Optical Simulation of Neutrino Oscillations in Binary Waveguide Arrays

Andrea Marini, Stefano Longhi, Fabio Biancalana

We theoretically propose and investigate an optical analogue of neutrino oscillations in a pair of vertically displaced binary waveguide arrays with longitudinally modulated effective refractive index. Optical propagation is modeled through coupled-mode equations, which in the continuous limit converge to two coupled Dirac equations for fermionic particles with different mass states, analogously to neutrinos. In addition to simulating neutrino oscillation in the noninteracting regime, our optical setting enables us to explore neutrino interactions in extreme regimes that are expected to play an important role in massive supernova stars. In particular, we predict the quenching of neutrino oscillations and the existence of topological defects, i.e., neutrino solitons, which in our photonic simulator should be observable as excitation of optical gap solitons propagating along the binary arrays at high excitation intensities.

Structure of the sets of mutually unbiased bases with cyclic symmetry

U. Seyfarth, L. L. Sanchez-Soto, G. Leuchs

Mutually unbiased bases that can be cyclically generated by a single unitary operator are of special interest, for they can be readily implemented in practice. We show that, for a system of qubits, finding such a generator can be cast as the problem of finding a symmetric matrix over the field. 2 equipped with an irreducible characteristic polynomial of a given Fibonacci index. The entanglement structure of the resulting complete sets is determined by two additive matrices of the same size.

Electric field sensing with high spatial resolution via a charged "flying particle" optically guided inside hollow-core PCF

D. S. Bykov, O. A. Schmidt, T. G. Euser, P. St. J. Russell

We report an electric field sensor based on a charged microparticle that is optically trapped, and moved to and fro, inside a hollow-core photonic crystal fibre (PCF). Transverse electric fields displace the particle, altering the transmitted optical power. The transmission change is found to be linear with fields in the 0.1-50 kV/m range, with a flat frequency response from 0.01 to similar to 1 kHz. In a first test, the field pattern near a multi-element electrode was resolved with a spatial resolution of 1 mm. This unique "flying particle" sensor allows electric field mapping over long distances (the lowest loss hollow core PCF has a 3 dB length of similar to 3 km) and is suitable for inaccessible or harsh environments.

Generation and subwavelength focusing of longitudinal magnetic fields in a metallized fiber tip

Daniel Ploss, Arian Kriesch, Hannes Pfeifer, Peter Banzer, Ulf Peschel

We demonstrate experimentally and numerically that in fiber tips as they are used in NSOMs azimuthally polarized electrical fields (broken vertical bar E-azi broken vertical bar(2) / broken vertical bar E-tot broken vertical bar(2) approximate to 55% +/- 5% for lambda(0) = 1550 nm), respectively subwavelength confined (FWHM approximate to 450 nm approximate to lambda(0)/3.5) magnetic fields, are generated for a certain tip aperture diameter (d = 1.4 mu m). We attribute the generation of this field distribution in metal-coated fiber tips to symmetry breaking in the bend and subsequent plasmonic mode filtering in the truncated conical taper. (C) 2014 Optical Society of America

Atmospheric continuous-variable quantum communication

B. Heim, C. Peuntinger, N. Killoran, I. Khan, C. Wittmann, Ch Marquardt, G. Leuchs

We present a quantum communication experiment conducted over a point-topoint free-space link of 1.6 km in urban conditions. We study atmospheric influences on the capability of the link to act as a continuous-variable (CV) quantum channel. Continuous polarization states (that contain the signal encoding as well as a local oscillator (LO) in the same spatial mode) are prepared and sent over the link in a polarization multiplexed setting. Both signal and LO undergo the same atmospheric fluctuations. These are intrinsically auto-compensated which removes detrimental influences on the interferometric visibility. At the receiver, we measure the Q-function and interpret the data using the framework of effective entanglement (EE). We compare different state amplitudes and alphabets (two-state and four-state) and determine their optimal working points with respect to the distributed EE. Based on the high entanglement transmission rates achieved, our system indicates the high potential of atmospheric links in the field of CV quantum key distribution.

Interaction of Relativistic Electron-Vortex Beams with Few-Cycle Laser Pulses

Armen G. Hayrapetyan, Oliver Matula, Andrea Aiello, Andrey Surzhykov, Stephan Fritzsche

We study the interaction of relativistic electron-vortex beams (EVBs) with laser light. Exact analytical solutions for this problem are obtained by employing the Dirac-Volkov wave functions to describe the (monoenergetic) distribution of the electrons in vortex beams with well-defined orbital angular momentum. Our new solutions explicitly show that the orbital angular momentum components of the laser field couple to the total angular momentum of the electrons. When the field is switched off, it is shown that the laser-driven EVB coincides with the field-free EVB as reported by Bliokh et al. [Phys. Rev. Lett. 107, 174802 (2011)]. Moreover, we calculate the probability density for finding an electron in the beam profile and demonstrate that the center of the beam is shifted with respect to the center of the field-free EVB.

Practical transformation media for mode-matched interaction of light with single quantum emitters

I. Chremmos, E. Kallos

The efficient interaction of light with single quantum emitters depends critically on the modal overlap between the incident and scattered photons. This usually calls for high-numerical-aperture optics in order to match the dipole radiation pattern of the emitter in free space. Such a requirement can be alleviated if the emitter is embedded in a medium that shapes its radiation into a collimated output beam. We here present simple-to-realize, all-dielectric and isotropic transformation media that perform such a mode conversion.

Nonparaxial Bessel-like beams following curved trajectories

Nikolaos K. Efremidis, Ioannis D. Chremmos

We introduce a new class of nonparaxial optical beams with a Bessel-like profile that are capable to laterally shift along fairly arbitrary trajectories during propagation in free space. Numerical simulations confirm our theoretical predictions. (C) 2014 Optical Society of America

Designing Thin Film-Capped Metallic Nanoparticles Configurations for Sensing Applications

Muhammad Y. Bashouti, Adi-Solomon de la Zerda, Dolev Geva, Hossam Haick

Thin film-capped metallic nanoparticles (TFCMNPs) hold big promise for rapid, low-cost, and portable tracing of gas analytes. We show that sensing properties can be controlled by the configuration of the TFCMNPs. To this end, two methods were developed: layer by layer (LbL) and drop-by-drop, i.e., drop casting (DC). The TFCMNP prepared via LbL method was homogeneous and gradually increased in thickness, absorbance, and conductivity relative to TFCMNP prepared via DC method. However, our results indicate that the sensing of TFCMNP devices prepared via DC is significantly higher than that of equivalent LbL devices. These discrepancies can be explained as follows: LbL forms a high dense layer of TFCMNPs without vacancies, and a well-controlled deposition of NPs. The distance between the adjacent NPs is controlled by the capped ligands and the linker molecules making a rigid TFCMNP. Thus, exposing LbL devices to analyte induces a marginal change in the NP-NP distance. However, in DC devices, the analyte induces major change in the NP distances and permittivity due to their lack of connection, making the sensing much more pronounced. The DC and LbL methods used thiol and amine ligands-capped metallic nanoparticles to demonstrate the applicability of the methods to all types of ligands. Our results are of practical importance for integrating TFCMNPs in chemiresistive sensing platforms and for (bio) and chemical sensing applications.

Suppression and splitting of modulational instability sidebands in periodically tapered optical fibers because of fourth-order dispersion

Andrea Armaroli, Fabio Biancalana

We study the modulational instability induced by periodic variations of group-velocity dispersion in the proximity of the zero dispersion point. Multiple instability peaks originating from parametric resonance coexist with the conventional modulation instability because of fourth-order dispersion, which in turn is suppressed by the oscillations of dispersion. Moreover, isolated unstable regions appear in the space of parameters because of imperfect phase matching. This confirms the dramatic effect of periodic tapering in the control and shaping of MI sidebands in optical fibers. (C) 2014 Optical Society of America