Elżbieta Bereś-Pawlik

Study of mid-infrared laser action in chalcogenide rare earth doped glass with Dy 3+ , Pr 3+ and Tb 3+

We present a study of chalcogenide glass fiber lasers doped with Dy3+, Pr3+ or Tb3+ that would operate in the mid-infrared wavelength range. A set of chalcogenide glass samples doped with different concentrations of rare earth ions is fabricated. The modeling parameters are directly extracted from FTIR absorption measurements of the fabricated bulk glass samples using Judd-Ofelt, Fuchtbauer–Ladenburg theory and McCumber theory. The modeling results show that, for all the dopants considered, an efficient mid-infrared laser action is possible if optical losses are kept at the level of 1dB/m or below.

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.

Large-mode-area photonic crystal fiber with double lattice constant structure and low bending loss

We report on a bendable photonic crystal fiber for short pulse high power fiber laser applications. This fiber uses a double lattice structure and enables single mode operation with a very large mode area that reaches 1454 µm² when the fiber is kept straight and 655 µm² in the fiber bent around a 10 cm radius. Single mode operation is enforced by the very large bending loss in excess of 50 dB/m experienced by the higher order modes, whilst bending loss for the fundamental mode is smaller than 0.01 dB/m. We outline the principles of our fiber design and we explore the guiding properties of the fiber.

Theoretical study of population inversion in active doped MIR chalcogenide glass fibre lasers (invited).

We study the mechanism of the population inversion in mid-infrared fibre lasers based on a chalcogenide glass host doped with active lanthanide ions. Three lanthanide dopant ions are considered: terbium, dysprosium and praseodymium. We predict the relevant trivalent ion level populations and gain. The simulation parameters were obtained by fabricating and optically characterising a series of trivalent ion doped chalcogenide glass samples. We also provide simple analytical expressions that aid the design of the cascade lasing process.

Applying optical design methods to the development of application specific photonic crystal fibres

Photonic Crystal Fibres (PCFs) are well known for allowing the implementation of specific waveguiding features that cannot be achieved with conventional optical fibres. This results from the design flexibility of the holey structure in the PCF cladding and/or core regions. Today PCFs have found applications for example in supercontinuum generation, optical sensing and fibre lasers. They are now also being combined with fibre Bragg gratings, more specifically in the fields of optical fibre sensing and all-fibre laser applications. In this contribution we discuss how we applied micro-optical design methods based on commercially available software such as MODE Solutions and FDTD Solutions from Lumerical Solutions, Inc. and COMSOL Multiphysics® combined with MATLAB® scripting and additional optimization methods to develop microstructured fibres for three different purposes, i.e. PCF structures that facilitate Bragg grating inscription, PCF structures that enable temperature insensitive pressure measurements and bendable PCFs with a very large mode area for high power short pulse fibre lasers. For the three cases we describe the fibre design methods and property simulations as well as the tolerance studies that take into account manufacturing imperfections as well as possible variations in material parameters.

Application of Negative Curvature Hollow-Core Fiber in an Optical Fiber Sensor Setup for Multiphoton Spectroscopy

In this paper, an application of negative curvature hollow core fiber (NCHCF) in an all-fiber, multiphoton fluorescence sensor setup is presented. The dispersion parameter (D) of this fiber does not exceed the value of 5 ps/nm × km across the optical spectrum of (680–750) nm, making it well suited for the purpose of multiphoton excitation of biological fluorophores. Employing 1.5 m of this fiber in a simple, all-fiber sensor setup allows us to perform multiphoton experiments without any dispersion compensation methods. Multiphoton excitation of nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) with this fiber shows a 6- and 9-fold increase, respectively, in the total fluorescence signal collected when compared with the commercial solution in the form of a hollow-core photonic band gap fiber (HCPBF). To the author’s best knowledge, this is the first time an NCHCF was used in an optical-fiber sensor setup for multiphoton fluorescence experiments.

Dispersion properties of double-clad hollow-core photonic bandgap fibers based on a circular lattice cladding

The major challenges in developing a fiber-optic nonlinear endomicroscope are efficient excitation light delivery and nonlinear optical signals collection, beam scanning, and probe miniaturization [1-4]. Therefore, double-clad PCFs (DCPCF) are used in nonlinear endomicroscope which can play a dual role of ultrashort pulse delivery and efficient collection of nonlinear optical signals [4]. However, due to dispersion of DCPCF, dispersion compensation systems are required. In this paper the dispersion properties and losses of new design of double-clad hollow-core photonic bandgap fibers (DCPBGFs) based on a circular lattice are investigated for the first time, by using a finite difference time domain method.

Anti-Resonant Hollow Core Fibers with Modified Shape of the Core for the Better Optical Performance in the Visible Spectral Region—A Numerical Study

In this paper, we present numerical studies of several different structures of anti-resonant, hollow core optical fibers. The cladding of these fibers is based on the Kagomé lattice concept, with some of the core-surrounding lattice cells removed. This modification, by creating additional, glass-free regions around the core, results in a significant improvement of some important optical fiber parameters, such as confinement loss (CL), bending loss (BL), and dispersion parameter (D). According to the conducted simulations (with fused silica glass being the structure’s material), CL were reduced from ~0.36 dB/m to ~0.16 dB/m (at 760 nm wavelength) in case of the structure with removed cells, and did not exceed the value of 1 dB/m across the 700–850 nm wavelength range. Additionally, proposed structure exhibits a remarkably low value of D—from 1.5 to 2.5 ps/(nm × km) at the 700–800 nm wavelength range, while the BL were estimated to be below 0.25 dB/m for bending radius of ~1.5 cm. CL and D were simulated, additionally, for structures made of acrylic glass polymethylmethacrylate, (PMMA), with similarly good results—DPMMA ∊ [2, 4] ps/(nm × km) and CLPMMA ≈ 0.13 dB/m (down from 0.41 dB/m), for the same spectral regions (700–800 nm bandwidth for D, and 760 nm wavelength for CL).

Theoretical investigation of temperature optical sensor setup with spectrally adjusted fiber Bragg gratings

In this work we would like to exhibit theoretical investigation of correlated fiber Bragg gratings (FBGs) for sensor applications. The spectra of FBGs have been simulated so as to overlap each other. There have been performed analysis of reflected optical power for different sensing FBGs using self-written program. Different width of scanning FBGs have been applied in order to obtain various response of sensor setup. The comparison study of these FBGs have been done. This work presents the results of simulations for reflected optical power with regard to different temperatures surrounding sensing FBGs.

Temperature monitoring system using correlated FBGs

This paper presents a novel, simple, low-cost and repeatable quasi-distributed optical sensor system using specially designed fibre Bragg gratings (FBGs). The main idea consists in modulation of optical power by inscribed FBGs. The optical power changes with regard to outer parameters which have an influence on dedicated FBGs. The unique configuration is provided by proper characteristics of FBGs spectra. Instead of advanced and high-cost systems we demonstrate a concept of a low-cost sensor network using specially correlated FBGs.