Theoretical formulation to shape versatile propagation characteristics of 3-layerstubular waveguides

International audienceThis study introduces an analytical formalism to shape the quantication of photonic modes devoted to global 3-layer-tubular waveguides (including hollow cylindrical structures). Thereby we have implemented such an overall frame and focus on the asymptotic behavior and the cut-off limit discussions

Guides d'onde rubans en Polydimethylsiloxane (PDMS) a large gamme spectrale pour des applications en photonique intégrée

National audienceLa réalisation et la caractérisation de guides d'onde ruban constitués du même matériau polymère à la fois pour le coeur et pour la gaine sont présentées. Ces structures guidantes sont fabriquées à partir de polydimethylsiloxane (PDMS), qui a été retenu pour sa très bonne transparence sur une large gamme spectrale, notamment aux courtes longueurs d'onde (jusqu'à 240 nm) et pour son processus de mise en forme par lithographie douce, méthode simple et bas coût. De premiers tests d'injection optique ont montré que le guidage était effectif dans le visible à 635 nm et à 447 nm et les pertes optiques ont été estimées à quelques dB.cm-1 à 635 nm et à une dizaine de dB.cm-1 à 447 nm

Versatile Analytical Approach for Assessing Harmonic Distortion in Current-Driven Electrodynamic Loudspeakers

International audienceCurrent-driven loudspeakers have been studied for a long time because they are in great demand by discriminating audiophiles. The latest market research provides clear motivation for producing adequate innovative designs and simple theoretical solutions to address the nonlinear properties of these loudspeakers. Thus, the aim of this paper is to present a compact analytical approach to assess the harmonic distortion that deteriorates the audio quality of electrodynamic loudspeakers, while separately considering the effect of varying the primary respective parameters. Taylor polynomials are conveniently used to derive simple expressions for the first five harmonic distortion lines of the entire spectrum: the significance of each parameter under consideration is rendered transparent using this methodology. This analytical approach is validated by performing a numerical analysis using Simulink software and can easily be implemented using a standard spreadsheet application. We also note that the acceleration of the diaphragm is referenced to the acceleration due to gravity in this study

Direct injection in organic SU8 nanowires and nanotubes for waveguiding properties investigation

International audienceWe report photonic concepts related to injection and sub-wavelength propagation in nanofibers (nanowires and nanotubes). These nanostructures are fabricated by the wetting template method leading to aspect ratio of over 250. At first, injection into nanowires and nanotubes of SU8, a photoresist used for integrated photonics, was successfully achieved by using polymer microlensed fibers with sub-micronic radius of curvature. Theoretical simulation by finite domain time-dependent (FDTD) method was used to determine the sub-wavelength propagation for nanowires and nanotubes and corroborate this coupling phenomena. The original confinment of energy density into SU8 nanotubes is highlighted. Finally, characterisation of propagation losses is reported by using a cut-back method transposed to such nanotubes and determined to range between 1 and 2 dB/mm. Both injection and cut-back method developed here are compatible with any sub-micronic structures. This work on SU8 nanofibers suggests broader perspectives for future nanophotonics

AFM Analysis on Polymer Optical Micro-Resonators: Investigation on Quality Factor Origin

International audienceThis paper deals with the surface analysis of spherical polymeric optical micro-resonators in order to correlate surface defects with optical characteristics. Atomic force microscopy was used on structures to determine surface quality, which is the main origin of optical scattering losses. Surface morphologies were numerically treated to enable a relevant investigation on surface parameters such as root mean square (RMS) roughness (30.1 +/- 3.0 nm) or correlation length (few microns) necessary to express optical quality factors. A statistical analysis was conducted for calibration of these parameters as a function of cavities' diameter. Results are in perfect agreement with spectral analyses performed in parallel on others structures. This comparison highlights the main role of scattering losses on quality factor origin

Fabrication and optical characterization of pedestal micro-structures on DUV210 polymer: waveguides structures towards micro-resonators

International audienceThe paper presents the global design, fabrication and optical characterizations of pedestal waveguides and 2D microresonators made of DUV210 polymer. These particular geometries are achieved thanks to specific deep-UV lithography procedures allowing sub-lambda development coupled to chemical etching able to shape such pedestal configuration on various optical microstructures. Scanning electron microscopy images have confirmed their features. Moreover, such families of pedestal structures were characterized experimentally, including the optical losses measurements for the waveguides and the optical resonance responses for two kinds of microresonators. Optical studies of single mode propagation losses measurements have been performed by a cut back method leading to values close to 20 dB/cm at a 635 nm wavelength. Additionally, resonant spectral analysis has been performed into pedestal rings and racetracks microresonators with a broadband laser source centered at 795 nm, demonstrating the presence of expected theoretical resonances. Free spectral range values of 2.86 nm and 2.51 nm have been measured for these new designed pedestal resonators on DUV210 related to quality factor values superior to 520 and 610 respectively

Improvement of efficient coupling and optical resonances by using taper-waveguides coupled to cascade of UV210 polymer micro-resonators

International audienceIn this paper, we report the overall design, fabrication and optical characterization of single and multiple resonant micro-structures patterned on the UV210 polymer and shaped by adequate deep-UV lithography procedures. Various families of ring and racetrack forms are investigated with different geometrical dimensions linked to the micro-resonators and the specific taper-waveguides and gaps allowing the optimized coupling. Well defined photonic structures families in the sub-micrometer range obtained by this deep UV-light process are clearly confirmed through scanning electron microscopy. In order to evaluate and quantify the efficiency of the sub-micrometer coupling, the recirculation of the light and the quality of the optical resonance aspects, a global study including top view intensity imaging, spectral measurements and Fast Fourier Transform analysis is performed for all these devices based on single and multiple family resonators. The experimental TE-mode resonance transmissions reveal a complete agreement with the period of the theoretically expected resonances. A maximum value of the quality factor Q = 3.5 x 10^3 at 1035 nm with a 3.2 times higher resonance contrast is assessed for cascade of triple micro-resonators respect to the photonic devices based on only one micro-resonator. In addition, these UV210 circuits made of specific tapers coupling to cascade loops act directly on the improvement of the evanescent coupling and resonances in terms of quality factor and extinction rate, by selecting successively and more precisely the optical mode resonance. All these designs and low cost technological reproducible steps, and furthermore the devices and protocol measurements are markedly suitable for mass fabrication and metrology applications

Transferable Integrated Optical SU8 Devices: From Micronic Waveguides to 1D-Nanostructures

International audienceWe report on optical components for integrated optics applications at the micro-and nanoscale. Versatile shapes and dimensions are achievable due to the liquid phase processability of SU8 resist. On the one hand, by adjusting the UV-lithography process, waveguiding structures are patterned and released from their original substrate. They can be replaced on any other substrate and also immerged in liquid wherein they still show off efficient light confinement. On the other hand, filled and hollow 1D-nanostructures are achievable by the wetting template method. By exploiting the large range of available SU8 viscosities, nanowires of diameter ranging between 50 nm and 240 nm, as well as nanotubes of controllable wall thickness are presented. Optical injection, propagation, and coupling in such nanostructures are relevant for highly integrated devices

A novel deep-UV polymer for integrated photonics: waveguides structures towards cascade of multiple micro-resonators

International audienceAn overview of targeted current research on integrated photonics based on the new deep-UV210 organic material is given. We report on the interest in this new material and properties coupled to deep-ultraviolet (DUV) lithography processes towards the realization and optical characterization of sundry photonics structures. Such structures include sub-wavelength waveguides, pedestal and tapers waveguides until serial of optical micro-resonators (MRs) shaped as disk, ring, stadium and racetrack

Native spider silk as a biological optical fiber.

International audienceIn this study, we demonstrate the use of eco-friendly native spider silk as an efficient optical fiber in air, highly bent fibers, and physiological liquid. We also integrated the silk filament in a photonic chip made of polymer microstructures fabricated by UV lithography. The molding process is non-destructive for silk and leads to an efficient micro-optical coupling between silk and synthetic optical structures. These optical performances combined with the unique biocompatibility, bioresorbability, flexibility, and tensile strength of silk filaments pave the way for new applications in biological media and for original biophotonic purposes