Efficient dielectric-plasmonic interconnect is significant in the design of future electronic-photonic integrated circuits that deal with large data transfer. We propose three designs and analysis of small-footprint c...
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Efficient dielectric-plasmonic interconnect is significant in the design of future electronic-photonic integrated circuits that deal with large data transfer. We propose three designs and analysis of small-footprint couplers that are located at the interface between dielectric and plasmonic waveguides. To the best of our knowledge, our proposed couplers outperform all the works reported in the literature in several aspects including size and coupling efficiency (CE). Our results indicate that the optimum dimensions of the proposed couplers are determined based on whether the coupler is located in the metal side or dielectric side, or the coupler extends equally in both types of materials. The proposed couplers work over a broad frequency range achieving a CE above 88% at the optical communications wavelength 1550 nm. In addition, our results indicate that the CE can be further increased to above 93% by increasing the width of the dielectric waveguide before it is connected to the coupler. Moreover, our proposed designs provide a considerable alignment tolerance, which is needed when aligning the dielectric waveguide to the metal-dielectric-metal waveguide. Our proposed couplers have an impact on the design and miniaturization of nanoscale all-optical devices. (C) The Authors.
In this paper, we propose a new variety of strong field confinement, ultra-compact size, easy-to-integrate spoof surface plasmon polariton (SSPP) waveguides based on double-sided parallel-strip lines (DSPSL), which ar...
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In this paper, we propose a new variety of strong field confinement, ultra-compact size, easy-to-integrate spoof surface plasmon polariton (SSPP) waveguides based on double-sided parallel-strip lines (DSPSL), which are formed by etching opposite spiral grooves on the upper and lower metal layers of the DSPSL. By analyzing the dispersion characteristics, we found that the opposite spiral grooves can significantly reduce the asymptotic frequency of the dispersion curve. Compared with the conventional comb-shaped SSPP structures at the same asymptotic frequency, the size of the structure is reduced to 19.85%, which facilitates miniaturization and integration of microwave devices. A broadband transition is also designed to achieve smooth impedance and momentum matching for the proposed SSPP waveguide. Owing to the dual-conductor structure, the proposed waveguides can be easily integrated with active devices and can also support low-frequency or time-domain signals without causing distortions. The proposed SSPP waveguides have strong field confinement and can concentrate the field around the spiral groove, implying great potential applications in sensing and detection. In parallel, we also designed two notch filters based on the proposed SSPP waveguide, which can achieve adjustable narrowband or broadband filtering by loading different capacitors. The proposed design can be widely used in various plasmonic devices, which opens up a new door to build up large-scale plasmonic integrated circuits in the microwave and terahertz regimes.
An enriched finite element method is presented to numerically solve the eigenvalue problem on electromagnetic waveguides governed by the Helmholtz equation. In this work, a highly efficient, simple and precise higher ...
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An enriched finite element method is presented to numerically solve the eigenvalue problem on electromagnetic waveguides governed by the Helmholtz equation. In this work, a highly efficient, simple and precise higher order subparametric method was developed using a 2D automated mesh generator performed with JuliaFEM. The transcendence computerized discretization code in Julia is developed for the present work. For curved waveguide structures, meshes with one side and curving higher orders are proposed with triangular elements with parabolic arcs. The technique is shown for distinct waveguide constructions, and the results are compared with the strongest numerical or analytical results available. The results demonstrate that the proposed methodology is effective and accurate for generating finite element simulations for complex structures with black holes and irregular topology due to no curvature loss. This article presents a finding cutoff frequency performed with JuliaFEM-an open-source program. Analysis results produced by commercial software are considered for the comparison and show that the calculation results between the two programs do not differ significantly. This procedure can be used to achieve the most effective transmission of energy for electromagnetic applications.
Silica waveguides are often etched by reactive ion etch (RIE) processes. These processes can leave residual topography that can increase optical loss. We investigated the relation between optical loss and various RIE ...
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Silica waveguides are often etched by reactive ion etch (RIE) processes. These processes can leave residual topography that can increase optical loss. We investigated the relation between optical loss and various RIE etch. A wet etch step meant to remove microstructures was also considered and compared. Ridge waveguides were fabricated in plasma enhanced chemical vapor deposited films by three different RIE processes, each with a different gas composition, pressure setting, and applied power setting. Half of each set of waveguides were also subjected to a hydrofluoric acid (HF) solution. The waveguides were tested for optical transmission via the cutback method. The transmission vs waveguide length measurements were plotted to fit an exponential curve and the optical loss and measurement uncertainty for each waveguide set was calculated. Clear distinctions in optical loss were found between the different RIE processes. The HF treatment also has an effect, significantly reducing optical loss for two processes and increasing it for the third. Of the tested RIE processes, one can be suggested for silica waveguides. It results in the lowest optical loss and coincidently has the fastest etch rate.
Nonreciprocal waveguides play an important role in microwave and optical systems. Here we present a new concept for a one-way meta-waveguide: a waveguide that supports a guided mode in one direction while waves travel...
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Nonreciprocal waveguides play an important role in microwave and optical systems. Here we present a new concept for a one-way meta-waveguide: a waveguide that supports a guided mode in one direction while waves traveling in the opposite direction leak out into the waveguide cladding. This is achieved by placing a metasurface atop of a ferrite slab, and judiciously phase matching two radiant and one subradiant meta-waveguide modes in order to enhance the magneto-optical response and to create an accidental Dirac cone in the reciprocal space. By applying an in-plane magnetic field, the reciprocal and nonreciprocal contributions to magneto-optical response can interfere constructively/destructively depending on the propagation direction, thereby shifting the apex of the Dirac cone and creating a one-way propagation bandgap. The idea of one-way leaky-cladding waveguide provides an alternative way of designing nonreciprocal devices that do not require a gap in the Dirac cone.
The dual beam guides for transverse-electric and transverse-magnetic polarizations of electromagnetic (EM) wave and elastic wave in defect-free phoxonic crystals are reported. The realization for phoxonic virtual wave...
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The dual beam guides for transverse-electric and transverse-magnetic polarizations of electromagnetic (EM) wave and elastic wave in defect-free phoxonic crystals are reported. The realization for phoxonic virtual waveguides relies on dual flat equifrequency contours (EFCs) enabling self-collimation for EM and elastic waves. As a possible application of our work, the enhanced acousto-optic (AO) interaction in this kind of defect-free phoxonic waveguide, just as it does in defect-based waveguides, is further studied. Results show that obvious shifts of the transmission peaks of EM waves exist for both polarizations during one period of the elastic wave, and single-phonon exchange dominates the AO interaction. This kind of phoxonic virtual waveguide provides an effective platform to enhance AO interaction and exhibits some advantage over defect-based waveguides by properly manipulating the photonic and phononic dispersion surfaces. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Broadband, low-loss, low-dispersion propagation of terahertz pulses in compact waveguide chips is indispensable for terahertz integration. Conventional 2D photonic crystals (PCs) based terahertz waveguides are either ...
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Broadband, low-loss, low-dispersion propagation of terahertz pulses in compact waveguide chips is indispensable for terahertz integration. Conventional 2D photonic crystals (PCs) based terahertz waveguides are either all-metallic or all-dielectric, having either high propagation losses due to the Ohmic loss of metal, or a narrow transmission bandwidth restricted by the range of single-mode operation in a frequency range defined by the PC bandgap, respectively. To address this problem, a hybrid (metal/dielectric) terahertz waveguide chip is developed, where the guided mode is completely confined by parallel gold plates and silicon PCs in vertical and lateral directions, respectively. A unique multiwafer silicon-based fabrication process, including gold-silicon eutectic bonding, micropatterning, and Bosch silicon etching, is employed to achieve the self-supporting hybrid structure. Theoretical and experimental investigations demonstrate that the hybrid waveguide supports a single-mode transmission covering 0.367-0.411 THz (bandwidth of 44 GHz, over twice wider than that of all-silicon PC waveguides) with low loss (below 0.05 dB mm(-1)) and low group velocity dispersion (from -8.4 to -0.8 ps THz(-1) mm(-1)). This work enables more compact, wideband terahertz waveguides and auxiliary functional components that are integratable in chips toward ultra-high-density integrated terahertz devices in particular in the field of wireless communications.
In this paper, a general methodology to study rigorous discontinuities in open waveguides is presented. It relies on a full vector description given byMaxwell's equations in the framework of the finite element met...
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In this paper, a general methodology to study rigorous discontinuities in open waveguides is presented. It relies on a full vector description given byMaxwell's equations in the framework of the finite element method. The discontinuities are not necessarily small perturbations of the initial waveguide and can be very general, such as plasmonic inclusions of arbitrary shapes. The leaky modes of the invariant structure are first computed and then injected as incident fields in the full structure with obstacles using a scattered field approach. The resulting scattered field is finally projected on the modes of the invariant structure making use of their bi-orthogonality. The energy balance is discussed. Finally, the modes of open waveguides periodically structured along the propagation direction are computed. The relevant complex propagation constants are compared to the transmission obtained for a finite number of identical cells. The relevance and complementarity of the two approaches are highlighted on a numerical example encountered in infrared sensing. Open source models allowing us to retrieve most of the results of this paper are provided. (c) 2020 Optical Society of America
Crossing losses in silicone optical waveguides are related to the magnitude and spatial extent of the waveguide refractive index gradient. When processing conditions are altered, the refractive index gradient can vary...
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Crossing losses in silicone optical waveguides are related to the magnitude and spatial extent of the waveguide refractive index gradient. When processing conditions are altered, the refractive index gradient can vary substantially, even when the formulation remains constant. Controlling the refractive index gradient requires control of the concentration of small molecules present within the core and clad layers. Developing a fundamental understanding of how small molecule migration drives changes in crossing loss requires the ability to examine chemical functionality over small length scales, which is a natural fit for atomic force microscopy-infrared spectroscopy (AFM-IR). In this work, AFM-IR spectra from model bilayer stacks are initially examined to understand molecular migration that occurs from heating the core and clad layers. The results of these model studies are then applied to photopatterned waveguide builds, where structure-function relationships are constructed between values of crossing loss and the concentration of C-H and O-H functionalities present in the core and clad layers. Results show that small molecule evaporation and migration are competing processes that need to be controlled to minimize crossing loss.
Optics, playing an ever-important role in life, is developing toward miniaturization and integration. Particularly, the field programming of integrated optics will benefit its functionality and durability, thus is hig...
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Optics, playing an ever-important role in life, is developing toward miniaturization and integration. Particularly, the field programming of integrated optics will benefit its functionality and durability, thus is highly pursued. Here, through precisely controlling the space-variant orientations of anisotropic liquid crystals (LCs), various graded-index waveguides are demonstrated in a homogeneous medium. Straight/bending waveguides and ring resonators are fabricated via LC photopatterning. They exhibit pronounced polychromatic light-guiding performance. Thanks to their intrinsic external-stimuli responsivity, the thermal switchability and polarization tunability are verified. By selectively polymerizing, robust functional components and active connecting waveguides can be realized on the same chip. It provides a practical and universal solution to programmable integrated optics, and extends the applications of microstructured soft matter even in wearable photonics.
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