Multi-dielectric Structures Research Articles

Array of photonic hooks generated by multi-dielectric structure

Generation of array of photonic hooks (PHs) by a multi–dielectric structure that consists of periodically arrayed scatterer units has been systematically studied. The study focuses on the effects of geometric and optical parameters of the multi–dielectric structure on the characteristics of generated PHs, especially their bending angles. These geometric and optical parameters include size, shape, refractive index and number of scatterer units, and their adjacent spacing. The results show that the spacing, size and refractive index play a predominant role in tailoring the performance of the PHs array, and the spacing affects mainly the characteristics of a pair of symmetrical PHs while the size and refractive index differences between scatterer units affect mainly those of asymmetrical PHs as a result of the introduction of optical inhomogeneity. In the aspect of scatterer shape, for a multi–dielectric structure that consists of some cylinders, as the light wave is incident parallel (perpendicular) to the cylinder axis, its scattering characteristics are similar to those of the multi–dielectric structure that consists of some cuboids (spheres). In particular, for a structure consisted of cylinders or cuboids with long length in the z direction, an intensive photonic nanojet is additionally generated and located between the paired PHs provided that the wave is incident perpendicular to the cylinder axis or the longest side of cuboid. In the aspect of scatterer unit number, the multi–dielectric structures of odd and even scatterer units generate PHs with different characteristics. The paired PHs generated by multi–dielectric structure with equal spacings always bend outward. However, the paired PHs may bend inward provided that the multi–dielectric structure is designed properly. We have also studied the features of 2D PHs array. The results show that the 2D PHs array displays similar features to the 1D case. The application potential of both 1D and 2D PHs arrays is evaluated.

Floating Random Walk-Based Capacitance Extraction for General Non-Manhattan Conductor Structures

The non-Manhattan conductor geometry existing in some capacitance extraction problems brings difficulty to the floating random walk (FRW) method using cubic transition domains. In this paper, techniques are proposed to enhance the FRW method for handling the structures with non-Manhattan conductors. Based on the aligned-box distances and corresponding calculating approaches, the techniques for generating the Gaussian surface and constructing axis-aligned transition cubes are proposed. A practical strategy is then proposed to judge the domination relationship of non-Manhattan conductor blocks for building the space management structure with candidate list. Finally, the strategy using rotated transition cube and related space management technique are proposed to make further acceleration. Experiments on 3-D interconnect structures including from 8 to 1000 non-Manhattan blocks show that the proposed method is from $2.9 {\times }$ to $96 {\times }$ faster than a simple extension of the original FRW method. The proposed method is also up to $39 {\times }$ faster than a boundary element method-based solver. Additional experiments are carried out to further validate the accuracy and efficiency of the proposed techniques, and to demonstrate their suitability for large and multi-dielectric structures.

Fast Random Walk Based Capacitance Extraction for the 3-D IC Structures With Cylindrical Inter-Tier-Vias

3-D integrated circuits (3-D ICs) make use of the vertical dimension for smaller footprint, higher speed, lower power consumption, and better timing performance. In 3-D ICs, the inter-tier-via (ITV) is a critical enabling technique because it forms vertical signal and power paths. Accordingly, it is imperative to accurately and efficiently extract the electrostatic capacitances of ITVs using field solvers. Unfortunately, the cylindrical via shape presents major challenges to most of the existing methods. To address this issue, we develop a novel floating random walk (FRW) method by rotating the transition cube to suit the cylindrical surface, devising a special space management technique, and proposing accelerating techniques for structures with large-sized through-silicon-vias. Experiments on typical ITV structures suggest that the proposed techniques is up to hundreds times faster than a simple FRW approach and the boundary element method-based algorithms, without loss of accuracy. In addition, compared with extracting the square-approximation structures, the proposed techniques can reduce the error by $10 \times $ . Large and multidielectric structures have also been tested to demonstrate the versatility of the proposed techniques.

Scattering losses in multidielectric structures designed for giant optical field enhancement

Multidielectric coatings are analytically designed to reach total absorption and maximum field enhancement at resonances. A resonant multi-dielectric stack was fabricated to be resonant at 633nm for an incidence of 45° under TE-polarization. Field enhancement was expected to be around 1000. We discuss the mismatch with the enhancement measured using near field microscopy and using the scattering effect. In particular, scattering was investigated to serve as a far field characterization of such giant optical fields.

Praseodymium-doped planar multidielectric microcavities: induced lifetime changes over the emission spectrum

We study lifetime modifications induced by luminescent microcavities in the case of praseodymium-doped planar Ta2O5–SiO2 multidielectric structures. From the experimental point of view we measure different decay times of the 1D2 excited level for different wavelengths in the inhomogeneous praseodymium emission spectrum. Decay times depend on the spectral detuning between considered ions and the cavity, and we observe significant changes around the resonance wavelength of the microcavity. The decay times are explained with an electromagnetic modal analysis of spontaneous emission developed in the case of less-loss microcavities.

Transverse operator study of a large class of multidielectric waveguides

The transverse operator method is described for the study of different kinds of dielectric waveguides. The longitudinal section electric (LSE) modes and longitudinal section magnetic (LSM) modes of a corresponding dielectric stratified waveguide, also known as TE-to-x and TM-to-x modes, have been chosen as the basis eigenfunctions, allowing rapid numerical convergence. The dispersion characteristics of some multidielectric waveguide structures have been obtained, as well as their attenuation constants. The results are compared to those previously published or measured and show good agreement. This formulation can be applied to other multidielectric structures with no modification.

Characterization of charge injection and trapping in scaled SONOS/MONOS memory devices

In this paper we investigate scaled SONOS/MONOS (polysilicon-oxide-nitride-oxide-semiconductor)/(metal-oxide-nitride-oxide-semiconductor) memory devices, and the characterization of storage traps in the nitride. The amphoteric and closely-compensating trap models, which describe the positive and negative charging of the nitride “memory” layer, have been compared. “Scaled” complementary SONOS and MONOS nonvolatile memory transistors with the nitride thickness ranging from 85 to 185 A have been designed and fabricated. The linear voltage-ramp method, which measures the flatband voltage shift and separates the charges at the injecting boundary during the WRITE/ERASE operations, has been employed to study non-steady state trapping in the nitride of “scaled” complementary SONOS/MONOS devices for low voltage E 2PROM's (electrically erasable and programmable read only memories). We have demonstrated a differential, saturated flatband voltage shift of 6.5 V with a ±8 V programming voltage for scaled-down devices with dimensions of 20 A for the tunnel oxide, 85 A for the nitride, and 51 A for the blocking oxide. Charge injection and trapping in scaled multi-dielectric structures have been modelled with an amphoteric trap concept. The trap density N T0 , ≈ 10 19 cm −3, effective capture cross section of electrons and holes, \\ ̂ gs n +, \\ ̂ gs p − ≈10 −13 cm 2 , and effective capture cross section of neutral charge states, \\ ̂ gs n 0, \\ ̂ gs p 0 ≈ 10 −14 cm 2 , have been determined with an amphoteric trap model.