Experimental study of the delayed threshold phenomenon in a semiconductor laser

An experimental study of the delayed threshold phenomenon in a Vertical Extended Cavity Semiconductor Emitting Laser is carried out. Under modulation of the pump power, the laser intensity exhibits a hysteresis behavior in the vicinity of the threshold. The temporal width of this hysteresis is measured as a function of the modulation frequency, and is proved to follow the predicted scaling law. A model based on the rate equations is derived and used to analyze the experimental observations. A frequency variation of the laser around the delayed threshold and induced by the phase-amplitude coupling is predicted and estimated

Feed rate modeling in circular–circular interpolation discontinuity for high-speed milling

In this paper, a modeling approach is presented in order to evaluate feed rate during a circular interpolation in high-speed milling. The developed model depends on the type of discontinuity and the kinematic performance of the machine tool. To begin with, a feed rate modeling for circular interpolation with continuity in tangency is developed. After, the discontinuity in tangency between two circular interpolations is replaced by discontinuity in curvature by adding a fillet which is in relation to the functional tolerance ε imposed in the part design. An experimental study has been carried out to validate the models

Observation of slow light in the noise spectrum of a vertical external cavity surface emitting laser

The role of coherent population oscillations is evidenced in the noise spectrum of an ultra-low noise lasers. This effect is isolated in the intensity noise spectrum of an optimized single-frequency vertical external cavity surface emitting laser. The coherent population oscillations induced by the lasing mode manifest themselves through their associated dispersion that leads to slow light effects probed by the spontaneous emission present in the non-lasing side modes.Comment: accepted for publication in Phys. Rev. Let

Simulation of the deflected cutting tool trajectory in complex surface milling

Since industry is rapidly developing, either locally or globally, manufacturers witness harder challenges due to the growing competitivity. This urges them to better consider the four factors linked to production and output: quality, quantity, cost and price, quality being of course the most important factor which constitutes their main concern. Efforts will be concentrated—in this research—on improving the quality and securing more accuracy for a machined surface in ball-end milling. Quality and precision are two essential criteria in industrial milling. However, milling errors and imperfections, duemainly to the cutting tool deflection, hinder the full achieving of these targets. Our task, all along this paper, consists in studying and realizing the simulation of the deflected cutting tool trajectory, by using the methods which are available. In a future stage, and in the frame of a deeper research, the simulation process will help to carry out the correction and the compensation of the errors resulting from the tool deflection. The corrected trajectory which is obtained by the method mirror will be sent to the machine. To achieve this goal, the next process consists—as a first step—in selecting a model of cutting forces for a ball-end mill. This allows to define—later on—the behavior of this tool, and the emergence of three methods namely the analytical model, the finite elements method, and the experimental method. It is possible to tackle the cutting forces simulation, all along the tool trajectory, while this latter is carrying out the sweeping of the part to be machined in milling and taking into consideration the cutting conditions, as well as the geography of the workpiece. A simulation of the deflected cutting tool trajectory dependent on the cutting forces has been realized

Modeling and simulation of high speed milling centers dynamics

High speed machining is a milling operation in industrial production of aeronautic parts, molds and dies. The parts production is being reduced because of the slowing down of the machining resulting from the tool path discontinuity machining strategy. In this article, we propose a simulation tool of the machine dynamic behavior, in complex parts machining. For doing this, analytic models have been developed expressing the cutting tool feed rate. Afterwards, a simulation method, based on numerical calculation tools, has been structured. In order to validate our approach, we have compared the simulation results with the experimental ones, for the same examples

Cancer Rehabilitation Indicators for Europe

Little is known of cancer rehabilitation needs in Europe. EUROCHIP-3 organised a group of experts to propose a list of population-based indicators used for describing cancer rehabilitation across Europe. The aim of this study is to present and discuss these indicators. A EUROCHIP-3 expert panel reached agreement on two types of indicators. (a) Cancer prevalence indicators. These were proposed as a means of characterising the burden of cancer rehabilitation needs by time from diagnosis and patient health status. These indicators can be estimated from cancer registry data or by collecting data on follow-up and treatments for samples of cases archived in cancer registries. (b) Indicators of rehabilitation success. These include: return to work, quality of life, and satisfaction of specific rehabilitation needs. Studies can be performed to estimate these indicators in individual countries, but to obtain comparable data across European countries it will be necessary to administer a questionnaire to randomly selected samples of patients from population-based cancer registry databases. However, three factors complicate questionnaire studies: patients may not be aware that they have cancer; incomplete participation in surveys could lead to bias; and national confidentiality laws in some cases prohibit cancer registries from approaching patients. Although these studies are expensive and difficult to perform, but as the number of cancer survivors increases, it is important to document their needs in order to provide information on cancer control

Observation of noise phase locking in a single-frequency VECSEL

We present an experimental observation of phase locking effects in the intensity noise spectrum of a semiconductor laser. These noise correlations are created in the medium by coherent carrier-population oscillations induced by the beatnote between the lasing and non-lasing modes of the laser. This phase locking leads to a modification of the intensity noise profile at around the cavity free-spectral-range value. The noise correlations are evidenced by varying the relative phase shift between the laser mode and the non-lasing adjacent side modes

Laser à semiconducteur à 852 nm bifrequence pompé optiquement pour les horloges atomiques CPT (poster)

National audienceNous présentons un laser à semiconducteur en cavité externe pompé optiquement, émettant sur deux fréquences optiques polarisées perpendiculairement, destiné au piégeage cohérent d'atomes (CPT) de Cs. L'émission est accordable autour de 852 nm. La différence de fréquence est ajustée grâce à une lame électro-optique autour de 9,2 GHz. La longueur d'onde du mode ordinaire est stabilisée sur la raie D2 du Cs et la différence de fréquence est asservie sur un signal de référence RF. En fonctionnement stabilisé, nous caractérisons les sources de bruits du laser afin d'évaluer les performances du laser en vue de son application dans une horloge atomique CPT

Dual-frequency VECSEL for atomic clocks using coherent population trapping

Workshop on Laser Diodes for Space Applications, Nov 2015, Palaiseau, FranceAtomic frequency references provide high-precision stable signals, which are crucial in the most demanding applications as high bitrate communication networks, high-end inertial navigation, or satellite positioning. One way to obtain those laser fields with low intensity-and frequency-noise is to use the dual-frequency and dual-polarization emission of an optically-pumped vertical external-cavity semiconductor laser (OP-VECSEL)

factors influencing acute and late toxicity in the era of adjuvant hypofractionated breast radiotherapy

Abstract Purpose To evaluate toxicity in breast cancer patients treated with anthracycline and taxane based chemotherapy and whole breast hypofractionated radiotherapy, and to identify the risk factors for toxicity. Methods and materials 537 early breast cancer patients receiving hypofractionated radiotherapy after conservative surgery were enrolled from April 2009 to December 2014, in an Italian cancer institute. The dose was 42.4 Gy in 16 daily fractions, 2.65 Gy per fraction. The boost to the tumor bed was administered only in grade III breast cancer patients and in patients with close or positive margins. Acute and late toxicity were prospectively assessed during and after radiotherapy according to RTOG scale. The impact of patients clinical characteristics, performed treatments and dose inhomogeneities on the occurrence of an higher level of acute skin toxicity and late fibrosis has been evaluated by univariate and multivariate analysis. Results The mean age was 74 (range 46–91 yrs). 27% of patients received boost. 22% of cases (n = 119) received also chemotherapy. The median follow-up was 32 months. G1 and G2/G3 acute skin toxicity were 61.3% and 20.5% and G1 and G2/G3 late fibrosis 12.6% and 4.3% respectively. Chemotherapy (p = 0.04), diabetes (p = 0.04) and boost administration (p Conclusions The results of our study, according to the large randomized trials, confirmed that hypofractionated whole breast irradiation is safe, and only the boost administration seems to be an important predictor for toxicity. Chemotherapy does not impact on acute and late skin toxicity