Tunable Triple Plasmonically Induced Transparency in Triangular Cavities Coupled with an MDM Waveguide

Jingyu Zhang,Chang Liu,Dongchao Fang,Yang Gao,Jincheng Wang,Hengli Feng,Zuoxin Zhang,Lingling Ran,Lehui Wang

doi:10.3390/photonics9020100

Jingyu Zhang, Chang Liu + Show 7 more

Open Access

https://doi.org/10.3390/photonics9020100

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Journal: Photonics	Publication Date: Feb 9, 2022
Citations: 2	License type: CC BY 4.0

Affiliation: Heilongjiang University

Abstract

In this paper, a side-coupled triangle cavity in a plasmonic waveguide structure is proposed and numerically analyzed by the finite-difference time-domain (FDTD) method and coupled mode theory (CMT). Triple plasmonically induced transparency (PIT) was achieved when an extra triangle was added into the structure, and the transmission characteristics were investigated. This novel structure has a maximal sensitivity of 933 nm/RIU when used as a sensor and a contrast ratio of 4 dB. Moreover, the tunability of PIT can be realized by filling the nematic liquid crystal (NLC) E7 into the triangles. The refractive index of E7 changes with the applied electric field. Given that E7 is also sensitive to temperature, this structure can be used as a temperature sensor with a sensitivity of 0.29 nm/°C. It is believed that this tunable structure with PIT may have potential applications in highly integrated optical circuits.

Highlights

Surface plasmon polaritons (SPPs), as special electromagnetic evanescent waves, propagate along the metal–dielectric interface and exponentially attenuate perpendicular to the interface [1]
Using an analogous strategy, Xie et al proposed a plasmonic metasurface consisting of a series of arrays on a silicon substrate, in order to detect the changes in kanamycin sulfate amounts at a relatively low concentration [6]
plasmonically induced transparency (PIT) attracts a significant amount of attention and can be achieved in many different plasmonic structures, e.g., graphene nanostrips [17], MDM

Summary

Introduction

Surface plasmon polaritons (SPPs), as special electromagnetic evanescent waves, propagate along the metal–dielectric interface and exponentially attenuate perpendicular to the interface [1]. PIT attracts a significant amount of attention and can be achieved in many different plasmonic structures, e.g., graphene nanostrips [17], MDM waveguides [18], and metamaterials [19] Among these structures, various PIT devices based on an MDM waveguide have been proposed such as optical switches [20], sensors [21], and filters [22]. Another triangular cavity was added into the structure to realize a PIT effect. When NLC E7 is added into the triangular cavities, the transparency window can be manipulated by the director angle of E7 This structure can be employed as a temperature sensor with a sensitivity of 0.29 nm/◦ C because E7 is sensitive to temperature change. It is believed that this compact structure with tunable PIT can be used in other plasmonic devices

Materials and Methods

Theoretical Analysis of Structure

Theoretical Design of PIT

Realization of Tunable PIT

Temperature Analysis of PIT

Conclusions