Chirped-grating output couplers in dielectric waveguides

This paper reports on the method of fabrication and first experiments of chirped (variable period) gratings in a dielectric waveguide. Such gratings, which are proposed as a new optical building block, are used in this work as focusing output couplers

Chirped gratings in integrated optics

Gratings with variable periods (chirped gratings) have been fabricated by recording the interference pattern of a collimated laser beam with a converging beam generated by a cylindrical lens. An analysis is presented for the behavior of the chirped gratings as a function of wavelength, the angle between the illuminating beams, the F number of the lens, and its position. To calculate the power radiated into air, the coupled-mode equations are solved for the case of a waveguide with chirped surface corrugation. Experimentally, chirped gratings have been etched on the surface of an optical waveguide and used to couple light out of the waveguide. It was found that the light was focused outside the waveguide, and the fraction of the power radiated into air compared favorably with the theoretical calculation. The focal point outside the waveguide was found to move by about 1 cm when the wavelength was changed by 500 Å-in agreement with theoretical estimates

Broad-band grating filters for thin-film optical waveguides

Broad-band grating filters have been fabricated on glass thin-film waveguides and evaluated with a tunable dye laser. Measured and calculated filter responses were found to be in good agreement. Grating filters with bandwidths of 300 and 150 Å, and reflectivities of 18 and 40%, respectively, are reported

Linearity and enhanced sensitivity of the Shipley AZ-1350B photoresist

The properties of the Shipley AZ-1350B positive photoresist used with the Shipley AZ-303A developer were investigated. It was found that the use of AZ-303A developer results in a significant improvement of the sensitivity and the linearity of the photoresist. The unexposed etch rate of the photoresist was 35 Å ± 5 Å/sec. Gratings of high efficiency have been successfully fabricated using the above combination of photoresist and developer

Strategies to control therapeutic antibody glycosylation during bioprocessing: synthesis and separation.

Glycosylation can be a critical quality attribute (CQA) in biologic manufacturing. In particular, it has implications on the half-life, immunogenicity and pharmacokinetics of therapeutic monoclonal antibodies (mAbs) and must be closely monitored throughout drug development and manufacturing. To address this, advances have been made primarily in upstream processing, including mammalian cell line engineering to yield more predictably glycosylated mAbs, and the addition of media supplements during fermentation to manipulate the metabolic pathways involved in glycosylation. A more robust approach would be a conjoined upstream-downstream processing strategy. This could include implementing novel downstream technologies, such as the use of Fc gamma-based affinity ligands for the separation of mAb glycovariants. This review highlights the importance of controlling therapeutic antibody glycosylation patterns, the challenges faced in terms of glycosylation during mAb biosimilar development, current efforts both upstream and downstream to control glycosylation and their limitations, and the need for research in the downstream space in order to establish holistic and consistent manufacturing processes for the production of antibody therapies. This article is protected by copyright. All rights reserved

Chirped-grating demultiplexers in dielectric waveguides

A wavelength-selective beamsplitter has been realized by fabricating chirped (variable period) grating in an optical waveguide. This beamsplitter can demultiplex a signal traveling in a fiber and send each frequency component to a different fiber

A powerful intervention: general practitioners' use of sickness certification in depression

<b>Background</b> Depression is frequently cited as the reason for sickness absence, and it is estimated that sickness certificates are issued in one third of consultations for depression. Previous research has considered GP views of sickness certification but not specifically in relation to depression. This study aimed to explore GPs views of sickness certification in relation to depression.<p></p> <b>Methods</b> A purposive sample of GP practices across Scotland was selected to reflect variations in levels of incapacity claimants and antidepressant prescribing. Qualitative interviews were carried out between 2008 and 2009.<p></p> <b>Results</b> A total of 30 GPs were interviewed. A number of common themes emerged including the perceived importance of GP advocacy on behalf of their patients, the tensions between stakeholders involved in the sickness certification system, the need to respond flexibly to patients who present with depression and the therapeutic nature of time away from work as well as the benefits of work. GPs reported that most patients with depression returned to work after a short period of absence and that it was often difficult to predict which patients would struggle to return to work.<p></p> <b>Conclusions</b> GPs reported that dealing with sickness certification and depression presents distinct challenges. Sickness certificates are often viewed as powerful interventions, the effectiveness of time away from work for those with depression should be subject to robust enquiry