Extension of an FFT-Based Beam Propagation Method to Plasmonic and Dielectric Waveguide Discontinuities and Junctions

Abstract

We adapted a fast Fourier transform-based Beam Propagation Method (FFT-BPM) to investigate waveguide discontinuities in plasmonic waveguides. The adaptation of the FFT-BPM to treat transverse magnetic (TM) fields requires the circumvention of two major difficulties: the mixed derivatives of the magnetic field and waveguide refractive index profile in the TM wave equation and the step-like index change at the transverse metal-dielectric boundary of the plasmonic guide and the transverse boundaries of the dielectric waveguide as well. An equivalent-index method is adopted to transform TM fields to transverse electric (TE) ones, thus enabling the benefit of the full power and simplicity of the FFT-BPM. Moreover, an appropriate smoothing function is used to approximate the step-like refractive index profile in the transverse direction. At the junction plane, we used an accurate combined spatial-spectral reflection operator to calculate the reflected field. To validate our proposed scheme, we investigated the modal propagation in a silicon waveguide terminated by air (like a laser facet in two cases: with and without a coating layer). Then we considered a subwavelength plasmonic waveguide (metal-insulator-metal MIM) butt-coupled with a dielectric waveguide, where the power transmission efficiency has been calculated and compared with other numerical methods. The comparison reveals good agreement.Waals materials layers (like graphene) or through multilayered heterostructures. This leads to strong nonlinearities, large photonic forces, and enhanced emission and absorption probabilities. A practical approach toward nanoscale light trapping and manipulation is offered by interfaces separating media with permittivities of opposite signs [5]. Graphene plasmons are very promising to be the best alternative to noble-metal plasmons as they exhibit much tighter confinement and relatively long propagation distances, with the advantage of being highly tunable via electrostatic gating [6].The integration of plasmonic-based devices and photonic devices will eventually lead to an interfacing between plasmomic and photonic guides. Especially, butt-coupling plasmonic and dielectric guides is one of the most efficient ways for light transmission between highly confined modes and low-loss guided wave structures [7]. It is worthy to note that subwavelength optical confinement modes, allows the efficient and beneficial use of compact photonic devices like nanoscale photodetectors; thus, improving noise immunity, response speed and power dissipation in optical communication devices [8,9].The versatility of the FFT-BPM in the simulation of wide range of photonic devices is well understood [10][11][12][13][14]. In this paper, for the sake of simplicity, we shall consider two-dimensional structures invariant in the y-direction. The main essence of the BPM is simple: propagation in a reference homogenous medium over a small distance ∆z followed by phase correction that takes into account the spatial dependence of the refractive index of the me...

An Optical Universal Plasmon-Based Biosensor for Virus ‎‎Detection

“…Accordingly, the FFT-BPM has been ignored, in spite of its powerfulness, simplicity and accuracy [ 18 ]. Fortunately, [ 19 – 21 ] the traditional FFT-BPM has been revisited and reformulated to handle TM fields recently. Moreover, this renewed version of the FFT-BPM has been applied to some delicate problem, such as butt-coupling between plasmonic and dielectric waveguide [ 19 , 21 ], and taking into account back-reflected field.…”

“…Fortunately, [ 19 – 21 ] the traditional FFT-BPM has been revisited and reformulated to handle TM fields recently. Moreover, this renewed version of the FFT-BPM has been applied to some delicate problem, such as butt-coupling between plasmonic and dielectric waveguide [ 19 , 21 ], and taking into account back-reflected field. This motivated us to tackle the problem under the consideration in this research by the novel framework of FFT-BPM as will be shown.…”

Daugiasluoksnių puslaidininkinių ir dielektrinių mikrobangų įtaisų tyrimas

“…Yra du pagrindiniai būdai sukurti technologinę paklausą atitinkančius sprendimus: naujų struktūrų ir konstrukcijų naudojimas bei medžiagų naudojimas (Saad et al, 2020). Šis poreikis nulemia naujų įtaisų kūrimo ir tyrimo metodų paiešką (Martinez et al, 2019;Shaaban et al, 2019).…”