Stacked volume holographic gratings for extending the operational wavelength range in LED and solar applications.

A novel stacking procedure is presented for volume phase holographic gratings (VPHGs) recorded in photopolymer material using Corning Willow Glass as a flexible substrate in order to achieve broader angular and spectral selectivity in a diffractive device with high efficiency for solar and LED applications. For the first time to our knowledge, we have shown a device designed for use with a white LED that has the same input and output angles and high efficiency when illuminated by different wavelengths. In this paper, two VPHGs were designed, experimentally recorded, and tested when illuminated at normal incidence. The experimental approach is based on stacking two individual gratings in which the spatial frequency and slant have been tailored to the target wavelength and using real-time on-Bragg monitoring of the gratings in order to control the recorded refractive index modulation, thereby optimizing each grating efficiency for its design wavelength. Lamination of the two gratings together was enabled by using a flexible glass substrate (Corning Willow Glass). Recording conditions were studied in order to minimize the change in diffraction efficiency and peak diffraction angle during lamination and bleaching. The final fabricated stacked device was illuminated by a white light source, and its output was spectrally analyzed. Compared to a single grating, the stacked device demonstrated a twofold increase in angular and wavelength range. The angular and wavelength selectivity curves are in good agreement with the theoretical prediction for this design. This approach could be used to fabricate stacked lenses for white light LED or solar applications.

Sternocleidomastoid Abscess Mimicking a Thyroid Swelling in a Young Female.

Primary pyomyositis is a bacterial infection of skeletal muscle with acute or subacute clinical course. This usually present with localized abscess.We report a case of an 18 years old female presenting with swelling in midline of neck moving with deglutition mimicking a thyroid swelling. On further investigation patient was confirmed to have sternocleidomastoid myositis. Previous case reports have showed various etiologies for development of abscess. After thorough examination and investigations, patient was found to have an idiopathic sternocleidomastoid abscess which responded well to empirical antibiotic therapy.This is a very uncommon condition and very sparsely reported and so far, to the best of our knowledge there is no case report from India.

Kyrle's Disease: A Rare Skin Manifestation of Diabetes Mellitus.

Kyrle's disease is a rare skin disorder which is characterized by hyperkeratotic papules and nodules with a central keratotic plug mostly located in lower limbs. Exact etiology of Kyrle's disease is unknown, but its association has been reported sparsely with renal disorders, uremic patients on dialysis, diabetes mellitus, liver disease and paraneoplastic syndromes, tuberculosis and some fungal diseases. We report Kyrle's disease in a middle aged female suffering from diabetes mellitus with diabetic nephropathy on hemodialysis.