Extremely short-length surface plasmon resonance sensors

The impact of the system design on the control of coupling between planar waveguide modes and surface plasmon polaritons (SPP) is analyzed. We examine how the efficiency of the coupling can be enhanced by an appropriate dimensioning of a multi-layer device structure without using additional gratings. We demonstrate that by proper design the length of the device can be dramatically reduced through fabrication a surface plasmon resonance sensor based on the SPP-photon transformation rather then on SPP dissipation

Recent advances in plasmonic sensor-based fiber optic probes for biological applications

Funding: This research was funded by National Natural Science Foundation of China (NSFC), grant number [61675008]. Acknowledgments: KN wishes to thank The Royal Society Kan Tong Po International Fellowship 2018 for the travel fund to visit Hong Kong Polytechnic University and Shenzhen Science and Technology Innovation Commission (Project GJHZ20180411185015272).Peer reviewedPublisher PD

Novel concept of multi-channel fiber optic surface plasmon resonance sensor

A novel multi-channel fiber optic surface plasmon resonance (SPR) sensor is reported. The sensing structure consists of a single-mode optical fiber, covered with a thin gold layer, which supports a surface plasmon (SP), and a Bragg grating. The Bragg grating induces coupling between the forward-propagating fundamental core mode and the back-propagating SP-cladding mode. As the SP-cladding modes are highly sensitive to changes in the refractive index of the surrounding medium, the changes can be accurately measured by spectroscopy of these hybrid modes. Multichannel capability is achieved by employing a sequence of Bragg gratings of different periods and their reading via the wavelength division multiplexing. Theoretical analysis and optimization based on the coupled-mode theory (CMT) is carried out and performance characteristics of the sensor are determined

Overview of the Characteristics of Micro- and Nano-Structured Surface Plasmon Resonance Sensors

The performance of bio-chemical sensing devices has been greatly improved by the development of surface plasmon resonance (SPR) based sensors. Advancements in micro- and nano-fabrication technologies have led to a variety of structures in SPR sensing systems being proposed. In this review, SPR sensors (from typical Kretschmann prism configurations to fiber sensor schemes) with micro- or nano-structures for local light field enhancement, extraordinary optical transmission, interference of surface plasmon waves, plasmonic cavities, etc. are discussed. We summarize and compare their performances and present guidelines for the design of SPR sensors

Fiber optics based surface plasmon resonance for label-free optical sensing

With the advancement in the laser technology and availability of low cost optical fibers, there is an increasing trend towards adoption of optical fibers as sensing element for development of optical sensors probes especially point-of-care sensing for environmental, biomedical and clinical application. Refractive index measurement through surface plasmon resonance has evolved to be, one of the most sensitive transducer for label-free sensing with high sensitivity. Surface plasmon resonance is a surface sensitive optoelectronic phenomenon, where light incident on a plasmonic metal surface at a given angle can excite a surface-bound electromagnetic wave, a surface plasmon. Associated with the surface plasmon is an evanescent field that probes local changes in the refractive index of the ambient medium that are used for monitoring analyte- supramolecular/ bio-molecular ligand interactions. Present review outlines a concise view on theoretical aspects of fiber optics based surface plasmon resonance phenomenon and comprehensive updated review on research and development for progression in the design of fiber optics based SPR sensors

Investigation of a SPR based refractive index sensor using a single mode fiber with a large D shaped microfluidic channel

In this work, a highly sensitive surface plasmon resonance (SPR) sensor based on a single mode fiber (SMF) incorporating a large microfluidic channel (MFC) for refractive index (RI) sensing is designed and optimized using a full-vectorial finite element method (FEM). The fluidic channel size can be varied according to the requirement due to the availability of the large cladding diameter of SMF, which makes it simple and easy to fabricate. The proposed novel sensor is favourable to both analytes and metallic strips. The D-shaped hollow section above the core is filled with the measurand analytes and a gold (Au) strip is deposited on the base of the MFC, as it is known as the most attractive metal for SPR. Our numerical simulations illustrate that the confinement loss of the designed sensor is highly influenced by the distance of the MFC from the core along with the width and thickness of the Au strip. The designed sensor shows an average sensitivity of 1350 nm/RIU and maximum sensitivity of 8250 nm/RIU in the sensing range of 1.33-1.35 and 1.41-1.43, respectively. However, for a small variation of na at a step of 0.005, within ranges like 1.415, 1.420, and 1.425, we have achieved a maximum sensitivity of 7000 nm/RIU, 9000 nm/RIU and 11000 nm/RIU, respectively. This novel SPR sensor with MFC can open up a new opportunity in the application of chemical and biological sensing

A numerical approach into new designs for SPR sensors in D-type optical fibers

This thesis investigates how to improve the performance of current designs of optical fiber sensors based on Surface Plasmon Resonance, and how to use a better understanding of the physical and sensing principles behind them to propose new sensing concepts and ideas. We adopt a methodology based on numerical simulations because they provide a better insight onto the operation of these sensors and because they allow an easy and quick way of testing new designs and concepts without the need to fabricate the sensors. We also show that these simulations have a good agreement with experimental results. We adopt a systematic approach to investigate the various parameters that influence the sensor performance, and present different sensors designs, where we study the localization, optical properties, shape and size of the metal components, combined with different type of fibers, resulting in the coupling between the plasmon and optical modes. Furthermore, we verify that choosing the optical modes used in sensing in multimode fibers can also have advantages. We investigate the use of modern artificial materials, such as metamaterials, as well as the inclusion of multiple wires in the fiber to enhance the performance of the SPR sensor. At a more fundamental level, we show that the control of the coupling between multiple plasmon modes in metal components and the optical modes in the fiber constitutes a new way to improve the performance of the sensor and can be inclusively used to develop a new type of SPR sensors capable of measuring simultaneously two variables, such as the external refractive index and temperatureEsta tese investiga como é possível melhorar o desempenho das estruturas atuais dos sensores de fibra ótica baseados em Ressonância Plasmónica de Superfície (SPR), bem como compreender melhor os princípios físicos e de sensorização na base do seu funcionamento, permitindo propor novos conceitos de sensores. Foi utilizada uma metodologia baseada em simulações numéricas, pois proporcionam um melhor entendimento do funcionamento desses sensores, constituindo uma maneira simples e rápida de testar novas estruturas e conceitos, sem a necessidade de fabricar os sensores. Mostra-se também que essas simulações têm uma boa concordância com os resultados experimentais. Foi adotada uma abordagem em que se investiga sistematicamente os diversos parâmetros que influenciam o desempenho do sensor e se apresentam diferentes estruturas de sensores onde foram estudadas a localização, propriedades óticas, forma e tamanho dos componentes metálicos, combinados com diferentes tipos de fibras, resultando no acoplamento entre os modos plasmónicos e os modos óticos. Também foi verificado que a escolha dos modos óticos utilizados na deteção em fibras multimodo pode apresentar vantagens. Foi investigado ainda o uso de materiais artificiais recentemente desenvolvidos, de que são exemplo os metamateriais, bem como, a inclusão de múltiplos fios metálicos na fibra, de forma a melhorar o desempenho dos sensores SPR. A um nível mais fundamental, foi demonstrado que o controlo do acoplamento entre os múltiplos modos plasmónicos gerados nos componentes metálicos e os modos óticos propagados na fibra constitui uma nova forma de melhorar o desempenho do sensor. Tal pode ser inclusivamente utilizado para desenvolver um novo tipo de sensores SPR capazes de medir simultaneamente duas variáveis, como por exemplo o índice de refração externo e a temperatura