The impact of nonequilibrium gain in a spectral laser diode model

We describe the inclusion of nonequilibrium gain into a self-consistent 2.5D CW spectral laser diode model and report on the use of this model to investigate the origin of gain compression in a 975 nm high-brightness tapered QW laser diode. Nonequilibrium gain is calculated using a dynamic gain model, which simulates the dynamic relaxation of the quantum well carrier energy distributions under the influence of steady-state electrical and optical excitation. Calculated gain and spontaneous emission spectra are included in the laser model via parameterised look up tables. Both simulated and experimentally measured intracavity spontaneous emission spectra show an increased carrier density and a blue-shift of the gain maximum with increasing bias caused by carrier heating and spectral hole burning. The accurate incorporation of nonequilibrium gain compression is therefore vital for the accurate prediction of the operating characteristics of these devices and for the experimental determination of the active region temperature.     

Numerical modelling of Tb<Superscript>3+</Superscript> doped selenide-chalcogenide multimode fibre based spontaneous emission sources

A model is developed of a terbium (III) ion doped selenide chalcogenide glass fibre source that provides spontaneous emission within the mid-infrared (MIR) wavelength range. Three numerical algorithms are used to calculate the solution and compare their properties.     

Machine Learning Algorithms for Prediction of the Quality of Transmission in Optical Networks

Increasing demand in the backbone Dense Wavelength Division (DWDM) Multiplexing network traffic prompts an introduction of new solutions that allow increasing the transmission speed without significant increase of the service cost. In order to achieve this objective simpler and faster, DWDM network reconfiguration procedures are needed. A key problem that is intrinsically related to network reconfiguration is that of the quality of transmission assessment. Thus, in this contribution a Machine Learning (ML) based method for an assessment of the quality of transmission is proposed. The proposed ML methods use a database, which was created only on the basis of information that is available to a DWDM network operator via the DWDM network control plane. Several types of ML classifiers are proposed and their performance is tested and compared for two real DWDM network topologies. The results obtained are promising and motivate further research.     

Peroxidatische Indigocarmin-Schnellentfärbung mit OH−-Ionen als Katalysator

Ohne Zusammenfassung     

Thermal performance investigation of DQW GaInNAs laser diodes

In this work, we optimize the thermal performance of a double quantum well GaInNAs ridge waveguide laser using an accurate in-house 2D electro-opto-thermal laser simulator. The simulator has shown good agreement with experiments after a detailed calibration procedure. Using calibrated material parameters, we investigate the influence of the cladding doping level on the heat generation within the laser. It is found that due to the competition between Joule heating and free carrier absorption, an optimum cladding doping level exists.     

Design strategies to increase the brightness of gain guided tapered lasers

The basic operating principles of gain guided tapered lasers are studied in detail by means of numerical simulations. The carrier induced lensing effect caused by spatial hole burning is described as the main mechanism limiting the device performance. The influence of the following design parameters in the maximum output power and beam brightness is analyzed: refractive index step of the ridge waveguide section, angle and length of the tapered section, and the use of beam spoilers. The results provide design guidelines for improving the device performance.     

Arbitrary truncation order three-point finite difference method for optical waveguides with stepwise refractive index discontinuities

An exact finite difference (FD) representation of the second-order derivative on three nodes is presented and used to obtain an FD algorithm that allows achieving an arbitrary truncation order. The FD weights are calculated analytically using the series that expresses the field value at a given FD node in terms of the field value and its derivatives at a neighboring node, when a stepwise discontinuity in the refractive index distribution is present between the nodes. The results obtained confirm that the proposed algorithm is accurate, efficient, and achieves the predicted improved performance.     

Structure related beam propagation

The general theory of a class of structure related (SR) non-orthogonal coordinate systems is introduced for the first time. Special cases of this type of coordinate system used separately or in combination can automatically follow the local geometry of many common optical waveguide designs, thereby facilitating the fast and accurate simulation of photonic circuits, when incorporated within a FD-BPM algorithm. Substantial savings in run time and memory are possible in comparison with standard FD-BPM in rectangular coordinates.