Silicon graphene waveguide tunable broadband microwave photonics phase shifter

We propose the use of silicon graphene waveguides to implement a tunable broadband microwave photonics phase shifter based on integrated ring cavities. Numerical computation results show the feasibility for broadband operation over 40 GHz bandwidth and full 360 degrees radiofrequency phase-shift with a modest voltage excursion of 0.12 volt. (C) 2014 Optical Society of AmericaThe authors wish to acknowledge the financial support given by the Research Excellency Award Program GVA PROMETEO 2013/012.Capmany Francoy, J.; Doménech Gómez, JD.; Muñoz Muñoz, P. (2014). Silicon graphene waveguide tunable broadband microwave photonics phase shifter. Optics Express. 22(7):8094-8100. https://doi.org/10.1364/OE.22.008094S8094810022

Source mechanism of long period events recorded by a high density seismic network during the 2008 eruption on Mount Etna

129 Long Period (LP) events, divided into two families of similar events, were recorded by the 50 stations deployed on Mount Etna in the second half of June 2008. During this period lava was flowing from a lateral fracture after a summit strombolian eruption. In order to understand the mechanisms of these events, we perform moment tensor inversions. Inversions are initially kept unconstrained to estimate the most likely mechanism. Numerical tests show that unconstrained inversion leads to reliable moment tensor solutions because of the close proximity of numerous stations to the source positions. However, single forces cannot be accurately determined as they are very sensitive to uncertainties in the velocity model. Constrained inversions for a crack, a pipe or an explosion then allow us to accurately determine the structural orientations of the source mechanisms. Both numerical tests and LP event inversions emphasise the importance of using stations located as close as possible to the source. Inversions for both families show mechanisms with a strong volumetric component. These events are most likely generated by cracks striking SW-NE for both families and dipping 70 degrees SE (Family 1) and 50 degrees NW (Family 2). For Family 1 events, the crack geometry is nearly orthogonal to the dike-like structure along which events are located, while for Family 2 the location gave two pipe-like bodies which belong to the same plane as the crack mechanism. The orientations of the cracks are consistent with local tectonics, which shows a SW-NE weakness direction. The LP events appear to be a response to the lava fountain occurring on the 10th of May, 2008 as opposed to the flank lava flow.AD 25/02/201