Four-wave mixing enhanced white-light cavity

We discuss in-medium propagation dynamics in a white light cavity that leads to an enhancement of the cavity's bandwidth without reducing its maximum intensity buildup. We analyze the spatiotemporal dynamics of our system with a full simulation of the field propagation in a regime that leads to strong absorption of the control fields. We find that an additional coherent field is generated within the medium via four-wave mixing. This self-generated field leads to a backaction of the medium onto the probe field. Counter intuitively, this pronounced in-medium dynamics throughout the propagation leads to an additional enhancement of the cavity bandwidth.Comment: 5 pages, 4 figure

Phase modulation induced by cooperative effects in electromagnetically induced transparency

We analyze the influence of dipole-dipole interactions in an electromagnetically induced transparency setup at high density. We show both analytically and numerically that the polarization contribution to the local field strongly modulates the phase of a weak pulse. We give an intuitive explanation for this local field induced phase modulation and show that it distinctively differs from the nonlinear self-phase modulation a strong pulse experiences in a Kerr medium

Light propagation in dense and chiral media

Die elektromagnetischen Eigenschaften von Licht werden in der Quantenoptik meist auf die elektrische Komponente reduziert. Ein Medium, das sowohl mit der elektrischen als auch mit der magnetischen Komponente wechselwirkt, wäre jedoch aus technologischer Sicht sehr interessant. Ein vor kurzem vorgeschlagener Ansatz, um die magnetische Antwort zu verstärken, basiert auf hoher Dichte sowie induzierter Chiralität. Eine Kombination von beidem ist jedoch experimentell zur Zeit nicht umsetzbar. Diese Arbeit untersucht Lichtpropagation in dichten und in chiralen Medien, wobei beide Konzepte getrennt und in experimentell zugänglichen Parameterbereichen behandelt werden. Im Einzelnen analysieren wir ein sog. Closed-Loop System, demonstrieren ein Schema zur Kontrolle der Gruppengeschwindigkeit im UV-Bereich, zeigen, wie parametrische Prozesse in der Lichtpropagation verwendet werden können und erläutern den Einfluss hoher Gasdichte auf einen verlangsamten Lichtpuls. Wir leiten die Wellengleichung für Medien mit induzierter Chiralität her und lösen sie auf Basis der allgemeinen Mediumsantwort. In einem konkreten Beispiel verwenden wir die erarbeiteten Konzepte, um Lichtpropagation mit chiraler Wechselwirkung zu untersuchen. Dabei stellen wir fest, dass ein chirales Medium die optimale Umsetzung eines Closed-Loop Phasenkontrollschemas ermöglicht und so die Dynamik eines verlangsamten Lichtpulses während der Propagation kontrolliert werden kann. Außerdem zeigen unsere Ergebnisse, dass bereits mit heutigen experimentellen Methoden Parameter erreichbar sind, bei denen die magnetische Komponente des Probefelds relevant wird

Group velocity control in the ultraviolet domain via interacting dark-state resonances

The propagation of a weak probe field in a laser-driven four-level atomic system is investigated. We choose mercury as our model system, where the probe transition is in the ultraviolet region. A high-resolution peak appears in the optical spectra due to the presence of interacting dark resonances. We show that this narrow peak leads to superluminal light propagation with strong absorption, and thus by itself is only of limited interest. But if in addition a weak incoherent pump field is applied to the probe transition, then the peak structure can be changed such that both sub- and superluminal light propagation or a negative group velocity can be achieved without absorption, controlled by the incoherent pumping strength

Analysis of the construction of the hightemperature gas infrared radiator with the use of virtual prototyping

Method of virtual prototyping with the following mathematical modeling was used to simulate the heat-mass exchange and combustion during the operation of high-temperature gas infrared radiators, and to find optimal technical solutions for its design. The most authoritative and approved software product Ansys Multiphysics was used. The results of the mathematical modeling of heat and mass transfer in a turbulent reaction medium with combustion reproduce the experimental data produced by a measurement in real operating conditions of the gas-fired infrared heat emitter. The temperature distribution along the height of the ceramic nozzle was established. Obtained results enable estimation of the ignition and combustion zones

Pilot study on HTR2A promoter polymorphism, −1438G/A (rs6311) and a nearby copy number variation showed association with onset and severity in early onset obsessive-compulsive disorder

A previous study showed that a single nucleotide polymorphism (SNP), −1438G/A (rs6311), found in the transcriptional control region of the gene that encodes the serotonin-receptor 2A (HTR2A) was associated with obsessive-compulsive disorder (OCD) in a sample of children and adolescents. In this study, we reanalyzed the association of this SNP with OCD in an enlarged population of 136 cases (55 previous+81 new cases) and compared them to 106 newly recruited, healthy, age-matched controls. We also investigated whether this SNP or its copy number variations (CNV) was associated with OCD severity and age of onset. The CNV was analyzed in a DNA region located near rs6311. The results confirmed the association between the A-allele and early onset OCD in children and adolescents, with an odds ratio (OR) of 1.69 [95% CI (1.17, 2.46); p=0.005]. Strikingly, we found that carriers of one copy (deletion) of the CNV were associated with a very early onset OCD (2.5years earlier than the typical onset), and they had increased CY-BOCS scores (8.7 points higher compared to "normal” CNV and duplications); which is related to increased severity of OCD symptoms (p=0.031; p=0.004, respectively). Compared to the normal CNV and duplications, the association between the deletion and OCD showed an OR of 7.56 [95% CI (1.32, 142.84); p=0.020]. These results pointed to the functional importance of this promoter region of HTR2A; it influenced the occurrence, the onset, and the severity of OC

Studying global processing in autism and attention-deficit/hyperactivity disorder with gaze movements: The example of a copying task

Recent discussions in the literature, along with the revision of the Diagnostic and Statistical Manual (DSM) (American Psychiatric Association 2013), suggest aetiological commonalities between the highly comorbid Attention-Deficit/Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD). Addressing this discussion requires studying these disorders together by comparing constructs typical to each of them. In the present study, we investigate global processing, known to be difficult for participants with ASD, and Intra-Subject Variability (ISV), known to be consistently increased in participants with ADHD, in groups, aged 10–13 years, with ADHD (n = 25), ASD without comorbid ADHD (ASD-) (n = 13) and ASD with ADHD (ASD+) (n = 18) in comparison with a typically developing group (n = 22). A Copying task, typically requiring global processing and in this case particularly designed using equally complex stimuli to also measure ISV across trials, was selected. Oculomotor measures in this task proved to be particularly sensitive to group differences. While increased ISV was not observed in the present task in participants with ADHD, both ASD groups looked longer on the figure to be drawn, indicating that global processing takes longer in ASD. However, the ASD+ group fixated on the figure only between drawing movements, whereas the ASD- group did this throughout the drawing process. The present study provides evidence towards ASD and ADHD being separate, not-overlapping, disorders. Since the pure ASD- group was affected more by central coherence problems than the ASD+ group, it may suggest that neuropsychological constructs interact differently in different clinical groups and sub-groups

Nonlinear Effects in Pulse Propagation through Doppler-Broadened Closed-Loop Atomic Media

Nonlinear effects in pulse propagation through a medium consisting of four-level double-$\Lambda$-type systems are studied theoretically. We apply three continous-wave driving fields and a pulsed probe field such that they form a closed interaction loop. Due to the closed loop and the finite frequency width of the probe pulses the multiphoton resonance condition cannot be fulfilled, such that a time-dependent analysis is required. By identifying the different underlying physical processes we determine the parts of the solution relevant to calculate the linear and nonlinear response of the system. We find that the system can exhibit a strong intensity dependent refractive index with small absorption over a range of several natural linewidths. For a realistic example we include Doppler and pressure broadening and calculate the nonlinear selfphase modulation in a gas cell with Sodium vapor and Argon buffer gas. We find that a selfphase modulation of $\pi$ is achieved after a propagation of few centimeters through the medium while the absorption in the corresponding spectral range is small.Comment: 4 figure