Elio Pone

Drawing of the hollow all-polymer Bragg fibers

Drawing of the hollow all-polymer Bragg fibers based on PMMA/PS and PVDF/PC materials combinations are demonstrated. Hole collapse during drawing effects the uniformity of a photonic crystal reflector in the resultant fiber. We first investigate how the core collapse effects fiber transmission properties. We then present modelling of fluid dynamics of hollow multilayer polymer fiber drawing. Particularly, hole collapse during drawing and layer thickness non-uniformity are investigated as a function of draw temperature, draw ratio, feeding speed, core pressurization and mismatch of material properties in a multilayer. Both the newtonian and non-newtonian cases are considered assuming slender geometries.

Guiding in the visible with "colorful" solid-core Bragg fibers.

We report on the fabrication and characterization of solid-core all-polymer Bragg fibers consisting of a large-diameter polymethyl methylacrylate (PMMA) core surrounded by 50 alternating PMMA/Polystyrene (PS) polymer layers. By modifying the reflector layer thickness we illustrate that bandgap position can be adjusted at will in the visible. Moreover, such fibers are intensely colored in both the transmission and the outside reflection modes. Potential applications of such fibers are discussed.

Boundary integral method for the challenging problems in bandgap guiding, plasmonics and sensing

A boundary integral method [1] for calculating leaky and guided modes of microstructured optical fibers is presented. The method is rapidly converging and can handle a large number of inclusions (hundreds) of arbitrary geometries. Both, solid and hollow core photonic crystal fibers can be treated efficiently. We demonstrate that for large systems featuring closely spaced inclusions the computational intensity of the boundary integral method is significantly smaller than that of the multipole method. This is of particular importance in the case of hollow core band gap guiding fibers. We demonstrate versatility of the method by applying it to several challenging problems.

Refractive index profile of fused-tapered fiber couplers.

We investigate the refractive index profile evolution during the tapering of fused couplers. We assume the refractive index to be a linear function of the dopant concentration. The evolution of the refractive index profile is obtained by solving the diffusion-convection equation. The couplers are cleaved at different positions along the coupler axis, and the real refractive index profiles, measured using Refracted-Near-Field technique, are compared with the numerical solutions.

Refractive index profile of fused-fiber couplers cross-section

We investigate the refractive index profile of the cross-section of fused type fiber-optic couplers by solving the convective diffusion equation. We assume the refractive index to be a linear function of the dopant concentration. The viscous sintering of the optical fibers is considered as the motion of an incompressible Newtonian fluid which is driven by the surface tension acting at the free boundary. The internal velocity field is obtained using conformal mapping methods. We present numerical solutions of the resulting equations and compare them with experimental observations.

Newtonian and Non-Newtonian Models of the Hollow All-Polymer Bragg Fiber Drawing

Profile development during the isothermal drawing of the hollow all-polymer Bragg fibers is studied in the case when surface tension is strong enough to cause a hole collapse. The viscoelastic model of polymer flow is considered, and a comparison with the simpler Newtonian and generalized Newtonian models is made. The effects of draw ratio, draw temperature, feeding speed, core pressurization, and mismatch of material properties in the multilayer structure are investigated. A relation between the hole collapse and the layers nonuniformity is presented, and their effect on the fiber-transmission properties is investigated

Analysis of the birefringence of solid-core air-silica microstructured fibers

The origin and the behavior of the birefringence of solid-core air-silica microstructured fibers is described with the help of a simple approximate model. The first two modes of three different types of fibers are studied. Numerical results, obtained from both finite element and boundary integral methods calculations, are presented to support the validity of the model and to delineate its limits.

Heating of microstructured optical fibers due to absorption of the propagating light

Numerical and analytical models of the heat transfer in gas-filled microstructured optical fibers exhibiting material absorption of the propagating light are presented. The simulation domain is subdivided into two parts, with finite-difference discretization used in the microstructured region and analytical expansion used in the homogeneous cladding region. An intuitive analytical model is then developed to account for the fiber heating, demonstrating good agreement with the numerical method. In the application to the problem of temperature distribution in holey fibers, we find that maximal temperature rise in such fibers is a sensitive function of the diameter-to-pitch ratio while being only weakly sensitive to the wavelength-to-pitch ratio.

A pressure sensor based on the loss birefringence of a microstructured optical fiber containing metal coated elliptical inclusions

By measuring splitting in the wavelengths of maximum propagation losses of the two originally degenerate plasmonic/fiber core modes, one can detect 8.10-4 ellipticity of the silver coated air inclusions. Application in pressure sensing is suggested.

Fabrication of the hollow all-polymer Bragg fibers

Drawing of the PMMA/PS and PVDF/PC based, hollow all-polymer Bragg fibers are demonstrated. Effects of core collapse and multilayer nonuniformity on fiber transmission are considered. Non-newtonian dynamics modelling of Bragg fiber drawing is performed.