Parametric, Optimization-Based Study on the Feasibility of a Multisegment Antisolvent Crystallizer for in Situ Fines Removal and Matching of Target Size Distribution

Peer reviewedPostprin

Narrow-Linewidth Distributed Feedback Channel Waveguide Laser in Al2_2O3_3:Er3+^{3+}

We report on the fabrication and characterization of a distributed feedback channel waveguide laser in erbium-doped aluminium oxide on a standard thermally oxidized silicon substrate. Holographically-written surface-relief Bragg gratings have been integrated with the aluminium oxide waveguides via reactive ion etching of a silicon dioxide overlay film. The laser operates at a wavelength of 1545.2 nm and exhibits a threshold of 2.2 mW absorbed pump power, while it produces a maximum output power of 3 mW. The emission is TE polarized and has a Lorentzian linewidth of 1.70±0.58 kHz, which corresponds to a Q-factor of 1.14×E11

High-Q distributed-Bragg-grating laser cavities

Applying Bragg gratings in Al2O3 channel waveguides, we demonstrate distributed Bragg reflectors with Q-factors of 1.02x10e6. An integrated Al2O3:Yb3+ waveguide laser with 67% slope efficiency and 47 mW output power is achieved with such cavities

Hypertensive Disorders of Pregnancy and Future Cardiovascular Health.

Hypertensive disorders of pregnancy (HDP) occur in almost 10% of gestations. These women are known to have higher cardiovascular morbidity and mortality later in life in comparison with parous controls who had normotensive pregnancies. Several studies have demonstrated that women with preeclampsia present in a state of segmental impaired myocardial function, biventricular chamber dysfunction, adverse biventricular remodeling, and hypertrophy, a compromised hemodynamic state and indirect echocardiographic signs of localized myocardial ischemia and fibrosis. These cardiac functional and geometric changes are known to have strong predictive value for cardiovascular disease in non-pregnant subjects. A "dose effect" response seems to regulate this relationship with severe HDP, early-onset HDP, coexistence of fetal growth disorders, and recurrence of HDP resulting in poorer cardiovascular measures. The mechanism underlying the relationship between HDP in younger women and cardiovascular disease later in life is unclear but could be explained by sharing of pre-pregnancy cardiovascular risk factors or due to a direct impact of HDP on the maternal cardiovascular system conferring a state of increased susceptibility to future metabolic or hemodynamic insults. If so, the prevention of HDP itself would become all the more urgent. Shortly after delivery, women who experienced HDP express an increased risk of classic cardiovascular risk factors such as essential hypertension, renal disease, abnormal lipid profile, and diabetes with higher frequency than controls. Within one or two decades after delivery, this group of women are more likely to experience premature cardiovascular events, such as symptomatic heart failure, myocardial ischemia, and cerebral vascular disease. Although there is general agreement that women who suffered from HDP should undertake early screening for cardiovascular risk factors in order to allow for appropriate prevention, the exact timing and modality of screening has not been standardized yet. Our findings suggest that prevention should start as early as possible after delivery by making the women aware of their increased cardiovascular risk and encouraging weight control, stop smoking, healthy diet, and daily exercise which are well-established and cost-effective prevention strategies

Characterization of thermally treated PECVD SiON layers.

PECVD Silicon Oxynitride (SiON) layers with different refractive indices (1.472-1.635) were grown and characterized. The as-deposited layers have good thickness uniformity (~1%) and a high homogeneity of the refractive index (~ 5x10-4) over the wafer area. For telecommunication application, however, the optical losses of the as-deposited layers are unacceptably high. Therefore, the loss reduction upon annealing as well as the impact of the elevated temperature on the remaining layer properties has been studied. Annealed waveguides with optical losses as low as 0.2 dB/cm at λ = 1550 nm have been realized

The diurnal evolution of the urban heat island of Paris: a model-based case study during Summer 2006

The urban heat island (UHI) over Paris during summer 2006 was simulated using the Advanced Regional Prediction System (ARPS) updated with a simple urban parametrization at a horizontal resolution of 1 km. Two integrations were performed, one with the urban land cover of Paris and another in which Paris was replaced by cropland. The focus is on a five-day clear-sky period, for which the UHI intensity reaches its maximum. The diurnal evolution of the UHI intensity was found to be adequately simulated for this five day period. The maximum difference at night in 2 m temperature between urban and rural areas stemming from the urban heating is reproduced with a relative error of less than 10%. The UHI has an ellipsoidal shape and stretches along the prevailing wind direction. The maximum UHI intensity of 6.1 K occurs at 23:00 UTC located 6 km downstream of the city centre and this largely remains during the whole night. An idealized one-column model study demonstrates that the nocturnal differential sensible heat flux, even though much smaller than its daytime value, is mainly responsible for the maximum UHI intensity. The reason for this nighttime maximum is that additional heat is only affecting a shallow layer of 150 m. An air uplift is explained by the synoptic east wind and a ramp upwind of the city centre, which leads to a considerable nocturnal adiabatic cooling over cropland. The idealized study demonstrates that the reduced vertical adiabatic cooling over the city compared to cropland induces an additional UHI build-up of 25%. The UHI and its vertical extent is affected by the boundary-layer stability, nocturnal low-level jet as well as radiative cooling. Therefore, improvements of representing these boundary-layer features in atmospheric models are important for UHI studies

Tolerance and application of polarization independent waveguide for communication devices

A polarization independent optical waveguide structure has been developed and optimized towards minimized dependence on deviations in the processing parameters and very low processing complexity. The tolerance analysis was based on typical parameters of the silicon oxynitride technology. The optimized waveguide structure meets the criterion of a channel birefringence within 5x10-5 taking the processing tolerance into account. Moreover, it was found that the channel birefringence is thickness independent (within the 10-5 criterion) over a range of up to 200 nm. The optimized waveguide, fulfilling also the remaining demands of the application, has been applied for the realization of a passband flattened add-drop multiplexing device with 0.4 nm free spectral range and 0.03 nm TE-TM shift

Use of integrated optical waveguide probes as an alternative to fiber probes for sensing of light backscattered from small volumes

We show that for light collection from thin samples, integrated probes can present a higher efficiency than conventional fiber probes, despite having a smaller collection area. Simulation results are validated by experiments

Arrayed-waveguide-grating light collector for on-chip spectroscopy

We present a novel arrayed-waveguide-grating (AWG) device with improved external (biomedical) signal collection for use in on-chip spectroscopy. The collection efficiency of the device is compared to that of a standard AWG. We also present experimental results on the collection efficiency and size of the collection volume