Boris T. Kuhlmey

Multipole method for microstructured optical fibers. I. Formulation

We describe a multipole method for calculating the modes of microstructured optical fibers. The method uses a multipole expansion centered on each hole to enforce boundary conditions accurately and matches expansions with different origins by use of addition theorems. We also validate the method and give representative results.

Ultrasensitive photonic crystal fiber refractive index sensor

We introduce a refractive index sensing geometry exploiting modes beyond cutoff in a selectively infiltrated PCF. We demonstrate a detection limit of 4.6×10−7 RIU and sensitivity of 30,100nm/RIU, a one-order-of-magnitude improvement over previous PCF sensors.

Fluid-Filled Solid-Core Photonic Bandgap Fibers

We review the field of fluid-filled solid-core photonic bandgap fibers (SC-PBGF): we present the mechanisms and models of light guidance in these fibers, and how the guidance properties are sensitive to the refractive index of the infiltrated fluid. We discuss how this sensitivity can be used for creating tunable devices such as filters, delay lines and tunable non-linear pulse propagation experiments. We review refractive index sensors based on SC-PBGFs, including band edge sensing, SC-PBGF based long period grating sensing and new results on selectively filled SC-PBGFs which are the most sensitive microstructured fiber based sensors to date. We also discuss practical aspects of fluid filling.

Modal cutoff in microstructured optical fibers

We analyze the nature of modal cutoff in microstructured optical fibers of finite cross section. In doing so, we reconcile the striking endlessly single-mode behavior with the fact that in such fibers all propagation constants are complex. We show that the second mode undergoes a strong change of behavior that is reflected in the losses, effective area, and multipolar structure. We establish the parameter subspace in which the fibers are single mode and an accurate value for the limit of the endlessly single-mode regime.

Foundations of photonic crystal fibres

Photonic Crystals Optical Waveguides Photonic Crystal Fibres (PCF) PCF Materials and Fabrication Finite Element Method Propagation Modes Problems in Dielectric Waveguides The Multipole Method Rayleigh Method Pole Hunting Properties of MOF Twisted Fibres.

Selective coating of holes in microstructured optical fiber and its application to in-fiber absorptive polarizers

An interesting feature of microstructured optical fibers (MOFs) is that their properties can be adjusted by filling or coating of the holes. Some applications require selective filling or coating, which has proved experimentally demanding. We demonstrate selective coating of MOFs with metal and use it to fabricate an in-fiber absorptive polarizer.

Ultrafast nonlinear optofluidics in selectively liquid-filled photonic crystal fibers

Selective filling of photonic crystal fibers with different media enables a plethora of possibilities in linear and nonlinear optics. Using two-photon direct-laser writing we demonstrate full flexibility of individual closing of holes and subsequent filling of photonic crystal fibers with highly nonlinear liquids. We experimentally demonstrate solitonic supercontinuum generation over 600 nm bandwidth using a compact femtosecond oscillator as pump source. Encapsulating our fibers at the ends we realize a compact ultrafast nonlinear optofluidic device. Our work is fundamentally important to the field of nonlinear optics as it provides a new platform for investigations of spatio-temporal nonlinear effects and underpins new applications in sensing and communications. Selective filling of different linear and nonlinear liquids, metals, gases, gain media, and liquid crystals into photonic crystal fibers will be the basis of new reconfigurable and versatile optical fiber devices with unprecedented performance. Control over both temporal and spatial dispersion as well as linear and nonlinear coupling will lead to the generation of spatial-temporal solitons, so-called optical bullets.

Dispersion management with microstructured optical fibers: ultraflattened chromatic dispersion with low losses.

We numerically demonstrate ultraflattened chromatic dispersion with low losses in microstructured optical fibers (MOFs). We propose using two different MOF structures to get this result. Both structures are based on a subset of a triangular array of cylindrical air holes; the cross sections of these inclusions are circular, and a missing hole in the fibers middle forms the core. In this MOF structure the diameters of the inclusions increase with distance from the fiber axis until the diameters reach a maximum. With this new design and with three different hole diameters, it requires only seven rings to reach the 0.2-dB/km level at lambda = 1.55 microm with a variation amplitude of dispersion below 3.0 x 10(-2) ps nm(-1) km(-1) of lambda = 1.5-1.6 microm. With the usual MOF (made from holes of identical diameter), we show that at least 18 hole rings are required for losses to decrease to < 1 dB/km at lambda = 1.55 microm.

Metallic mode confinement in microstructured fibres

We report the first long, uniform, optical fibers in which visible light is guided in a single mode by metallic reflection. We describe the fabrication, experiment and characterization of these metallic optical fibers and compare them with theoretical calculations.

Microstructured optical fibers: where’s the edge?

We establish that Microstructured Optical Fibers (MOFs) have a fundamental mode cutoff, marking the transition between modal confinement and non-confinement, and give insight into the nature of this transition through two asymptotic models that provide a mapping to conventional fibers. A small parameter space region where neither of these asymptotic models holds exists for the fundamental mode but not for the second mode; we show that designs exploiting unique MOF characteristics tend to concentrate in this preferred region.