Seminar of the Institute 2009

A Statistical Treatment of Cross-Polarization Modulation in DWDM Systems with Applications to Data Transmission
Dr. Marcus Winter (Fachgebiet Hochfrequenztechnik, TU Berlin)

Abstract
After briefly reviewing the theory of cross-polarization modulation (XPolM), we present a model to predict stochastic properties of the effect for a large range of transmission links with fibers of arbitrary dispersive properties. These properties include the distribution of the polarization states of an initially polarized signal after propagation, as well as the nonlinear degree of polarization reduction as a measurable quantity sufficient to describe the magnitude of the effect.
Furthermore, we examine how XPolM affects the transmission of DPSK data as well as RZ-QPSK-modulated data in polarization-multiplexed systems (being a prime candidate for 100Gbit Ethernet).

OFC'2009 Review
René Bonk

General trends in high speed optical systems and product development activities within SHF for 100G system research & development
Dr. Thomas Lee, SHF Communication Technologies AG, Berlin

The presentation is intended as a brief overview of current high speed system development, and the general trend in the 100 GbE environment as the much awaited outcome of the IEEE standard activity will reach its conclusion in mid-2010.  The second part of the talk is to give an outline of SHF’s high speed test and measurement development activity positioned to address the needs of the 100 Gbps R&D community

Activities in the Department of Electronic Science, University Delhi
Prof. Enakshi Khular Sharma

Ge/SiGe Multiple Quantum Wells: Electronic States and Optical Properties
Eleonora Gatti

The integration of optical devices and interconnects on CMOS technology appears as one of the most promising approaches to increase the performances of electronic devices. Ge/SiGe multiple quantum wells (MQWs) represent an interesting way to reach such an integration because of their compatibility with Si technology and their good optical properties due to quantum confinement. The results of one of the first detailed studies of the optical properties and electronic states of these structures via optical absorption and photoluminescence (PL) measurements are presented. Absorption spectra are characterized by sharp excitonic transitions involving quantum confined states at Г point even at room temperature, confirming optical properties similar to those of direct gap semiconductors. Continuous wave PL spectra show for the first time recombination involving quantum confined states in Ge QWs at the Г and the L points and confirm the type I band alignment of these structures. Time-resolved PL preliminary measurements provide decay times of few ns. These results concur to achieve a detailed picture of the exciton recombination in Ge/SiGe multiple quantum wells.

Experimental Characterization of Silicon-Organic-Hybrid (SOH)
Siegwart Bogatscher (Intermediate Talk Diplomarbeit)

Metal-Insulator-Transition in disordered, interacting Fermi systems within exact Kohn-Sham potentials
Density Functional Theory (DFT) is one of the most widely used numerical tools to study properties of interacting Fermi systems. However it is not clear, if the DFT is abel to discribe the physics beyond the groundstate energy. In our work we consider the question whether DFT is able to describe the quantum phase transitions based on the interplay of disorder and interaction. To this end we calculate exact Kohn-Sham potentials for disordered, interacting, half-filled, one-dimensional Fermi systems from the local densities obtained from the Density Matrix Renormalization Group (DMRG) calculations. In the framework of Anderson localization one-dimensional systems are always localized. However, for attractive interaction the real system undergoes a phase transition to a metallic phase at a finite interaction. Here we report on the manifestation of this phase transition in the effective non-interacting DFT description.
Martin Moch

Improvement of the setup to experimentally measure the absolute extinction cross section of individual magnetic split-ring resonators
In order to completely control an electromagnetic wave, it is necessary to have access to both, its electric and its magnetic component. Using microscopic, artificial electric and magnetic dipoles, metamaterials potentially provide the needed tool to do so. Split-ring resonators (SRR) are one possibility to realize a magnetic dipole.
While the properties of SRR-arrays have already been explored, the measurement of the extinction cross section of one single, or few SRRs is necessary to understand their individual properties, and to learn about the interaction between few of those "artificial atoms".
As this has been realized experimentally by Husnik et al. the goal of this diploma thesis was to considerably decrease the duration of measurement based on the original setup.
Jens Maisenbacher

Spatial Entanglement Characterization in a Biphoton Beam Several schemes in quantum imaging rely on multi-photon absorption.
Therefore a detailed knowledge of the temporal and spatial correlations of the photons used is desired. The correlations of space-momentum entangled biphotons are investigated. A pair of photons is generated by type II parametric down conversion and subsequently a biphoton is created utilizing a Hong-Ou-Mandel interference. To obtain a complete mapping of the biphoton’s space and momentum cross sections, the near and far field of the crystal is analysed by a Hanbury-Brown-Twiss like setup with two single mode fiber probes.
Dipl.-Phys. Dietmar Korn