Abstract-This paper reports on an integrated mechanooptical waveguide ON-OFF switch, where an absorbing element is moved into and out of the evanescent field of the guided mode in order to achieve switching. For the electrostatically driven devices, an extinction ratio of 65 dB at an actuation voltage of 2.5 V has been achieved in a 9.5-mm-long device for a wavelength of 632.8 nm. The calculated mechanical fundamental resonance frequency is 1.95 kHz. The device design enables future vacuum sealing that will annihilate the squeeze damping which, in the present device, reduces the response time to 10 s. Full-wafer scale fabrication is enabled by using standard silicon technology, chemical mechanical polishing and aligned wafer bonding. The devices can be used for channel selection purposes in integrated optical sensor arrays.Index Terms-Chemical mechanical polishing, integrated optic nanomechanical effect, integrated optics, microelectromechanical devices, micromechanooptical devices, optical modulators, wafer bonding, waveguide attenuators.
High-extinction on-off modulators are essential for channel selection in integrated-optical sensor arrays. We report a standard SiON-technology-based electrostatically driven integrated mechano-optical waveguide on-off intensity modulator. On-off modulation is achieved by movement of an absorbing element into and out of the evanescent field of the guided mode. An extinction ratio of >37 dB at an actuation voltage of <30 V was achieved in a 6 mm x 4 mm device for a wavelength of 632.8 nm. Full wafer-scale fabrication is made possible by use of chemical mechanical polishing and aligned wafer bonding.
During the last decades the southern part of the North Sea has been exposed to high inputs of micropollutants from various sources.
Within the framework of the project Management Analysis North Sea (MANS), studies have been carried out to quantify the impact of anthropogenic pollution inputs on coastal water quality, sediments and biota.
In order to study the effects of different managerial actions an integrated modelling framework has been developed to enable a spatial evaluation. In this regard special attention has been given to:–the reduction of river inputs, as a result: of domestic and industrial waste water treatment–the storage of dredging sludge from the Rhine-Meuse estuary.
It is shown by the results of this study that input reductions of heavy metals since 1980 have resulted in a significant reduction of concentrations in Dutch coastal waters. Long-term simulation of accumulation of pollutants in the sediment, however, showed that due to the long time scale the reduction of the seabed can take several decades. Similar conclusions can be drawn for organic micropollutants, although the input reductions seem to be less pronounced.
Based on bioaccumulation modelling, the pollution of the sediment proved to be an important source for uptake of micropollutants in the food web. This study also made clear that significant reductions of North Sea pollution can be established if combined actions are taken. Reduction of pollutants from the Rhine-Meuse estuary, together with the storage of polluted dredging sludge from the Rotterdam harbours, will result in a significant reduction of the state of pollution of the coastal waters of the Netherlands.
In order to assess the rate and risk of North Sea pollution an integrated modelling framework of physical, chemical and biological models was developed, calibrated and applied to study environmental management strategies.
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