Photonic Crystal Fiber SPR Liquid Sensor Based on Elliptical Detective Channel

A D-Shaped SPR-Based PCF Sensor with an Extremely High-Amplitude Sensitivity for Measuring the Refractive Index

In this work, a new D-shaped photonic crystal fibre sensor structure based on surface plasmon resonance (SPR) is purposed for measurement of analyte refractive index (RI). In this design, a silica cylinder is polished into a D-shaped silica material structure with a flattened surface where two Au nanowires are coated. Some air holes are omitted to form the core mode region. With the implementation of gold nanowires and a core region for the exciting SPR effect with variate physical values, analyte RI can be measured with a wavelength coverage from 850 to 1350nm. The numerical simulation shows the maximum wavelength sensitivity of the purposed design achieves 19,600nm/RIU with an RI coverage from 1.37 to 1.42. Moreover, the sensor has a tremendous amplitude sensitivity and the maximum absolute value is about 2300RIU-1. Benefiting from these outstanding performance, the purposed structure can be given priority when it is applied in biomedical detecting and environmental assessment science.

Numerical Analysis of Highly Sensitive Twin-Core, Gold-Coated, D-Shaped Photonic Crystal Fiber Based on Surface Plasmon Resonance Sensor

This research article proposes and numerically investigates a photonic crystal fiber (PCF) based on a surface plasmon resonance (SPR) sensor for the detecting refractive index (RI) of unknown analytes. The plasmonic material (gold) layer is placed outside of the PCF by removing two air holes from the main structure, and a D-shaped PCF-SPR sensor is formed. The purpose of using a plasmonic material (gold) layer in a PCF structure is to introduce an SPR phenomenon. The structure of the PCF is likely enclosed by the analyte to be detected, and an external sensing system is used to measure changes in the SPR signal. Moreover, a perfectly matched layer (PML) is also placed outside of the PCF to absorb unwanted light signals towards the surface. The numerical investigation of all guiding properties of the PCF-SPR sensor is completed using a fully vectorial-based finite element method (FEM) to achieve the finest sensing performance. The design of the PCF-SPR sensor is completed using COMSOL Multiphysics software, version 1.4.50. According to the simulation results, the proposed PCF-SPR sensor has a maximum wavelength sensitivity of 9000 nm/RIU, an amplitude sensitivity of 3746 RIU^-1, a sensor resolution of 1 × 10^-5 RIU, and a figure of merit (FOM) of 900 RIU^-1 in the x-polarized direction light signal. The miniaturized structure and high sensitivity of the proposed PCF-SPR sensor make it a promising candidate for detecting RI of analytes ranging from 1.28 to 1.42.

Development of a multi-functional SPR sensing system using a square glass rod with two gold-deposited adjacent faces

A multi-functional sensing system based on surface plasmon resonance (SPR) phenomenon using a square glass rod with two gold-deposited adjacent faces was developed in this work. This sensor system consists of a unpolarized light-emitting diode, a gold-deposited square glass rod, a polarizing beam splitter, and two photodiodes. The SPR responses of two adjacent faces are independently and simultaneously measured with a polarizing beam splitter and two PDs. The response property of the gold-deposited face was confirmed using methanol solutions of ethylene glycol. The response curve of the sensor of the 45 nm gold-deposited face was compared with the theoretical curve calculated using multi-layer Fresnel equations. It was confirmed that the experimental curve is similar to the theoretical one. An evaluation was carried out on the square glass rod, which has an unmodified face and Teflon AF2400 coated gold-deposited face as multi-functional sensor. It was confirmed that this sensor can simultaneously measure the ethanol concentration in the glucose mix solution and refractive index of the sample from the calibration curve. Since this sensor can measure multiple components simultaneously, expected applications to various fields include medical diagnosis, food analysis, and environmental monitoring.

A High Refractive Index Plasmonic Micro-Channel Sensor Based on Photonic Crystal Fiber

A new concave shaped high refractive index plasmonic sensor with a micro-channel is proposed in this work, which comprises an analyte channel in the core hole. The sensor is elaborately designed to reduce the interference effect from the metal coating. Furthermore, the impact of the proposed structure on the sensitivity is also investigated by engineering the geometric parameters using the finite element method. We select gold as the plasmonic material in this theoretical study because it is widely used to fabricate plasmonic and metamaterial devices due to its chemical stability and compatibility. According to wavelength interrogation technique, simulations results show that this sensor can obtain maximal wavelength sensitivity of 10,050 nm/refractive index unit. In view of the excellent indicators of this device, it has important development potential in chemical and biological research fields.