Fast Polarization Changes Research Articles

Active meta polarizer for terahertz frequencies

Active meta polarizers based on phase-change materials have recently led to emerging developments in terahertz devices and systems for imaging, security, and high-speed communications. Existing technologies of adaptive control of meta polarizers are limited to the complexity of external stimuli. Here, we introduce an active terahertz polarizer consisting of a single layer of large array patterns of vanadium dioxide material integrated with metallic patch matrix to dynamically reconfigure the polarization of the terahertz waves. The proposed active polarizer is simple in structure and can independently manipulate the polarization of the incident THz waves in two orthogonal directions. In addition, the device can also be performing as a highly efficient reflector at the same frequencies. We demonstrate that efficient and fast polarization changes of THz waves can be achieved over a wide operating bandwidth. Compared with other active polarizers using mechanical, optical and thermal controls, it can be conveniently manipulated with DC bias without any external actuators, intense laser source or heater. Therefore, with the advantages of high efficiency, compact size, low loss, low cost and fast response, the proposed polarizer can be highly integrative and practical to operate within adaptive terahertz circuits and systems.

Locating Regions of Polarization Activity in WDM Systems

We propose a method for determining the spatial position of fast polarization changes in a WDM system. In particular, we demonstrate that the PMD (polarization mode dispersion) vector and Stokes parameters for each WDM (wavelength division multiplexing) channel can be employed to find with an accuracy, shown to be less than 15% in most simulated cases, the position of the sources of rapid polarization fluctuations in a link with a mean DGD (differential group delay) greater than 15 ps. The technique can also be applied to locate hinge positions provided that only a single hinge is active at any given time.

Fast Adaptive Polarization and PDL Tracking in a Real-Time FPGA-Based Coherent PolDM-QPSK Receiver

Fast polarization changes of 40 krad/s and 6-dB polarization-dependent loss (PDL) are tracked in a 2.8-Gb/s real-time coherent quadrature phase-shift keying receiver. The tolerance against fast polarization changes and PDL is measured for different polarization control time constants. The sensitivity penalty of the receiver at a polarization change speed of 40 krad/s is 0.7 dB at bit-error rate (BER) of 1times 10-3, with a BER floor of 6.1times10-7. With an additional PDL of 6 dB, these figures become 1.7 dB and 9.6 times 10-6, respectively.

Coherent Digital Polarization Diversity Receiver for Real-Time Polarization-Multiplexed QPSK Transmission at 2.8 Gb/s

This letter presents a coherent digital polarization diversity receiver for real-time polarization-multiplexed synchronous quadrature phase-shift keying transmission with distributed feedback lasers at a data rate of 2.8 Gb/s. The tolerance against fast polarization changes and polarization-dependent loss is evaluated for different filter widths in the carrier recovery circuit. The minimum achieved bit-error rate is 3.4 times 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-7</sup> .

WDM system integration of micromachined tunable two-chip Fabry–Pérot filters

Due to their large tuning range, simple tuning mechanism and high finesse, micromachined tunable two-chip Fabry–Pérot filters are very promising candidates for Wavelength Division Multiplex (WDM) systems. This paper focusses on the characterization of system integrated filters in terms of Bit Error Rate (BER) measurements. A 2.5 GBit/s data stream could be selected without being affected by crosstalk from the 100 GHz spaced neighbouring channels. If the signal suffers from chirp, the filter can improve the extinction ratio. Most important for filter operation under realistic conditions is their rotational resonator symmetry design. Otherwise the filter cannot handle fast polarization changes.

High-intense pulsed electron emission by fast polarization changes in ferroelectrics

Abstract The phenomenon of high-intensity pulsed electron emission from ferroelectrics, discovered at CERN in 1988, has attracted much interest and is today a subject of investigation all over the word. Applications of this new kind of electron source are manifold, since the emission effect does not rely on the quality of the vacuum, the electrons may have an initial kinetic energy up to several keV, the pulse duration can be varied, and the cross-section of the source may be determined from the electrode geometry. Thus, research and development on the Ferroelectric Electron Beam Source (FEBS) is wide-ranging and comprises pulse generation of femtosecond to microsecond duration, high current cathodes, large area emitters, micro sources, and electron emission from ferroelectric thin films. The phenomenon is initiated by suddenly unbalancing the charge equilibrium of the ferroelectric, and the emission of the pulsed electron beam is part of the relaxation process. A convenient method of achieving the initia...

The use of ferroelectrics for acceleration of charged particles

Several mechanisms are described which lead to fast polarization changes in ferroelectric materials. The resulting surface charges may ultimately generate electric field spikes on the order of 1 GV/m. The fast response of ferroelectric materials to phase transitions under the influence of external electrical and/or mechanical stress allows the design of structures which emit and accelerate charged-particle beams. >

Fast polarization changes in ferroelectrics and their application in accelerators

Several mechanisms are described which change the polarization in ferroelectric material. Provided the change is too rapid for the related surface charges to be screened or neutralized, the high charge density can lead to strong electric fields. The fields may possibly be used for emission and acceleration of electrons. First results of experiments are reported in which fast spontaneous polarization changes by reversal or phase transition have been demonstrated. Electrons of 25 keV energy have been observed, emitted from triglycine sulfate (TGS) crystals during phase transition while being slowly heated across the Curie temperature. With fast polarization changes, electron beams of even higher energy and density are expected.

Fast polarization changes in PZT ceramics by high-voltage pulses

Abstract Experiments on fast spontaneous polarization changes in PZT ceramics are described. The interactions between spontaneous polarization Ps and space-charge polarization Psp.ch. are discussed. The fast polarization changes are made with the aim of producing electron beam emission and acceleration from ferroelectric surfaces.