Matthieu Bellec

Silver clusters embedded in glass as a perennial high capacity optical recording medium.

[∗] Dr. A. Royon , Dr. M. Bellec , G. Papon , Dr. B. Bousquet , Prof. L. Canioni Centre de Physique Moleculaire Optique et Hertzienne University of Bordeaux 351 Cours de la Liberation, 33405 Talence (France) E-mail: l.canioni@cpmoh.u-bordeaux1.fr K. Bourhis , Dr. T. Cardinal Institut de Chimie de la Matiere Condensee de Bordeaux University of Bordeaux 87 Avenue du Docteur Schweitzer, 33608 Pessac (France) Dr. Y. Deshayes Laboratoire de l ′ Integration du Materiau au Systeme University of Bordeaux 351 Cours de la Liberation, 33405 Talence (France)

Selective enhancement of topologically induced interface states in a dielectric resonator chain

The recent realization of topological phases in insulators and superconductors has advanced the search for robust quantum technologies. The prospect to implement the underlying topological features controllably has given incentive to explore optical platforms for analogous realizations. Here we realize a topologically induced defect state in a chain of dielectric microwave resonators and show that the functionality of the system can be enhanced by supplementing topological protection with non-hermitian symmetries that do not have an electronic counterpart. We draw on a characteristic topological feature of the defect state, namely, that it breaks a sublattice symmetry. This isolates the state from losses that respect parity-time symmetry, which enhances its visibility relative to all other states both in the frequency and in the time domain. This mode selection mechanism naturally carries over to a wide range of topological and parity-time symmetric optical platforms, including couplers, rectifiers and lasers.

Three-dimensional optical data storage using third-harmonic generation in silver zinc phosphate glass

We demonstrate the possibility of three-dimensional optical data storage inside a specific zinc phosphate glass containing silver by using third-harmonic generation (THG) imaging. Information is stored inside the glass with femtosecond laser irradiation below the refractive index modification threshold. We use the same laser for THG readout. The capability of storage with this technique is discussed.

Beat the diffraction limit in 3D direct laser writing in photosensitive glass

Three-dimensional (3D) femtosecond laser direct structuring in transparent materials is widely used for photonic applications. However, the structure size is limited by the optical diffraction. Here we report on a direct laser writing technique that produces subwavelength nanostructures independently of the experimental limiting factors. We demonstrate 3D nanostructures of arbitrary patterns with feature sizes down to 80 nm, less than one tenth of the laser processing wavelength. Its ease of implementation for novel nanostructuring, with its accompanying high precision will open new opportunities for the fabrication of nanostructures for plasmonic and photonic devices and for applications in metamaterials.

Topological transition of Dirac points in a microwave experiment.

By means of a microwave tight-binding analogue experiment of a graphenelike lattice, we observe a topological transition between a phase with a pointlike band gap characteristic of massless Dirac fermions and a gapped phase. By applying a controlled anisotropy on the structure, we investigate the transition directly via density of states measurements. The wave function associated with each eigenvalue is mapped and reveals new states at the Dirac point, localized on the armchair edges. We find that with increasing anisotropy, these new states are more and more localized at the edges.

Three-dimensional direct femtosecond laser writing of second-order nonlinearities in glass

We demonstrate that direct femtosecond laser writing in silver-containing zinc and gallium phosphate glass enables generation of three-dimensional (3D) optical second-order nonlinear microstructures having an χ(2) value about 2.5 times that of quartz. The proposed physical model involves photo-reduction, photo-dissociation, and migration of silver species within the glass matrix. 3D laser-written second-order nonlinear structures could become a new class of nonlinear optical components.

Faithful communication Hamiltonian in photonic lattices

Faithful communication is a necessary precondition for large scale all-optical networking and quantum information processing. Related theoretical investigations in different areas of physics have led to various proposals in which finite discrete lattices are used as channels for short-distance communication tasks. Here, in the framework of femtosecond-laser-written waveguide arrays, we present the first experimental realization of such a channel with judiciously engineered couplings.

Tight-binding couplings in microwave artificial graphene

We experimentally study the propagation of microwaves in an artificial honeycomb lattice made of dielectric resonators. This evanescent propagation is well described by a tight-binding model, very much like the propagation of electrons in graphene. We measure the density of states, as well as the wave function associated to each eigenfrequency. By changing the distance between the resonators, it is possible to modulate the amplitude of next-(next)-nearest-neighbors hopping parameters and to study their effect on the density of states. The main effect is the density of states becoming dissymmetric and a shift of the energy of the Dirac points. We study the basic elements: an isolated resonator, a two-level system and a square lattice. Our observations are in good agreement with analytical solutions for corresponding infinite lattice.

Towards second-harmonic generation micropatterning of glass surface

Thermal poling of sodium borophosphate niobium glasses, previously coated with a thin silver layer micropatterned by femtosecond laser irradiation, is demonstrated. The field-assisted ion-exchange process for fabricating planar surface in this glass substrate is analyzed. Inside the silver ablated lines obtained by femtosecond laser irradiation, we clearly observe a change in the distribution of the frozen electrostatic field that is modulated by the Ag+/Na+ ion-exchange process during the thermal poling.

Manipulation of edge states in microwave artificial graphene

Edge states are an important ingredient in understanding transport properties of graphene nanoribbons. We study experimentally the existence and the internal structure of edge states under uniaxial strain of the three main edges: zigzag, bearded, and armchair. The experiments are performed on artificial microwave graphene flakes, where the wavefunctions are obtained by direct imaging. We show that uniaxial strain can be used to manipulate the edge states: a single parameter controls their existence and their spatial extension into the ribbon. By combining a tight-binding approach and topological arguments, we provide an accurate description of our experimental findings. A new type of zero-energy state appearing at the intersection of two edges, namely the corner state, is also observed and discussed.