Performance analysis of an SMF-/MMF-based single/double/quadruple tapered optical fiber structure

Development and stability analysis of an S-tapered optical fiber-based sensor structure

In this paper, three S-tapered fiber (STF) structures with different diameters (40, 60, and 80 µm) are fabricated using conventional single-mode fiber. First, the reproducibility of the proposed S-tapered structure is confirmed through an analysis of the diameter distribution. Considering the transmitted intensities of the three various diameter, S-tapered structures reveal that the STF with a 40 µm diameter produces more evanescent waves and is more sensitive to external refractive index variations. Therefore, the STF structure with a 40 µm diameter was evaluated for the detection of different concentration of glucose solutions, demonstrating that the structure has the potential to be utilized to develop a highly sensitive fiber sensor.

Design and performance enhancement of an all-optical demultiplexer for optical computing applications employing photonic crystals

In this paper, a photonic crystal (PhC) based 1×2 demultiplexer is designed to work efficiently at 1550n m, which is the operating wavelength of optical communication. In designing a 1×2 demultiplexer, the PhC structure employs Y-shaped square-lattice silicon rods with air as its basis in accordance with the principle of beam interference. This study presents a 15×15 rod-based PhC optimized structure with air as its background. Several distinct phase studies are carried out making use of a wide variety of lattice constant and refractive index values of PhCs. The design achieves enhanced performance in accordance with parameters such as having higher contrast ratio of 15.64 dB, high transmission efficiency of 77.92%, fast response time of 15.03 fs, and low insertion loss of 1.08 dB with optimal values for refractive index (RI), silicon rod radius, and lattice constant. The results of the simulation that used the finite-difference-time-domain technique illustrate the good performance of this structure, which exhibits a higher contrast ratio and bit rate, average transmitted power, and fewer power losses.

Humanoid shaped optical fiber plasmon biosensor functionalized with graphene oxide/multi-walled carbon nanotubes for histamine detection

Histamine is a biologically active molecule that serves as a reliable predictor of the quality of fish. In this work, authors have developed a novel humanoid-shaped tapered optical fiber (HTOF) biosensor based on the localized surface plasmon resonance (LSPR) phenomenon to detect varying histamine concentrations. In this experiment, a novel and distinctive tapering structure has been developed using a combiner manufacturing system and contemporary processing technologies. Graphene oxide (GO)/multi-walled carbon nanotubes (MWCNTs) are immobilized on the HTOF probe surface to increase the biocompatibility of biosensor. In this instance, GO/MWCNTs are deployed first, then gold nanoparticles (AuNPs). Consequently, the GO/MWCNTs help to give abundant space for the immobilization of nanoparticles (AuNPs in this case) as well as increase surface area for the attachment of biomolecules to the fiber surface. By immobilizing AuNPs on the surface of the probe, the evanescent field can stimulate the AuNPs and excite the LSPR phenomena for sensing the histamine. The surface of the sensing probe is functionalized with diamine oxidase enzyme in order to enhance the histamine sensor's particular selectivity. The proposed sensor is demonstrated experimentally to have a sensitivity of 5.5 nm/mM and a detection limit of 59.45 µM in the linear detection range of 0-1000 µM. In addition, the probe's reusability, reproducibility, stability, and selectivity are tested; the results of these indices show that the probe has a high application potential for detecting histamine levels in marine products.

Development of a core-offset-based SMS fiber structure for detection of various biomolecules

This paper discusses the details about the fabrication of single-mode fiber (SMF)- and multi-mode fiber (MMF)-based core-offset sensor structures for biomolecules detection. SMF-MMF-SMF (SMS) and SMF-core-offset MMF-SMF (SMS structure with core-offset) are proposed in this paper. In the conventional SMS structure the incident light is introduced from the SMF to the MMF and then passes through the MMF to the SMF. However, in the SMS-based core offset structure (COS) the incident light is introduced from the SMF to the core offset MMF and then passes through the MMF to the SMF, and more incident light leaks at the fusion point between the SMF and the MMF. This structure causes more incident light to leak out from the sensor probe, forming evanescent waves. By analyzing the transmitted intensity, the performance of COS can be improved. The results show that the structure of the core offset has great potential for the development of fiber-optic sensors.

Novel Optical Fiber-Based Structures for Plasmonics Sensors

Optical fiber sensors based on surface plasma technology have many unique advantages in specific applications such as extreme environmental monitoring, physical parameter determination, and biomedical indicators testing. In recent decades, various kinds of fiber probes with special structures were developed according to special processing such as tapering, splicing, etching, fiber balls, grating etc. In this paper, the fabrication technology, characteristics, development status and application scenarios of different special optical fiber structures are briefly reviewed, including common processing equipment. Furthermore, many special novel optical fiber structures reported in recent years are summarized, which have been used in various kinds of plasmonic sensing work. Then, the fiber-plasmonic sensors for practical applications are also introduced and examined in detail. The main aim of this review is to provide guidance and inspiration for researchers to design and fabricate special optical fiber structures, thus facilitating their further research.

Optimization of an all-optical three-input universal logic gate with an enhanced contrast ratio by exploiting a T-shaped photonic crystal waveguide

Universal gates (NAND and NOR) are used for any electronic circuit that is affordable and straightforward to build all logic gates (LoG). In this work, the T-shaped 2D photonic crystal (PhC) is exploited to design a three-input universal LoG premised on the beam-interference principle. The design criteria of pitch (a), rod radius (r), and refractive index (n) are employed to obtain a high impact output. The methodologies of plane wave expansion and finite-difference time-domain are employed for examining the framework of universal LoG at 1550 nm wavelengths (λ). The suggested universal LoG design has a compact size of 8.4µm×4.8µm. Additionally, the structure yields a high contrast ratio (CR) of 20.37 dB for the NAND LoG and 28.45 dB for the NOR LoG, and maximum transmission efficiency of 50.6% and 70% for the NAND and NOR gates; correspondingly, the best and worst three-input NAND gate response times are 19.5 ps and 21.4 ps. Similarly, the response time of the three-input NOR gate is 26 ps. The proposed universal gate's primary goal is to offer a high CR and a compact structure while being compatible with any other logic gate.