Co-propagation of QKD & 6 Tb/s (60x100G) DWDM channels with ~17 dBm total WDM power in single and multi-span configurations

We report co-propagation experiments of the quantum channel (at 1310 nm) of a Quantum Key Distribution (QKD) system with Dense Wavelength Division Multiplexing (DWDM) data channels in the 1550 nm range. Two configurations are assessed. The first one is a single span configuration where various lengths of Standard Single Mode Fiber (SSMF) (from 20 to 70 km) are used and the total WDM channels power is varied. The Secure Key Rate (SKR) and the Quantum Bit Error Ratio (QBER) are recorded showing that up to ~17 dBm total power of 30 or 60 channels at 100 Gb/s can coexist with the quantum channel. A metric to evaluate the co-propagation efficiency is also proposed to better evaluate the ability of a QKD system to provide secure keys in a co-propagation regime. The second experiment is a three spans link with a cascade of three QKD systems and two trusted nodes in a 184 km total link length. We report the transmission of a coherent 400 Gb/s Dual Polarization DP-16QAM (Quadrature Amplitude Modulation) channel that transports a QKD secured 100 GbE data stream, with other fifty-four 100 Gb/s WDM channels. Encryption is demonstrated at the same time as co-propagation.Comment: arXiv admin note: text overlap with arXiv:2305.1374

Coupled Dipole Method Determination of the Electromagnetic Force on a Particle over a Flat Dielectric Substrate

We present a theory to compute the force due to light upon a particle on a dielectric plane by the Coupled Dipole Method (CDM). We show that, with this procedure, two equivalent ways of analysis are possible, both based on Maxwell's stress tensor. The interest in using this method is that the nature and size or shape of the object, can be arbitrary. Even more, the presence of a substrate can be incorporated. To validate our theory, we present an analytical expression of the force due to the light acting on a particle either in presence, or not, of a surface. The plane wave illuminating the sphere can be either propagating or evanescent. Both two and three dimensional calculations are studied.Comment: 10 pages, 8 figures and 3 table

Electrodynamics in complex systems: Application to near-field probing of optical microresonators

This paper discusses recent theoretical efforts to develop a general and flexible method for the calculation of the field distributions around and inside complex optical systems involving both dielectric and metallic materials. Starting from the usual light-matter coupling Hamiltonian, we derive a self-consistent equation for the optical field in arbitrary optical systems composed of N different subdomains. We show that an appropriate solving procedure based on the real-space discretization of each subdomain raises the present approach to the rank of an accurate predictive numerical scheme. In order to illustrate its applicability, we use this formalism to address challenging problems related to nonradiative energy transfers in near-field optics. In particular, we investigate in detail the detuning of a microresonator probed by a near-field optical probe.</p

Optical properties of glasses or films containing nanoclusters: a numerical simulation

International audienceA numerical simulation was developed in order to determine the linear optical properties of an inhomogeneous medium. The method, based on a volume integral equation, takes multiple scattering into account. Consequently, it allows one to deal with media with high concentrations of inhomogeneities for which interactions between particles become significant and analytical theories often fail to predict the optical properties. It is shown that the simulation can be used as a reference solution in comparing the validity domain of different analytical theories. Then, the dielectric anomaly is studied when metallic clusters are situated close to a vacuum dielectric interface. The influences of the inclusions filling fraction, the interface and the distribution function of the position of the particles are analyzed

Near field scattered by subsurface particles

International audienceA volume integral method is developped in order to study the scattering of a plane wave by a small particle placed below a metallic surface. The scattering patterns produced in the near field are analysed. For p-polarization, a plasmon is excited producing interferences along the surface. It is shown that this interference pattern might be used to measure the dielectric constant of the metal. The scattered field has a pronounced maxima for p-polarization if the particle is close to the interface. This effect is due to a resonant interaction between the surface and the dipole already identified in the context of SERS as an image enhancement effect. Finally, the resolution of a near field detection of a subsurface scatterer is discussed on the basis of the transverse extension of the scattered field

Structure of the electromagnetic field in a slab of photonic crystal

International audienceWe simulate the s-polarized electromagnetic field diffracted by a truncated two-dimensional lattice. We observe strong decay of the transmittivity for frequencies lying in the gaps displayed by the dispersion relation of the infinite crystal and find regular oscillations outside these gaps. The structure of the field in the lattice is explained in terms of modes of its infinite counterpart. In particular, the oscillations are related to the resonance in the layer of propagating Bloch waves, just as in a Fabry–Perot interferometer. This interpretation enables us to retrieve the dispersion relation. Finally, we study the symmetry properties of the modes and show that for certain frequencies the transmissivity of the system is null under symmetric illumination but nonzero under antisymmetric lighting or vice versa

Scattering of a surface plasmon polariton by a surface defect

International audienceBy means of a Green-function, volume-integral-equation approach we study numerically the scattering of a surface plasmon polariton at a planar vacuum-metal interface by dielectric and metallic defects that are either embedded in the metal substrate or are situated in the vacuum region on the substrate. We calculate the transmission and reflection coefficients for the surface plasmon polariton, as well as the efficiency of its conversion into volume electromagnetic waves in the vacuum propagating away from the surface. We also compute the near field in the vicinity of the surface defect