Intrinsically directional light emitters are potentially important for applications in photonics including lasing and energy-efficient display technology. Here, we propose a new route to overcome intrinsic efficiency limitations in light-emitting devices by studying a CdSe nanoplatelets monolayer that exhibits strongly anisotropic, directed photoluminescence. Analysis of the two-dimensional k-space distribution reveals the underlying internal transition dipole distribution. The observed directed emission is related to the anisotropy of the electronic Bloch states governing the exciton transition dipole moment and forming a bright plane. The strongly directed emission perpendicular to the platelet is further enhanced by the optical local density of states and local fields. In contrast to the emission directionality, the off-resonant absorption into the energetically higher 2D-continuum of states is isotropic. These contrasting optical properties make the oriented CdSe nanoplatelets, or superstructures of parallel-oriented platelets, an interesting and potentially useful class of semiconductor-based emitters.

Metallic nanostructures support extreme localization and enhancement of optical fields via surfaceplasmon (SP) resonances. Although SP are associated with giant enhancements of nonlinear phenomena such as second-harmonic generation (SHG), the role of SP in the process, whether as a field-enhancing catalyst or as a quasiparticle converted in the interaction, has remained experimentally elusive. We demonstrate how k-space spectroscopy can distinguish between the plasmonic and photonic SHG processes that occur in a metal nanofilm when it is optically driven via the Kretschmann geometry. The results revealed a nonlinear interaction where two SP annihilate to create a second-harmonic photon. This knowledge has implications for realizing the inverse process, plasmonic parametric downconversion, which could act as a coherent source of entangled SP pairs.

We show that two-photon absorption (TPA) is highly anisotropic in CdSe nanoplatelets, thus promoting them as a new class of directional two-photon absorbers with large cross sections. Comparing two-dimensional k-space spectroscopic measurements of the one-photon and two-photon excitation of an oriented monolayer of platelets, it is revealed that TPA into the continuum is a directional phenomenon. This is in contrast to one-photon absorption. The observed directional TPA is shown to be related to fundamental band anisotropies of zincblende CdSe and the ultrastrong anisotropic confinement. We recover the internal transition dipole distribution and find that this directionality arises from the intrinsic directionality of the underlying Bloch and envelope functions of the states involved. We note that the photoemission from the CdSe platelets is highly anisotropic following either one- or two-photon excitation. Given the directionality and high TPA cross-section of these platelets, they may, for example, find employment as efficient logic AND elements in integrated photonic devices, or directional photon converters.

The overall visual prognosis of RAMA was good, even after macular complications. VA remained unchanged in the observed and the laser groups and was comparable in all groups after 3 years. Based on an individual treatment decision, all therapies were effective and efficient. If subfoveal haemorrhage caused a macular hole, the VA outcome was limited.

Because of the growing demand of geriatric rehabilitation, objective and clear indication decisions are needed with respect to limited financial resources. The aim of an interdisciplinary consensus group was to critically evaluate the most commonly used tests of functional performance of the lower limbs and to recommend useful tests to document progress of inpatient rehabilitation. Assessment of standing, walking, walking with a dual-task, sit-to-stand transfer, lying-to-sit-to-stand transfer, and stair climbing were recommended to document functional performance of the lower limbs and to describe rehabilitation targets. Future research is needed, because reasonably validated assessment tools do not exist for all of these domains. In addition to a standardized assessment of physical capacity, physical activity and participation with regard to the International Classification of Functioning, Disability, and Health (ICF) context have to be assessed. Body fixed sensors seem to be a promising assessment tool to objectively document progress in rehabilitation.

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Zusammenfassung Hintergrund Die akute makuläre Neuroretinopathie (AMNR) ist eine seltene, ein- oder beidseitige Erkrankung der Makula. Betroffene Patienten, zumeist junge Frauen, beklagen plötzlich aufgetretene Zentralskotome. Diese korrespondieren mit scharf begrenzten rötlich-braunen makulären Läsionen. Ophthalmoskopisch sind sie häufig kaum auszumachen, eine deutlich bessere Darstellung erlaubt das Infrarotreflexionsbild. Es zeigt sich eine oft blütenartige Gruppierung der flachen ovalen oder keilförmigen Einzelläsionen um die Fovea. Patienten und Methoden Retrospektive Fallserie von 4 Patienten mit AMNR. Die klinisch-morphologischen Merkmale werden unter Berücksichtigung verschiedener bildgebender Verfahren demonstriert. Ergebnisse 4 junge Frauen (26, 27, 28, 29 Jahre) bemerkten plötzlich aufgetretene Flecken im zentralen Gesichtsfeld. In 3 Fällen bestanden diese beidseits. Drei Frauen berichteten über grippale Prodromi. Bei allen 4 Patientinnen zeigten sich bei voller Sehschärfe unauffällige vordere und hintere Augenabschnitte. Die korrespondierenden retinalen Läsionen wurden erst in der Infrarotaufnahme der optischen Kohärenztomografie (OCT) entdeckt. In der OCT zeigten sich im Läsionsbereich dezente Defekte im Bereich der Fotorezeptoraußensegmente. Die Nachbeobachtungszeit betrug zwischen 9 und 36 Monaten. Es zeigte sich bei allen Patientinnen eine Regredienz der Symptomatik mit zumindest partieller Erholung der Netzhautarchitektur. Schlussfolgerung Patienten mit AMNR erleben plötzlich auftretende ein- oder beidseitige Skotome im zentralen Gesichtsfeld bei oft nur geringer Beeinträchtigung der Sehschärfe. Die Prognose ist unterschiedlich; so gibt es Verlaufsformen mit Selbstlimitierung und völliger Regredienz der Läsionen, aber auch persistierende Visusreduktionen. Bei fehlender kausaler Therapieoption wird zumeist ein exspektatives Management favorisiert.