John Bigeon

Injection and waveguiding properties in SU8 nanotubes for sub-wavelength regime propagation and nanophotonics integration

We report photonic concepts related to injection and sub-wavelength propagation in nanotubes, an unusual but promising geometry for highly integrated photonic devices. Theoretical simulation by the finite domain time-dependent (FDTD) method was first used to determine the features of the direct light injection and sub-wavelength propagation regime within nanotubes. Then, the injection into nanotubes of SU8, a photoresist used for integrated photonics, was successfully achieved by using polymer microlensed fibers with a sub-micronic radius of curvature, as theoretically expected from FDTD simulations. The propagation losses in a single SU8 nanotube were determined by using a comprehensive set-up and a protocol for optical characterization. The attenuation coefficient has been evaluated at 1.25 dB mm(-1) by a cut-back method transposed to such nanostructures. The mechanisms responsible for losses in nanotubes were identified with FDTD theoretical support. Both injection and cut-back methods developed here are compatible with any sub-micronic structures. This work on SU8 nanotubes suggests broader perspectives for future nanophotonics.

Efficient active waveguiding properties of Mo6 nano-cluster-doped polymer nanotubes

We investigate 1D nanostructures based on a Mo6@SU8 hybrid nanocomposite in which photoluminescent Mo6 clusters are embedded in the photosensitive SU8 resist. Tens of micrometers long Mo6@SU8-based tubular nanostructures were fabricated by the wetting template method, enabling the control of the inner and outer diameter to about 190 nm and 240 nm respectively, as supported by structural and optical characterizations. The image plane optical study of these nanotubes under optical pumping highlights the efficient waveguiding phenomenon of the red luminescence emitted by the clusters. Moreover, the wave vector distribution in the Fourier plane determined by leakage radiation microscopy gives additional features of the emission and waveguiding. First, the anisotropic red luminescence of the whole system can be attributed to the guided mode along the nanotube. Then, a low-loss propagation behavior is evidenced in the Mo6@SU8-based nanotubes. This result contrasts with the weaker waveguiding signature in the case of UV210-based nanotubes embedding PFO (poly(9,9-di-n-octylfluorenyl-2,7-diyl)). It is attributed to the strong reabsorption phenomenon, owing to overlapping between absorption and emission bands in the semi-conducting conjugated polymer PFO. These results make this Mo6@SU8 original class of nanocomposite a promising candidate as nanosources for submicronic photonic integration.

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

We 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.

Nanosources and waveguiding in polymer-based nanowires and nanotubes(Conference Presentation)

Besides inorganic semiconducting and dielectric nanowires, the study of pi-conjugated and hybrid 1D-nanostructures is a fastly growing domain of research because of the great versatility offered by their architectures at the scale of the characteristic physical lengths. Novel nano-architectures give opportunities to control the optoelectronic properties, that could result in new paradigms for devices, such as nano-sources for tagging, sensing and lasing. Moreover, the 1D geometry promotes sub-wavelength optical propagation and cavity effects suitable for integrated nanophotonic devices (for a review, see [1]). Here, the color control in coaxial hybrid nanowires and the visible light propagation in polymeric nanotubes are reported, as well as nanosources combined within a single nanowire waveguide. In the first study, we propose an alternative strategy to get bright nano-emitters whose spectral emission can be precisely and simply anticipated. It consists in minimizing the role of charge and energy transfer mechanisms between the two species, in contrast to the common donor-acceptor strategy. In a practical way, the first key point is the selection of two luminophores with no overlapping in their absorption and emission spectral range. The second key point is the spatial separation of the two types of luminophores in a coaxial geometry to prevent charge and energy transfer. [2] For nanowires fabricated by a template strategy, this was achieved by first depositing nanotubes of a pi-conjugated green polymer with a solvent-assisted method. Then, the nanotubes were filled with a PMMA-red emitter composite. It has been shown that this strategy promotes a simple and fine tuning of the photoluminescence features with both species in similar concentration. These advantages could make our strategy a new paradigm for nano-emitters. In the second study, the propagation of light in the visible range along polymeric nanotubes has been investigated. The case of nanotubes is of particular interest because only few studies are reported in the literature and it permits higher interactions between the propagating light and both the surrounding medium and the inner channel, highly suited for nanosensors. The light was directly injected within nanotubes of SU-8 photoresist (a standard in integrated microdevices). The attenuation coefficient estimated by a cut-back like method has typical values of about 10 dB/cm. Simulation by FDTD has shown that most of the losses are due to leakages through the SiO2 substrate. [3] Thus, such polymeric nanowires and nanotubes are very competitive structures as sub-wavelength waveguides. Recent developments focused on combining fluorescent conjugated molecules within passive polymeric nanotubes will also be reported. [1] A. Garreau, J.L. Duvail Advanced Optical Materials 2, 1122-1140 (2014) [2] A. Garreau et al., ACS Nano 7, 2977–2987 (2013) [3] J. Bigeon, N. Huby, J.L. Duvail, B. Beche, Nanoscale 6, 5309 (2014)

Sub-wavelength optical propagation in passive and active 1D-nanostructures

atmospheric optical communications DTU Orbit (11/08/2019) Málaga statistical distribution: the new universal analytical propagation model for atmospheric optical communications Recently, a new and generalized statistical model, called Málaga or simply M distribution, has been proposed to characterize the irradiance fluctuations of an unbounded optical wavefront (plane and spherical waves) propagating through a turbulent medium under all irradiance fluctuation conditions in homogeneous, isotropic turbulence. Málaga distribution was demonstrated to have the advantage of unifying most of the proposed statistical models derived until now in the scientific literature in a closed-form and mathematically-tractable expression. Furthermore, it unifies most of the proposed statistical models for the irradiance fluctuations derived in the bibliography providing, in addition, an excellent agreement with published plane wave and spherical wave simulation data over a wide range of turbulence conditions (weak to strong). In this communication, reviews of its different features are discussed including a new interpretation and a physical interpretation of its parameters is provided. It is worth noting that the proposed expressions of this Málaga distribution together with their physical interpretation provide a very valuable tool for analyzing the effects of turbulence induced scintillation in atmospheric optical communication links under any turbulence conditionsT energies involved in weak chiral interactions occurring between Odorant Binding Proteins (OBPs) and Carvone Enantiomers are evaluated, down to a few KJ/mol, by means of a water-gated organic field-effect transistor (WGOFET) whose Au-gate is modified with a porcine-OBP (pOBP) self-assembled monolayer. The output current measured is dependent on the concentration of the analytes and pM concentrations can be detected. The binding curves also are significantly different between the two enantiomers. The modelling of the two curves allows the energies associated with the OBPCarvone complexes formation to be independently extracted, from the very same set of data. From the dissociation constants the standard freeenergy, the complex formation at the electrode is derived, while the threshold voltage shifts gives information on the electrostatic component. This approach, representing a unique tool to quantitatively investigate low-energy bio-chemical interactions, is rather general as it relies on the relative dielectric constants of the protein-SAMs and of the organic semiconductors being much lower than that of water. The role of the OBPs in the olfaction system is still under debate and the detection of neutral odorant species at the pM level by means of a WGOFET adds relevant pieces of information to the understanding of the odor perception mechanism at the molecular level.S nanoparticles have been extensively studied due to their potential applications and novel properties. Although different methods have been reported for the synthesis of these semiconductor materials, more environmental-friendly approaches continue to attract attention. Here, we focus on the II–VI types of semiconductor nanoparticles as they represent ideal systems for dimension-dependent properties. In this report, nanosecond laser was used to effect the decomposition of metal complexes, and also the nucleation process of nanoparticles in polymer solutions. CdS, ZnS, and ZnO nanoparticles were successfully prepared. The effect of change in concentration of the polymer solutions on the properties of the nanoparticles was studied. The morphology, structure, and optical properties of the nanoparticles were investigated. An increase in concentration of the polymer solution influenced the morphology of the nanoparticles, and also resulted in a decrease in the band gap energy of the nanoparticles. These are ascribed to the increase in adsorption centres and reduction in the coalescent process of the nanoparticles in the polymeric matrix.Nanophotonics and biophotonics Track:6-4 Nanodevices and nanophotonics In the field of nanophotonics, the understanding of optical phenomena related to sub-wavelength guiding in 1D-nanostructures is a fundamental interest for devices down-scaling. We present theoretical and experimental investigation of light propagation in original passive and active organic nanotubes. For this, polymer nanotubes has been designed and developed by the template wetting method. To characterize their optical behavior and in particular the sub-wavelength propagation, numerical and experimental tools have been developed. Modelling phenomena propagating in these nanofibers was performed by the numerical FDTD method. The effects of the geometry of these nanotubes and nanowires have been investigated. In particular, the effect of the diameter (outer and inner diameter for nanotubes) on the propagation behavior (energy distribution, losses), as well as the effect of the substrate, have been determined. Experimentally, two types of nanofibers were studied. First, direct injection into passive nanofibers of SU8 polymer was performed through a microlensed optical fiber. A striking result is the assessment of optical losses measured by the cutback around 1.25 dB/mm for nanotubes of external and internal diameters respectively 240 nm and 120 nm. This appears very competitive compared to other systems currently envisaged for integratednanophotonics. Second, active polymer nanofibers (polyfluorene PFO) embedded in a waveguiding polymer were elaborated and appeared to be an efficient design for a nano-source.

POLYMER NANOTUBES FOR INTEGRATD OPTICS

Organic nanotubes are elaborated by the wetting template method enabling control of aspect ratio. Their propagation is then highlighted by an injection with low radius of curvature-optical fiber and by an optical coupling with integrated polymer structures.