In this work, we show the feasibility of using the evanescent field of a microfiber to excite the fluorescence of a fluorophore deposited on the surface of a polymer optical fiber. The fluorescence intensity gathered by the polymer optical fiber from the emitted on its surface has been measured for several gaps with the excitation fiber, showing a remarkable influence of the evanescent field at distances as high as 2.5mm. A further development of a device based on wrapping the microfiber around the polymer one has been measured, proving a more efficient fluorescence excitation.
In this work we experimentally show how the technology of surface plasmon resonance (SPR) in doubly deposited uniform- waist tapered optical fiber sensors (DLUWTs) can be extended into the visible region (around 520 nm) by changing the thicknesses of the deposited layers. In this way, by using DLUWTs we can cover, in an easy and versatile way, a total wavelength range over 1000 nm wide, having shown in the past how this same kind of sensors can be usable in the communication band. The possibilities of fiber sensors can then be applied to the region of visible wavelengths, which is very interesting from the biological point of view.
The history of optics is a very rich field of science and it is possible to find many simple and significant examples of the
application and success of the experimental method and therefore is a very good tool to transmit to the student the way science proceeds and to introduce the right spirit of critical analysis, building and testing of models, etc. Optical phenomena are specially well suited for this because in fact optical observations and experiments have made science advance in a crucial way in many different periods of history, because they are in many cases quite visual, quite simple in concept and it is very easy to produce experimental setups in classrooms. Also, the intrinsic multidisciplinary character of Optics, which is a subject that has historically influenced in a notorious way fields as art, philosophy, religion and cultural and social studies in general, provide a very wide frame that permits to apply these examples to many different auditories. We present here some reflections about the role that history of optics can play in teaching and show some real examples of its application during the many years that we have been employing it in the context of the Optics School of the Complutense University of Madrid, Spain.
A miniature fiber Bragg grating strain rosette is presented. The proposed design is made possible through
the development of low curvature radius lossless tapers, thus offering advantages in miniaturization of the
rosette configuration. We report on the experimental validation of the miniature rosette design,
demonstrating its effective operation.
In this work, the performance of uniform-waist tapered optical fiber sensors based on SPR with Indium Nitride (InN) as
dielectric layer has been experimentally studied. The obtained results show that the overall performance in terms of
reliability, long term stability and sensitivity is improved. Furthermore, the dependence of the sensitivity with the
thickness of the dielectric layer is also studied, showing that increases as the thickness decreases while the well known
trend to excite the surface plasmons at longer wavelengths or higher refractive index of the outer medium is kept. Thus, a
novel application of the InN to optical fiber sensors is demonstrated. The use of this material would be of great interest to
produce new, improved, SPR-based devices for chemical and biological sensing.
In this work we present experimental results that confirm the influence of an absorptive surrounding medium in the behavior
of conventional SPR fiber sensors. It can be observed that when a plasmon resonance coincides with a wavelength
absorbed by the medium, the depth of the dip is affected, as predicted in the simulations. The results are important from
the basic point of view, since the influence of absorptive medium in plasma waves has not been sufficiently studied up to
date and they can also be used as the basis for a new method of SPR-based refractometry selective to specific analytes
without the need of the addition of recognizing elements to the transducer.
It is shown how the design possibilities offered by double-layer uniform-waist tapered optical fibers (DLUWTs) permit
to move the wavelength detection range to adapt the response of the sensors to varied conditions. In particular, we have
obtained very good experimental curves showing that we can achieve plasmon resonances in the C-band of the optical
communications, around 1.5 μm, for the range of refractive indices of aqueous media, highly interesting in the
biosensors field. Also, we show results for other interesting wavelength region, around 500 nm, where we can take
advantage of the absorption peaks of the analytes. Finally, we explore the possibilities of using InN as a dielectric
material for the second layer of the deposition. These results contribute to considerably expand the applicability and
performance of SPR fiber sensors.
A new interrogation method based on Fibre Bragg Gratings (FBG) for Surface Plamon Resonance (SPR) sensors in
the region of refractive indices of aqueous solutions is described. Two FBGs are selected with their Bragg wavelengths
at opposite sides of the plasmon resonance peak. The response of the system can be made independent of the
fluctuations of the optical power source, and the linearity and the sensitivity of the sensor are improved. The use of the
spectral selectivity of gratings for the interrogation of SPR sensors in different configurations is also promising in terms
of multiplexing, temperature referencing or multiparameter detection.
A collection of lubricant oils from different types of turbines, which were characterized by different degrees of
degradation, were analyzed by means of UV-VIS-NIR absorption spectroscopy, fluorescence spectroscopy and scattering
measurements. All these measurements were performed by means of optical fiber-based instrumentation that made use of
LEDs or compact lamps for illumination and miniaturized spectrometers for detection. Multivariate data analysis was
used to successfully correlate the wide optical spectral signature of lubricant oils to some of the most important
parameters for indicating the degree of degradation of the oil, such as TAN, JOAP-index, water content, and phosphorus.
Although many optical fiber sensors have been proposed for chemical, environmental or biological measurements, it
seems that the potential of this kind of devices has not been fully exploited. In this paper we discuss the possibilities of
doubly-deposited uniform-waist tapered fibers (DL-UWTs) for the development of new sensors that can become a new
standard in the field of Surface Plasmon Resonance (SPR) based sensors and contribute to the extension of the range of
application of fiber technology to the mentioned fields. We also compare different configuration and evaluate some
relevant features of DL-UWTs, as the possibility of fully independence of polarization or the excitation of multiple
plasmons.
An optical-fiber salinometer has been evaluated during a two-week measurement campaign in the Baltic Sea. The obtained results in three different tests are presented in comparison with those obtained with a standard electric CTD sonde commercially available.
Novel devices consisting of uniform-waist tapered optical fibers with a double layer (metal plus dielectric) deposition are presented and their properties in terms of optical transmission are studied. Excitation of surface plasmons in the metallic layers is experimentally shown. These devices can be used as basis for new sensors.
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