Superlens-Assisted Laser Nanostructuring of Long Period Optical Fiber Gratings (LPGs) for Enhanced Refractive Index Sensing

We present an innovative method to enhance Long Period Optical Fiber Gratings (LPGs) for refractive index sensing using microsphere-assisted superlens laser nanostructuring. This technique involves self-assembling a silica microsphere monolayer on LPGs' outer surface, followed by pulsed laser irradiation to generate nanoholes (300-500 nm) forming nanohole-structured LPGs (NS-LPGs). In experiments, two nanohole densities were compared for their impact on sensing performance in sucrose and glycerin solutions. The nanostructured NS-LPGs showed improved sensitivity by 16.08% and 19.57% compared to regular LPGs, with higher nanohole density yielding greater enhancement. Importantly, the permanent nanohole structures ensure durability in harsh environments, surpassing conventional surface-coating-based LPGs. Further improvements can be achieved by refining nanostructuring density and controlling nanohole size and depth. Our work represents a notable advancement in LPG sensor engineering, prioritizing surface nanostructuring over nano-coating, promising enhanced refractive index sensing applications.Comment: 13 pages, 5 figure

(INVITED)Chemical sensors based on long period fiber gratings: A review

Fiber optic devices are being increasingly employed in the fields of chemical and environmental sensing due to their important features, such as high accuracy, small size, chemical inertness, remote operation and multiplexing capabilities. In this work, a thorough review about the design, fabrication and characterization of fiber optic chemical sensors based on long period grating (LPG) technology is reported. The emphasis is placed on transducer designs and features as well as the techniques to enhance the sensitivity. Subsequently, coating materials to be deposited around the grating region, providing a selective response to the target analytes are described in detail. Finally, the different applications are reviewed, mainly related to the monitoring of environmental parameters, volatile organic compounds, hazardous gases, heavy metal ions, corrosion, marine salinity and food quality. The aim of this work is to deliver a comprehensive analysis regarding the state-of-the-art solutions about LPG-based chemical sensors and to summarize the current shortcomings and upcoming research paths

Graphene-Based Long-Period Fiber Grating Surface Plasmon Resonance Sensor for High-Sensitivity Gas Sensing

A graphene-based long-period fiber grating (LPFG) surface plasmon resonance (SPR) sensor is proposed. A monolayer of graphene is coated onto the Ag film surface of the LPFG SPR sensor, which increases the intensity of the evanescent field on the surface of the fiber and thereby enhances the interaction between the SPR wave and molecules. Such features significantly improve the sensitivity of the sensor. The experimental results demonstrate that the sensitivity of the graphene-based LPFG SPR sensor can reach 0.344 nm%−1 for methane, which is improved 2.96 and 1.31 times with respect to the traditional LPFG sensor and Ag-coated LPFG SPR sensor, respectively. Meanwhile, the graphene-based LPFG SPR sensor exhibits excellent response characteristics and repeatability. Such a SPR sensing scheme offers a promising platform to achieve high sensitivity for gas-sensing applications

Estudo Computacional de Biochip em Fibra ?ptica Baseado na Resson?ncia de Pl?smons de Superf?cie

O fen?meno de Resson?ncia de Pl?smons de Superf?cie (RPS) tem sido utilizado para a produ??o de biossensores por apresentar vantagens, como a possibilidade de miniaturiza??o, baixo custo, alta sensibilidade, alta seletividade e velocidade de resposta. Este trabalho tem como objetivo realizar um estudo computacional dos biossensores RPS em fibra ?ptica convencional (s?lica e/ou pol?mero). Neste caso, a casca da fibra ? removida na regi?o sensora, e o n?cleo ? recoberto por uma camada fina de metal, formando o biochip ?ptico. A an?lise computacional ? realizada com o aux?lio do software MATLAB, em que foi implementado o modelo de multicamadas de Fresnel, e o software COMSOL Multiphysics, baseado no m?todo dos elementos finitos, para a modelagem do biochip. O objetivo ? modificar e investigar os par?metros geom?tricos (dimens?es da fibra, espessura da camada met?lica) e eletromagn?ticos (comprimento de onda, ?ndice de refra??o, ?ngulo de incid?ncia, dentre outros) do biochip. Al?m disso, o tipo de metal utilizado ? de fundamental import?ncia, uma vez que sua oxida??o pode implicar na diminui??o do desempenho do biossensor, em contato com o analito (solu??o aquosa). O uso de metais nobres, como Ouro e Prata, na configura??o do biossensor oferece bons resultados, observados por meio dos valores de FWHM e refletividade, tanto para a ocorr?ncia do fen?meno RPS, quanto ao se analisar os par?metros de desempenho do biossensor. An?lises foram realizadas utilizando os modos de interroga??o angular e espectral. Por fim, tamb?m s?o consideradas configura??es de biochip com camadas de grafeno dispostas nas interfaces metal-fibra e metal-analito, com o fito de estudar a possibilidade de aumento da transmissividade do campo el?trico evanescente. Os resultados das an?lises s?o mostrados e discutidos

Diseño y caracterización de estructuras resonantes y estrategias de concentración avanzada aplicadasa dispositivos fotónicos

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Óptica, leída el 23-09-2020Efficient low-cost optoelectronic devices are used for many applications, for example, energy production, and sensing. The development of these devices can be step-forward using nanophotonic and nanoplasmonic structures. In this dissertation we propose, design, and analyze several nanostructures to improve the performance of these devices. For energy applications, we select amorphous silicon hydrogenated, and perovskite/crystallinesilicon tandem solar cells. We choose amorphous silicon solar cells because this material is abundant, non-toxic, long-life compared to organic solar cells, and can be fabricated at a low cost. The tandem perovskite/crystalline silicon solar cells are devices with potential power conversion efficiency > 30 %. Our designs are based on dielectric nanostructures. We applied a 1D nanostructure array to the top and bottom of amorphous silicon hydrogenated solar cells, in two separate designs. The absorption enhancement within the auxiliary layers of these devices is dissipated as heat and partially mitigate the defects resulted from the Staebler Wronski effect. A metasurface in the form of multilayer gratings embedded in the active layer of the perovskite top cell of the tandem device, improves the absorption efficiency in the whole device. A sawtooth periodic back texture has been optimized and tested to work with the metasurfacef or further improvement of the device performance. These nanostructures are arranged to maximize the absorption efficiency of the selected solar cells, mainly by reducing their total reflectance. The analysis and calculations are completed by modeling the conditions of the sun illumination, i.e, unpolarized light, and oblique incidence. The performance of the devices is calculated under these conditions...Los dispositivos optoelectrónicos eficientes y de bajo coste se utilizan en muchas aplicaciones. Por ejemplo, en la producción de energía y en sensores. La incorporacion de estructuras nanofotónicas y nanoplasmónicas es un paso adelante en el desarrollo de estos dispositivos. En esta tesis doctoral proponemos, diseñamos y analizamos varias nano-estructuras que mejoran el rendimiento de estos dispositivos. En aplicaciones para energía, hemos selecionado células de silicio amorfo hidrogenado, y células tándem de perovskitas y silicio cristalino. Hemos elegido las células solares de silicio cristalino porque es un material abundante, no tóxico, de larga vida comparada con las células orgánicas y fabricadas a bajo coste. Las células tándem perovskita/silicio cristalino son dispositivos con eficiencias de conversión superiores al 30 %. Nuestros diseños están basados en nano-estructuras dieléctricas. Hemos aplicado una nano-estructura periódica 1D a la superficie anterior y posterior de células solares de silicio amorfo hidrogenado en dos diseños separados. El aumento de la absorción en las capas auxiliares de estas células se disipa como calor y mitiga parcialmente los defectos producidos por el efecto Staebler-Wronski. Una metasuperficie hecha con redes apiladas en capas incluidas en las capa activa de la porción superior de una célula tándem mejora la eficiencia de absorción de todo el dispositivo...Fac. de Ciencias FísicasTRUEunpu