Modeling passive mode-locking in InAs quantum dot lasers with tapered gain sections

We propose a computationally efficient approach for the simulation and design of index-guided quantum-dot (QD) passively mode-locked lasers with tapered gain section; the method is based on the combination of simulations based on a finite differ-ence beam-propagation-method and dynamic simulations of mode-locking via a multi-section delayed differential equation model. The impact of varying the taper full angle on the pulse duration and peak power is investigated; simulations show that a correct choice of this parameter enables the generation of sub-picosecond optical pulses with peak power exceeding 5

Plant biodiversity in habitats of Community interest of Mediterranean large scale grazing systems

Large scale grazing systems are one of the best examples of adaptation of agro-pastoral activities and environmental limitation in the European marginal rural areas. They support high biodiversity levels and therefore they are recognized as an important part of European high nature values farmlands. They are also a source of agro-ecosystem services and they are linked with the history of the resident populations and for this reason many cultural landscapes are associated with them. Because of the socio-economical changes of the last decades, large scale grazing systems have been greatly reduced. Agro-pastoral activities intensification and abandonment are the main factors that threaten their conservation. With them could disappear an important part of biodiversity and a part of historical and cultural roots of humanity. Therefore, their conservation is included in the European rural development policies and nature preservation strategies. In this thesis I describe the studies that I have carried out in order to investigate different aspects of Mediterranean large scale grazing systems with the aim to contribute to the knowledge concerning the conservation status and biodiversity levels in habitats of Community interest linked with them. The surveys were made at different spatial scale in order to investigate the ecosystemic processes using a suitable level of detail

FDTW Approach for Simulation of QD lasers and SOAs

We present a Finite Difference Travelling Wave (FDTW) approach for the simulation of InAs/GaAs quantum dot devices. Several examples of applications will be discussed starting from simple QD-SLDs structures up to passive single section and two section mode-locked lasers

Modeling passive mode-locking in InAs quantum dot lasers with tapered gain sections

We propose a computationally efficient approach for the simulation and design of index-guided quantum-dot (QD) passively mode-locked lasers with tapered gain section; the method is based on the combination of simulations based on a finite differ-ence beam-propagation-method and dynamic simulations of mode-locking via a multi-section delayed differential equation model. The impact of varying the taper full angle on the pulse duration and peak power is investigated; simulations show that a correct choice of this parameter enables the generation of sub-picosecond optical pulses with peak power exceeding 5

Numerical Analysis of Passively Mode-Locked Quantum-Dot Lasers With Absorber Section at the Low-Reflectivity Output Facet

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Coherence function control of Quantum Dot Superluminescent Light Emitting Diodes by frequency selective optical feedback.

Low coherent light interferometry requires broad bandwidth light sources to achieve high axial resolution. Here, Superluminescent Light Emitting Diodes (SLDs) utilizing Quantum Dot (QD) gain materials are promising devices as they unify large spectral bandwidths with sufficient power at desired emission wavelengths. However, frequently a dip occurs in the optical spectrum that translates into high side lobes in the coherence function thereby reducing axial resolution and image quality. We apply the experimental technique of frequency selective feedback to shape the optical spectrum of the QD-SLD, hence optimizing the coherence properties. For well-selected feedback parameters, a strong reduction of the parasitic side lobes by a factor of 3.5 was achieved accompanied by a power increase of 40% and an improvement of 10% in the coherence length. The experimental results are in excellent agreement with simulations that even indicate potential for further optimizations

Simulation and Analysis of Dynamic Regimes Involving Ground and Excited State Transitions in Quantum Dot Passively Mode-Locked Lasers

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Reconstructing and Reprogramming the Tumor-Propagating Potential of Glioblastoma Stem-like Cells

Developmental fate decisions are dictated by master transcription factors (TFs) that interact with cis-regulatory elements to direct transcriptional programs. Certain malignant tumors may also depend on cellular hierarchies reminiscent of normal development but superimposed on underlying genetic aberrations. In glioblastoma (GBM), a subset of stem-like tumor-propagating cells (TPCs) appears to drive tumor progression and underlie therapeutic resistance, yet remain poorly understood. Here, we identify a core set of neurodevelopmental TFs (POU3F2, SOX2, SALL2, OLIG2) essential for GBM propagation. These TFs coordinately bind and activate TPC-specific regulatory elements, and are sufficient to fully reprogram differentiated GBM cells to ‘induced’ TPCs, recapitulating the epigenetic landscape and phenotype of native TPCs. We reconstruct a network model that highlights critical interactions and identifies novel therapeutic targets for eliminating TPCs. Our study establishes the epigenetic basis of a developmental hierarchy in GBM, provides detailed insight into underlying gene regulatory programs, and suggests attendant therapeutic strategies