Microwave plasmonic mixer in a transparent fibre-wireless link.

To cope with the high bandwidth requirements of wireless applications1, carrier frequencies are shifting towards the millimetre-wave and terahertz bands2-5. Conversely, data is normally transported to remote wireless antennas by optical fibres. Therefore, full transparency and flexibility to switch between optical and wireless domains would be desirable6,7. Here, we demonstrate for the first time a direct wireless-to-optical receiver in a transparent optical link. We successfully transmit 20 and 10 Gbit/s over wireless distances of 1 and 5 m at a carrier frequency of 60 GHz, respectively. Key to the breakthrough was a plasmonic mixer directly mapping the wireless information onto optical signals. The plasmonic scheme with its subwavelength feature and pronounced field confinement provides a built-in field enhancement of up to 90'000 over the incident field in an ultra-compact and CMOS compatible structure. The plasmonic mixer is not limited by electronic speed and thus compatible with future terahertz technologies.

Plasmonic modulator with >170 GHz bandwidth demonstrated at 100 GBd NRZ.

We demonstrate a plasmonic Mach-Zehnder (MZ) modulator with a flat frequency response exceeding 170 GHz. The modulator comprises two phase modulators exploiting the Pockels effect of an organic electro-optic material in plasmonic slot waveguides. We further show modulation at 100 GBd NRZ and 60 GBd PAM-4. The electrical drive signals were generated using a 100 GSa/s digital to analog converter (DAC). The high-speed and small-scale devices are relevant for next-generation optical interconnects.

Plasmonic phased array feeder enabling ultra-fast beam steering at millimeter waves.

In this paper, we demonstrate an integrated microwave phoneeded for beamtonics phased array antenna feeder at 60 GHz with a record-low footprint. Our design is based on ultra-compact plasmonic phase modulators (active area <2.5µm2) that not only provide small size but also ultra-fast tuning speed. In our design, the integrated circuit footprint is in fact only limited by the contact pads of the electrodes and by the optical feeding waveguides. Using the high speed of the plasmonic modulators, we demonstrate beam steering with less than 1 ns reconfiguration time, i.e. the beam direction is reconfigured in-between 1 GBd transmitted symbols.

Pre-equalization technique enabling 70 Gbit/s photonic-wireless link at 60 GHz.

In this paper, we demonstrate a 70 Gbit/s photonic-based wireless link at 60 GHz using a single RF carrier and a single polarization. This high capacity is achieved by using 32QAM modulation with a symbol rate of 14 GBd. We show a novel pre-equalization technique that enables usage of such very high bandwidths at 60 GHz. Our work indicates that the consumer oriented 60 GHz band could be a viable alternative to more expensive E-band or sub-THz links for high capacity photonic wireless transmission, mobile backhauling and last-mile high-capacity connections.

High speed plasmonic modulator array enabling dense optical interconnect solutions.

Plasmonic modulators might pave the way for a new generation of compact low-power high-speed optoelectronic devices. We introduce an extremely compact transmitter based on plasmonic Mach-Zehnder modulators offering a capacity of 4 × 36 Gbit/s on a footprint that is only limited by the size of the high-speed contact pads. The transmitter array is contacted through a multicore fiber with a channel spacing of 50 µm.

Timing, carrier frequency and phase recovery for OFDM and Nyquist signals using a mean modulus algorithm.

Efficient algorithms for timing, carrier frequency and phase recovery of Nyquist and OFDM signals are introduced and experimentally verified. The algorithms exploit the statistical properties of the received signals to efficiently derive the optimum sampling time, the carrier frequency offset, and the carrier phase. Among the proposed methods, the mean modulus algorithm (MMA) shows a very robust performance at reduced computational complexity. This is especially important for optical communications where data rates can exceed 100 Gbit/s per wavelength. All proposed algorithms are verified by simulations and by experiments using optical M-ary QAM Nyquist and OFDM signals with data rates up to 84 Gbit/s.

Real-time Nyquist signaling with dynamic precision and flexible non-integer oversampling.

We demonstrate two efficient processing techniques for Nyquist signals, namely computation of signals using dynamic precision as well as arbitrary rational oversampling factors. With these techniques along with massively parallel processing it becomes possible to generate and receive high data rate Nyquist signals with flexible symbol rates and bandwidths, a feature which is highly desirable for novel flexgrid networks. We achieved maximum bit rates of 252 Gbit/s in real-time.

Oligonucleotides as coding molecules in an anti-counterfeiting system.

Due to the growing numbers of counterfeited products on the world market, there is a huge demand for new and forgery-proof marking systems. We developed a unique system using "molecular beacons" with well adapted thermodynamic parameters. This marking system consists of the three components: DNA tag (a label or directly printing), detection pen (contains the "molecular beacon " solution), and DNA-scanner (reads the specific signal triggered by the detection pen even at daylight). The vast coding capacity of DNA combined with the highly specific signal offers a degree of security that is unmatched by conventional identification technologies.

Use of microbial transglutaminase for the enzymatic biotinylation of antibodies.

Nowadays many reagents are available for the biotinylation of proteins. As most of them bind to amino groups of the protein the degree of labelling differs from batch to batch and the possibility exists that the biological activity of the target protein may be affected by the labelling procedure. In the present study we have investigated an enzymatic approach to biotinylation using microbial transglutaminase (MTGase) from Streptoverticillium mobaraense. The proposed method is particularly suitable when only a few biotin molecules need to be attached to the target proteins. The enzyme catalyses the acyl transfer reaction between gamma-carboxyamide groups and various primary amines. This was exploited for biotinylation using two amino-modified biotin derivatives, biotinamido-5-pentylamin (BIAPA) and biotinoyl-1,8-diamino-3, 6-dioxaoctane (BIDADOO) as acyl acceptors and a monoclonal IgG against the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) as the acyl donor. Kinetic studies revealed that the MTGase-mediated reaction proceeds with low velocity and is almost complete after 34 h. Conjugation ratios ranging from 1.1 to 1.9 biotins per IgG were found by mass spectrometry. To investigate the influence of antibody conjugation on antigen binding a competitive ELISA for the determination of 2,4-D employing MTGase-biotinoylated IgGs was developed. In this assay lower limits of detection of 0.3 and 1.0 microg/l of 2,4-D were achieved with BIDADOO- and BIAPA-modified antibodies, respectively.

Microbial transglutaminase-mediated synthesis of hapten-protein conjugates for immunoassays.

Hapten-protein conjugates are essential in many immunochemical assays, in particular, in assays employing titration or competitive assay formats. By exploitation of the catalytic properties of the microbial transglutaminase from Streptoverticillium mobarense sp. (MTGase), i.e., acyl transfer between gamma-carboxamide groups and various primary amines, new techniques for the synthesis of hapten-protein conjugates were developed. This is demonstrated by two examples. The feasibility of MTGase for hapten-protein conjugate synthesis was studied by coupling the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) to casein. Different procedures for the synthesis and the immobilization of these 2,4-D-casein conjugates were evaluated, comprising (i) a batch procedure, (ii) coupling of 2,4-D to an already immobilized layer of casein, and (iii) a method for simultaneous immobilization and conjugation. Kinetic studies revealed that conjugate formation in the batch procedure was almost complete after approx 2 h. By employing the conjugates in a competitive ELISA, detection limits as low as 0.05 microgram/L 2,4-D were reached. Using the approach with simultaneous immobilization and conjugation, the time for the whole assay could be reduced to only 2 h. Finally, to demonstrate the versatility of the enzymatic synthesis of hapten-protein conjugates, an ELISA for 2,4,6-trinitrotoluene (TNT) determination based on transglutaminase-synthesized conjugates was developed. In this assay, a detection limit as low as 0.04 microgram/l TNT was obtained.