Dual-polarized highly sensitive plasmonic sensor in the visible to near-IR spectrum

We propose and numerically characterize the optical characteristics of a novel photonic crystal fiber (PCF) based surface plasmon resonance (SPR) sensor in the visible to near infrared (500–2000 nm) region for refractive index (RI) sensing. The finite element method (FEM) is used to design and study the influence of different geometric parameters on the sensing performance of the sensor. The chemically stable plasmonic material gold (Au) is used to produce excitation between the core and plasmonic mode. On a pure silica (SiO2) substrate, a rectangular structured core is used to facilitate the coupling strength between the core and the surface plasmon polariton (SPP) mode and thus improves the sensing performance. By tuning the geometric parameters, simulation results show a maximum wavelength sensitivity of 58000 nm/RIU (Refractive Index Unit) for the x polarization and 62000 nm/RIU for the y polarization for analyte refractive indices ranging from 1.33 to 1.43. Moreover, we characterize the amplitude sensitivity of the sensor that shows a maximum sensitivity of 1415 RIU−1 and 1293 RIU−1 for the x and y polarizations, respectively. To our knowledge, this is the highest sensitivity for an SPR in published literature, and facilitates future development of sensors for accurate and precise analyte measurement. The sensor also attains a maximum figure of merit (FOM) of 1140 and fine RI resolution of 1.6 × 10−6. Owing to strong coupling strength, high sensitivity, high FOM and improved sensing resolution, the proposed sensor is suited for real-time, inexpensive and accurate detection of biomedical and biological analytes, biomolecules, and organic chemicals.Md. Saiful Islam, Jakeya Sultana, Ahmmed. A. Rifat, Rajib Ahmed, Alex Dinovitser, Brian W.-H. Ng, Heike Ebendorff-Heidepriem and Derek Abbot

A Highly Sensitive Gold-Coated Photonic Crystal Fiber Biosensor Based on Surface Plasmon Resonance

In this paper, we numerically demonstrate a two-layer circular lattice photonic crystal fiber (PCF) biosensor based on the principle of surface plasmon resonance (SPR). The finite element method (FEM) with circular perfectly matched layer (PML) boundary condition is applied to evaluate the performance of the proposed sensor. A thin gold layer is deposited outside the PCF structure, which acts as the plasmonic material for this design. The sensing layer (analyte) is implemented in the outermost layer, which permits easy and more practical fabrication process compared to analyte is put inside the air holes. It is demonstrated that, at gold layer thickness of 40 nm, the proposed sensor shows maximum sensitivity of 2200 nm/RIU using the wavelength interrogation method in the sensing range between 1.33-1.36. Besides, using an amplitude interrogation method, a maximum sensitivity of 266 RIU-1 and a maximum sensor resolution of 3.75 × 10-5 RIU are obtained. We also discuss how phase matching points are varied with different fiber parameters. Owing to high sensitivity and simple design, the proposed sensor may find important applications in biochemical and biological analyte detection

Mode-multiplexed waveguide sensor

Optical sensors enable quantification of analyte concentrations noninvasively without being affected from electromagnetic fields. The development of single-mode waveguides (WGs) is simple approach; however, limitations in the spatial distribution of the refractive index and the inability to sense multiple samples at the same time. Here, we demonstrate a multi-mode WG model and matrix inversion method (MIM) to improve spatial information in at least one dimension. This method is used to optimize and estimate three external stimulus properties in TE00, TE01 and TM00 multiplexed modes for a semitriangular ring resonator configuration. The multi-mode WG and MIM may have applications in the development of biosensors for multianalyte detection

Optical microring resonator based corrosion sensing

A refractive index (RI) based corrosion sensor that could measure the oxidation of iron metal to iron-oxide was numerically investigated with a finite element method. The sensor is based on an optical microring resonator with periodically arranged iron nanodisks (NDs) in a ring waveguide (WG). The microring resonator showed a linear resonance frequency shift as iron was oxidized due to RI variation and back scattered light, as compared to conditions with no ND ring. The resonance wavelength shift depended on the number of NDs and the spacing between the NDs. Free spectral range and sensor sensitivity were 40 nm and 517 nm RIU-1 with 10 NDs with 50 nm spacing. Optimization of the sensor parameters allowed a two-fold improvement in sensitivity and achieved a quality factor of 188. The sensitivity and Q-factor showed a linear relationship with increasing ND numbers and spacing. The microring resonator based optical corrosion sensor will find applications in real-time, label-free corrosion quantification

Terahertz sensing in a hollow core photonic crystal fiber

A terahertz sensor based on a hollow core photonic crystal fiber has been proposed in this paper for chemical analyte detection in the terahertz frequency range. The Zeonex-based asymmetrical hollow core is filled with an analyte and surrounded by a number of asymmetrical rectangular air holes bounded by a perfectly matched layer with absorbing boundary conditions. The performance of the proposed sensor is numerically investigated by using finite element method-based COMSOL software. It is found that a hollow core provides a high relative sensitivity as well as low transmission loss. Moreover, simplicity in design facilitates manufacturability, making it practical for a number of different biological and industrial applications.Md. Saiful Islam, Jakeya Sultana, Ahmmed A. Rifat, Alex Dinovitser, Brian Wai-Him Ng, Derek Abbot