Arnaud Royon

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)

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.

Femtosecond laser induced photochemistry in materials tailored with photosensitive agents [Invited]

This article deals with the recent advances in photochemistry in optical materials induced by femtosecond laser pulses. The field of investigation of this paper is limited to bulk solid isotropic transparent materials (glasses and polymers), specifically tailored with photoactive agents. The formation mechanisms of laser-induced color centers, nanoclusters, nanoparticles and nanocrystallites are reviewed and argued, in particular the influence of the temperature during or after the laser irradiation. The relation between the photo-induced structures and the optical property modifications are discussed, as well as some applications.

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.

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.

Third-Harmonic Generation Microscopy for Material Characterization

Third harmonic generation microscopy is described in the frame work of the theory of harmonic generation with Gaussian focused beams inside a bulk material as well as at the vicinity of an interface. This model is then applied to characterize different types of materials in terms of electronic third-order susceptibility. Examples of bulk glasses, poled glasses, laser-induced modifications in glasses and nanoparticles in solution are given in order to give a survey of the broad application field of THG microscopy in material characterization.

Patterning linear and nonlinear optical properties of photosensitive glasses by femtosecond structured light.

We report on structured light-induced femtosecond direct laser writing (DLW) under tight focusing in non-commercial silver-containing zinc phosphate glass, which leads to original patterns of fluorescent silver clusters. These fluorescence topologies show unique features of frustrated diffusion of charged species, giving rise to distorted silver cluster spatial distributions. Fluorescence and second harmonic generation correlative microscopy demonstrate the realization of structured light-induced direct laser poling, resulting from a laser-induced permanent and stable electric field buried inside the modified glass. Thus, structured light-induced DLW remarkably enables both linear and nonlinear patterning. This work highlights the interest of optical phase engineering to obtain nontrivial beam profiles and subsequent photo-induced patterns that cannot be reached under Gaussian beam irradiation.

Dense arrays of microscopic optical vortex generators from femtosecond direct laser writing of radial birefringence in glass

We report on the generation of permanent singular light mode converters at the microscale using femtosecond direct laser writing in photo-thermo-refractive glass. It relies on the irreversible light-induced radial birefringence in the bulk of the material. The ability of such birefringence pattern to convert the spin angular momentum of light into orbital optical angular momentum is exploited to demonstrate the production of large arrays of optical vortex generators with surface densities up to 104cm-2.

Second-harmonic generation in sodium and niobium borophosphate glasses after poling under field-assisted silver ions anodic injection

Monovalent silver ions, resulting from a thin silver layer initially deposited at the anode surface, have been introduced using the field-assisted ion-exchange technique in sodium niobium borophosphate glasses. A reproducible susceptibility χ(2) could be gained after this poling treatment, although a drop in the nonlinearity is observed due to the introduction of silver ions. From energy dispersive x-ray spectroscopy, it has been found that the nonlinear layer is characterized by a strong migration of sodium ions 4 μm deep inside the anode side, which have been partially replaced by silver ions. These results indicate a complex space-charge-migration process during the poling treatment, which is involved in the decrease in the mean second-harmonic generation signal.