Numerical study of guided modes in arrays of metallic nanowires

We numerically investigate the band structure and guided modes within arrays of metallic nanowires. We show that bandgaps appear for a range of array geometries and that these can be used to guide light in these structures. Values of attenuation as low as 1.7 dB/cm are predicted for arrays of silver wires at communications wavelengths. This is more than 100 times smaller than the attenuation of the surface plasmon polariton modes on a single silver nanowire. © 2007 Optical Society of America

Spectroscopic and thermal properties of GeS2-based chalcohalide glasses

The low phonon energy of germanium sulphide glasses makes them ideal candidates as hosts for 1.3µm fibre amplifier applications. However, the GeS2 glass host suffers from a major drawback of poor rare-earth ion solubility. In an efficient device, the solubility of Pr ions has to be enhanced, without adversely affecting either the thermal or the spectroscopic properties of the glass. In the present investigation, we report the synthesis and optical properties of modified GeS2-based chalcohalide glasses with excellent thermal characteristics suitable for drawing low-loss optical fibres

Intensity measurement bend sensors based on periodically tapered soft glass fibers

We demonstrate a novel technique for tapering periodically an all-solid soft glass fiber, consisting of two types of lead silicate glasses, by the use of a focused CO2 laser beam and investigate the bend sensing applications of the periodically-tapered soft glass fiber. Such a soft glass fiber with periodic microtapers could be used to develop promising bend sensors with a sensitivity of -27.75 µW/m-1 by means of measuring the bend-induced change of light intensity. The proposed bend sensor exhibits a very low measurement error of down to ±1%

1.9µm operation of a Tm:Lead germanate glass waveguide laser

We report what we believe to be the first planar-technology waveguide laser in the 2-µm region. Laser operation of the 3H4 to 3H6 transition of Tm3+ ions in a lead germanate glass host has been observed in an ion-implanted planar waveguide

Improved large-mode area endlessly single-mode photonic crystal fibers

We numerically study the possibilities for improved large-mode area endlessly single mode photonic crystal fibers for use in high-power delivery applications. By carefully choosing the optimal hole diameter we find that a triangular core formed by three missing neighboring air holes considerably improves the mode area and loss properties compared to the case with a core formed by one missing air hole. In a realized fiber we demonstrate an enhancement of the mode area by ~30 % without a corresponding increase in the attenuation.Comment: 3 pages including 3 eps-figures. Accepted for Optics Letter

Engineering of composite metallic microfibers towards development of plasmonic devices for sensing applications

The paper discusses the analysis of tapered hybrid composite microfibers based on a metal-core and dielectric-cladding composite material system. Its advantages over the pure metal tips conventionally used, are the inherent enhanced environmental robustness due to inert borosilicate cladding and the capability of multiple excitation of the tapered nanowire through the length of the fiber due to the enabled total internal reflection at the borosilicate/air interface. Simulations through finite element method (FEM) have demonstrated an improved field enhancement at the tapered region of such microfibers. Furthermore, experimental results on tapering in copper based microfibers together with light coupling and propagation studies will be demonstrated revealing the potential for the development of plasmonic devices for sensing applications

Low-loss criterion and effective area considerations for photonic crystal fibers

We study the class of endlessly single-mode all-silica photonic crystal fibers with a triangular air-hole cladding. We consider the sensibility to longitudinal nonuniformities and the consequences and limitations for realizing low-loss large-mode area photonic crystal fibers. We also discuss the dominating scattering mechanism and experimentally we confirm that both macro and micro-bending can be the limiting factor.Comment: Accepted for Journal of Optics A - Pure and Applied Optic

Effects of taper parameters on free spectral range of non-adiabatic tapered optical fibers for sensing applications

We investigated the effects of taper parameters on the free spectral range of transmission spectrum of non-adiabatic tapers. From experimental results, the optimum profile for the tapered fiber in terms of taper angle, waist diameter, and length are 11.500 mrad, 10 μm, and 20 mm, respectively

A 1.9µm thulium doped lead germanate waveguide laser

Tm3+ doped lead germanate glass has already been shown to be a promising source of 1.9µm radiation using the 3H4 to 3H6 transition in a fibre geometry. The maximum vibrational energy of these glasses lies between that of silica and heavy metal fluoride glasses. This increases the radiative lifetime of the upper laser level in comparison to silicates while increasing the multiphonon non-radiative decay from the 3F4 pumping level into the upper laser level in comparison to fluorides. Thus the 1.9µm Tm3+ laser performance is enhanced in these glasses bringing fibre laser thresholds easily within reach of diode pumping. Recent work has also shown that such glasses give very low propagation loss guides (0.15 dB/cm) when implanted with He ions. Here we report lasing in a planar ion-implanted waveguide in Tm-doped lead germanate. This is the first report of lasing for thulium in any planar waveguide system and this is also the longest wavelength so far reported for such systems. This is also the first report of lasing in a glass host using ion-implantation as the means of waveguide fabrication

All-optical switching and strong coupling using tunable whispering-gallery-mode microresonators

We review our recent work on tunable, ultrahigh quality factor whispering-gallery-mode bottle microresonators and highlight their applications in nonlinear optics and in quantum optics experiments. Our resonators combine ultra-high quality factors of up to Q = 3.6 \times 10^8, a small mode volume, and near-lossless fiber coupling, with a simple and customizable mode structure enabling full tunability. We study, theoretically and experimentally, nonlinear all-optical switching via the Kerr effect when the resonator is operated in an add-drop configuration. This allows us to optically route a single-wavelength cw optical signal between two fiber ports with high efficiency. Finally, we report on progress towards strong coupling of single rubidium atoms to an ultra-high Q mode of an actively stabilized bottle microresonator.Comment: 20 pages, 24 figures. Accepted for publication in Applied Physics B. Changes according to referee suggestions: minor corrections to some figures and captions, clarification of some points in the text, added references, added new paragraph with results on atom-resonator interactio