Graphene-Coated Two-Layer Dielectric Loaded Surface Plasmon Polariton Rib Waveguide With Ultra-Long Propagation Length and Ultra-High Electro-Optic Wavelength Tuning

Tao Ma,Yufang Liu,Fang Wang,Keping Long,Heng Liu,Chongxiu Yu,Xian Zhou,Jinhui Yuan

doi:10.1109/access.2020.2999395

Abstract

A graphene-coated two-layer dielectric loaded surface plasmon polariton (GTDLSPP) rib waveguide is designed. The mode characteristics and electro-optic (EO) modulation performances of the four hybrid plasmonic modes (HPMs) in the designed waveguide are simulated by using the finite element method. The simulation results show that a 10 3 mm-scale propagation length and an effective mode field area of ~λ 2 /1333 are obtained by adjusting the bias voltage. The EO wavelength tunings are -68.6, -42.0, -49.7, and -11.1 nm/V for the HPM 1, HPM 2, HPM 3, and the peak 2 of HPM 4, which are two orders of magnitude larger than those of other EO modulation structures. For the peak 1 of the HPM 4, the EO wavelength tuning is the piecewise linear. For a 150-μm long waveguide, the modulation depths of ~98.7, ~87.9, and 99.5%, and FWHMs of ~450, ~100, and ~42 nm can be achieved for the HPM 1, HPM 2, and HPM 3. For the HPM 4, there are two peaks in the transmission spectrum. The modulation depths are ~97.3 and 75.2%, and FWHMs are ~92 and ~34 nm for the peaks 1 and 2. There is a tradeoff between the modulation depth and FWHM for different waveguide lengths. The GTDLSPP rib waveguide designed has small size, high modulation depth, broad bandwidth, and compatibility with the CMOS technology, soit has potential applications in the EO tunable devices, optical interconnects, and optical switches.

Highlights

The development of integrable optical signal processing technology requires ultra-compact on-chip photonic devices and systems [1]
By combining the advantages of the graphene HPW (GHPW), Si3N4, and two-layer dielectric loaded surface plasmon polariton (TDLSPP) waveguide, we propose a graphenecoated two-layer dielectric loaded surface plasmon polariton (GTDLSPP) rib waveguide
The simulation results show that the graphene-coated two-layer dielectric loaded surface plasmon polariton (GTDLSPP) rib waveguide can achieve a 103 mm-scale propagation length and a max (FoM) of ∼106

Summary

INTRODUCTION

The development of integrable optical signal processing technology requires ultra-compact on-chip photonic devices and systems [1]. The GHPW-based modulators combine the advantages of the graphene and plasmonic waveguides. A GHPW modulator based on graphene-hexagonal-boron-nitride-graphene sandwich is analyzed [30], where the modulator has a high ER of 39.75 dB and a large bandwidth of 190.5 GHz. By optimizing the parameters, a modulation depth of 3 dB is achieved within a broad wavelength range from 1400 to 1600 nm. Silicon nitride (Si3N4) waveguide has low propagation loss, relatively small refractive index (RI) contrast, large bandgap, and compatibility with the CMOS process [33]. It is considered as an ideal candidate for building the optical modulators [34].

STRUCTURE DESIGN OF THE GTDLSPP RIB WAVEGUIDE

THE EO MODULATION PERFORMANCES

CONCLUSIONS