Optical bistability in three-wave-mixing processes with guided waves

In this paper the response curves of an integrated Optical three-wave-mixing configuration are investigated. In contrast to degenerate four-wave-mixing (DFWM) configurations the shape of the response curves can be dynamically tuned by one of the input intensities and frequency switching is possible. For contradirectional input wave launching, optical bistability can occur. The versatility of the operational principle should permit the implementation of an opto-optical modulator, switch, limiter, or a logical device respectively within a fixed configuration.     

Van der Waals Attraction in Multilayer Structures

The dispersion energy between multilayer systems is calculated from the energy of the electromagnetic field fluctuations, which originate in the interspace and are repeatedly reflected or transmitted by all interfaces. The resulting energy terms are summed explicitly for the case of a periodic double layer by means of combinatorial analysis. The dispersion energy between different layers turns out to be of longer range than that resulting from a pairwise integration of d^-6 interactions, on account of the large number of additional reflection terms. The reflection terms of order 1 ≥ 5 even show extremes in their dependence on the separation a₂. However, their generally decreasing weight makes it very unlikely that these extremes might also be encountered in the dispersion energy.     

Photooxidation von Leukofarbstoffen. III. Sensibilisierte Photooxidation von Leukofluoreszein

Photooxidation of Leuco Dyes. III. Sensitized Photooxidation of Leuco Fluorescein Quantum yields of the sensitized photooxidation of leuco fluorescein are reported. Fluorescein and benzophenone were found to be efficient sensitizers of photooxidation of leuco fluorescein. There is a characteristic dependence of quantum yields on concentration of leuco fluorescein and oxygen in the solution. The results are discussed on the basis of reaction scheme proposed for the sensitized formation of fluorescein.     

Preparation of YBa2Cu3O7−x by thermal decomposition of coprecipitated oxalates

Yttrium, barium and copper oxalates are coprecipitated quantitatively from metal acetate solutions with oxalic acid in water-acetone mixtures. The particle-size distribution of the precipitate can be controlled by the precipitation conditions. Thermal decomposition of the coprecipitate leads to single-phase YBa₂Cu₃O_7-x . Despite the intermediate formation of BaCO₃, the minimal reaction temperature (770 °C) is clearly lower than that for the solid-state reaction. Results of differential thermal analysis and isothermal thermogravimetry are discussed. The products are characterized by X-ray diffraction and infrared spectroscopy.     

Jonckheere‐Terpstra test for nonclassical error versus log‐sensitivity relationship of quantum spin network controllers

The selective information transfer in spin ring networks by energy landscape shaping control has the property that the error, 1‐prob, where prob is the transfer success probability, and the sensitivity of the error to spin coupling uncertainties are statistically increasing across a family of controllers of increasing error. The need for a statistical hypothesis testing of a concordant trend is made necessary by the noisy behavior of the sensitivity versus the error as a consequence of the optimization of the controllers in a challenging error landscape. Here, we examine the concordant trend between the error and another measure of performance, ie, the logarithmic sensitivity, used in robust control to formulate a well‐known fundamental limitation. Contrary to error versus sensitivity, the error‐versus‐logarithmic‐sensitivity trend is less obvious because of the amplification of the noise due to the logarithmic normalization. This results in the Kendall τ test for rank correlation between the error and the log sensitivity to be somewhat pessimistic with marginal significance level. Here, it is shown that the Jonckheere‐Terpstra test, because it tests the alternative hypothesis of an ordering of the medians of some groups of log sensitivity data, alleviates this statistical problem. This identifies cases of concordant trend between the error and the logarithmic sensitivity, ie, a highly anticlassical feature that goes against the well‐known sensitivity versus the complementary sensitivity limitation.     

Van Der Waals Attraction Between Macroscopic Bodies

A general dispersion formula is derived, which represents the dispersion energy between two bodies A and B by their macroscopic screened fluctuation fields. These fluctuation fields are calculated exactly in the case of half-spaces and spheres. In the case of half-spaces the Lifshitz dispersion formula is obtained. The dispersion energy between spheres is found to vary as 1/d for separations d small compared with the radii and to be proportional to 1/d ⁶ for separations d large compared with the radii. The effect of layers adsorbed on the surfaces of the spheres on the dispersion energy is calculated. The dielectric properties of the adsorbed layers predominate over those of the bulk material for separations d smaller than the layer thickness.     

Ultrafast carrier dynamics in p-doped inAs/GaAs quantum-dot amplifiers

Using a differential transmission pump-probe experiment in heterodyne detection, the ultrafast gain and refractive-index dynamics of the ground-state transition in InAs/GaAs quantum- dot amplifiers emitting near 1.3 mum at working condition, that is at room temperature and under electrical injection were measured. An ultrafast gain recovery on a subpicosecond time scale is observed at high electrical injection indicating fast carrier relaxation into the dot ground state, which is appealing for high-speed applications with these devices. Comparing p-doped and undoped devices of otherwise identical structure and operating at the same gain, a faster absorption recovery but a slower gain dynamics in p-doped amplifiers was observed. This finding should help in elucidating the role of p-doping in the design of QD-based devices with high-speed performances.