Plasmonic sensors based on metal nanostructure are widely used in the field of sensing due to their feature of remarkable local field strength enhancement. However, the inherent damping of the metal results in wide full width at half maximum (FWHM) of spectrum, which greatly affects the sensing performance. In recent years, the dielectric nanostructure based on low-loss and high refractive index has attracted great interest of researchers. In this paper, we introduce the dielectric nanodisk array structure coupling with metal film to realize ultra-narrow band sensor. The simulation results show that the FWHM of dielectric nanodisks with identical period is reduced by 4 times than the counterpart of Au-disks. Simultaneously, when the thickness of nanodisks is changed, the sensing performances of the dielectric array maintain unchanged, providing the excellent tolerance of preparation. In addition, the structure was prepared experimentally using template transfer technology, and refractive index sensing was carried out. The experimental results are consistent with the simulation. This research provides an effective way towards improving the performance of sensor.
A novel and simple optical fiber structure with a section of no-core fiber for measuring hydrogen concentration is presented. Palladium is sputtered to form the coating on the no-core fiber by magnetron sputtering coater. Under different hydrogen conditions, the absorption of hydrogen induced refractive index changes on the outside coating of no core fiber will lead to the variations of the optical output spectrum. Different concentrations of hydrogen are tested, from 4%-0.5%, shows the concentration is relevant with the response time and recovery time. The response time of this sensor is from 300s (4% H2) to 1800s (0.5% H2) depending on the hydrogen concentration. The recovery time of this sensor is from 1200s (4% H2) to 4800s (0.5% H2) depending on the hydrogen concentration. Furthermore, the repeatability and response time of the sensor of this study are investigated experimentally.
We propose and demonstrate an open-cavity fiber extrinsic Fabry-Perot (FP) interferometer (EFPI), fabricated by using 800 nm femtosecond (fs) laser micromachining, for refractive index (RI) measurement. The sensor probe consists of two single-mode fiber (SMF) and a notched hollow-core fiber (HCF) fused together to form an all-silica structure of SMFHCF-SMF. The open micro-cavity is formed by removing part of the HCF in the center of its surface by fs laser micromachining technology, allowing liquid or gaseous sample to flow in. Such a sensor can provide an extremely highprecision RI measurement of 10-6 RIU (refractive index unit) and the sensitivity can reach up to 4×105 nm/RIU within the range between 1.355 and 1.374.
We proposed a compact and cost-effective red–green dual-color fiber optic surface plasmon resonance (SPR) sensor based on the smartphone. Inherent color selectivity of phone cameras was utilized for real-time monitoring of red and green color channels simultaneously, which can reduce the chance of false detection and improve the sensitivity. Because there are no external prisms, complex optical lenses, or diffraction grating, simple optical configuration is realized. It has a linear response in a refractive index range of 1.326 to 1.351 (R2 = 0.991) with a resolution of 2.3 × 10 − 4 RIU. We apply it for immunoglobulin G (IgG) concentration measurement. Experimental results demonstrate that a linear SPR response was achieved for IgG concentrations varying from 0.02 to 0.30 mg / ml with good repeatability. It may find promising applications in the fields of public health and environment monitoring owing to its simple optics design and applicability in real-time, label-free biodetection.
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