International Conference on Quantum Physics and Nuclear Engineering March 14-16, 2016 London, UK

Shien-Kuei Liaw has received double Doctorates in Photonics Engineering from National Chiao-Tung University in 1999 and in Mechanical Engineering from National Taiwan University in 2014, respectively. He has joined the Chunghua Telecommunication, Taiwan, in 1993. Since then, he has been working on optics communication and fiber based devices. He was a Visiting Researcher at Bellcore (now Telcordia), US for six months in 1996 and a Visiting Professor at University of Oxford, UK in 2011. Currently, he is a distinguished Professor at National Taiwan University of Science and Technology (NTUST). He has been awarded about 37 patents and has published 240 journal articles and international conference presentations. He has been actively contributing for various conferences as program chair, organizing committee chair, session chair and invited speaker. His research interests are in optical sensing, optical communication, fiber optics and reliability testing.

Wideband optical amplifiers have become increasingly important in the rapid growth of data traffic in optical communications and optical networks. So far, there are many types of optical amplifier such as doped fiber amplifier (DFA), Raman fiber amplifier (RFA) and semiconductor fiber amplifier (SOA). DFAs are optical amplifiers that used a doped optical fiber as a gain medium to amplify optical signals. The most common example is the erbium doped fiber amplifier (EDFA), where the core of a silica fiber is doped with trivalent erbium ions and can be efficiently pumped with laser light source at a wavelength of 980 nm or 1480 nm and exhibits gain in the C+L band region. In our prior work, we proposed hybrid fiber amplifiers (EDFA and RFA). This type of hybrid fiber amplifier has advantages of high gain, gain equalization and either dispersion compensated. In this paper, we investigated a high power co-doped hybrid fiber amplifier. It composed of an EDFA and an erbium ytterbium co-doped fiber amplifier (EYDFA). We set EDFA at 1st stage to reduce the noise figure and EYDFA at 2nd and 3rd to amplify the signal power. The main reasons why we used EYDFA were the possibility of doping the fiber with high gain, pump efficiency and the broadening of the absorption band from 850 to1100 nm which offers greater flexibility in selection of the pump wavelength. The maximum gain was around 34 dB with 0 dBm signal power and the NF was around 4.53 dB. The slope efficiency and polarization dependent gain (PDG) were 28% and 0.35 dB, respectively. In addition, the bit error rate (BER) performance between 32 and 64 ports splitter was 0.88 dB. This kind of hybrid EDFA/EYDFA may find vast applications in WDM long-haul systems and optical networks.

Georgios Konstantinou is a PhD Graduate student in the University of Cyprus.

Berry's phase has recently turned out to be one of the most important quantities in the field of Solid State Physics. It is a quantum mechanical phase of a geometric origin that emerges when some parameters become time-dependent and are subjected to a cyclic and adiabatic evolution in the parameter space. Through the well-known Chern-Gauss-Bonnet theorem, some specific type of Berry's phase is a topological invariant, and at the same time is directly related to certain response functions (such as the Hall conductivity), with the experimental consequence that it is so robust that it can be used as a criterion of existence of non-trivial topological states in modern materials, such as Topological Insulators. In this work, we review the basic applications of Berry curvature (a crucial byproduct of Berry’s geometric analysis) in the newly discovered topological materials. We include not only the standard Chern number (the integer that appears in the Chern-Gauss-Bonnet topological invariant – and, experimentally, in the Integer Quantum Hall Effect), but also some of our recent observations on other topological invariants as well, such as the Gauss linking number (describing the linking of Berry flux tubes, some type of Berry tangles that may appear under suitable conditions). An updated discussion of all known topological invariants is presented that reveals the richness of both topology and quantum physics.

Kyriakos Kyriakou is a PhD Graduate student in the University of Cyprus.

The semi-classical equations of motion have been the corner-stone for describing electrons dynamics in solids. In recent years, they have been extended with a term called anomalous velocity, derived under adiabatic approximations. We derive an exact equation with no adiabatic approximations for the evolution of electronic average position, with the electron being in an extended state. This is accomplished by extending the Hellmann – Feynman theorem to time-dependent parameters with quantal dynamics. A direct application gives a general formula for the electronic current in a solid that consists of three terms. The first one has the well-known group velocity form and the other two are anomalous corrections that seem to have a simple interpretation, the second one being a magnetization current and the last one a polarization current. Both currents are found to have a profound topological nature originating from Berry curvature quantities. Employing discrete symmetries we find that, when an external electric field is applied to a crystal with inversion symmetry, the total bulk magnetization current is zero and a dissipation-less topological current is produced on the surface (owing to inversion symmetry breaking) which is found to be quantized as a consequence of the non-trivial topology of the wave functions in the Brillouin zone. When the electron wave functions are not single-valued in the entire momentum space, this quantization can be attributed to dislocations lines (lines of wave-function-phase-singularities with respect to the momentum variables) where the wave-function does not vanish. The method can also be directly applied to the quantum Hall effect resulting to the quantization of the Hall conductivity with no adiabatic approximations or Kubo formula.

Zachary Shollar is currently pursuing his Master of Science in Nuclear Engineering at Purdue University. During his employment as a Research Assistant under Dr. Robert Bean, he has worked towards understanding graphene and its application in radiation detection. Upon graduation, he plans to take the experience gained and work in a capacity to solve problems involving radiation detection, nuclear security, or nuclear forensics.

Graphene as a radiation detection material is a burgeoning research field with much promise. There are still many questions left to address, however, and one is the scaling of graphene from micrometers dimensions up to millimeter dimensions. This is addressed by testing the electrical response of a graphene field effect transistor, at larger scales. The device architecture consisted of using chemical vapor deposition grown monolayer graphene, which had a manufactured grain width of up to 10 μm. The graphene field effect device consisted of ~525 μm n-type Silicon (1-10 Ohm-cm), 300 nm thermal oxide, and then the monolayer graphene. Four sizes of graphene, 3000 x 500 μm2, 600 x 100 μm2, 300 x 50μm2, and 60 x 10 μm2 were patterned onto the device. Each strip had four metal contacts, placed at various distances along the length of the graphene strip, and ending along the width’s centerline. A two probe resistance measurement of each strip was conducted, as well as graphene resistance response for several back gate voltage sweeps. The results show the scalability of graphene field effect devices as the graphene dimensions are increased to larger sizes, offering insight into the potential of large scale graphene based radiation detectors.