Electromagnetic analysis for optical coherence tomography based through silicon vias metrology.

This paper reports on progress in the analysis of time-domain optical coherence tomography (OCT) applied to the dimensional metrology of through-silicon vias (TSVs), which are vertical interconnect accesses in silicon, enabling three-dimensional (3D) integration in microelectronics, and estimates the deviations from earlier, simpler models. The considered TSV structures are 1D trenches and circular holes etched into silicon with a large aspect ratio. As a prerequisite for a realistic modeling, we work with spectra obtained from reference interferograms measured at a planar substrate, which fully includes the dispersion of the OCT apparatus. Applying a rigorous modal approach, we estimate the differences to a pure ray tracing technique. Accelerating our computations, we focus on the relevant fundamental modes and apply a Fabry-Perot model as an efficient approximation. Exploiting our results, we construct and present an iterative procedure based on the minimization of a merit function, which concludes TSV heights reliably, accurately, and rapidly from measured interferograms.

High-power air-clad large-mode-area photonic crystal fiber laser.

We report on a 2.3 m long air-clad ytterbium-doped large-modearea photonic crystal fiber laser generating up to 80 W output power with a slope efficiency of 78%. Single transverse mode operation is achieved with a mode-field area of 350 microm2. No thermo-optical limitations are observed at the extracted ~35W/m, therefore such fibers allow scaling to even higher powers.

Stability of an Er-Yb-doped fiber distributed-feedback laser with external reflections.

The maximum tolerable amplitude backreflection coefficient r(ext,c) into a fiber distributed-feedback laser before the onset of instability has been investigated. r(ext,c) was found to decrease with increasing external cavity lengths up to ~320 m and to be proportional to the relative linewidth of the relaxation oscillation resonance. The tolerable length of Rayleigh backscattering standard telecom fiber was found to be 135-200 m. An observed degradation in the laser stability and slope efficiency at low pump powers is believed to be due to UV-induced saturable absorbers.

Cladding-pumped passively mode-locked fiber laser generating femtosecond and picosecond pulses.

Passively mode-locked fiber lasers cladding pumped by broad-area diode-laser arrays are described. With a dispersion-compenstated erbium-ytterbium fiber oscillator, 200-fs pulses with pulse energies up to 100 pJ are generated at a wavelength of 1560 nm. In a highly dispersive cavity, pulse widths of 3 ps with pulse energies up to 1 nJ are obtained. A saturable absorber is used for pulse startup, whereas nonlinear polarization evolution is exploited for steady-state pulse shaping. An environmentally stable design is ensured by use of a compensation scheme for linear polarization drifts in the cavity.

Calbindin-D28K and the peptidergic neuroendocrine system in rat gut: an immunohistochemical study.

Calbindin-D28K was immunohistochemically localized in myenteric and submucosal plexuses throughout the rat intestine. Calbindin-D28K immunoreactivity was found in about half of myenteric neurons and in more than 90% of submucosal neurons. Calbindin-D28K was also observed in nerve processes running inside ganglia, muscle layers and lamina propria. No correlation could be established between the presence of calbindin-D28K and the distribution of neuropeptides localized in this study (VIP, enkephalin, somatostatin and substance P). In addition, some endocrine-like cells of the ileum were calbindin-D28K-positive. Half of these endocrine cells also contained neurotensin but none of the other neuropeptides investigated.

Hemophilic arthropathy: effect of home care on treatment patterns and joint disease.

To evaluate the efficacy of home care therapy on hemophilic arthropathy, data were analyzed in 19 patients with hemophilia who had been on home therapy for more than four years. Usage of replacement material, number of bleeding episodes, and clinical and radiographic assessment of joint status were evaluated. Patients were divided into three treatment groups (prophylaxis, combination, and episodic care) for further comparison. In all treatment groups, a significant decrease in product usage occurred with age (P < 0.01). The number of bleeding episodes also decreased significantly with age (P < 0.01). The patients' joints which were clinically and radiographically normal on entry into home therapy remained free of arthropathic changes. The outcome of diseased joints varied across treatment groups, with a majority of these joints remaining stable. Younger patients evidenced new and progressive arthropathy, whereas older patients demonstrated stable arthropathy. Although no single treatment protocol appears to be indicated for all patients with hemophilpia, a treatment goal may be to treat younger patients actively in order to preserve normal joint status, stablize diseased joints, and prevent subsequent disability.