Marek Napierala

Extremely large-mode-area photonic crystal fibre with low bending loss.

We report on the design of a novel flexible very large mode area photonic crystal fibre for short pulse high peak power fibre laser and beam delivery applications. This fibre has an extremely large mode area exceeding 2500 microm(2) when kept straight and over 1000 microm(2) when bent over a 10 cm radius at a wavelength of 1064 nm. In addition our fibre exhibits very small fundamental mode bending loss below 10(-2) dB/m. The large difference between the propagation loss levels of fundamental and higher order modes forces efficient single-mode guidance in the fibre core while bent. This allows using the fibre to build compact high power laser systems. The paper further explores the major features of this fibre including: the dependence of the mode field area on the fibre core shape, the influence of the bending radius and of the bending direction as well as the impact of manufacturing tolerances on the fibre specifications.

Experimental study of dispersion characteristics for a series of microstructured fibers for customized supercontinuum generation

We demonstrate an experimental study of the chromatic dispersion properties for a series of microstructured fibers (MSFs) dedicated for a supercontinuum generation. With white-light interferometry application we analyze experimentally how the small variations of structural parameters, i.e. an air-hole diameter and a lattice constant, influence dispersion characteristics in different groups of MSFs. Our study provides useful information on how to design the fiber which is less sensitive to the fabrication imperfections. Moreover those investigations are the initial step to the development of the customized or tunable supercontinuum light sources based on MSFs with slightly changed structural parameters which can generate light with a different spectrum range, adapted to a proper application.

Cross talk analysis in multicore optical fibers by supermode theory

We discuss the theoretical aspects of core-to-core power transfer in multicore fibers relying on supermode theory. Based on a dual core fiber model, we investigate the consequences of this approach, such as the influence of initial excitation conditions on cross talk. Supermode interpretation of power coupling proves to be intuitive and thus may lead to new concepts of multicore fiber-based devices. As a conclusion, we propose a definition of a uniform cross talk parameter that describes multicore fiber design.

Passive Multimode Fibre Optic Structures

The paper presents possibilities to use multimode network structures in commercial applications

Study on the Sensing Coating of the Optical Fibre CO2 Sensor

Optical fibre carbon dioxide (CO2) sensors are reported in this article. The principle of operation of the sensors relies on the absorption of light transmitted through the fibre by a silica gel coating containing active dyes, including methyl red, thymol blue and phenol red. Stability of the sensor has been investigated for the first time for an absorption based CO2 optical fiber sensor. Influence of the silica gel coating thickness on the sensitivity and response time has also been studied. The impact of temperature and humidity on the sensor performance has been examined too. Response times of reported sensors are very short and reach 2–3 s, whereas the sensitivity of the sensor ranges from 3 to 10 for different coating thicknesses. Reported parameters make the sensor suitable for indoor and industrial use.

Experimental Investigation of Supercontinuum Generation in Photonic Crystal Fibers Pumped With Sub-ns Pulses

We experimentally investigate a supercontinuum generation in a series of photonic crystal fibers pumped with sub-ns pulses. The fibers are designed to have zero dispersion wavelengths close to 1064 nm, but they differ with respect to the lattice constant and air hole size. We focus on the supercontinuum generation mechanism and on the shape of spectra generated with the use of these photonic crystal fibers. A comprehensive study on the influence of the fiber structural parameters on the supercontinuum outcome indicates how to tailor these parameters for specific application where particular spectral characteristics are desired.

Bragg Gratings Inscription in Highly Birefringent Microstructured POFs

We report for the first time, the fast inscription of high-quality Bragg gratings in highly birefringent microstructured polymer optical fibers by the phase mask method using 248-nm UV radiation. The fibers birefringence is created through a special design of the structure of holes through the fiber. A Bragg grating in these type of fibers allows the creation of two reflection peaks, where the peak separation is related to the phase birefringence.

Fiber optic gas sensor for on-line CO2 monitoring

An optical fiber CO2 gas sensor is reported in this work. Sensor is based on the change of absorption of a selected dye dissolved in an organically modified silica coating of an optical fiber. CO2 in the atmosphere decreases the pH of the deposited active layer, which eventually leads to the change of the fiber transmittance. Elaborated sensor exhibits high sensitivity, short response time and good stability, which makes it suitable for potential industrial, agricultural and household use. Described method can also be used for sensing other gases in sensor matrices.

Microtips at photonic crystal fibers as functional elements for near-field scanning optical microscopy probes

We present the process of the microtip fabrication at the LMA-10 fiber designed for near-field scanning optical microscopy probes. Facilitation of manufacturing procedure as well as proper focusing conditions of such elements are the main advantages of such microelements production.

Dual-core fiber based strain sensor for application in extremely high temperatures

This paper focuses on the utilization of crosstalk phenomenon to construct an innovative strain sensor. In our experiments, we take advantage of special fiber design and technology of fiber post-processing in order to receive strain sensing areas. We present results, which indicate possibility of achieving strain sensitivity at level of several mε/nm with negligible temperature cross-sensitivity at the same time. Furthermore after coating the sensor with the developed copper and gold coatings, it can be easily applied in extremely high temperature (e.g. 500–800 °C) and/or aggressive media applications.