Integration of low loss vertical slot waveguides on SOI photonic platforms for high efficiency carrier accumulation modulators.

Silicon accumulation type modulators offer prospects of high power efficiency, large bandwidth and high voltage phase linearity making them promising candidates for a number of advanced electro-optic applications. A significant challenge in the realisation of such a modulator is the fabrication of the passive waveguide structure which requires a thin dielectric layer to be positioned within the waveguide, i.e. slotted waveguides. Simultaneously, the fabricated slotted waveguide should be integrated with conventional rib waveguides with negligible optical transition losses. Here, successful integration of polysilicon and silicon slot waveguides enabling a low propagation loss 0.4-1.2 dB/mm together with an ultra-small optical mode conversion loss 0.04 dB between rib and slot waveguides is demonstrated. These fabricated slot waveguide with dielectric thermal SiO2 layer thicknesses around 6 nm, 8 nm and 10 nm have been characterized under transmission electron microscopy allowing for strong carrier accumulation effects for MOS-capacitor electro-optic modulators.

'Pai Syndrome' with anterior alveolar polyp: A variant of a rare clinical entity.

'Pai syndrome' (PS) is a rare congenital syndrome. Presented here, a new-born baby-girl who exhibited the characteristic features of having a midline nasal (septal) polyp, an anterior alveolar process polyp, and a pericallosal lipoma associated with corpus callosum dysgenesis of the brain. Both polyps were lined with stratified-squamous epithelium. The overall features were largely consistent with those described by Pai et al., in 1987. A midline cleft-lip (with or without cleft-alveolus) is one of the most common features of the syndrome which was however absent in this case. Instead, an anterior alveolar polyp is present, which is relatively rare.

Suspended low-loss germanium waveguides for the longwave infrared.

Germanium is a material of high interest for mid-infrared (MIR) integrated photonics due to its complementary metal-oxide-semiconductor (CMOS) compatibility and its wide transparency window covering the 2-15 µm spectral region exceeding the 4 and 8 µm limit of the silicon-on-insulator platform and Si material, respectively. In this Letter, we report suspended germanium waveguides operating at a wavelength of 7.67 µm with a propagation loss of 2.6±0.3 dB/cm. To the best of our knowledge, this is the first demonstration of low-loss suspended germanium waveguides at such a long wavelength. Suspension of the waveguide is achieved by defining holes alongside the core providing access to the buried oxide layer and the underlying Si layer so that they can be wet etched using hydrofluoric acid and tetramethylammonium hydroxide, respectively. Our MIR waveguides create a new path toward long wavelength sensing in the fingerprint region.

Primary bilateral tubal adenocarcinoma associated with uterine leiomyomas.

Primary adenocarcinoma of the fallopian tube is the least common primary malignant tumor of the female genital tract. Bilaterality is also rare. Often the diagnosis is mistaken for ovarian tumor or tubo-ovarian mass. A case of bilateral primary tubal adenocarcinoma of serous type associated with uterine leiomyomas, without evidence of metastasis occurring in a postmenopausal woman is being reported.

Phaeochromocytoma at the root of the mesentery.

A 65-year-old male reported with a freely mobile abdominal lump and hypertension. Though pre-operatively and intra-operatively, we have suspected the lump to be a mesenteric cyst, postoperative histopathological examination revealed it to be phaeochromocytoma which is rare. In view of its extra-adrenal site of presentation and rarity, this case is reported herein.

Puetz-Jeghers syndrome involving appendix.

Puetz-Jegher's syndrome is an autosomal dominant hereditary disease, which is characterized by hamartomatous polyposis and mucocutaneous pigmentation mainly over the circum-oral region. Patients with Peutz-Jeghers syndrome seek medical attention whenever there are complications such as intussusception, bleeding from the polyps, etc. Occasionally, gastrointestinal tract malignancies have been reported in Peutz-Jeghers syndrome. In this paper, we report a patient with Peutz-Jeghers syndrome who had multiple complications and polyposis involving the appendix, because involvement of the appendix is extremely rare in Peutz-Jeghers syndrome.

Colorectal cancer in younger patients.

Colorectal cancer is uncommon in India and particularly so in the younger age group below 40 years. The present study reports 18 patients with colorectal cancer between the age of 21 to 30 years. Rectum (n = 15, 83%) was the commonest site of the lesion and rectal bleed was the presenting feature in most (n = 16, 89%). Histopathologically, 9 (50%) had poorly differentiated adenocarcinoma. The tumor was unresectable in 5 patients (28%). Fourteen patients (78%) had advanced cancer indicated by TNM stage III or IV disease. Among the 13 patients subjected to surgical treatment followed by adjuvant chemotherapy, only 3 had long term disease free survival beyond 2 years. None of these patients had family history of colonic cancer or polyposis coli. In conclusion, colorectal cancer in younger age is not infrequent and had advanced stage at the time of clinical presentation with poor outcome.

Paraganglioma in the nasopharynx.

A 50-year old male presented with swollen right eyelids, bleeding per nostrils and a vague left post-auricular swelling for 4 months. Posterior rhinoscopy revealed one pinkish polypoidal mass in the posterior nare and roof of nasopharynx. FNAC from the post-auricular swelling suggested metastatic undifferentiated carcinoma. Incisional biopsy was done form the nasopharynx and histopathological examination proved it to be a malignant paraganglioma. The case is reported for its rarity.