Beata Zsigri

Strained silicon as a new electro-optic material.

For decades, silicon has been the material of choice for mass fabrication of electronics. This is in contrast to photonics, where passive optical components in silicon have only recently been realized. The slow progress within silicon optoelectronics, where electronic and optical functionalities can be integrated into monolithic components based on the versatile silicon platform, is due to the limited active optical properties of silicon. Recently, however, a continuous-wave Raman silicon laser was demonstrated; if an effective modulator could also be realized in silicon, data processing and transmission could potentially be performed by all-silicon electronic and optical components. Here we have discovered that a significant linear electro-optic effect is induced in silicon by breaking the crystal symmetry. The symmetry is broken by depositing a straining layer on top of a silicon waveguide, and the induced nonlinear coefficient, χ(2) ≈ 15 pm V-1, makes it possible to realize a silicon electro-optic modulator. The strain-induced linear electro-optic effect may be used to remove a bottleneck in modern computers by replacing the electronic bus with a much faster optical alternative.

Direct experimental and numerical determination of extremely high group indices in photonic crystal waveguides.

We report on time-of-flight experimental measurements and numerical calculations of the group-index dispersion in a photonic crystal waveguide realized in silicon-on-insulator material. Experimentally group indices higher than 230 has been observed. Numerical 2D and 3D time-domain simulations show excellent agreement with the measured data.

A novel photonic crystal fibre design for dispersion compensation

A novel dispersion compensating microstructured fibre design is proposed. The fibre has a honeycomb cladding structure with an up-doped core region, and is designed to match the relative dispersion slope of standard single-mode fibre. A dispersion value below ?1350?ps?nm?1?km?1 at 1550?nm has been predicted.

Multi-channel WDM RZ-to-NRZ format conversion at 50 Gbit/s based on single silicon microring resonator

We comprehensively analyze multiple WDM channels RZ-to-NRZ format conversion using a single microring resonator. The scheme relies on simultaneous suppression of the first order harmonic components in the spectra of all the RZ channels. An optimized silicon microring resonator with free spectral range of 100 GHz and Q value of 7900 is designed and fabricated for this purpose. Multi-channel RZ-to-NRZ format conversion is demonstrated experimentally at 50 Gbit/s for WDM channels with 200 GHz channel spacing using the fabricated device. Bit error rate (BER) measurements show very good conversion performances for the scheme.

Direct UV written Michelson interferometer for RZ signal generation using phase-to-intensity modulation conversion

An integrated Michelson delay interferometer structure making use of waveguide gratings as reflective elements is proposed and fabricated by direct ultraviolet writing. Successful return-to-zero alternate-mark-inversion signal generation using phase-to-intensity modulation conversion is demonstrated up to 40 Gb/s using the device. Compared to other implementations, the device is compact, inherently stable, and allows for easy customization of the pulsewidth by proper positioning of the gratings on a single coupler structure.

Demonstration of Broadcast, Transmission, and Wavelength Conversion Functionalities Using Photonic Crystal Fibers

Broadcasting functionality using cross-phase modulation in a nonlinear optical loop mirror utilizing 100-m highly nonlinear (HNL) photonic crystal fiber (PCF) as nonlinear element is demonstrated. This work presents entirely PCF-based network functionalities including broadcasting, transmission, and wavelength conversion. Broadcasting on four channels, transmission of one selected channel through one partially dispersion compensated 10.4-km PCF transmission link and wavelength conversion using four-wave mixing in a 50-m HNL-PCF at the ingress of the target subnetwork have been successfully demonstrated

Simple and efficient methods for the accurate evaluation of patterning effects in ultrafast photonic switches

Although patterning effects (PEs) are known to be a limiting factor of ultrafast photonic switches based on semiconductor optical amplifiers (SOAs), a simple approach for their evaluation in numerical simulations and experiments is missing. In this work, we experimentally investigate and verify a theoretical prediction of the pseudo random binary sequence (PRBS) length needed to capture the full impact of PEs. A wide range of SOAs and operation conditions are investigated. The very simple form of the PRBS length condition highlights the role of two parameters, i.e. the recovery time of the SOAs as well as the operation bit rate. Furthermore, a simple and effective method for probing the maximum PEs is demonstrated, which may relieve the computational effort or the experimental difficulties associated with the use of long PRBSs for the simulation or characterization of SOA-based switches. Good agrement with conventional PRBS characterization is obtained. The method is suitable for quick and systematic estimation and optimization of the switching performance.

0.87 Tbit/s 160 Gbaud dual-polarization D8PSK OTDM transmission over 110 km

The feasibility of transmitting 0.87 Tbit/s dual polarization D8PSK-OTDM over 110 km is, for the first time, demonstrated along with 0.44 Tbit/s single polarization D8PSK-OTDM over 220 km in conventional 55-km span SMF+DCF link.

Demodulation of DPSK signals up to 40 gb/s using a highly birefringent photonic bandgap fiber

Phase-to-intensity modulation conversion of differential phase-shift keying signals is successfully demonstrated at 10 and 40 Gb/s using a polarization Mach-Zehnder delay interferometer implemented with only 2.4 m of a highly birefringent air-guiding photonic bandgap (PBG) fiber. Such a PBG fiber exhibits a birefringence one order of magnitude larger than that of conventional polarization-maintaining fibers, thus enabling the realization of compact interferometers. Furthermore, its single material nature is expected to result in reduced temperature sensitivity

Generation, transmission and wavelength conversion of an 80 Gbit/s RZ-DBPSK-ASK signal

An 80 Gbit/s RZ-DBPSK-ASK signal is generated using orthogonal phase and amplitude modulation. We demonstrate its transmission over an 80 km SMF+DCF fibre span, and wavelength conversion using FWM in a highly nonlinear PCF