Design of more efficient luminescent solar concentrators by using peripherally dye-doped stacked optical fibers.

Ways of improving the optical efficiency of luminescent solar concentrators based on multiple poly(methyl methacrylate) plastic optical fibers peripherally doped with two promising types of dyes are analyzed by means of a Monte-Carlo computational model developed by us. By comparing the performance of optical fibers doped with lumogen red and lumogen yellow, or combinations of them at several concentrations, this work clarifies how to achieve a better compromise between the trapping efficiency of the sunlight and the reabsorption of the light emitted by the mixture in stacked optical fibers connected to a photovoltaic solar cell.

POF-Based Solar Concentrators Incorporating Dyes and Europium Chelates.

In this paper, useful models that enable time-efficient computational analyses of the performance of luminescent solar concentrators (LSCs) are developed and thoroughly described. These LSCs are based on polymer optical fibers codoped with organic dyes and/or europium chelates. The interest in such dopants lies in the availability of new dyes with higher quantum yields and in the photostability and suitable absorption and emission bands of europium chelates.

Modelling of polymer optical fiber-based solar concentrators.

A comprehensive model for the theoretical simulation of luminescent solar concentrators (LSCs) has been developed and examined. It can simulate the interdependent effects of multiple dopants having two main electronic energy states, which are incorporated simultaneously into the fiber core, as well as the effect of the cladding. The available experimental results appear to confirm the accuracy of the model, which is a valuable tool for gaining insight into the behavior of LSC prototypes, since it may guide the designers at the early stages of optimization processes.

Effects of Fabrication Methods on the Performance of Luminescent Solar Concentrators Based on Doped Polymer Optical Fibers.

In this work, we detail two types of fabrication processes of four polymer optical fibers doped with lumogen dyes. The fiber preforms have been manufactured with two different methods: extrusion and casting. We have compared the performance of the two types of fibers as luminescent solar concentrators by calculating their optical efficiencies and concentration factors.

Characterization of Double-Doped Polymer Optical Fibers as Luminescent Solar Concentrators.

This work reports on a diameter dependence analysis of the performance as luminescent solar concentrators of three self-fabricated polymer optical fibers (POFs) doped with a hybrid combination of dopants. The works carried out include the design and self-fabrication of the different diameter fibers; an experimental analysis of the output power, of the output irradiance and of the fluorescent fiber solar concentrator efficiency; a comparison of the experimental results with a theoretical model; a study of the performance of all the fibers under different simulated lighting conditions; and a calculation of the active fiber length of each of the samples, all of them as a function of the fiber core diameter. To the best of our knowledge, this paper reports the first analysis of the influence of the POF diameter for luminescent solar concentration applications.

Fabrication of Active Polymer Optical Fibers by Solution Doping and Their Characterization.

This paper employs the solution-doping technique for the fabrication of active polymer optical fibers (POFs), in which the dopant molecules are directly incorporated into the core of non-doped uncladded fibers. Firstly, we characterize the insertion of a solution of rhodamine B and methanol into the core of the fiber samples at different temperatures, and we show that better optical characteristics, especially in the attenuation coefficient, are achieved at lower temperatures. Moreover, we also analyze the dependence of the emission features of doped fibers on both the propagation distance and the excitation time.

Characterization of Chromatic Dispersion and Refractive Index of Polymer Optical Fibers.

The chromatic dispersion and the refractive index of poly(methyl methacrylate) polymer optical fibers (POFs) have been characterized in this work by using a tunable femtosecond laser and a Streak Camera. The characterization technique is based on the measurement of the time delays of light pulses propagating along POFs at different wavelengths. Polymer fibers of three different lengths made by two manufacturers have been employed for that purpose, and discrepancies lower than 3% have been obtained in all cases.

Optical Characterization of Doped Thermoplastic and Thermosetting Polymer-Optical-Fibers.

The emission properties of a graded-index thermoplastic polymer optical fiber and a step-index thermosetting one, both doped with rhodamine 6G, have been studied. The work includes a detailed analysis of the amplified spontaneous emission together with a study of the optical gains and losses of the fibers. The photostability of the emission of both types of fibers has also been investigated.

Optical Fiber Sensors for Aircraft Structural Health Monitoring.

Aircraft structures require periodic and scheduled inspection and maintenance operations due to their special operating conditions and the principles of design employed to develop them. Therefore, structural health monitoring has a great potential to reduce the costs related to these operations. Optical fiber sensors applied to the monitoring of aircraft structures provide some advantages over traditional sensors.

Amplified spontaneous emission in graded-index polymer optical fibers: theory and experiment.

In this work we analyze experimentally and theoretically the properties of amplified spontaneous emission (ASE) in a rhodamine-6G-doped graded-index polymer optical fiber. A theoretical model based on the laser rate equations describes the ASE features successfully. The dependence of the ASE threshold and efficiency on fiber length is analyzed in detail.

An optical fiber bundle sensor for tip clearance and tip timing measurements in a turbine rig.

When it comes to measuring blade-tip clearance or blade-tip timing in turbines, reflective intensity-modulated optical fiber sensors overcome several traditional limitations of capacitive, inductive or discharging probe sensors. This paper presents the signals and results corresponding to the third stage of a multistage turbine rig, obtained from a transonic wind-tunnel test. The probe is based on a trifurcated bundle of optical fibers that is mounted on the turbine casing.

Side-illumination fluorescence critical angle: theory and application to F8BT-doped polymer optical fibers.

In this work we have analyzed theoretically and experimentally the critical angle for the emission generated in doped polymer optical fibers as a function of different launching conditions by using the side-illumination fluorescence technique. A theoretical model has been developed in order to explain the experimental measurements. It is shown that both the theoretical and experimental critical angles are appreciably higher than the meridional critical angle corresponding to the maximum acceptance angle for a single source placed at the fiber axis.

A comprehensive analysis of scattering in polymer optical fibers.

The aim of this paper is to investigate the properties of the inhomogeneities that give rise to light scattering in polymer optical fibers (POFs). We perform several measurements in two commercial POFs of identical characteristics: these measurements, based on the side-illumination technique, consist in the detection of the total amount of scattered light guided along a POF sample under different launching conditions and in the acquisition of the corresponding near- and far-field patterns. We carry out complementary computer simulations considering inhomogeneities of different sizes at different positions inside the POF.

A self-tunable Titanium Sapphire laser by rotating a set of parallel plates of active material.

In a recent work, the authors reported the experimental demonstration of wavelength tuning in a single birefringent plate of Ti:sapphire crystal based on its own birefringence properties. In that device, the thickness of the active plate, limited by the width of the single order tuning spectral region, imposed a strong constraint in the power performance of the laser. The aim of this work is to overcome this limitation by using a set of several identical birefringent plates so that the wavelength tuning of the laser is obtained by synchronously rotating the plates in their own plane.

Ultrafast random laser emission in a dye-doped silica gel powder.

We report efficient random lasing in a ground powder of a novel solid-state material based on silica gel containing SiO(2) nanoparticles embedding rhodamine 6G (Rh6G) dye. Basic properties of random lasing such as emission kinetics, emission spectrum, and threshold of stimulated emission are investigated by using real-time spectroscopy. The laser-like emission dynamics can be accurately described by a light diffusive propagation model.