Lossless Tapers, Gaussian Beams, Free-Space Modes: Standing Waves Versus Through-Flowing Waves

It was noticed in the past that, to avoid physical inconsistencies, in Marcatili's lossless tapers through-flowing waves must be drastically different from standing waves. First, we reconfirm this by means of numerical results based on an extended BPM algorithm. Next, we show that this apparently surprising behavior is a straightforward fallout of Maxwell's equations. Very similar remarks apply to Gaussian beams in a homogeneous medium. As a consequence, Gaussian beams are shown to carry reactive powers, and their active power distributions depart slightly from their standard pictures. Similar conclusions hold for free-space modes expressed in terms of Bessel functions.Comment: 19 pages and 6 figure

Graphene-assisted control of coupling between optical waveguides

The unique properties of optical waveguides electrically controlled by means of graphene layers are investigated. We demonstrate that, thanks to tunable losses induced by graphene layers, a careful design of silicon on silica ridge waveguides can be used to explore passive PT-symmetry breaking in directional couplers. We prove that the exceptional point of the system can be probed by varying the applied voltage and we thus propose very compact photonic structures which can be exploited to control coupling between waveguides and to tailor discrete diffraction in arrays

Role of dispersion in pulse emission from a sliding-frequency fiber laser

6openopenRomagnoli, M.; Wabnitz, Stefan; Franco, P.; Midrio, M.; Bossalini, L.; Fontana, F.M., Romagnoli; Wabnitz, Stefan; P., Franco; M., Midrio; L., Bossalini; F., Fontan

Diseño de una rectena de onda completa de triple frecuencia

Modern communication systems use multifrequency or broadband antennas in order to provide multiple communication services. One of the biggest problems associated to all these systems comes from their batteries life cycle. Nowadays, great efforts are being undertaken in order to harvest energy from as many places as possible. In addition, if the two cycles of the corresponding wave could be used, it would be good in order to increase the RF-DC power conversion. This paper presents a multifrequency and full wave-rectifying antenna for microwave applicatio

Chirp management in silicon-graphene electro absorption modulators

We study the frequency chirp properties of graphene-on-silicon electro-absorption modulators (EAMs). By experimentally measuring the chirp of a 100 \ub5m long single layer graphene EAM, we show that the optoelectronic properties of graphene induce a large positive linear chirp on the optical signal generated by the modulator, giving rise to a maximum shift of the instantaneous frequency up to 1.8 GHz. We exploit this peculiar feature for chromatic-dispersion compensation in fiber optic transmission thanks to the pulse temporal lensing effect. In particular, we show dispersion compensation in a 10Gb/s transmission experiment on standard single mode fiber with temporal focusing distance (0-dB optical-signal-to-noise ratio penalty) of 60 km, and also demonstrate 100 km transmission with a bit error rate largely lower than the conventional Reed-Solomon forward error correction threshold of 10 123

Frequency addressing of nano-objects by electrical tuning of optical antennas

We first analyze the equivalent circuit parameters of linear wire optical nano-antennas in uniaxial anisotropic media. We then exploit the electro-optic response of a bipolar nematic liquid crystal to demonstrate tuning of an optical antenna using a low frequency external electric field as the control mechanism

Polarization Independent Unidirectional Scattering with Turnstile Nanoantennas

We study the scattering behavior of a dielectric cross-dipole nanoantenna in the near-infrared spectral range when it is excited by a circular polarized plane wave. We theoretically demonstrate, for optimized geometrical parameters of the proposed turnstile structure, the possibility to simultaneously obtain a unidirectional scattering and a specific circular polarization of the scattered field. Our results open new functionalities for metamaterials and optical nanoantennas

Comprehensive Analysis of Graphene Geometric Diodes: Role of Geometrical Asymmetry and Electrostatic Effects

A self-consistent Monte Carlo/3-D Poisson simulator has been developed to analyze the current asymmetry in graphene geometric diodes. The model couples ballistic transport in the graphene layer with 3-D electrostatics in the graphene and oxide substrate. Results are given in terms of transmission coefficients and currents at the two terminals of the diode. We prove that while the current asymmetry is mainly induced by ballistic transport in the asymmetric structure, the electrostatics plays a relevant role that tends to substantially counterbalance the geometrical effect