Adam Filipkowski

Dispersion management in soft glass all-solid photonic crystal fibres

The development of all-solid photonic crystal fibres for nonlinear optics is an alternative approach to air-glass solid core photonic crystal fibres. The use of soft glasses ensures a high refractive index contrast (> 0.1) and a high nonlinear coefficient of the fibres. We report on the dispersion management capabilities in all-solid photonic crystal fibres taking into account four thermally matched glasses which can be jointly processed using the stack-and-draw fibre technique. We present structures with over 450 nm broadband flat normal dispersion and ultra-flat near zero anomalous dispersion below 5 ps/nm/km over 300 nm dedicated to supercontinuum generation with 1540 nm laser sources. The development of an all-solid photonic crystal fibre made of F2 and NC21 glasses is presented. The fibre is used to demonstrate supercontinuum generation in the range of 730–870 nm (150 nm) with flatness below 5 dB.

Large diameter nanostructured gradient index lens.

In this paper we report on the development and optical properties of nanostructured gradient index microlenses with good chromatic behavior. We introduce a new fabrication concept for the development of large diameter nanostructured gradient index microlenses based on quantized gradient index profiles and the use of nanostructured meta-rods. We show a dependence of the quality of performance on the number of refractive index levels and the lens diameter. Measurements carried out at 633 and 850 nm show good optical properties and similar focal lengths for both wavelengths.

Nanostructured gradient index microaxicons made by a modified stack and draw method.

We report the design and fabrication of nanostructured gradient index microaxicons suitable for integration with optical fibers. A structure with the effective refractive index decreasing linearly from the center to the edges (i.e., an axicon) was designed using a combination of a simulated annealing method and the effective medium theory. The design was verified numerically with beam propagation method simulations. The axicons were made by the modified stack and draw method and integrated with optical fibers. The optical properties of the fabricated elements were measured and showed good agreement with the numerical simulations. The fabricated axicons produced an extended line focus at a distance from about 70 to 160 μm from the lens facet with a minimum FWHM diameter of 8 μm at 90 μm. At smaller distances, an interference pattern is observed both in the experiment and in simulations, which is attributed to the uneven effective refractive index profile at the structure.

Nanostructured graded-index core chalcogenide fiber with all-normal dispersion–design and nonlinear simulations

We propose a new approach to developing of graded-index chalcogenide fibers. Since chalcogenide glasses are incompatible with current vapor deposition techniques, the arbitrary refractive index gradient is obtained by means of core nanostructurization by the effective medium approach. We study the influence of graded-index core profile and the core diameter on the fiber dispersion characteristics. Flat, normal dispersion profiles across the mid-infrared transmission window of the assumed glasses are easily obtained for the investigated core nanostructure layouts. Nonlinear propagation simulations enable to expect 3.5-8.5 µm spectrum of coherent, pulse preserving supercontinuum. Fabrication feasibility of the proposed fiber is also discussed.

High resolution Shack-Hartmann sensor based on array of nanostructured GRIN lenses

We present a novel method for the development of a micro lenslets hexagonal array. We use gradient index (GRIN) micro lenses where the variation of the refraction index is achieved with a structure of nanorods made of 2 types of glasses. To develop the GRIN micro lens array, we used a modified stack-and-draw technology which was originally applied for the fabrication of photonic crystal fibers. This approach results in a completely flat element that is easy to integrate with other optical components and can be effectively used in high refractive index medium as liquids. As a proof-of-concept of the method we present a hexagonal array of 469 GRIN micro lenses with a diameter of 20 µm each and 100% fill factor. The GRIN lens array is further used to build a Shack-Hartmann detector for measuring wavefront distortion. A 50 lens/mm sampling density is achieved.

Diffractive optics development using a modified stack-and-draw technique.

We present a novel method for the development of diffractive optical elements (DOEs). Unlike standard surface relief DOEs, the phase shift is introduced through a refractive index variation achieved by using different types of glass. For the fabrication of DOEs we use a modified stack-and-draw technique, originally developed for the fabrication of photonic crystal fibers, resulting in a completely flat element that is easy to integrate with other optical components. A proof-of-concept demonstration of the method is presented-a two-dimensional binary optical phase grating in the form of a square chessboard with a pixel size of 5 μm. Two types of glass are used: low refractive index silicate glass NC21 and high refractive index lead-silicate glass F2. The measured diffraction characteristics of the fabricated component are presented and it is shown numerically and experimentally that such a DOE can be used as a fiber interconnector that couples light from a small-core fiber into the several cores of a multicore fiber.

Formation of optical vortices with all-glass nanostructured gradient index masks

We report the development of microscopic size gradient index vortex masks using the modified stack-and-draw technique. The vortex mask has a form of flat surface all-glass plate. Its functionality is determined by an internal nanostructure composed of two types of soft glass nanorods. The generation of optical vortices with charges 1 and 2 is demonstrated.

Development of large core microstructured polymer optical fiber

In this paper we report the in-house synthesis of optical grade PMMA suitable for fiber development and fabrication of a large core micro-structured polymer optical fiber (mPOF). We have designed an mPOF with a core area of 580 μm2 and single mode performance at a wavelength of 650 nm. The photonic cladding is composed of 3 rings of air holes with a filling factor of 0.58 ensuring in practice a single mode performance at the design wavelength of 650 nm. The designed mPOF fiber was fabricated using the stack and draw technique, however some deformation of the structure of the photonic cladding has been observed during final stage of fiber drawing. The influence of this development imperfection on the overall fiber performance has been modeled. Finally the optical properties of the fabricated fiber were measured and a comparison between these and the modeled properties was made.

Nanostructured micro-optics based on a modified stack-and-draw fabrication technique

Abstract We present the latest results in the fabrication of micro-optical components using a novel nanostructuring process. This low-cost fabrication technology, which exploits advances in the development of photonic crystal fibres, uses a modified stack-and-draw technique where macroscopic distributions of thermally and mechanically matched glasses are reduced in scale by repeated draw-down and restacking procedures until the individual glass features are significantly below the wavelength of incident light. We demonstrate that this fabrication technique is suitable for the creation of large diameter high numerical aperture micro-lenses for light collection and concentration purposes and broadband form birefringent materials.

Nonlinear soft oxide glasses for microstructured optical fibers development

In this paper we report on design and development of three types of the soft oxide glasses devoted to microstructured optical fibers manufacturing. The lead-bismuth glasses are synthesized in three-component oxide system of PbO-Bi2O3- Ga2O3 and in a complex five-component oxide system of SiO2-Ga2O3-Bi2O3-PbO-CdO. The tellurite glasses are synthesized in oxide system of TeO2-WO3-PbO-Na2O-Nb2O5 with various concentration of WO3 (5-38%mol) and PbO (0-18%mol). Measurements of glass transmittance are performed over the range 200nm-10μm. Linear thermal expansion coefficients and characteristic temperatures of glasses are determined based on dilatometer and Leitz heat microscope measurements. A use of Differential Scanning Calorimetry (DSC) method and crystallization tests (isothermal treatment) allows estimating the thermal stability of the glasses and susceptibility to crystallization. As a reference, similar measurements are performed for commercially available lead-silicate glasses SF57 and SF6, which are considered for development of nonlinear microstructured fibres. The glasses with an optimum resistance for devitrification during multiple thermal processing are selected among all developed glasses for further fibre development. We present a method for development of preform and subpreform elements as tubes, capillaries and rods used in the stack-and-draw technique of the fiber manufacture. We report also successful development of subpreform components of microstructured fibers based on selected tellurite and lead-bismuth glasses.