Guided wave optics in periodically poled KTP: quadratic nonlinearity and prospects for attosecond jitter characterization

For the first time to our knowledge, continuous nonsegmented channel waveguides in periodically poled KTiOPO4 with guided orthogonal polarizations are used to demonstrate type II background-free second harmonic generation in the telecom band with 1.6%/(W cm2) normalized conversion efficiency. This constitutes a 90-fold improvement in aggregate conversion efficiency over its free space counterpart. Simulations show that the guided wave device should enable the measurement of timing fluctuations of optical pulse trains at the attosecond level in an optical cross correlation scheme

Wandlungen der Unterwelt bei Thomas Mann und James Joyce

Der Titel befasst sich mit dem literarischen Motiv der Unterwelt in den Werken von Thomas Mann und James Joyce. Das Einführungskapitel ist den literarischen Vorläufern gewidmet, die das Motiv erstmals behandeln und auf welche die beiden Autoren regelmäßig rekurrieren. Ausgehend von den Erzählungen Thomas Manns nimmt die Autorin sodann eine eingehende Analyse des katabatischen Topos bei beiden Autoren vor. Sie wendet sich den Erzählungen und den Romanen Thomas Manns und James Joyce zu, um in einem abschließenden Kapitel einen Vergleich anzustellen, der aufzeigt, wie ähnlich die beiden Zeitgenossen den Topos der Unterwelt begreifen. Der Durchgang durch das Schattenreich bedeutet ihnen eine tiefgreifende Selbst- und Welterkenntnis, die letztlich zu einer Akzeptanz des Bösen in der Welt und einem modernen Humanismus-Begriff führen

Multistep Parametric Processes in Nonlinear Optics

We present a comprehensive overview of different types of parametric interactions in nonlinear optics which are associated with simultaneous phase-matching of several optical processes in quadratic nonlinear media, the so-called multistep parametric interactions. We discuss a number of possibilities of double and multiple phase-matching in engineered structures with the sign-varying second-order nonlinear susceptibility, including (i) uniform and non-uniform quasi-phase-matched (QPM) periodic optical superlattices, (ii) phase-reversed and periodically chirped QPM structures, and (iii) uniform QPM structures in non-collinear geometry, including recently fabricated two-dimensional nonlinear quadratic photonic crystals. We also summarize the most important experimental results on the multi-frequency generation due to multistep parametric processes, and overview the physics and basic properties of multi-color optical parametric solitons generated by these parametric interactions.Comment: To be published in Progress in Optic

3Rd-Order Nonlinearity Of 4-Dialkylamino-4\u27Nitro-Stilbene Wave-Guides At 1319 Nm

The intensity dependent optical properties of 4-dialkylamino-4\u27nitro-stilbene polymer channel waveguides were measured at 1319 nm with a pulse modulated Mach-Zehnder interferometer to be n2 = 0.8 x 10(-13) cm2/W and beta2 \u3c 0.08 cm/GW. This material is promising for all-optical switching at 1319 nm because it satisfies both the W and T figures of merit

Avidity Maturation of Humoral Response Following Primary and Booster Doses of BNT162b2 mRNA Vaccine Among Nursing Home Residents and Healthcare Workers

Infections, despite vaccination, can be clinically consequential for frail nursing home residents (NHR). Poor vaccine-induced antibody quality may add risk for such subsequent infections and more severe disease. We assessed antibody binding avidity, as a surrogate for antibody quality, among NHR and healthcare workers (HCW). We longitudinally sampled 112 NHR and 52 HCWs who received the BNT162b2 mRNA vaccine after each dose up to the Wuhan-BA.4/5-based Omicron bivalent boosters. We quantified anti-spike, anti-receptor binding domain (RBD), and avidity levels to the ancestral Wuhan, Delta, and Omicron BA.1 & 4/5 strains. The primary vaccination series produced substantial anti-spike and RBD levels which were low in avidity against all strains tested. Antibody avidity progressively increased in the 6–8 months that followed. Avidity significantly increased after the 1st booster but not for subsequent boosters. This study underscores the importance of booster vaccination among NHR and HCWs. The 1st booster dose increases avidity, increasing vaccine-induced functional antibody. The higher cross-reactivity of higher avidity antibodies to other SARS-CoV-2 strains should translate to better protection from ever-evolving strains. Higher avidities may help explain how the vaccine’s protective effects persist despite waning antibody titers after each vaccine dose

All-Optical Integrated Mach-Zehnder Switching Due To Cascaded Nonlinearities

We demonstrate all-optical switching using the cascaded second order nonlinearity in a fully integrated, asymmetric Mach Zehnder interferometer implemented in lithium niobate channel waveguides. We obtained an 8:1 switching ratio

Femtosecond optical parametric oscillator based on periodically poled KTiOPO4

We report a femtosecond optical parametric oscillator based on a periodically poled KTiOPO4 crystal for which quasi-phase matching is achieved with a 24-μm poling period. The singly resonant parametric oscillator, synchronously pumped by a Ti:sapphire laser at a wavelength of 758 nm, generates a signal at 1200 nm and an idler at 2060 nm. The maximum signal power conversion efficiency of the device is 22% with a pump depletion of 69%. We tune the signal wavelength over a 200-nm band by changing the cavity length. In addition, pump wavelength tuning provides output tunability in the 1000-1235-nm range. © 1998 Optical Society of America

G protein–independent Ras/PI3K/F-actin circuit regulates basic cell motility

Phosphoinositide 3-kinase (PI3K)γ and Dictyostelium PI3K are activated via G protein–coupled receptors through binding to the Gβγ subunit and Ras. However, the mechanistic role(s) of Gβγ and Ras in PI3K activation remains elusive. Furthermore, the dynamics and function of PI3K activation in the absence of extracellular stimuli have not been fully investigated. We report that gβ null cells display PI3K and Ras activation, as well as the reciprocal localization of PI3K and PTEN, which lead to local accumulation of PI(3,4,5)P3. Simultaneous imaging analysis reveals that in the absence of extracellular stimuli, autonomous PI3K and Ras activation occur, concurrently, at the same sites where F-actin projection emerges. The loss of PI3K binding to Ras–guanosine triphosphate abolishes this PI3K activation, whereas prevention of PI3K activity suppresses autonomous Ras activation, suggesting that PI3K and Ras form a positive feedback circuit. This circuit is associated with both random cell migration and cytokinesis and may have initially evolved to control stochastic changes in the cytoskeleton