Novel Bloch wave excitation platform based on few-layer photonic crystal deposited on D-shaped optical fiber

Abstract

With the goal of ultimate control over the light propagation, photonic crystals currently represent the primary building blocks for novel nanophotonic devices. Bloch surface waves (BSWs) in periodic dielectric multilayer structures with a surface defect is a well-known phenomenon, which implies new opportunities for controlling the light propagation and has many applications in the physical and biological science. However, most of the reported structures based on BSWs require depositing a large number of alternating layers or exploiting a large refractive index (RI) contrast between the materials constituting the multilayer structure, thereby increasing the complexity and costs of manufacturing. The combination of fiber–optic-based platforms with nanotechnology is opening the opportunity for the development of high-performance photonic devices that enhance the light-matter interaction in a strong way compared to other optical platforms. Here, we report a BSW-supporting platform that uses geometrically modified commercial optical fibers such as D-shaped optical fibers, where a few-layer structure is deposited on its flat surface using metal oxides with a moderate difference in RI. In this novel fiber optic platform, BSWs are excited through the evanescent field of the core-guided fundamental mode, which indicates that the structure proposed here can be used as a sensing probe, along with other intrinsic properties of fiber optic sensors, as lightness, multiplexing capacity and easiness of integration in an optical network. As a demonstration, fiber optic BSW excitation is shown to be suitable for measuring RI variations. The designed structure is easy to manufacture and could be adapted to a wide range of applications in the fields of telecommunications, environment, health, and material characterization.

Research Advances on Fiber-Optic SPR Sensors with Temperature Self-Compensation

“…In general, fiber-based SPR sensing with temperature self-compensation has shown attractive promise, and there are still some challenges for this type of sensors: (1) the SPR resonance absorption spectra have a wide bandwidth in the submicron range, which severely limits the measurement sensitivity; (2) the problems of practical use still exist, and further steps should be taken based on the research of sensing mechanisms and structural innovations; (3) the vast majority of fiber-based SPR sensors use wavelength modulation, and the demodulation equipment is relatively expensive, so diverse demodulation methods need to be further developed. Nevertheless, the fiber-based SPR sensing technology is still emerging, and will burst out with new vitality and vigor when combined with new materials, new structures, and new technologies—for example, Bloch surface wave (BSW)/Tamm mode-based fiber optical sensors (including D-shaped fiber and PCF) [ 93 , 94 ], which are analogous to SPR but possess better performance.…”

High Aspect-Ratio Open Grating Fabry-Perot Resonator for High-Sensitivity Refractive Index Sensing

“…This illustrates that strong coupling associated with good responsivity reduces the Q. Therefore, the overall FoM does not change a great deal [10], [12], so a sharp response is associated with a small change in the position of the resonance. The way to get around this trade-off is to design a resonator where the analyte is an intrinsic part of the resonator rather than just an external load.…”

“…Generally, high bulk responsivity 𝑅 𝑏𝑢𝑙𝑘 , narrow FWHM and high FoM are desired. Efforts have been made to increase the responsivity or narrow the FWHM with plasmonic sensors based on surface plasmon resonance (SPR) [2], [3], [6], long-range SPR [11], photonic sensors such as photonic crystal sensors based on Bloch surface waves [12] and whispering gallery mode sensors such as microring resonators [13]. These approaches allow label-free detection of proteins, viruses and various molecules found in human body that are indicative in disease diagnosis and treatment with high precision and sensitivity [14]- [17].…”

Figure of Merit Comparison Between Surface Plasmon Resonance and Bloch Surface Waves

“…On the other hand, BSW's are generated at the interface between a photonic crystal (PhC) and a dielectric (or between two PhCs) [2], producing sharp resonances in the optical spectrum due to the symmetry breaking caused by the PhC -dielectric interface. While the experimental observation of BSW's was made almost five decades ago [5], it is now emerging as a new field for sensing purposes, and a few experimental realizations have already been reported [6]. In this work, a comparison between these two ESW's is made, focusing on the external RI sensitivity and resolution, which are key parameters for optical sensor application in real world scenarios.…”