Amplitude Interrogation Method Research Articles

A unique wheel-shaped exposed core LSPR-PCF sensor for dual-peak sensing: Applications in the optical communication bands, M-IR region and biosensing

Photonic Crystal Fibers (PCF) effectiveness in practice decreases if the fabrication of the sensor becomes too complex. Keeping this in mind, we propose a one-of-a-kind wheel shaped PCF sensor with an exposed core containing only three air holes with exceptional sensing features. The sensor is equipped with dual plasmonic layers, Indium Tin Oxide (ITO, 10 % wt) and silver (Ag) with a coating of TiO2 to enhance the sensing capabilities and provide protection against oxidation. The sensor's distinctive configuration enables it to exhibit two distinct peaks within a range of refractive index from 1.32 to 1.38 for y-polarization and from 1.35 to 1.38 for x-polarization. The sensor specifications have been optimized to achieve the maximum levels of wavelength sensitivity (WS) and double peak shift sensitivity (DPSS). The sensor portrays a WS of 50,652 nm/RIU and the highest DPSS ever recorded, measuring 50,000 nm/RIU. Additionally, the sensor exhibits a significantly high scale of amplitude sensitivity (AS) of 1668.34 RIU−1 which is a very remarkable value considering silver as plasmonic material along with an outstanding figure of merit (FOM) of 1017.11 RIU−1. In addition, our sensor is able to manifest resolutions in the order of 10−6, demonstrating a resolution of 5.94 × 10−6 RIU with the deployment of amplitude interrogation method and 1.97 × 10−6 RIU with the wavelength interrogation method. The design spans an extensive spectrum, covering ultraviolet to mid-infrared wavelengths, enabling detection of biomolecules and biochemicals, along with operation in the optical communication band.

Design of a nanoscale gold-coated photonic crystal fiber biosensor

A simple two-layer refractive index sensor based on surface plasmon resonance has been proposed in this work, which evinces high sensitivity for detecting unknown analytes. This sensor design includes hexagonal- and octagonal-shaped air-hole rings, which have been introduced in the first and second layers, respectively. By performing this amalgamation of different types of air holes, this gold-coated plasmonic sensing scheme provides the broad sensing limit of the analyte, which is 1.32–1.40. The sensing performance has been examined by applying the finite element method, which is being used for modeling complex and irregular-shaped geometry. The wavelength interrogation method has demonstrated a maximal wavelength sensitivity of 9,000 nm/RIU (refractive index unit). The maximal amplitude sensitivity of 1902 RIU−1 has been exhibited in the y-polarized mode using the amplitude interrogation method. Moreover, the maximal sensor resolution of 1.11 × 10−5 RIU covers the entire sensing range. Furthermore, by adjusting the air-hole diameter, pitch, and depth of the gold layer coating, many more investigations have been demonstrated in this design. This highly sensitive sensor is very convincing to be used in many applications like chemical, biological, and also in physical sensing analyses.

Surface plasmon resonance sensor composed of microstructured optical fibers for monitoring of external and internal environments in biological and environmental sensing

To achieve simultaneous detection of analytes with different states in internal and external environments, A microstructured optical fibers (MOFs) biochemical sensor based on surface plasmon resonance (SPR) is proposed. The micro-polished dual-open-loop structure with anti-corrosive gold as the sensing layer is designed, which greatly improves the phase matching between fundamental mode and plasmonic mode to further stimulate SPR effect. Numerical simulation by the full-vector finite element method (FEM) reveals that the even mode for y-polarized state has better sensing properties due to the more eminent electric field distribution and shift of the confinement loss peak. In order to better evaluate and analyze the output characteristics of this sensor, the wavelength modulation and amplitude interrogation methods are adopted. The results manifest that the maximum wavelength sensitivity (WS) of 20,000 nm/RIU and amplitude sensitivity (AS) of 208.21 RIU−1 with resolution (R) of 10−6 order can be acquired in operable infrared region (900–2,750 nm). Furthermore, this sensor has realized a broad range of detection for gas and liquid analytes with RIs from 1.00 to 1.38. On account of its simple structure, low cost, and industrial compatibility, this sensor has large potential in environmental and biological applications such as atmospheric monitoring, sewage treatment, food safety, humoral regulation, and medical diagnosis.

Dual polarized surface plasmon resonance refractive index sensor via decentering propagation-controlled core sensor

Refractive index (RI) is a unique attribute of bio-analytes which highly relies upon their concentrations or the activity/infectivity of the microbes. In this paper, a dual-polarized surface plasmon resonance (SPR) RI sensor based on a decentered propagation-controlled core photonic crystal fiber (PCF) has been studied. Fine-tuned light guidance is realized by scaling down the core air holes. The external surface of the fiber is metalized with a thin gold layer that maximizes the chemical stability by reducing the chances of oxidation. The deposition of the core from the central position reduces the core to analyte distance resulting in efficient coupling as well as greater sensitivity. Finite element method (FEM) based numerical investigation warrants promising sensing performances in wavelength and amplitude interrogation methods. The proposed sensor is viable for the RI range from 1.33 to 1.39, where it demonstrates the highest wavelength sensitivities of 13,700 and 15,400 nm/RIU and highest amplitude sensitivities of 852 RIU-1 and 654 RIU-1 in x-and y-polarized modes, respectively. It also exhibits high sensor resolutions of 7.30 × 10−6 RIU and 6.49 × 10−6 RIU, and high figure of merits of 216 and 256 RIU-1 for x and y-polarized modes, respectively. Along with the liberty of selecting light sources, the highly sensitive nature of the sensor will enable accurate detections of different organic compounds and bio-molecules.

Highly sensitive double D-shaped channel photonic crystal fiber based plasmonic refractive index sensor

In this paper, a highly sensitive miniaturized surface plasmon resonance (SPR) based photonic crystal fiber (PCF) sensor is presented for a wide range of analyte sensing. Gold is selected as the plasmonic metal for its higher chemical stability and titanium oxide works as the adhesive layer for gold attachment on silica. The plasmonic metal and the sensing medium are placed exterior to the surface of the sensor design to make it fitting for practical applications. By a careful arrangement of the periodic arrangement of the refractive index in the design, the generation of the evanescent fields is fine-tuned to obtain the phase matching between the leaky core guided mode and the surface plasmon polariton (SPP) mode. Numerical simulations have been carried out by employing the finite element method (FEM) with the consideration of a perfectly matched layer (PML) to absorb surface radiations. The proposed sensor shows a maximum wavelength sensitivity of 34,000 nm/RIU (refractive index units) and a maximum amplitude sensitivity of 331 RIU−1, investigated by using the wavelength and the amplitude interrogation methods, respectively, for the analyte sensing range of 1.16 to 1.37 RI (refractive index). The sensor also exhibits a wavelength resolution of 2.94×10−6 RIU which indicates a high detection accuracy. On that, the proposed sensor would be an excellent candidate for a wide range of RI detection, applicable for various purposes such as chemical detections, medical diagnostics, bio-sensing, and other low RI analytes.

Photonic Crystal Fiber Pollution Sensor Based on the Surface Plasmon Resonance Technology

Photonic Crystal Fiber (PCF) based on the Surface Plasmon Resonance (SPR) effect has been proposed to detect polluted water samples. The sensing characteristics are illustrated using the finite element method. The right hole of the right side of PCF core has been coated with chemically stable gold material to achieve the practical sensing approach. The performance parameter of the proposed sensor is investigated in terms of wavelength sensitivity, amplitude sensitivity, sensor resolution, and linearity of the resonant wavelength with the variation of refractive index of analyte. In the sensing range of 1.33 to 1.3624, maximum sensitivities of 1360.2 nm ∕ RIU and 184 RIU−1 are achieved with the high sensor resolutions of 7 ×10-5 RIU and 5.4× 10−5 RIU using wavelength and amplitude interrogation methods, respectively. The proposed sensor could be established to detect various refractive index (RI) of pollutions in water.

Surface plasmon resonance chemical sensor composed of a microstructured optical fiber for the detection of an ultra-wide refractive index range and gas-liquid pollutants

A surface plasmon resonance (SPR) chemical sensor comprising microstructured optical fiber (MOF) is designed for refractive index (RI) sensing in the visible to near-infrared (0.42-1.60 µm) region (NIR) as well as detection of gas-liquid pollutants. To realize mode coupling and facilitate manufacturing, gold with inert and plasmonic properties and an analyte sensing layer are introduced to the external surface of the MOF. The sensor is analyzed by the full-vector finite element method (FEM) and the wavelength and amplitude interrogation methods are adopted to evaluate the sensing characteristics. Our analysis reveals a maximum wavelength sensitivity (WS) of 15,000 nm/RIU, amplitude sensitivity (AS) of 1,603.37 RIU-1, and resolution (R) of 6.67×10−6 RIU in the determination of analyte RIs spanning an ultra-wide range between 1.00 and 1.45. Furthermore, the figure of merit (FOM) and signal-to-noise ratio (SNR) of the sensor are 295.01 RIU−1 and 2.95, respectively. On account of its simple structure, low cost, and industrial compatibility, this multi-functional sensor has tremendous potential in the chemical industry, environmental monitoring, and safety control such as harmful gas monitoring, industrial wastewater and domestic sewage detection.

Design of surface plasmon resonance based both side polished photonic crystal fiber for highly efficient refractive index sensor

In this paper, both sides flat photonic crystal fiber-based surface plasmon resonance (PCF-SPR) sensor has been proposed. In this external sensing mechanism based sensor, we have used gold as plasmonic material with an adhesive TiO2 layer over it, enhancing the interaction between analyte channel and gold metal. Using the wavelength interrogation and amplitude interrogation method, the maximum wavelength and amplitude sensitivities are obtained 22,800 nm/RIU and 947 RIU−1, respectively, for analyte range 1.30–1.40 with a maximum wavelength resolution of 4.38 × 10−6. With Full-width half maxima (FWHM) around 45 nm, the sensor provides a high figure of merit (FOM) 507 RIU−1. The proposed sensor can be fabricated from newly available technologies such as the sol-gel method, stack and draw method for several practical applications in the bio-medical field, bio-chemical field to provide higher and accurate sensing results. The presented sensor has also played a vital role in cancer cell detection with higher sensing performance.

Design and analysis of dual polarized Au and TiO2-coated photonic crystal fiber surface plasmon resonance refractive index sensor: an extraneous sensing approach

In this work, a photonic sensor based on photonic crystal fiber and surface plasmon resonance to analyze the refractive index (RI) of analytes varying from 1.440 to 1.480 is presented. A dual hexagonal lattice of air holes is reported in this proposed sensor design. The combination of titanium dioxide (TiO2) and gold (Au) is used as a plasmonic material in this sensor. The sensing capability of the proposed sensor is inspected in terms of wavelength sensitivity, amplitude sensitivity, sensor resolution, linearity of resonance wavelength, and figure of merit (FOM). Theoretical analysis of the sensor is performed for both quasi TM mode and quasi TE mode. Numerical investigation shows that wavelength sensitivity of 12 , 000 nm RIU − 1, is obtained for both TM mode and TE mode using the wavelength interrogation method. AS of 3307 and 3619 RIU − 1 is obtained for TM mode and TE mode, respectively, using the amplitude interrogation method. A maximum sensor resolution of 8.33 × 10 − 6 RIU is obtained for both TM mode and TE mode, respectively. The linear relationship of resonant wavelength with RI produces R2 = 0.9991 and R2 = 0.9970 for degree 2, for TM mode and TE mode, respectively. The FOM obtained from the proposed sensor is 139.53 and 187.50 for TM mode and TE mode, respectively.

Dual core four open channel circularly slotted gold coated plasmonic biosensor

In this paper, a four open channel dual-core photonic crystal fiber (OC-DC-PCF) refractive index (RI) sensor is numerically investigated by finite element method (FEM) based software for the detection of unknown biomolecules. To create the surface plasmon resonance (SPR) effect, novel plasmonic material gold (Au) is externally deposited to the selected slotted region which makes this design cost-effective. We obtain the maximum wavelength sensitivity (WS) 38000 nm/RIU and the amplitude sensitivity (AS) of 1286 RIU−1 by using wavelength and amplitude interrogation method respectively. The average spectral sensitivity is 6308 nm/RIU. The maximum figure of merit (FOM) of 760 RIU along with the maximum sensor resolution of 2.63×10−6 RIU is achieved within the analyte RI range of 1.33 to 1.45 for this design which is better than the reported existing works. According to its high sensitivity and cost-effective nature, large detection range, high linearity and FOM, low propagation loss, and low fabrication complexity- it can be an appreciable competitor in the region of bio sensing. The proposed sensor can detect successfully the biomolecules like water, ethanol, fused silica, silicone oil, kerosene, acetone, glucose solution, Teflon, cornea, lens, liver and intestinal mucosa of human etc.

Numerical analysis of gold coating based quasi D-shape dual core PCF SPR sensor

In this article, a Quasi D-Shape dual core Photonic Crystal Fiber Surface Plasmon Resonance sensor is offered and numerically analyzed. The offered model is established comprising of circular air holes having an external sensing polishing layer coated with gold (Au) in order to ensure simple and straightforward design. The performance parameters are examined by means of modal analysis incorporated finite element method utilizing COMSOL multiphysics software. The sensor performance is analyzed with modifying the geometrical parameters like metal (Au) layer and pitch. It is observed; this model shows maximum amplitude sensitivity of 230 RIU−1 and wavelength sensitivity of 15,000 nm-RIU−1 incorporating amplitude interrogation method and wavelength interrogation method, respectively. The Figure of Merit is similarly considered and measured to 45 per RIU inbetween the refractive index ranging 1.42 RIU to 1.46 RIU. As a final point, a comparison has been given among the work explained in this paper with existing works.

Open-channel-based dual-core D-shaped photonic crystal fiber plasmonic biosensor.

A simple dual-core D-shaped plasmonic refractive index (RI) sensor with an open-arch channel is introduced in this paper. A thin plasmonic gold layer is inserted on the slotted portion, which makes the sensor cost effective. By introducing a ring in the flat surface of the D-shaped structure, the coupling effect is increased, which enhances sensor performance. The commonly used finite element method is applied to characterize sensor performance. Numerical investigation under the wavelength interrogation method shows maximum spectral sensitivities of 16,000 nm/RIU and 17,000 nm/RIU along with corresponding resolutions of 6.25×10-6RIU and 5.88×10-6RIU for x and y polarizations, respectively. In tandem with this, maximum amplitude sensitivities governed by the amplitude interrogation method are calculated at about 2,603.7000RIU-1 and 3,432.1929RIU-1 for x and y polarizations, respectively. The proposed sensor exhibits high figures of merit of 320RIU-1 and 283.33RIU-1 for x and y polarizations, respectively, in the RI detection range of 1.33 to 1.44. Moreover, the impact on sensitivity with the overall sensor behavior is analyzed by altering geometrical parameters such as pitch, air hole diameter, and gold layer thickness. So, with an eye toward sensor performance and economic viability, this sensor is assignable to bio-sensing applications.

Design of dual polarized tetra core PCF based plasmonic RI sensor for visible-IR spectrum

In this research work, a susceptible refractive index (RI) biosensor has been presented which can operate in visible to near-infrared region, i.e (500–2000 nm) on a tetra core “photonic crystal fiber (PCF)” based on the “surface plasmon resonance (SPR).” The efficiency of the proposed RI sensor is analyzed in terms of “wavelength sensitivity (WS), amplitude sensitivity (AS), sensor resolution (SR), and linearity of the resonance wavelength.” Using amplitude interrogation method, maximum AS of 7200 RIU−1 is obtained for x−polarization and 4725 RIU−1 for y−polarization, respectively. Similarly WS of 5000 nmRIU−1 and 10000 nmRIU−1 is obtained using a wavelength interrogation method for x−andy−polarization, respectively. Maximum SR of 2.00×10−5RIU and 1.00×10−5RIU is obtained for x−polarization and y−polarization, respectively. The maximum WS, AS, and SR are obtained for the analyte having a RI value of 1.335. A linear relation between resonant wavelength and RI produces R2=0.9832 and 0.9761 for x−andy−polarization, respectively.

Numerical development of high performance quasi D-shape PCF-SPR biosensor: An external sensing approach employing gold

In this paper, a proper concept of a kind of photonic crystal fiber known as D-shaped PCF sensor based on SPR or Surface Plasmon Resonance phenomenon has been discussed. The analysis has been performed numerically using FEM or Finite Element Method and PML (Perfectly Matched Layer) boundary conditions. Modal analysis has been performed keeping the smallest mesh as possible. The main mechanism of the sensor is the interaction between the core guided light beam and the metal layer surface that generates free electrons. The proposed sensor shows a refractive index detection range of 1.42–1.46 RIU, with a metal thickness variation of 35 nm-45 nm and a pitch variation of 1.8 μm–2.0 μm. The sensor obtained the highest sensitivity of 15000 nm/RIU with a maximum 6.67 × 10-6 RIU resolution, using the wavelength interrogation method. Average spectral sensitivity is 8000 nm/RIU. The amplitude interrogation method found a maximum sensitivity of 230 RIU−1 with a resolution of 4.348 × 10-5 RIU. The sensor also shows high linearity fitting and Figure of Merit (FoM). For ease of design, high detection range, high wavelength and amplitude sensitivity, less fabrication complexity, high linearity and stability, the sensor can be a great competitor of the PCF sensors previously proposed.

Design and analysis of photonic crystal fiber-based plasmonic microbiosensor: an external sensing scheme

In this paper, a highly sensitive gold-coated plasmonic microbiosensor, based on photonic crystal fiber (PCF), is proposed and numerically analyzed. To minimize the fabrication challenge and to aid the real-time detection capability of the sensor, the external sensing approach is utilized here. To introduce birefringence property, two rings with some missing air holes are used. Both the wavelength interrogations, as well as the amplitude interrogation method, have been used to determine the sensitivity of the modeled sensor. To demonstrate better performance, different structural parameters, e.g., the thickness of gold layer, pitch, and the diameter of air holes of the PCF, have been varied and investigated. The sensor shows a maximum possible wavelength sensitivity of 10,000 nm/RIU and a maximum possible amplitude sensitivity of 1250 RIU−1 with a sensor wavelength resolution of $$ 1.0 \times 10^{ - 5} $$ RIU. The proposed sensor exhibits an admirable figure of merit (FOM) of the highest value of 260.86 RIU−1 with an excellent linearity property of resonance wavelength in terms of analyte refractive indices. The designed sensor reveals promise for sensing and detecting different biological and biochemical liquid analytes of refractive index (RI) ranging from 1.33 to 1.39 with having enhanced performance.

Numerical Analysis of Midinfrared D-Shaped Photonic-Crystal-Fiber Sensor Based on Surface-Plasmon-Resonance Effect for Environmental Monitoring

An exciting prospect for the sensing community is the potential of midinfrared fiber sensors. Taking advantage of the design flexibility of photonic crystal fiber and the high excitation loss of gold layers, a high-performance midinfrared D-shaped sensor based on the surface-plasmon-resonance effect was designed and numerically investigated by a mature finite-element tool. Numerical results showed that the designed fiber is especially suitable for sensing. In an operating wavelength ranging from 2.9 to 3.6 μm, maximal wavelength sensitivity of 11,500 nm/refractive index unit (RIU) and a maximal refractive index (RI) resolution of 8.7 × 10−6 RIU were obtained by the wavelength-interrogation method when analyte RI varied from 1.36 to 1.37. Maximal amplitude sensitivity of 230 RIU−1 was obtained by the amplitude-interrogation method with a high linearity of 0.99519 and an adequate figure of merit of 142. Additionally, the sensor had good fabrication tolerance. Our sensor is a promising candidate for environmental monitoring.

Numerical Study of Circularly Slotted Highly Sensitive Plasmonic Biosensor: A Novel Approach

A highly sensitive Photonic Crystal Fiber (PCF) based Surface Plasmon Resonance (SPR) sensor is demonstrated in this paper in the optimized form of circular slotted lattice (CSL) structure. This proposed model performance is numerically scrutinized by using Finite Element Method (FEM) in presence of Perfectly Matched Layer (PML) and Scattering Boundary Condition. Plasmonic material ‘Gold’ which is chemically inert is used in this structure at the outer surface of the slotted area to mitigate fabrication challenge. This model indicates the highest wavelength sensitivity of 16000 nm/RIU using wavelength interrogation, the amplitude sensitivity of 780 RIU−1 by using amplitude interrogation method and the average spectral sensitivity of 6666 nm/RIU, respectively. Besides, this sensor has the potentiality of detecting analytes within Refractive Index (RI) range 1.4 to 1.46 with maximum wavelength resolution of 6.25 × 10−6 RIU and amplitude resolution of 1.28 × 10−6 RIU, respectively and the maximum figure of merits of 400 RIU−1. Moreover, the variation of structural parameters (such as pitch, plasmon layer thickness etc.) and the impact of these changes are also discussed in details. According to the high sensitivity performance, polynomial fit and high Figure of Merit (FOM), this amend structure can be a strong competitor in the field of biosensing.

Analysis of a gold coated plasmonic sensor based on a duplex core photonic crystal fiber

An exploration of a gold-coated dual-core with hexagonally arranged circular air holes SPR-PCF sensor is presented in this paper. Chemically inactive and stable material gold is provided as plasmonic material in this design. Placement of the gold layer outside of the PCF structure simplifies the detection process of this sensor and also assures fabrication feasibility. The performance of this sensor is investigated in terms of wavelength sensitivity, amplitude sensitivity, resolution, sensor length and linearity response by using the Finite Element Method (FEM) based COMSOL Multiphysics software. Maximum wavelength sensitivity is found to be 10,700 nm/RIU for analyte sensing range between 1.39 to 1.40 by using wavelength interrogation method as well as maximum amplitude sensitivity reaches about 1770 RIU-1 for analyte RI 1.39 by using amplitude interrogation method. Besides, the sensor's resolution is found to be 9.34×10-6. The outcome of alternating structural parameters such as gold layer thickness, pitch, air hole diameter, different shapes of air hole in the core is also discussed as well. The reported sensor might be a fruitful aspirant in the field of biological sample detection, organic chemical sensing and biomolecule recognition.

Surface plasmon resonance biosensor based on hexagonal lattice dual-core photonic crystal fiber.

In this paper, the guiding properties and sensor performance are numerically investigated for a dual-core hexagonal lattice photonic crystal fiber sensor based on surface plasmon resonance (SPR). Gold is used as the active plasmonic material in order to create resonance, and it is placed outside the fiber structure to facilitate the fabrication process. The finite-element method is used to numerically investigate the characteristics of the sensor. By means of wavelength and amplitude interrogation methods, it is found that the proposed sensor shows maximum wavelength sensitivity of 16,000 nm/RIU with $6.25 \times {10^{ - 6}}\,\,{\rm RIU}$6.25×10-6RIU resolution and amplitude sensitivity of $2255\,\,{{\rm RIU}^{ - 1}}$2255RIU-1 with $4.40 \times {10^{ - 6}}\,\,{\rm RIU}$4.40×10-6RIU resolution. The proposed SPR sensor can detect the analyte refractive index ranging from 1.33 to 1.40. This work also includes an investigation of the effect of changing the gold layer thickness, air-hole diameter, and analyte layer on the sensor performance from the optimized design. The proposed sensor could be employed to detect biological and biochemical analytes because of its simple design and promising results.

Microstructure optical fiber based plasmonic refractive index sensor

This work proposes a highly sensitive plasmonic sensing scheme on a simple circular lattice microstructure optical fiber (MOF) structure. The proposed sensor performance is evaluated by using the finite element method (FEM) in the presence of perfectly matched layer (PML) and scattering boundary conditions. The highest amplitude sensitivity of 1582.95 RIU−1 and wavelength sensitivity of 11,000 nm/RIU is gained using amplitude interrogation and wavelength interrogation method, respectively, for the proposed device. In addition, the maximum sensor resolution of 9.09 × 10−6 RIU is obtained and the suggested sensor gives the same sensing performance for both x- and y-polarized modes due to its symmetrical structure, hence, capable to identify any analyte having refractive index (RI) from 1.34 to 1.40. Moreover, the value of the coefficient of determination (R2 = 0.9926) of the resonance wavelength is achieved close to unity using the quadratic curve fitting. Due to having these promising results, the proposed RI sensor can be useful in the area of bio-sensing.