Planar leaky light-guides and couplers

A quantitative theory of light propagation in a dielectric slab guide with general cladding media is presented. It is based on a plane wave which bounces in a zigzag fashion along the guide as a result of total or partial reflections at the two surfaces of the film. Two mechanisms are considered which contribute to the attenuation of the guide: losses due to absorption in the slab and cladding materials, and radiation losses if the guide is a leaky one. We point out the significance of the Goos-Hänchen effect for all questions relating to the power flow in the slab guide. The theory is illustrated by discussing dispersion and attenuation of guides with various low-index and high-index claddings, operating above and below cutoff. The low-index leaky guide is considered particularly in detail. Its high attenuation by leakage can be reduced to practically acceptable values (<1d B/cm) by increasing the film thickness to ≳ 40λ. One application of this guide is in the leaky wave coupler. This coupler may be viewed as a prism-film coupler simplified by omission of the gap. It offers a new approach to the problem of broad-band coupling to thin-film light guides

Far infrared absorption of CsBr and CsI crystals doped with OH- and OD-

In CsBr:OH- both librational transitions and the “non Devonshire” line have been found. CsBr:OD- displays the expected isotope shift of a librator. Narrow lines in CsBr and CsI, observed directly above the two phonon lattice absorption, are tentatively explained as due to OH- aggregates

Self-generated and externally driven current oscillations in n-GaAs

Experimental investigations of self-generated and externally driven non-linear current oscillations due to impact ionization of shallow impurities in n-type GaAs at low temperatures are presented. The regular relaxation oscillations which appear at the onset of breakdown are destabilized by a magnetic field normal to the epitaxial layer and multifrequency oscillations and chaotic fluctuations following the Ruelle-Takens-Newhouse scenario can be found. Driving the self-generated oscillations with an external periodic bias voltage quasiperiodicity, mode locking, interaction and overlap of mode locked resonances and period doubling can be observed depending on frequency and amplitude of the external force. The reconstructed return maps, recorded phase diagrams and Devil's staircase agree with theoretical predictions based on the circle map and give new evidence of the universality of the transition from quasiperiodicity to chaos

Controlled foreign corporation rules and cross-border M&A activity

We investigate the influence of one main anti tax avoidance measure, controlled foreign corporation (CFC) rules, on cross-border merger and acquisition (M&A) activity on a global scale. Using three different statistical methods and a large M&A data set, we find that CFC rules distort ownership patterns due to a competitive advantage of multinational entities whose parents reside in non-CFC rule countries. First, we show that the probability of being the acquirer of a low-tax target decreases if CFC rules may be applicable to this target’s income. Second, we show that CFC rules distort the acquirer’s location choice of targets. Third, we show that CFC rules negatively affect the probability of being the acquirer in a cross-border M&A. Altogether, this study shows that for affected acquirer countries, CFC rules lead to less M&A activity in low-tax countries because profit shifting seems to be less feasible. This behavior change could result in an increase in global corporate tax revenue

Controlled foreign corporation rules and cross-border M&A activity

We investigate the influence of one main anti tax avoidance measure, controlled foreign corporation (CFC) rules, on cross-border merger and acquisition (M&A) activity on a global scale. Using three different statistical methods and a large M&A data set, we find that CFC rules distort ownership patterns due to a competitive advantage of multinational entities whose parents reside in non-CFC rule countries. First, we show that the probability of being the acquirer of a low-tax target decreases if CFC rules may be applicable to this target’s income. Second, we show that CFC rules distort the acquirer’s location choice of targets. Third, we show that CFC rules negatively affect the probability of being the acquirer in a cross-border M&A. Altogether, this study shows that for affected acquirer countries, CFC rules lead to less M&A activity in low-tax countries because profit shifting seems to be less feasible. This behavior change could result in an increase in global corporate tax revenue

Magnetoresistance of n-GaAs at filamentary current flow

A large number of sharp structures are observed in the 4.2 K magnetoresistance of n-GaAs biased above impurity breakdown in a regime where current flow is filamentary. Most of the structures cannot be attributed to spectral properties of the semiconductor such as impact excitation of shallow donors or the magnetoimpurity effect. Experimental results give evidence that these structures are caused by a redistribution of the filamentary current flow when one filament border is swept across an imperfection in the material

Photoluminescence rings in Corbino disk at quantizing magnetic fields

Spatially resolved photoluminescence of modulation doped AlGaAs/GaAs heterojunction was investigated in a sample of Corbino disk geometry subject to strong perpendicular magnetic fields. Significant spatial modulation of the photoluminescence was observed in form of one or more concentric rings which travelled across the sample when the magnetic field strength was varied. A topology of the observed structure excludes the possibility of being a trace of an external current. The effect is attributed to formation of compressible and incompressible stripes in a 2DEG density gradient across the sample.Comment: 5 two-column pages, 4 figures (one of them in color