Analysis of self-pulsating three-section DBR lasers

The characteristics of a three-section distributed Bragg reflector laser showing self-pulsation have been analyzed using a large signal time-domain traveling-wave simulator. The device dynamic properties have been investigated in all their complexity and analyzed as functions of the linewidth enhancement factor and of the injected current in the active and in the phase control sections. The simulation results have clearly shown the fundamental role of four wave mixing on the laser characteristics (output power, spectrum, etc.) and have been quantitatively correlated with the few available theoretical and experimental results. The considered self-pulsation operation frequencies around 40 GHz are of interest for practical applications

Design and simulation of DBR lasers with extended modulation bandwidth exploiting photon-photon resonance effect

In high-speed laser devices the occurrence of a pho-ton-photon resonance increases the modulation bandwidth sub-stantially. In this paper our attention is focused on the design of DBR lasers in which this effect is exploite

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

The equations of motion of a secularly precessing elliptical orbit

The equations of motion of a secularly precessing ellipse are developed using time as the independent variable. The equations are useful when integrating numerically the perturbations about a reference trajectory which is subject to secular perturbations in the node, the argument of pericenter and the mean motion. Usually this is done in connection with Encke's method to ensure minimal rectification frequency. Similar equations are already available in the literature, but they are either given based on the true anomaly as the independent variable, or in mixed mode with respect to the time through the use of a supporting equation to track the anomaly. The equations developed here form a complete and independent set of six equations in the time. Reformulations both of Escobal's and Kyner and Bennett's equations are also provided which lead to a more concise form.Comment: Accepted in Monthly Notices of the Royal Astronomical Society. Paper presented at the "New Trends in Astrodynamics and Applications VI" conference, Courant Institute of Mathematical Sciences, New York University New York, NY, 6-8 June 201

Trench width dependant deeply etched surface-defined InP gratings for low-cost high speed DFB/DBR

In this paper we are reporting a fabrication process for multi-section telecom lasers based on surface defined lateral gratings, which is compatible with low-cost high-throughput nano-imprint lithography. A new grating definition process is developed, which allow a better control of the cross section geometry to obtain higher coupling strength

Hierarchical organization of functional connectivity in the mouse brain: a complex network approach

This paper represents a contribution to the study of the brain functional connectivity from the perspective of complex networks theory. More specifically, we apply graph theoretical analyses to provide evidence of the modular structure of the mouse brain and to shed light on its hierarchical organization. We propose a novel percolation analysis and we apply our approach to the analysis of a resting-state functional MRI data set from 41 mice. This approach reveals a robust hierarchical structure of modules persistent across different subjects. Importantly, we test this approach against a statistical benchmark (or null model) which constrains only the distributions of empirical correlations. Our results unambiguously show that the hierarchical character of the mouse brain modular structure is not trivially encoded into this lower-order constraint. Finally, we investigate the modular structure of the mouse brain by computing the Minimal Spanning Forest, a technique that identifies subnetworks characterized by the strongest internal correlations. This approach represents a faster alternative to other community detection methods and provides a means to rank modules on the basis of the strength of their internal edges.Comment: 11 pages, 9 figure

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

Cavity optimization of 1.3um InAs/InGaAs quantum dot passively mode-locked lasers

Performance improving for monolithic two-section passively mode-locked (ML) quantum dot lasers has been systematically investigated using the Finite-Difference Traveling-Wave numerical model. Two approaches have been considered. For the first case, we changed simultaneously the length of the saturable absorber and the output facet reflectivity. We demonstrate that, by properly choosing these two parameters, a reduction of the pulse width from 3.4 ps to 1.1 ps and an increase the peak power 1 W to 1.6 W were obtained. For another case, we exchanged the optical power reflectivities at two end facets. We found that this approach can be used to further improve the ML stability for devices considered in the first approach where trailing edge instability is the main restrictio

Double-pass amplification of picosecond pulses with a tapered semiconductor amplifier

Double-pass amplification of picosecond pulses is demonstrated and compared with single-pass amplification. This was achieved using a two-section tapered semiconductor optical amplifier with a chirped quantum-dot active region and a mode-locked laser diode as a seed. Across the range of biasing conditions common to both configurations, an enhancement in signal gain of up to 7 dB and output power by a factor of 4.1 was seen in the double-pass amplifier, compared to the single-pass. Only marginal increases in pulse duration were observed in the double-pass regime compared to the single-pass amplifier, meaning that enhancements in output power were well translated into peak power. Furthermore, the two-section contact layout of the SOA allowed the pulse duration to be optimised for a given fixed output power, giving additional flexibility to the amplifier. These results demonstrate the suitability of this simple and versatile technique, which could become the new standard in amplification of ultrashort pulses