Four-port coupled channel-guide device based on 2D photonic crystal structure

We have fabricated and measured a four-port coupled channel-waveguide device using W1 channel waveguides oriented along ΓK directions in a two-dimensional (2D) hole-based planar photonic crystal (PhC) based on silicon-on-insulator (SOI) waveguide material, at operation wavelengths around 1550 nm. 2D FDTD simulations and experimental results are shown and compared. The structure has been designed using a mode conversion approach, combined with coupled-mode concepts. The overall length of the photonic crystal structure is typically about 39 μm and the structure has been fabricated using a combination of direct-write electron-beam lithography (EBL) and dry-etch processing. Devices were measured using a tunable laser with end-fire coupling into the planar structure

Study of transmission properties for waveguide bends by use of a circular photonic crystal

We study the transmission properties for the waveguide bends composed by a circular photonic crystal. Two types (Y and U type) of the waveguide bends utilizing the circular photonic crystal are studied. It has been shown, compared with the conventional photonic crystal waveguide bends, transmission properties for these bends can be significantly improved. Over a 6.4% bandwidth, less than 1-dB loss/bend are observed. U bent waveguide, i.e., $180^o$ bend, can be easily realized with low loss using the circular photonic crystal.Comment: 9 pages, 6 figure

The racer goby,

The discovery of the racer goby Babka gymnotrachelus in the transboundary Evros river basin, collected on September 10th 2018 at two locations very close to the Greek-Bulgarian and Greek-Turkish borderlines, is reported. This is a new addition to the non-native ichthyofauna of Greece and the Aegean Sea drainages, and it is the second non-native Ponto-Caspian goby to enter this river. Boat-based electrofishing sampling, following the EU Water Framework Directive monitoring program, provides first evidence of what is presumed to be a recently established population; most of the 13 collected specimens are juveniles and the species has not yet been located in the river's tributaries. Further study and international cooperation in monitoring and management of this and other alien species in the Evros are proposed

An annotated checklist of the Niphargidae (Crustacea: Amphipoda) of Greece

Despite Greece being a global hotspot of subterranean biodiversity, its hypogean fauna is largely neglected from both an ecological and conservational point of view. An overview of the Niphargidae occurring in Greece is presented as an annotated list of all available published records. These records have resulted in an updated species list reflecting taxonomic corrections and species distribution range in the Greek peninsula. A total of 23 species, attributed to 3 genera, is up to date known from Greece with a high rate of endemicity found particularly in Crete. The endemic species of Greece amount to 21 (91% of total species richness), with the remaining species distributing also in the Republic of North Macedonia. Currently, none of them is listed in the national, European or global IUCN Red Lists of Threatened Species. Considering the increasing habitat degradation due to anthropic pressure, groundwater harvesting and climate change we could lose rare and endemic species without even acknowledging their existence.SCOPUS: ar.jDecretOANoAutActifinfo:eu-repo/semantics/publishe