A multimode framework that can be utilized in the analysis and design of general, non-Hermitian periodic systems that comprise contemporary 2D materials is developed. The theoretical framework is based on the concept of Quasinormal Modes (QNMs) that can be used to efficiently retrieve the spectral response of periodic systems. Both sub- and super-wavelength lattice constants are examined with extra care to include propagating higher diffraction orders. The framework is employed in two indicative configurations, a graphene-based periodic metasurface that supports tightly confined graphene surface plasmons, and a periodic dielectric metasurface enhanced with a transition metal dichalcogenide layer that supports quasi bound states in the continuum. Both configurations are of fundamental and practical interest since they exhibit controllable resonant response and, in addition, the electromagnetic properties of the involved 2D materials can be electrically tuned. The Finite Element Method (FEM) is used to retrieve the QNMs, which are then fed to the framework to specify the spectral response for the zeroth and higher diffraction orders. Full-wave FEM simulations are used to verify the validity of obtained results.
We present a thorough numerical investigation of end-fire coupling between dielectric-loaded surface plasmon
polariton (DLSPP) and compact rib/wire silicon-on-insulator (SOI) waveguides. Simulations are based on the
three-dimensional vector finite element method. The interface geometrical parameters leading to optimum performance,
i.e., maximum coupling efficiency or, equivalently, minimum insertion loss (IL), are identified. We
show that coupling efficiencies as high as 85 % are possible. In addition, we quantify the fabrication tolerances
about the optimum parameter values. In the same context, we assess the effect of a metallic stripe gap and
that of a horizontal offset between waveguides on insertion loss. Finally, we demonstrate that by benefiting
form the low-loss coupling between the two waveguides, hybrid silicon-plasmonic 2 x 2 thermo-optic switching
elements can outperform their all-plasmonic counterparts in terms of IL. Specifically, we examine two hybrid
SOI-DLSPP switching elements, namely, a Mach-Zehnder Interferometer (MZI) and a Multi-Mode-Interference
(MMI) switch. In particular, in the MZI case the IL improvement compared to the all-plasmonic counterpart
is 4.5 dB. Moreover, the proposed hybrid components maintain the high extinction ratio, small footprint, and
efficient tuning traits of plasmonic technology.
We rst report on design, fabrication and characterizations of thermally-controlled plasmonic routers relying on
the interference of a plasmonic and a photonic mode supported by wide enough dielectric loaded waveguides. We
show that, by
owing a current through the gold lm on which the dielectric waveguides are deposited, the length
of the beating created by the interference of the two modes can be controlled accurately. By operating such a
plasmonic dual-mode interferometer switch, symmetric extinction ratio of 7dB are obtained at the output ports
of a 2x2 router. Next, we demonstrate ber-to-ber characterizations of stand-alone dielectric loaded surface
plasmon waveguide (DLSPPW) devices by using grating couplers. The couplers are comprised of dielectric loaded
gratings with carefully chosen periods and duty-cycles close to 0.5. We show that insertion loss below 10dB per
coupler can be achieved with optimized gratings. This coupling scheme is used to operate Bit-Error-Rate (BER)
measurements for the transmission of a 10Gbits/s signal along a stand-alone straight DLSPPW. We show in
particular that these waveguides introduce a rather small BER power penalty (below 1dB) demonstrating the
suitability of this plasmonic waveguiding platform for high-bit rate transmission.
Surface plasmons polaritons are electromagnetic waves propagating along the surface of a conductor. Surface plasmons photonics is a promising candidate to satisfy the constraints of miniaturization of optical interconnects. This contribution reviews an experimental parametric study of dielectric loaded surface plasmon waveguides ring resonators and add-drop filters within the perspective of the recently suggested hybrid technology merging plasmonic and silicon photonics on a single board (European FP7 project PLATON "Merging Plasmonic and Silicon Photonics Technology towards Tb/s routing in optical interconnects"). Conclusions relevant for dielectric loaded surface plasmon switches to be integrated in silicon photonic circuitry will be drawn. They rely on the opportunity offered by plasmonic circuitry to carry optical signals and electric currents through the same thin metal circuitry. The heating of the dielectric loading by the electric current enables to design low foot-print thermo-optical switches driving the optical signal flow.
A 1D photonic crystal slab based on preferential etching of commercially available silicon-on-insulator wafers is
presented. Compared to dry etching, anisotropic wet etching is more tolerant to errors as it is self-stopping on
crystallographic {111} planes and it produces a more precise geometry with symmetries and homothetic properties, with
surface roughness close to 1 nm. The resulting grooves are infiltrated by low viscosity liquid crystal having large
positive optical anisotropy. The use of slanted grooves provides advantages: first of all the complete filling of slanted
grooves is simplified when compared to vertical walls structures. Furthermore alignment is significantly facilitated.
Indeed the liquid crystal molecules tend to align with their long axis along the submicron grooves. Therefore by forcing
reorientation out of a rest position, the liquid crystal presents a choice of refractive indices to the propagating optical
field. The liquid crystal behavior is simulated by a finite element method, and coupled to a finite difference time domain
method. We investigate different photonic crystal configurations. Large tunability of bandgap edge for TE polarization is
demonstrated when switching the liquid crystal with an applied voltage. We have also studied the use of the same device
geometry as a very compact microfluidic refractometric sensor.
This paper investigates the tunable characteristics of various photonic crystal structures infiltrated with nematic liquid crystals. A triangular lattice of air cylinders drilled into silicon provides the photonic crystal structure and the nematic material is inserted either in all or in properly selected air voids in order to create one-dimensional cavities or directional couplers. We have shown in previous studies that the spectral properties of such geometries can be tuned by means of applying appropriate static electric fields, which eventually determine the orientation of the liquid crystal molecules inside the cylindrical cavities. The essential aspect of the present study is to consider various profiles for the nematic director, which are associated with different molecular anchoring conditions at the confining surfaces, as well as electric fields of various strengths and orientation. In particular, we examine the cases of homeotropic or tangential surface anchoring orientation in the strong or weak anchoring limit, and more specifically focus on determining the impact of the transition from strong to weak anchoring, both on the operation of each structure and the associated range of tuning.
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