The ability of a carboxylic acid functionalized spiropyran, SP, to act as a reversible and selective receptor for metal ions has been systematically examined. A series of spectroscopic measurements, combined with single-crystal X-ray diffraction have been employed in order to determine metal-ion sensitivity and selectivity, binding constants, solution compositions, binding kinetics as well as s...

A new method for suppression of coupling from guided optical modes into cladding modes in an optical fibre Bragg grating using a fibre with a strongly depressed cladding is proposed. Strong suppression of the coupling has been demonstrated both theoretically and experimentally. Optical fibre Bragg gratings have attracted much attention in recent years due to their numerous applications such as ...

An investigation of macrobending loss characteristics of a standard singlemode fiber (SMF28) for small bend radii is presented theoretically and experimentally, which includes the bend loss of the SMF28 with coating layers and the bare SMF28 after stripping the coating layers and chemical etching of partial cladding. The significant influence of reflection occurring at the interface between the...

In this work, a comparative study aimed to investigate the effects of cladding stripping on the external refractive index sensitivity in tapered and UV long period gratings is presented. Here, wet chemical etching combined with microscopic analysis allow us to identify the experimental dependence of the surrounding refractive index (SRI) sensitivity on the cladding radius for both grating types...

We developed an asymptotic formalism that fully characterizes the propagation and loss properties of a Bragg fiber with finite cladding layers. The formalism is subsequently applied to miniature air-core Bragg fibers with Silicon-based cladding mirrors. The fiber performance is analyzed as a function of the Bragg cladding geometries, the core radius and the material absorption. The problems of ...

We study the applicability of the weakly guiding approximation (WGA) to the modal analysis of an M-type optical fiber in which a ring-shaped core lies between two uniform cladding layers. Besides being dependent on the refractive indices, the accuracy of the approximation is shown to be substantially affected by the transverse dimensions of the core. The accuracy is characterized by calculating...

A long-period grating (LPG) based compact optical fiber sensor working in reflection mode is demonstrated. A technique to make a mirror on the cladding region of a fiber end-face to reflect only the cladding modes was realized by growing a polymeric microtip on the core region of the fiber end-face, by photopolymerization, followed by coating the fiber end-face with an aluminum film. Using the ...

Using the beam propagation method, an analytical expression of the reflection spectra of a Kretschmann configuration is derived in order to excite hybridized surface plasmonic polaritons (HSPPs). In this configuration, the cladding is a uniaxial dielectric with the optical axis parallel to the interface. The validity of the analytical expression is confirmed by a finite-difference time-domain a...

Confinement loss is comprehensively evaluated for TE, TM, and hybrid modes of Bragg fibers using a multilayer division method newly developed. We show the loss dependence on the core radius, wavelength, cladding index contrast, and the number of cladding pairs. The confinement loss is reduced in proportion to (a/b)(2N) and (n(2) (b)b/n(2) (a)a)(2N) for the TE and other three modes, respectively...

A highly porous optical-fiber cladding was developed for evanescent-wave fiber sensors, which contains sensor molecules, maintains guiding conditions in the optical fiber, and is suitable for sensing in aqueous environments. To make the cladding material (a poly(ethylene) glycol diacrylate (PEGDA) polymer) highly porous, a microsphere templating strategy was employed. The resulting pore network...