P. Vincze

Surface plasmon polariton absorption modulator.

A new compact electrically controlled surface plasmon polariton (SPP) absorption modulator operating at communication wavelengths is introduced. The modulator is controlled by changing the free carrier density and thereby the propagation loss of the SPP.

Six Hydrophobins Are Involved in Hydrophobin Rodlet Formation in Aspergillus nidulans and Contribute to Hydrophobicity of the Spore Surface

Hydrophobins are amphiphilic proteins able to self-assemble at water-air interphases and are only found in filamentous fungi. In Aspergillus nidulans two hydrophobins, RodA and DewA, have been characterized, which both localize on the conidiospore surface and contribute to its hydrophobicity. RodA is the constituent protein of very regularly arranged rodlets, 10 nm in diameter. Here we analyzed four more hydrophobins, DewB-E, in A. nidulans and found that all six hydrophobins contribute to the hydrophobic surface of the conidiospores but only deletion of rodA caused loss of the rodlet structure. Analysis of the rodlets in the dewB-E deletion strains with atomic force microscopy revealed that the rodlets appeared less robust. Expression of DewA and DewB driven from the rodA promoter and secreted with the RodA secretion signal in a strain lacking RodA, restored partly the hydrophobicity. DewA and B were able to form rodlets to some extent but never reached the rodlet structure of RodA. The rodlet-lacking rodA-deletion strain opens the possibility to systematically study rodlet formation of other natural or synthetic hydrophobins.

High-speed Plasmonic Modulators

Plasmonic modulators integrated with silicon photonic circuits are discussed. First, a 29 μm long phase modulator operating at 40Gbit/s is demonstrated. Then, an absorption modulator is presented exploiting the plasma effect in metal oxide layers.

PIPED: A silicon-plasmonic high-speed photodetector

Silicon-plasmonic photodetection based on internal photoemission exploits the intrinsic absorption in plasmonic waveguides at metal-dielectric interfaces. For this purpose we designed an asymmetric metal-semiconductor-metal waveguide with a width of 75 nm. Our plasmonic internal photoemission detector (PIPED) shows a rec-ord-high photocurrent sensitivity of up to S = 0.12 A / W for light at a wavelength of 1550 nm. The opto-electronic bandwidth is extremely large and allows data reception at rates of at least 40 Gbit/s. As another appli-cation, photomixing of two different optical carriers incident on the PIPED generates photocurrents with THz-frequencies, which can be used for short-range wireless communication. Finally, because in contrast to ordinary pin-photodetectors the sensitivity S(U) depends on the voltage U across the device, a PIPED can be employed for all-optical heterodyne reception and down-conversion of data on a THz carrier.

Growth of M- and A-plane GaN on LiGaO{sub 2} by plasma-assisted MBE

We have performed non‐polar M‐ and A‐plane GaN growth on LiGaO2 (LGO) by plasma‐assisted molecular beam expitaxy (MBE). We demonstrate that non‐polar GaN growth on LGO yields high phase purity and flat surfaces. We find that annealing of the substrates prior to growth is a suitable method for avoiding a peeling off of the film from the substrate after growth.