External cavity modes in Lang--Kobayashi and traveling wave models

We investigate a semiconductor laser with delayed optical feedback due to an external cavity formed by a regular mirror. We discuss similarities and differences of the well-known Lang--Kobayashi delay differential equation model and the traveling wave partial differential equation model. For comparison we locate the continuous wave states in both models and analyze their stability

Semiconductor laser under resonant feedback from a Fabry--Perot: Stability of continuous wave operation

We study the continuous-wave (CW) operation of a semiconductor laser subject to optical feedback from a Fabry-Perot resonator in a case where the emission is resonant to a reflection minimum of the resonator. This configuration is treated in the framework of Lang-Kobayashi equations. The nature of bifurcations and the stability of steady state solutions is analyzed in dependence on magnitude and phase of the feedback. In contrast to conventional optical feedback from a single mirror, the locus of external cavity modes is no more elliptic but represents a tilted eight with possible satellite bubbles. Below a critical feedback strength, which is analytically given, only one single mode exists representing the completely unchanged CW emission of the laser. In this weak-feedback regime, the feedback phase allows a noninvasive control of the CW emission and a tailoring of its small-signal response within wide limits. The obtained results are prototype for all-optical realizations of delayed feedback control

The effect of basic psychological needs on the flow experience in a digital gamified learning setting

IntroductionDigitalization and gamification offer numerous motivation-enhancing opportunities to design biology lessons. For example, digital, gamified learning settings can enhance lessons by offering intense experiences. Such lessons might offer the opportunity to witness flow during the learning activity. For learners, flow can be positively influenced by perceived autonomy, competence, and relatedness. However, previous research on biology lessons has not focused on the impacts of the basic need satisfaction on the flow experience in digital learning settings.MethodsTo address this research gap, using the topic of the locomotion systems of animals, we investigated students’ perceived autonomy, competence, and relatedness as possible predictors of their flow experience while processing a digital, gamified learning environment. The teaching unit was thematically focused on the locomotion system of animals. Our sample consisted of 161 students (46.6% female) from sixth to eighth grade. Students’ perceived satisfaction of their basic needs and their flow experience were evaluated.Results and DiscussionResults confirmed perceived autonomy and perceived competence as predictors of students’ flow experience. However, perceived relatedness had no impact on the flow experience. Our findings are in line with the current state of research and prove to be mostly consistent with previous results

High-frequency pulsations in DFB-lasers with amplified feedback

We describe the basic ideas behind the concept of DFB-lasers with short optical feedback for the generation of high-frequency self-pulsations (SPs) and show the theoretical background describing realized devices. It is predicted by theory that the SP frequency increases with increasing feedback strength. To provide evidence for this we propose a novel device design which employs an amplifier section in the integrated feedback cavity of a DFB-laser. We present results from numerical simulations and experiments. It has been shown experimentally that a continuous tuning of the SP frequency from 12 to 45GHz can be adjusted via the control of the feedback strength. The numerical simulations which are in good accordance with experimental investigations give an explanation for a self stabilizing effect of the SPs due to the additional carrier dynamic in the integrated feedback cavity

Reliability of prenatal detection of X-linked hypohidrotic ectodermal dysplasia by tooth germ sonography

Objective In X‐linked hypohidrotic ectodermal dysplasia (XLHED), dysfunction of ectodysplasin A1 (EDA1) due to EDA mutations results in malformation of hair, teeth, and sweat glands. Hypohidrosis, which can cause life‐threatening hyperthermia, is amenable to intrauterine therapy with recombinant EDA1. This study aimed at evaluating tooth germ sonography as a noninvasive means to identify affected fetuses in pregnant carrier women. Methods Sonography, performed at 10 study sites between gestational weeks 18 and 28, led to the diagnosis of XLHED if fewer than six tooth germs were detected in mandible or maxilla. The assessment was verified postnatally by EDA sequencing and/or clinical findings. Estimated fetal weights and postnatal weight gain of boys with XLHED were assessed using appropriate growth charts. Results In 19 of 38 sonographic examinations (23 male and 13 female fetuses), XLHED was detected prenatally. The prenatal diagnosis proved to be correct in 37 cases; one affected male fetus was missed. Specificity and positive predictive value were both 100%. Tooth counts obtained by clinical examination corresponded well with findings on panoramic radiographs. We observed no weight deficits of subjects with XLHED in utero but occasionally during infancy. Conclusion Tooth germ sonography is highly specific and reliable in detecting XLHED prenatally

ExoClock project: an open platform for monitoring the ephemerides of Ariel targets with contributions from the public

The Ariel mission will observe spectroscopically around 1000 exoplanets to further characterise their atmospheres. For the mission to be as efficient as possible, a good knowledge of the planets’ ephemerides is needed before its launch in 2028. While ephemerides for some planets are being refined on a per-case basis, an organised effort to collectively verify or update them when necessary does not exist. In this study, we introduce the ExoClock project, an open, integrated and interactive platform with the purpose of producing a confirmed list of ephemerides for the planets that will be observed by Ariel. The project has been developed in a manner to make the best use of all available resources: observations reported in the literature, observations from space instruments and, mainly, observations from ground-based telescopes, including both professional and amateur observatories. To facilitate inexperienced observers and at the same time achieve homogeneity in the results, we created data collection and validation protocols, educational material and easy to use interfaces, open to everyone. ExoClock was launched in September 2019 and now counts over 140 participants from more than 15 countries around the world. In this release, we report the results of observations obtained until the 15h of April 2020 for 120 Ariel candidate targets. In total, 632 observations were used to either verify or update the ephemerides of 84 planets. Additionally, we developed the Exoplanet Characterisation Catalogue (ECC), a catalogue built in a consistent way to assist the ephemeris refinement process. So far, the collaborative open framework of the ExoClock project has proven to be highly efficient in coordinating scientific efforts involving diverse audiences. Therefore, we believe that it is a paradigm that can be applied in the future for other research purposes, too

The effect of basic psychological needs on the flow experience in a digital gamified learning setting

Lüking S, Wünsche S, Wilde M. The effect of basic psychological needs on the flow experience in a digital gamified learning setting. Frontiers in Psychology. 2023;14:7 Seiten.**Introduction** Digitalization and gamification offer numerous motivation-enhancing opportunities to design biology lessons. For example, digital, gamified learning settings can enhance lessons by offering intense experiences. Such lessons might offer the opportunity to witness flow during the learning activity. For learners, flow can be positively influenced by perceived autonomy, competence, and relatedness. However, previous research on biology lessons has not focused on the impacts of the basic need satisfaction on the flow experience in digital learning settings. **Methods** To address this research gap, using the topic of the locomotion systems of animals, we investigated students’ perceived autonomy, competence, and relatedness as possible predictors of their flow experience while processing a digital, gamified learning environment. The teaching unit was thematically focused on the locomotion system of animals. Our sample consisted of 161 students (46.6% female) from sixth to eighth grade. Students’ perceived satisfaction of their basic needs and their flow experience were evaluated. **Results and Discussion** Results confirmed perceived autonomy and perceived competence as predictors of students’ flow experience. However, perceived relatedness had no impact on the flow experience. Our findings are in line with the current state of research and prove to be mostly consistent with previous results

External cavity modes in Lang-Kobayashi and traveling wave models

We investigate a semiconductor laser with delayed optical feedback due to an external cavity formed by a regular mirror. We discuss similarities and differences of the well-known Lang--Kobayashi delay differential equation model and the traveling wave partial differential equation model. For comparison we locate the continuous wave states in both models and analyze their stability

Semiconductor laser under resonant feedback from a Fabry-Perot resonator: Stability of continuous-wave operation

We study the continuous-wave (cw) operation of a semiconductor laser subject to optical feedback from a Fabry-Perot resonator in a case where the emission is resonant to a reflection minimum of the resonator. This configuration is treated in the framework of Lang-Kobayashi equations. The nature of bifurcations and the stability of steady state solutions is analyzed in terms of the dependence on magnitude and phase of the feedback. In contrast to conventional optical feedback from a single mirror, the locus of external cavity modes is not elliptic but represents a tilted eight with possible satellite bubbles. Below a critical feedback strength, which is analytically given, only one single mode exists representing the completely unchanged cw emission of the laser. In this weak-feedback regime, the feedback phase allows noninvasive control of the cw emission and a tailoring of its small-signal response within wide limits. The results obtained are a prototype for all-optical realizations of delayed feedback control

Travelling Wave Equations for Semiconductor Lasers with Gain Dispersion

This paper modifies the coupled mode model for semiconductor lasers, taking into account the gain dispersion of the optical waveguide. Fitting the true gain curve by a Lorentzian, we obtain a correction for the dielectric function of the waveguide. A review of the derivation of the coupled mode model from the Maxwell Equations, including the corrected dielectric function, leads to an extended set of model equations. This extended model consists of the modified coupled mode equations and additional polarization equations and reflects spectral selectivity due to the geometry (waveguide dispersion) as well as the material properties (material dispersion). Although it is mathematically more complex, it does not increase the computational effort for the dynamical simulation essentially and, thus, it should replace the original model at least for numerical calculations