Surface plasmon resonance-based fiber and planar waveguide sensors

Bulk surface Plasmons resonance devices have been researched for several decades. These devices have found a special niche as high-sensitivity refractive index sensor in biomedical applications. Recent advances in guided wave devices are rapidly changing the capabilities of such sensors, not only increasing convenience of use but also opening opportunities due to their versatility. This paper reviews many of these devices and presents some of their salient features

Real time monitoring of biofilm formation on coated medical devices for the reduction and interception of bacterial infections

Real time monitoring of bacterial attachment to medical devices provides opportunities to detect early biofilm formation and instigate appropriate interventions before infection develops. This study utilises long period grating (LPG) optical fibre sensors, incorporated into the lumen of endotracheal tubes (ETTs), to monitor in real time, Pseudomonas aeruginosa surface colonisation and biofilm formation. The wavelength shift of LPG attenuation bands was monitored for 24 h and compared with biofilm biomass, quantified using confocal fluorescence microscopy imaging. Biofilm formation was compared on uncoated ETTs and optical fibres, and on a biofilm resistant acrylate polymer, after challenge in an artificial sputum or minimal growth medium (RPMI-1640). The LPG sensor was able to detect a biofilm biomass as low as 81 µg/cm 2 , by comparison with the confocal image quantification. An empirical exponential function was found to the link optical attenuation wavelength shift with the inverse of the biofilm biomass, allowing quantification of biofouling from the spectral response. Quantification from the sensor allows infection interception and early device removal, to reduce, for example, the risk of ventilator associated pneumonia

Nano-grating assisted light absorption enhancement for msm-pds performance improvement: An updated review

The primary focus of this review article mainly emphasizes the light absorption enhancement for various nanostructured gratings assisted metal-semiconductor-metal photodetectors (MSM-PDs) that are so far proposed and developed for the improvement of light capturing performance. The MSM-PDs are considered as one of the key elements in the optical and high-speed communication systems for applications such as faster optical fiber communication systems, sensor networks, high-speed chip-to-chip interconnects, and high-speed sampling. The light absorption enhancement makes the MSM-PDs an ideal candidate due to their excellent performances in detection, especially in satisfying the high-speed or high-performance device requirements. The nano-grating assisted MSM-PDs are preordained to be decorous for many emerging and existing communication device applications. There have been a significant number of research works conducted on the implementa-tion of nano-gratings, and still, more researches are ongoing to raise the performance of MSM-PDs particularly, in terms of enhancing the light absorption potentialities. This review article aims to provide the latest update on the exertion of nano-grating structures suitable for further developments in the light absorption enhancement of the MSM-PDs

Hybrid Heterostructures for SPR Biosensor

Surface plasmon resonance (SPR) based biosensors have been enormously studied in the last decade for their better sensitivity. In recent years hybrid heterostructures are getting popularity to implement these SPR biosensors for their superior sensing capability. This chapter demonstrates the details of SPR technology with two recently studied prism-based hybrid heterostructures. These heterostructures are made up of conventional SPR biosensors with two additional layers of recently invented transition metal dichalcogenides, platinum di-selenide (PtSe2), and highly sensitive 2D material, tungsten di-sulfide (WS2). Angular interrogation method is discussed to investigate the sensing capabilities of the sensors which prove the superiority of the Ag-PtSe2-WS2 structure. The sensing capability of this structure has been found at least 1.67 times higher than that of the conventional non-hybrid structures, respectively, with comparable FOM and QF. A comparison table has been provided at the end of this chapter which also shows the impressive performance of the hybrid heterostructures for SPR biosensors. Proper demonstration with a suitable example of this chapter will emphasize the potential use of hybrid heterostructure based SPR biosensors in prospective medical diagnostics and biomedical detection applications

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

Method for Determining the Plasmon Resonance Wavelength in Fiber Sensors Based on Tilted Fiber Bragg Gratings

Surface plasmon resonance-based fiber-optic sensors are of increasing interest in modern sensory research, especially for chemical and biomedical applications. Special attention deserves to be given to sensors based on tilted fiber Bragg gratings, due to their unique spectral properties and potentially high sensitivity and resolution. However, the principal task is to determine the plasmon resonance wavelength based on the spectral characteristics of the sensor and, most importantly, to measure changes in environmental parameters with high resolution, while the existing indirect methods are only useable in a narrow spectral range. In this paper, we present a new approach to solving this problem, based on the original method of determining the plasmon resonance spectral position in the automatic mode by precisely calculating the constriction location on the transmission spectrum of the sensor. We also present an experimental comparison of various data processing methods in both a narrow and a wide range of the refractive indexes. Application of our method resulted in achieving a resolution of up to 3 × 10-6 in terms of the refractive index

Mejoramiento de la sensibilidad en un biosensor óptico multicapa con grafeno

Las excepcionales propiedades electrónicas y ópticas del grafeno tales como alta mobilidad de los portadores de carga, transparencia óptica, fotoluminiscencia, además de su flexibilidad, robustés, y con solo un átomo de espesor, ha permitido la creación de dispositivos de tamaño nanométrico o micrométrico con estabilidad ambiental. Estas propiedades permiten el uso de grafeno en dispositivos ópticos complejos tales como el láser de cristal fotónico, conmutador óptica, dispositivos lógicos, y sensores ópticos entre muchos otros. El grafeno es útil en sensores porque es un material multifuncional que puede medir la concentración de gases, presión, deformación, campo magnético, temperatura, luz, etcétera. En las tecnologías de detección óptica, el grafeno se ha utilizado para detectar agentes biológicos como drogas, biomoléculas, anticuerpos biológicos, biorreceptores sintéticos, micotoxinas, etcétera. En este trabajo, propusimos un biosensor compuesto por un metal/dielectrico 2D/ sistema multicapa de grafeno como base m´as en medio biológico a analizar. Hemos estudiado la sensibilidad de un biosensor de grafeno, a través de la reflexión total atenuada (ATR) mediante el método de matriz de transferencia, para diferentes valores de parámetros físicos y geométricos de la estructura. Encontramos que el biosensor es sensible al valor del potencial químico del grafeno. Por otro lado, encontramos que se mejora la sensibilidad al aumentar el número de láminas de grafeno

Optical Enhancement in Periodic Plasmonic Gratings for SERS and Metal-Semiconductor-Metal Photodetectors (MSM-PDs) Applications

This dissertation is aimed to numerically study the effect of plasmonic grating electrodes on the efficiency of metal-semiconductor-metal photodetectors (MSM PDs) and the sensitivity of Surface Enhanced Raman Spectroscopy (SERS). This research can benefit many areas of nanoscience and optics, including plasmonic applications, such as, super lenses, nano-scale optical circuits, optical filters, surface plasmon enhanced photo-detectors solar cells, imaging sensors, charge-coupled devices (CCD), and optical-fiber communication systems. Several parameters, wire widths and thickness, gap space, taper angle, and the incident wavelength and angle, were investigated. The goal of this research is to utilize the plasmonic phenomenon by using plasmonic gratings to develop and improve detectivity of metal-semiconductor-metal photodetectors (MSM-PDs) and sensitivity of SERS. The dissertation includes the study of the substrate type ‒ SiO2 and SiO2/Si for SERS applications, and GaAs substrates for MSM PDs ‒ on the optical enhancement. In addition, the impact of the period of the nanograting, single and dual-width structures, is examined as well. Then, a comparison is conducted between these types to determine the optimum periods. The results show that dual-width structures can improve the incident light two times more than the single-width structures. The work also introduces a new method, which incorporates the current density of the device when calculating the overall current enhancement in order to model real performance more accurately. Using this method indicates that since plasmonic hot spots align well with areas of large current density, the optical enhancement can play an even larger role in total current improvement. The impact of taper angles, positive and negative, is also studied in detail. The results suggest significant optical enhancements can be achieved by using tapered nanoslits instead of vertical sidewall structures. Finally, the effect of the incident wave angle on the enhancements is considered as well. Interestingly, the results show a significant role that incident wave angle can play on both the incident light enhancements

Surface plasmons for enhanced metal-semiconductor-metal photodetectors

Surface Plasmon Polaritons (SPPs) are quantized charge density oscillations that occur when a photon couples to the free electron gas of the metal at the interface between a metal and a dielectric. The extraordinary properties of SPP allow for sub-diffraction limit waveguiding and localized field enhancement. The emerging field of surface plasmonics has applied SPP coupling to a number of new and interesting applications, such as: Surface Enhanced Raman Spectroscopy (SERS), super lenses, nano-scale optical circuits, optical filters and SPP enhanced photodetectors. In the past decade, there have been several experimental and theoretical research and development activities which reported on the extraordinary optical transmission through subwavelength metallic apertures as well as through periodic metal grating structures. The use of SPP for light absorption enhancement using sub-wavelength metal gratings promises an increased enhancement in light collection efficiency of photovoltaic devices. A subwavelength plasmonic nanostructure grating interacts strongly with the incident light and potentially traps it inside the subsurface region of semiconductor substrates. Among all photodetectors, the Metal-Semiconductor-Metal photodetector (MSM-PD) is the simplest structure. Moreover, due to the lateral geometry of the MSM-PDs, the capacitance of an MSM-PD is much lower than capacitances of p-i-n PDs and Avalanche PDs, making its response time in the range of a few tens of picoseconds for nano-scale spacing between the electrode fingers. These features of simple fabrication and high speed make MSM-PDs attractive and essential devices for high-speed optical interconnects, highsensitivity optical samplers and ultra-wide bandwidth optoelectronic integrated circuits (OEIC) receivers for fibre optic communication systems. However, while MSM-PDs offer faster response than their p-i-n PD and avalanche PD counterparts, their most significant drawbacks are the high reflectivity of the metal fingers and the very-low light transmission through the spacing between the fingers, leading to very low photodetector sensitivity. This thesis proposes, designs and demonstrates the concept of a novel plasmonicbased MSM-PD employing metal nano-gratings and sub-wavelength slits. Various metal nano-gratings are designed on top of the gold fingers of an MSM-PD based on gallium arsenide (GaAs) for an operating wavelength of 830 nm to create SPP-enhanced MSM-PDs. Both the geometry and light absorption near the designed wavelength are theoretically and experimentally investigated. Finite Difference Time Domain (FDTD) simulation is used to simulate and design plasmonic MSM-PDs devices for maximal field enhancement. The simulation results show more than 10 times enhancement for the plasmonic nano-grating MSM-PD compared with the device without the metal nano-gratings, for 100 nm slit difference, due to the improved optical signal propagation through the nano-gratings. A dual beam FIB/ SEM is employed for the fabrication of metal nano-gratings and the sub-wavelength slit of the MSM-PD. Experimentally, we demonstrate the principle of plasmonics-based MSM-PDs and attain a measured photodetector responsivity that is 4 times better than that of conventional single-slit MSM-PDs. We observe reduction in the responsivity as the bias voltage increases and the input light polarization varies. Our experimental results demonstrate the feasibility of developing high-responsivity, low bias-voltage high-speed MSM-PDs. A novel multi-finger plasmonics-based GaAs MSM-PD structure is optimized geometrically using the 2-D FDTD method and developed, leading to more than 7 times enhancement in photocurrent in comparison with the conventional MSM-PD of similar dimensions at a bias voltage as low as 0.3V. This enhancement is attributed to the coupling of SPPs with the incident light through the nano-structured metal fingers. Moreover, the plasmonic-based MSM-PD shows high sensitivity to the incident light polarization states. Combining the polarization sensitivity and the wavelength selective guiding nature of the nano-gratings, the plasmonic MSM-PD can be used to design high-sensitivity polarization diversity receivers, integrating polarization splitters and polarization CMOS imaging sensors. We also propose and demonstrate a plasmonic-based GaAs balanced metalsemiconductor- metal photodetector (B-MSM-PD) structure and we measure a common mode rejection ratio (CMRR) value less than 25 dB at 830nm wavelength. This efficient CMRR value makes our B-MSM-PD structure suitable for ultra-high-speed optical telecommunication systems. In addition, this work paves the way for the monolithic integration of B-MSM-PDs into large scale semiconductor circuits. This thesis demonstrates several new opportunities for resonant plasmonic nanostructures able to enhance the responsivity of the MSM-PD. The presented concepts and insights hold great promise for new applications in integrated optics, photovoltaics, solidstate lighting and imaging below the diffraction limit. In Chapter 10 we conclude this thesis by summarizing and discussing some possible applications and future research directions based on SPP field concentration

Surface Plasmon Resonance Sensor Interogation with Cladding Modes Excited by Tilted Fiber Bragg Grating

RÉSUMÉ Le but de ce projet est de developer de nouvelles configurations de capteurs à résonance de plasmons de surface basés sur les réseaux de Bragg. Il se concentre sur l’étude de quatre configurations novatrices de capteurs à résonances de plasmons et de leur application en mesure d’indice de réfraction environnant. Premièrement, une nouvelle approche de mesure d’indice de réfraction utilisant un coupleur à double gaine et un réseau de Bragg pour capturer les modes de gaine en réflexion est démontrée. Le spectre optique ainsi que la puissance des modes de gaines sont obtenus à travers l’utilisation d’un coupleur à fibre à double gaine conçu sur mesure et connecté à un réseau de Bragg à haute réflectivité écrit dans une fibre photosensible standard légèrement inclinée et gravée de façon à la coupler au diamètre intérieur de la fibre à double gaine. Ce dispositif est capable de capturer les modes de gaines autant d’ordres inférieurs que supérieurs en réflexion de manière simple et efficace. Il devient alors possible de déterminer l’indice de réfraction environnant avec une extrême sensibilité à partir d’une perte de puissance mesurée de ≈ 91% de la puissance initiale permettant d’obtenir une résolution de 1.4333×10-5 unités d’indice de réfraction (UIR) entre 1.37 et 1.45. Le dispositif permet donc une large bande d’opération entre 1.30 et 1.45 UIR qui offre la possibilité de discriminer chacun des modes de gaine capturés. L’approche proposée peut être adaptée à plusieurs autres types de capteurs de courbure, température, indice de réfraction et d’onde évanescente. Deuxièmement, une nouvelle approche de capteur à résonance de plasmons de surface à fibre utilisant la configuration de coupleur à double gaine décrite précédemment ainsi qu’un réseau de Bragg incliné et recouvert d’or est démontrée. Cette nouvelle approche d’interrogation basée sur le spectre de réflexion offre une amélioration de la bande d’opération du dispositif en comparaison aux techniques préexistantes. Le dispositif permet la détection de résonances de plasmons de surfaces dans le spectre de réflexion et de transmission, permettant aisément une comparaison avec les techniques standards préexistantes qui utilisent le spectre de transmission. Le capteur possède aussi une large bande d’opération allant de 1.335 à 1.432 UIR et une sensibilité de 510.5 nm/UIR.----------ABSTRACT The objective of this Thesis is to develop novel schemes in surface Plasmon resonance (SPR) sensing with Bragg gratings. The thesis focuses on research studies on the sensing characteristics of four novel configurations of SPR and surrounding refractive indices (SRI) sensors. Firstly, a novel SRI measurement scheme has been demonstrated using a double-clad fiber coupler (DCFC) and a fiber Bragg grating (FBG) to capture cladding modes in reflection. The optical spectra and power in the cladding modes are obtained through the use of a specially designed DCFC spliced to a highly reflective FBG written into slightly cladding-etched standard photosensitive single mode fiber to match the diameter to the inner cladding of the DCFC. The device is capable of capturing low and high order backward propagating cladding modes simply and efficiently. The device is capable of measuring the SRI with an extremely high sensitivity with a total power drop by ≈ 91% of its initial value and a resolution of 1.433×10-5 RIU between 1.37 and 1.45 RIU. The device provides a large SRI operating range from 1.30 to 1.45 RIU with sufficient discrimination for all individual captured cladding modes. The proposed scheme can be adapted to many different types of bend, temperature, refractive index and other evanescent wave based sensors. Secondly, a novel optical fiber SPR sensor scheme is demonstrated using reflected guided cladding modes captured by the above mentioned DCFC, and excited in a gold coated fiber with a tilted Bragg grating (TFBG). This new interrogation approach which is based on the reflection spectrum provides an improvement in the operating range of the device over previous techniques. The device allows detection of SPR in the reflected spectrum and also in the transmitted spectrum as well, making it far easier in comparison with previous standard techniques which use the transmission spectrum. The sensor has a large operating range from 1.335 to 1.432 RIU, and a sensitivity of 510.5 nm/RIU. The device shows strong dependence on the polarization state of the guided core mode which can be used to turn the SPR on or off