A compact and broadband 3 dB power splitter using a fast quasi-adiabatic (FAQUAD) approach is proposed on the thin-film lithium niobate platform. The FAQUAD approach effectively speeds up the adiabatic mode evolution ...
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Widespread millimeter wave applications have promoted rapid development of system in package (SiP) and antenna in package (AiP). Most AiP structures take the form of flip chip onto antenna substrate, where signal inte...
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Widespread millimeter wave applications have promoted rapid development of system in package (SiP) and antenna in package (AiP). Most AiP structures take the form of flip chip onto antenna substrate, where signal interconnect losses are introduced by solder humps. The integration may be unavailable for chips with fine pad pitches. Fan-out wafer level package (FOWLP) with antenna patterning on redistributed layers (RDL) is another method for millimeter wave AiP. In this project, a hybrid integration AiP structure is developed. The microwave monolithic integrated circuit (MMIC) chip and antenna unit are integrated with chip-first FOWLP process. Multilayer organic substrate with fine pitch RDL interconnections meets the requirements of wideband antenna design. Modified coplanar waveguide is adopted to feed 2 x 2 aperture array formed on RDL layer. Package warpage is measured using Shadow Moire techniques. The antenna forms an aperture-coupled stacked patch array with bandwidth 25% and gain 8.5dBi for 60 GHz digital communication system. The proposed approach is a convenient hybrid integration solution adopting FOWLP process for millimeter wave AiP systems.
We developed a silicon computational spectrometer with a thermally reconfigurable self-coupled waveguide, achieving better than 0.1 nm resolution over a 75 nm bandwidth in a footprint smaller than 0.02 mm2 using a sin...
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The in-plane thermal conductance of a vacuum gap supporting the propagation of hybridized guided modes along its interfaces with two polar SiO2 materials is quantified and analyzed as a function of the gap distance an...
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The in-plane thermal conductance of a vacuum gap supporting the propagation of hybridized guided modes along its interfaces with two polar SiO2 materials is quantified and analyzed as a function of the gap distance and temperature. In contrast to the well-known cross-plane thermal conductance, we show that the in-plane one increases with the gap distance up to 1 cm, in which it takes its maxima that increase with temperature. A maximum thermal conductance per unit width of 103mW~m−1K−1 is found at 500 K, which is more than 6 (3) orders of magnitude higher than the corresponding one found in the near-field (far-field) regime. This top polariton thermal conductance along the cavity is pretty much equal to the radiative one predicted by Planck's theory and therefore it could be useful to amplify or evacuate heat currents along macroscale gaps.
Graphene nanoribbons (GNRs) are natural waveguides for electrons in graphene. Nevertheless, unlike micrometer-sized samples, conductance is nearly suppressed in these narrow graphene stripes, mainly due to scattering ...
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Graphene nanoribbons (GNRs) are natural waveguides for electrons in graphene. Nevertheless, unlike micrometer-sized samples, conductance is nearly suppressed in these narrow graphene stripes, mainly due to scattering with edge disorder generated during synthesis or cut. A possible way to circumvent this effect is to define an internal waveguide that isolates specific modes from the edge disorder and allows ballistic conductance. There are several proposals for defining waveguides in graphene;in this manuscript, we consider strain folds and scalar potentials and numerically evaluate these proposals' performance against edge and bulk disorder. Using the Green's function approach, we calculate conductance and the local density of states of zigzag GNRs and characterize the performance of these different physical waveguiding effects in both types of disorders. We found a general improvement in the electronic conductance of GNR due to the presence of the internal waveguiding, with the emergence of plateaus with quasi-ballistic properties and robustness against edge disorder. These findings are ready to be applied in modern nanotechnology and are being experimentally tested.
Surface bound states in the continuum (SBICs) have been found to occur in diverse settings, but so far always at the interface of nonhomogeneous media, such as discrete lattices or periodic systems. Here, we show that...
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Surface bound states in the continuum (SBICs) have been found to occur in diverse settings, but so far always at the interface of nonhomogeneous media, such as discrete lattices or periodic systems. Here, we show that they can also exist at the interface of homogeneous media, resulting in unique SBICs. Specifically, we found that, contrary to general belief, leaky Dyakonov states exist at the interface between materials that exhibit opposite signs of anisotropy. In addition, properly breaking the anisotropy symmetry leads to the formation of both guided states and also SBICs embedded within the continuum. A direct implication of our finding is the possibility to create SBICs and Dyakonov states in a whole new class of materials and metamaterials.
The generation of an optical near-field spot through a gradually varying thickness waveguide composed of metallic and dielectric thin films was comprehensively analyzed by the finite element method. The incident angle...
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The generation of an optical near-field spot through a gradually varying thickness waveguide composed of metallic and dielectric thin films was comprehensively analyzed by the finite element method. The incident angle of the excitation beam, excitation wavelength, and material dependent strength of the near-field hotspot were evaluated using three different material combinations. The analysis showed that the waveguide can generate a near-field spot with an electric field stronger than that of the excitation beam in the wide spectral range, reaching from visible 488 nm to mid-infrared 7000 nm (3.8-octave). From the wedge angle and excitation position dependency, the thin-film waveguide with varying thickness indicated the high stability, high freedom of design, and high tolerance to process precision. These manifold advantages progress optoelectronics, plasmonics, and nanotechnologies, including nanometric spectroscopy. (c) 2022 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://***/licenses/by/4.0/).
The rectangular cross-section waveguide made of PMMA is designed to efficiently transfer solar radiation from the source to the receiver, whether it be a (solar cell or a thermal reservoir) by the total internal refle...
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Silicon nitride (SiN) waveguides need to be thick to show low dispersion which is desired for nonlinear applications. However, high quality thick SiN produced by chemical vapour deposition (CVD) contains high internal...
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Silicon nitride (SiN) waveguides need to be thick to show low dispersion which is desired for nonlinear applications. However, high quality thick SiN produced by chemical vapour deposition (CVD) contains high internal stress, causing it to crack. Crack-free wafers with thick SiN can be produced by adding crack barriers. We demonstrate the use of dicing trenches as a simple single-step method to produce high quality (loss<0.5 dB/cm) crack-free SiN. We show Kerr-comb generation in a ring resonator to highlight the high quality and low dispersion of the waveguides. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
Ray tracing is replacing the less accurate statistical and empirical approaches of radio channel modeling. Although being high-frequency asymptotic method, ray tracing has been shown to be mathematically equivalent to...
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Ray tracing is replacing the less accurate statistical and empirical approaches of radio channel modeling. Although being high-frequency asymptotic method, ray tracing has been shown to be mathematically equivalent to purely analytical modal methods in rectangular tunnels and waveguides. The equivalence applies to modeling reflections using image theory, while other variants of the ray tracing algorithm are still subject to approximation errors that can systematically add up. Failure to recognize this leads to indiscriminate use of the less appropriate algorithmic variants. In particular, the use of ray tracing by ray launching can be questionable in tunnel environments, at least when characteristic sequences are used to avoid double counting errors. In addition to the known path inaccuracies, we first identify previously untreated inconsistent rays as the most problematic, leading to a significantly overestimated signal at distances greater than 100m. We show that the problem is not equivalent to double counting of rays since the inconsistent rays represent valid wavefronts for the points in space at which they are detected. The discrepancy arises from the use of reception spheres, which allow some spatial displacement of ray paths. We quantify the errors in terms of estimated power, channel impulse response, and delay spread in a rectangular tunnel. We propose an improvement in the double-count filters to detect inconsistent rays. However, evaluation of signals deeper in the tunnel at frequencies below 1GHz must still be avoided by ray launching due to the remaining path inaccuracies.
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