Analysis design and measurement of guided wave optical backplane interconnection

Optics has been long regarded as the prominent alternative to electronics, to address the serious interconnects bottleneck in high-speed backplane printed circuit boards. In this thesis, we present our work towards the realization of a robust and cost effective 10 Gb/s optically interconnected backplane aimed at switching and storage applications. In the course of this work, we experimentally analyzed optical waveguides and advanced electromagnetic theories and algorithms to explain light propagation phenomena. We experimentally characterized the insertion loss for dielectric waveguide bends of rectangular cross-section for a range of radii of curvature and waveguide widths and generated useful design rules. We then used the Beam Propagation Method (BPM) to separate insertion loss into its individual loss components and developed a ray-tracing model to gain further insight into propagation in waveguide bends. We developed a novel waveguiding component called the tapered bend, which integrated a tapered waveguide with a bend. We expanded intrinsic mode theory, widely known in the acoustic wave field, to explain adiabatic propagation phenomena in tapered bends before, at and after modal cut-off. The proposed electromagnetic theory has significant implications since it can be used for tapered waveguides in general inhomogeneous media. We experimentally measured the insertion loss of the tapered bend and characterized the coupling efficiency tolerance under source misalignment for a range of radii and taper ratios. We developed a semi-analytic algorithm to calculate the radiation modes of rectangular waveguides, based on a non-liner transformation of the wave equation and a Fourier decomposition method. The proposed method is very powerful and can be used in waveguides of arbitrary shape with some additional computational complexity. We applied the coupled mode theory to the computed radiation modes and we calculated the equilibrium distance, the steady state power distribution, and the propagation loss for multimode rectangular waveguides with sidewall roughness. These are the first reported calculations of this kind for rectangular waveguides, to the best of our knowledge. Finally, we designed a novel optical connector based on the mechanically transferable (MT) technology for accurate passive alignment between arrays of waveguides and active devices. In addition, we built a prototype optical backplane system to demonstrate the operation of our connector, and we monitored its performance by subjecting it to a test cycle of a number of engagements. We experimentally characterized the VCSEL sources used in the prototype and generated contour maps of coupling loss as a function of source misalignments. For the first time reported in literature, we measured cross-talk as a function of VCSEL lateral misalignment

Optimizing Horticulture Luminescent Solar Concentrators via Enhanced Diffuse Emission Enabled by Micro-Cone Arrays

Optimizing the photon spectrum for photosynthesis and improving crop yields presents an efficient pathway to alleviate global food shortages. Luminescent solar concentrators (LSCs), consisting of transparent host matrices doped with fluorophores, show excellent promise to achieve the desired spectral tailoring. However, conventional LSCs are predominantly engineered for photon harvesting, which results in a limited outcoupling efficiency of converted photons. Here, we introduce a scheme to implement LSCs into Horticulture (HLSC) by enhancing light extraction. The symmetry of the device is disrupted by incorporating micro-cone arrays on the bottom surface to mitigate Total Internal Reflection (TIR). Both Monte Carlo ray tracing simulations and experimental results have verified that the greatest enhancements in converted light extraction, relative to planar LSCs, are achieved using micro-cone arrays (base width 50 um, aspect ratio 1.2) with extruded (85.15% improvement) and protruded (66.55% improvement) profiles. Angularly resolved transmission measurements show that the HLSC device exhibits a broad angular radiation distribution. This characteristic indicates that the HLSC device emits diffuse light, which is conducive to optimal plant growth

Antimicrobial mechanisms of nanopatterned surfaces—a developing story

Whilst it is now well recognized that some natural surfaces such as seemingly fragile insect wings possess extraordinary antimicrobial properties, a quest to engineer similar nanopatterned surfaces (NPSs) is ongoing. The stake is high as biofouling impacts critical infrastructure leading to massive social and economic burden with an antimicrobial resistance (AMR) issue at the forefront. AMR is one of the most imminent health challenges the world is facing today. Here, in the effort to find more sustainable solutions, the NPSs are proposed as highly promising technology as their antimicrobial activity arises from the topographical features, which could be realized on multiple material surfaces. To fully exploit these potentials however, it is crucial to mechanistically understand the underlying killing pathways. Thus far, several mechanisms have been proposed, yet they all have one thing in common. The antimicrobial process is initiated with bacteria contacting nanopatterns, which then imposes mechanical stress onto bacterial cell wall. Hence, the activity is called “mechano-bactericidal”. From this point on, however, the suggested mechanisms start to diverge partly due to our limited understanding of force interactions at the interface. The aim of this mini review is to analyze the state-of-the-art in proposed killing mechanisms by categorizing them based on the characteristics of their driving force. We also highlight the current gaps and possible future directions in investigating the mechanisms, particularly by shifting towards quantification of forces at play and more elaborated biochemical assays, which can aid validating the current hypotheses

A Comparison Study between Isogeometric Analysis and Finite Element Analysis for Nonlinear Inelastic Dynamic Problems with Geomiso DNL Software

The new Geomiso DNL software is proposed to facilitate the use of isogeometric analysis for nonlinear inelastic dynamic applications. This hybrid software solution combines isogeometric analysis and 3D design with advanced spline techniques, such as NURBS and Tsplines. Its dual nature satisfies the rising industrial need for unification of the fields of computer-aided design (CAD) and computer-aided analysis (CAE), as it eliminates geometric errors by merging geometry design with mesh generation into a single procedure. This paper presents sample nonlinear applications in structural dynamics. Geomiso DNL is seen to handle these situations remarkably well, as the numerical examples exhibit significantly improved accuracy of the results, and reduced computational cost, when compared with finite element software packages. It is argued that Geomiso DNL is a new, more efficient, alternative to FEA software packages. This is the first time ever such a cloud-based program has been developed

Self-assembled porous polymer films for improved oxygen sensing

Absolute oxygen sensors based on quenching of phosphorescence have been the subject of numerous studies for the monitoring of biological environments. Here, we used simple fabrication techniques with readily available polymers to obtain high performance phosphorescent films. Specifically, evaporation-based phase separation and the breath figure technique were used to induce porosity. The pore sizes ranged from ∼ 37 nm to ∼ 141µm while the maximum average porosity achieved was ∼ 74%. The oxygen sensing properties were evaluated via a standarised calibration procedure with an optoelectronic setup in both transmission and reflection based configurations. When comparing non-porous and porous films, the highest improvements achieved were a factor of ∼ 7.9 in dynamic range and ∼ 7.3 in maximum sensitivity, followed by an improved linearity with a half-sensitivity point at 43% O2 V/V. Also, the recovery time was reduced by an order of magnitude in the high porosity film and all samples prepared were not affected by variations in the humidity of the surrounding environment. Despite the use of common polymers, the fabrication techniques employed led to the significant enhancement of oxygen sensing properties and elucidated the relation between porous film morphologies and sensing performance

Sensitive and specific detection of explosives in solution and vapour by surface-enhanced Raman spectroscopy on silver nanocubes

Surface-enhanced Raman spectroscopy (SERS) has been widely utilised as a sensitive analytical technique for the detection of trace levels of organic molecules. The detection of organic compounds in the gas phase is particularly challenging due to the low concentration of adsorbed molecules on the surface of the SERS substrate. This is particularly the case for explosive materials, which typically have very low vapour pressures, limiting the use of SERS for their identification. In this work, silver nanocubes (AgNCs) were developed as a highly sensitive SERS substrate with very low limit-of-detection (LOD) for explosive materials down to the femtomolar (10−15 M) range. Unlike typical gold-based nanostructures, the AgNCs were found suitable for the detection of both aromatic and aliphatic explosives, enabling detection with high specificity at low concentration. SERS studies were first carried out using a model analyte, Rhodamine-6G (Rh-6G), as a probe molecule. The SERS enhancement factor was estimated as 8.71 × 1010 in this case. Further studies involved femtomolar concentrations of 2,4-dinitrotoluene (DNT) and nanomolar concentrations of 1,3,5-trinitroperhydro-1,3,5-triazine (RDX), as well as vapour phase detection of DNT

A Multi-CAP Visible-Light Communications System With 4.85-b/s/Hz Spectral Efficiency

In this paper, we experimentally demonstrate a multiband carrierless amplitude and phase modulation format for the first time in VLC. We split a conventional carrierless amplitude and phase modulated signal into m subcarriers in order to protect from the attenuation experienced at high frequencies in low-pass VLC systems. We investigate the relationship between throughput/spectral efficiency and m, where m = {10, 8, 6, 4, 2, 1} subcarriers over a fixed total signal bandwidth of 6.5 MHz. We show that transmission speeds (spectral efficiencies) of 31.53 (4.85), 30.88 (4.75), 25.40 (3.90), 23.65 (3.60), 15.78 (2.40), and 9.04 (1.40) Mb/s (b/s/Hz) can be achieved for the listed values of m, respectively

Fibre-Optic Hydrophone For Detection of High-Intensity Ultrasound Waves

Fibre-optic hydrophones (FOHs) are widely used to detect high-intensity focused ultrasound (HIFU) fields. The most common type consists of an uncoated singlemode fibre with a perpendicularly cleaved end face. The main disadvantage of these hydrophones is their low signal-to-noise ratio (SNR). To increase the SNR, signal averaging is performed, but the associated increased acquisition times hinder ultrasound field scans. In this study, with a view to increase SNR whilst withstanding HIFU pressures, the bare FOH paradigm is extended to include a partially-reflective coating on the fibre end face. Here, a numerical model based on the general transfer-matrix method was implemented. Based on the simulation results, a single-layer, 172 nm TiO2-coated FOH was fabricated. The frequency range of the hydrophone was verified from 1 to 30 MHz. The SNR of the acoustic measurement with the coated sensor was 21 dB higher than of the uncoated one. The coated sensor successfully withstood a peak-positive pressure of 35 MPa for 6000 pulses