Optical detection and modulation at 2µm-2.5µm in silicon.

Recently the 2µm wavelength region has emerged as an exciting prospect for the next generation of telecommunications. In this paper we experimentally characterise silicon based plasma dispersion effect optical modulation and defect based photodetection in the 2-2.5µm wavelength range. It is shown that the effectiveness of the plasma dispersion effect is dramatically increased in this wavelength window as compared to the traditional telecommunications wavelengths of 1.3µm and 1.55µm. Experimental results from the defect based photodetectors show that detection is achieved in the 2-2.5µm wavelength range, however the responsivity is reduced as the wavelength is increased away from 1.55µm.

Defect-mediated resonance shift of silicon-on-insulator racetrack resonators.

We present a study on the effects of inert ion implantation of Silicon-On-Insulator (SOI) racetrack resonators. Selective ion implantation was used to create deep-level defects within a portion of the resonator. The resonant wavelength and round-trip loss were deduced for a range of sequential post-implantation annealing temperatures from 100 to 300 °C. As the devices were annealed there was a concomitant change in the resonance wavelength, consistent with an increase in refractive index following implantation and recovery toward the pre-implanted value. A total shift in resonance wavelength of ~2.9 nm was achieved, equivalent to a 0.02 increase in refractive index. The excess loss upon implantation increased to 301 dB/cm and was reduced to 35 dB/cm following thermal annealing. In addition to providing valuable data for those incorporating defects within resonant structures, we suggest that these results present a method for permanent tuning (or trimming) of ring resonator characteristics.

Spontaneous intramural hematoma of the esophagus.

Spontaneous intramural hematoma of the esophagus (SIHE) is a rare condition usually affecting middle-aged or elderly women. It presents as acute substernal or epigastric pain, typically accompanied by dysphagia or hematemesis. SIHE is not usually associated with vomiting, and is therefore clearly distinguished from emetogenic esophageal disorders, such as the Mallory-Weiss lesion and the Boerhaave syndrome. The diagnosis has traditionally been made by barium esophagram. Therapy is conservative; a favorable prognosis is the rule. The pathogenesis is in dispute. We present a case of SIHE without a discernible mucosal breach, suggesting a primary intramural bleed as the initiating event. We document the utility of computed tomographic scan and magnetic resonance imaging in the diagnosis of SIHE.

Gastrointestinal bleeding in aortic stenosis.

Gastrointestinal bleeding in aortic stenosis is an uncommon condition but when present it is often undiagnosed. The usual radiological proceedures fail to demonstrate the source of bleeding. Mesenteric angiography, however, will identify the lesion. The lesion is usually a vascular malformation located in the right colon. The angiodysplasia may also occur in other parts of the gastrointestinal tract. We have encountered five patients with aortic stenosis who had multiple massive hemorrhages of the lower gastrointestinal tract who defied diagnosis by the conventional methods. Mesenteric angiography, however, disclosed the orgin of the bleeding. In four patients vascular malformations were found in the right colon and one in the jejunum. Right hemicolectomy and partial jejunectomy resulted in a cure in all.