Tailoring the morphology of photowritten buried waveguides by helical trajectory in As2S3 glass

International audienceThis paper deals with the control of the refractive index variation (Δn) profile induced by femtosecond laser irradiation in the bulk of As2S3 glass. The writing technique consists of an original laser inscription based on a helical translation of the sample parallel to the laser beam. Instead of inscribing the core of the waveguide as usually performed, the laser beam is used to induce a negative refractive index variation and consequently to write the cladding of the waveguide. However, it should be noticed that the matter displacement resulting from local heating leads to a densification at the center of the helix which induces a positive Δn relatively to the matrix. Therefore, the structure of Δn is complex, being composed of a positive core surrounded by a negative cladding. The influence of different parameters on the Δn profiles such as the sample translation velocity, the pitch and the radius of the helical displacement, and the pulse energy are analysed. This study demonstrates that both Δn and its diameter can be varied in a wide range of values and picked independently, allowing the design of single or multimode buried infrared waveguid

Influence of NaX (X=I or Cl) additions on GeS2-​Ga2S3 based glasses

International audienceChalcogenide glasses in the pseudo-​ternary system NaX-​GeS2-​Ga2S3 (X=Cl or I) were synthesized. Different series were investigated in order to highlight the influence of the sodium halide addn. on two different host glasses (GeS2)​80(Ga2S3)​20 and (GeS2)​72(Ga2S3)​28. Macroscopic properties including d. and characteristic temps., such as glass transition temps. Tg and crystn. temp. Tx, were detd. for a max. molar content of NaX equal to 15​%. The evolution of the optical band-​gap and the chem. stability following the compn. were also studied. Cond. measurements were also performed and compared to other Li-​based GeS2-​Ga2S3 glasses. The results were discussed taking into account the cation and anion nature and also the glass packing d

Direct laser writing of low loss waveguide with independent control over the transverse dimension and the refractive index contrast between the core and the cladding

International audienceIn this Letter, we present the realization of a low-loss wave- guide in a chalcogenide glass by direct laser writing technique in a particular configuration that allows the independent control over the diameter of the core and the magnitude of the refractive index contrast with the cladding. The wave- guide is of multicore type and composed of 19 channels arranged on a hexagonal lattice. Each channel is obtained by stacking voxels of refractive index variation obtained by static exposure to femtosecond laser pulse burst. The distance between the channels can be used to vary the diameter of the waveguide, while the duration of laser burst controls the magnitude of the effective index and the propagation loss. We demonstrate that it can be reduced down to 0.11 dB/c

Direct Laser Writing of Mid-Infrared Straight and Bent Waveguides

International audienceDuring the last twenty years many efforts have been devoted to the development of direct laser writing technique for the manufacture of both passive and active optical devices in various materials [1]. As far as infrared spectral range is concerned, chalcogenide glasses are one of the most evident material to use for production of integrated component because of their wide transparency range from the visible up to more than 20 pm. Here we present a new method to produce waveguide by direct laser writing technique in germanium, gallium, and sulfur based glass (90 [0.80 GeS 2 - 0.20 Ga 2 S 3 ] - 10 CsCl) for mid-infrared applications

Ultrafast Laser Inscription of High-Performance Mid-Infrared Waveguides in Chalcogenide Glass

International audienceWe present the realization of mid-infrared waveguide by ultrafast laser inscription technique in a chalco-genide glass. Our approach is based on multicore waveguide that consists in an alignment on a mesh of positive refractive index channels placed parallel to each other. Two different meshes are investigated with different refractive index contrasts between the channel and the glass matrix. A detailed analysis of the performances at a wavelength of 4.5 mu m shows propagation losses of 0.20 +/- 0.05 dB/cm and coupling efficiencies higher than 60%

Direct femtosecond laser writing of low-loss waveguides in chalcogenide glasses for mid-infrared applications

International audienceDirect femtosecond laser writing technique is now widely used in particular in glass, to produce both passive and active photonic devices. This technique offers a real scientific opportunity to generate three-dimensional optical components. The chalcogenide glasses are of great interest since they possess a transparency window from the visible up to the midinfrared range. Moreover, they also have high optical non-linearity and high photosensitivity that facilitate the inscription of permanent refractive index modification. In this presentation, an original method based on both the filamentation phenomenon and a point-by-point technique will be described. The written waveguide is of multicore type and consists in parallel channels of positive ▵n placed parallel to each other on a hexagonal or a circular mesh. The performances in terms of optical losses at both 1.55 μm and 4.55 μm measured in such photowritten buried infrared waveguide are very competitive. This writing technique is particularly suitable for the design of single mode waveguide for wavelengths ranging from the visible up to the mid-infrared since the geometry of the inscription and the amplitude of the refractive index modification can be easily adapted. This also paves the way for the fabrication of advanced mid-infrared optical components such as Y-splitters

Direct femtosecond laser writing of buried infrared waveguides in chalcogenide glasses

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Femtosecond Laser Fabrication of Gradient Refractive Index Micro-Lenses in Chalcogenide Glass for Applications in Visible and Infrared Region

International audienceGradient refractive index (GRIN) lenses are optical components having spatial variations of in the material [1]. GRIN have been widely used for several applications such as correction aberrations [2], fiber coupling [3], imaging systems [4]. Many techniques developed fabrication lenses: chemical vapor deposition, ion exchange or neutron irradiation [5]. However, these cannot be applied all materials because their use depends composition [6]. In addition, femtosecond laser direct writing (FLDW) method is a very flexible technique to modify materials. This powerful allows controlling inscribed shape [6], especially scale <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mu \mathrm{m}$</tex> . this work, we focus on micro-lenses chalcogenide glasses (ChG) using FLDW method

Spatially resolved Raman analysis of laser induced refractive index variation in chalcogenide glass

International audienceWe report a detailed 2D μ-Raman analysis of the refractive index modification (Δn) induced by femtosecond laser filament in the bulk of Ge-Ga-S ternary chalcogenide glass. The invariant illumination and detection geometry during the 2D scanning, allows both qualitative and quantitative determination of the proportion of different structural units to be carried out. The results indicate that during the light-matter interaction, S3Ga-GaS3 ethane like groups are transformed into triclusters of Ga/S. The decreased population of edge- and corner-sharing GeS4/2 tetrahedra implies the formation of mixed triclusters : T/S where T = Ga and/or Ge. Finally, correlations between photostructural changes and Δn are presented