Search results for "Physics::Optics"

Surface plasmon-polariton amplifiers

2012

Propagation of surface plasmons at metal surfaces is receiving much interest nowadays because of its broad range of potential applications, like subwavelength photonics or biosensing. Although plasmonic devices achieve unique properties, surface plasmons suffer from high attenuation because of the absorption losses in the metal. This limitation can be overcome by providing the material adjacent to the metal with optical gain. Under these conditions, absorption losses are compensated and the propagation length of the plasmon is significantly increased. In this work, a review of plasmonic amplifiers is presented. To this end, the state of the art of such devices and the propagation characteri…

Finite-Size and Illumination Conditions Effects in All-Dielectric Metasurfaces

2022

Dielectric metasurfaces have emerged as a promising alternative to their plasmonic counterparts due to lower ohmic losses, which hinder sensing applications and nonlinear frequency conversion, and their larger flexibility to shape the emission pattern in the visible regime. To date, the computational cost of full-wave numerical simulations has forced the exploitation of the Floquet theorem, which implies infinitely periodic structures, in designing such devices. In this work, we show the potential pitfalls of this approach when considering finite-size metasurfaces and beam-like illumination conditions, in contrast to the typical infinite plane-wave illumination compatible with the Floquet t…

Waveguiding properties of a photonic crystal fiber with a solid core surrounded by four large air holes

2009

The polarization-dependent guiding properties of a hexagonal-lattice photonic crystal fiber with a solid-core surrounded by four large air holes are investigated. The appearance of a polarization dependent cutoff frequency, together with several parameters as the birefringence, the modal effective area, the group velocity dispersion and the polarization dependent loss are analyzed. A collection of fibers with different structural parameters were fabricated and characterized. An effective anti-guide structure from at least 450 nm to 1750 nm, a polarizing fiber with a polarization dependent loss of 16 dB/m at 1550 nm, and an endlessly singlemode polarization-maintaining fiber with group biref…

<title>Fibers supporting super-Gaussian beams: cladding effects</title>

1996

We define a matching function that describes the amplitude variations produced over supergaussian beams, by cladding optical fibers that, if uncladded, can sustain this type of beams as Eigenmodes.

2017

Tailored tellurite-glasses possess excellent thermo-viscous ability and linear/nonlinear optical properties. Here, bringing together the merits of these materials with fiber optic technology, we report on the first tellurite-based core-clad dual-electrode composite fiber made by direct, homothetic preform-to-fiber thermal co-drawing. The rheological and optical properties of the selected glasses allow both to regulate the metallic melting flow and to manage the refractive index core/clad waveguide profile. We demonstrate the electrical continuity of the electrodes over meters of fiber. We believe the drawing of architectures merging electrical and optical features in a unique elongated wave…

A Refractive Index Sensor Based on the Resonant Coupling to Cladding Modes in a Fiber Loop

2013

We report an easy-to-build, compact, and low-cost optical fiber refractive index sensor. It consists of a single fiber loop whose transmission spectra exhibit a series of notches produced by the resonant coupling between the fundamental mode and the cladding modes in a uniformly bent fiber. The wavelength of the notches, distributed in a wavelength span from 1,400 to 1,700 nm, can be tuned by adjusting the diameter of the fiber loop and are sensitive to refractive index changes of the external medium. Sensitivities of 170 and 800 nm per refractive index unit for water solutions and for the refractive index interval 1.40-1.442, respectively, are demonstrated. We estimate a long range resolut…

Resonant and thermal changes of refractive index in a heavily doped erbium fiber pumped at wavelength 980 nm

2004

We report a theoretical and experimental study of the refractive index variation in a heavily doped erbium silica fiber within the spectral range 1500-1580 nm under the pumping at the wavelength 980 nm. The two main contributions in the refractive index change are addressed the resonant part determined by the saturation effect in the fiber and the thermal part stemming from the fiber heating due to the excited-state absorption and Stokes losses. We demonstrate that the thermal contribution in the resultant refractive index change is a notable value, which is the feature of erbium fibers with a high concentration of erbium ions.

Fundamental-mode cutoff in liquid-filled Y-shaped microstructured fibers with Ge-doped core

2008

We report on the cutoff characteristics of a Ge-doped Y-shaped microstructured fiber in which the holes are filled with a liquid of refractive index higher than silica but lower than the Ge-doped core. It is found that the cutoff wavelength was very sensitive to temperature variations as a result of the refractive index changes of the liquid. The basic properties of such a fiber permit the fabrication of wideband tunable short-pass filters, as well as temperature sensors with high sensitivity. A temperature sensitivity of 25 nm/degrees C is reported.

Two-core transversally chirped microstructured optical fiber refractive index sensor

2014

We present a sensing architecture consisting of a two-core chirped microstructured optical fiber (MOF) for refractive index sensing of fluids. We show that by introducing a chirp in the hole size, the MOF can be a structure with decoupled cores, forming a Mach-Zehnder interferometer in which the analyte directly modulates the device transmittance by its differential influence on the effective refractive index of each core mode. We show that by filling all fiber holes with analyte, the sensing structure achieves high sensitivity (transmittance changes of 300 per RIU at 1.42) and has the potential for use over a wide range of analyte refractive index.

Plasmonic and diffractive nanostructures for light trapping—an experimental comparison

2015

Metal nanoparticles and diffractive nanostructures are widely studied for enhancing light trapping efficiency in thin-film solar cells. Both have achieved high performance enhancements, but there are very few direct comparisons between the two. Also, it is difficult to accurately determine the parasitic absorption of metal nanoparticles. Here, we assess the light trapping efficiencies of both approaches in an identical absorber configuration. We use a 240 nm thick amorphous silicon slab as the absorber layer and either a quasi-random supercell diffractive nanostructure or a layer of self-assembled metal nanoparticles for light trapping. Both the plasmonic and diffractive structures strongly…