it...

This thesis creates a numerical simulation scheme for a coupled ionic electronic device and uses it to simulate a memristor based on an organic conductor called poly(3,4 ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS). The modeled memristor consists of a thin PEDOT:PSS strip with a metal contact on both sides and a drop of an electrolyte solution with lithium and perchlorate ions. The conductivity of the memristor changes when the lithium ions in the electrolyte dedopes the PEDOT:PSS by bonding with PSS polymers. A numerical drift diffusion and a Poisson solver was implemented with special features to model the physical properties of the memristor. The developed simulation algorithm was tested using analytical solutions to the drift diffusion equations and Poisson's equation. 1-D and 2-D simulations were able to capture the essential physical effects. The comparison of 2-D simulations and the experimentalresults showed that proposed model worked as expected and produced results that were similar to an actual memristor. The work presented in this thesis showed promising results for the simulation of a memristor which can be improved in the future by additional modeling of the charge transport mechanisms.

No abstract

No abstract