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

Esteban Gonzalez-Valencia,Pedro Torres,Ignacio Del Villar

doi:10.1038/s41598-021-90504-z

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.

Highlights

With the goal of ultimate control over the light propagation, photonic crystals currently represent the primary building blocks for novel nanophotonic devices
Most of the Bloch surface waves (BSWs) excitation platforms require a large number of layers or materials with a large difference in refractive index (RI), we demonstrate that even a 3-layer stack on the fiber-based excitation platform can sustain TE-polarized BSWs using a 1DPC consisting of materials that have a moderate difference in RI
We have proposed and experimentally demonstrated a novel BSW excitation platform based on D-shaped optical fibers with few-layer 1DPC deposited on its flat surface using alternating thin layers of SnO2 and CuO

Summary

Introduction

With the goal of ultimate control over the light propagation, photonic crystals currently represent the primary building blocks for novel nanophotonic devices. 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. Most devices based on BSW excitation require a 1DPC with a large number of layers–higher than 1210,12,17–25 These configurations have been used in 1DPCs consisting of bilayers of materials with refractive index (RI) differences as small as 0.2 refractive index units (RIU)[12,17,18,19] up to moderate differences of 0.8 R IU10,20–25. Very few investigations on the BSW excitation in optical fibers have been published, and not all of them have experimental v erification[19,23,30,32,43]

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Results

Conclusion