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

Improving risk management for violence in mental health services: a multimethods approach

contractual_start_date: 07-2008 editorial_review_begun: 07-2014 accepted_for_publication: 06-2015contractual_start_date: 07-2008 editorial_review_begun: 07-2014 accepted_for_publication: 06-2015contractual_start_date: 07-2008 editorial_review_begun: 07-2014 accepted_for_publication: 06-2015contractual_start_date: 07-2008 editorial_review_begun: 07-2014 accepted_for_publication: 06-201

Investigations on photocurrent bi-stability of a two-color mode-locked quantum dot laser

In this paper, state-of-the-art research on two-color passively mode-locked InAs/InGaAs quantum dot lasers is reviewed with a focus on the influence of resistor Self-Electro-Optical Effect absorber biasing on emission-state transitions and on absorber photocurrent bi-stability. We start with the recently studied absorber photocurrent characteristics of quantum dot lasers with two different gain-bandwidth chirping and in particular the emissionstate-transition from sole ground-state lasing to two-color ground-state and excited-state lasing of the strongly chirped laser. By modifying the degree of chirping and the operating conditions, we extend this two-color lasing to a regime with a z-shaped emission-state and photocurrent transition. Finally, we find a z-shaped emissionstate and an absorber photocurrent bi-stability and hysteresis without the transition via a two-color operation regime. The emission-state and absorber photocurrent bi-stability and its dependences on biasing conditions are explained qualitativel

Dual-state absorber-photocurrent characteristics and bistability of two-section quantum-dot lasers

The peculiar behavior of the absorber photocurrent of two-section quantum-dot lasers with different gain-bandwidth chirping is studied numerically and by experiments. By biasing the absorber section of a strongly chirped laser with a self-generated positive voltage or with a reverse-bias, different emission-state lasing regimes also involving a smooth emission-state-transition from quantum-dot ground-state to excited state via simultaneous ground- and excited-state are observed. The gradual emission state and photocurrent transitions are simulated and are in excellent agreement with experiments. In contrast, in a mediumchirped laser a photocurrent and emission-state bistability with hysteresis is experimentally observed involving a transition from sole ground state to sole excited state. Thereby, no intermediate simultaneous dual-state emission regimes occur suggesting the exclusion of simultaneous dual-state emission and bistability. This peculiar bistable behavior is explained qualitatively and offers the potential to be exploited toward switching applications

Reverse excited state / ground state dynamics in mode-locked two-section quantum dot semiconductor lasers

In this contribution reverse emission state transition of a two-section quantum dot laser at a saturable absorber bias of zero volt (short circuit) is presented where lasing and mode-locking starts first on the energetically higher first excited-state (ES) and then, with increasing gain current, additional lasing and mode-locking on the energetically lower ground-state (GS) takes place. A huge coexistence regime as well as temporal simultaneity of both GS and ES mode-locking is experimentally confirmed. At the onset of two-state mode-locking shorter pulse widths are found for the GS as compared to the ES at the same gain current. A considerable shortening of the ES pulse widths is observed when GS mode-locking starts. These state-resolved emission dynamics are confirmed by time-domain travelling-wave equation modeling. Finally, by electrically shortening the saturable absorber via an external variable resistor, a resistor Self-Electro-Optical Devices (SEED) configuration is exploited and tailored emission state control is achieve

Objectives and Concepts of the European Ground Systems Common Core (EGS-CC)

The European Ground Systems – Common Core (EGS-CC) is a European initiative to develop a common infrastructure to support space systems monitoring and control in preand post-launch phases for all mission types. This will bring a number of benefits, such as the seamless transition from spacecraft Assembly, Integration and Testing (AIT) to mission operations, reduce cost and risk, support the modernisation of legacy systems and promote the exchange of ancillary implementations across organizations. The initiative is being undertaken as a collaboration of ESA, European National Agencies and European Prime Industry. In this paper we describe the main objectives of the EGS-CC initiative, the overall system concept and the features it will provide

Optically pumped Cs space clock development

International audienc

Picosecond pulse amplification up to a peak power of 42 W by a quantum-dot tapered optical amplifier and a mode-locked laser emitting at 1.26 mu m

We experimentally study the generation and amplification of stable picosecond-short optical pulses by a master oscillator power-amplifier configuration consisting of a monolithic quantum-dot-based gain-guided tapered laser and amplifier emitting at 1.26 μm without pulse compression, external cavity, gain-or Q-switched operation. We report a peak power of 42 W and a figure-of-merit for second-order nonlinear imaging of 38.5 W2 at a repetition rate of 16 GHz and an associated pulse width of 1.37 p