Rational design of an integrated directional coupler for wideband operation.

We consider a design procedure for directional couplers for which the coupling length is approximately wavelength-independent over a wide bandwidth. We show analytically that two coupled planar waveguides exhibit a maximum in the coupling strength, which ensures both wideband transmission and minimal device footprint. This acts as a starting point for mapping out the relevant part of phase space.

Microwave analogy of Förster resonance energy transfer and effect of finite antenna length.

The near-field interaction between quantum emitters, governed by Förster resonance energy transfer (FRET), plays a pivotal role in nanoscale energy transfer mechanisms. However, FRET measurements in the optical regime are challenging as they require nanoscale control of the position and orientation of the emitters. To overcome these challenges, microwave measurements were proposed for enhanced spatial resolution and precise orientation control.

Experimental observation of linear pulses affected by high-order dispersion.

We experimentally study the linear propagation of optical pulses affected by high-order dispersion. We use a programmable spectral pulse-shaper that applies a phase that equals that which would result from dispersive propagation. The temporal intensity profiles of the pulses are characterized using phase-resolved measurements.

Plasmonic Sensors beyond the Phase Matching Condition: A Simplified Approach.

The conventional approach to optimising plasmonic sensors is typically based entirely on ensuring phase matching between the excitation wave and the surface plasmon supported by the metallic structure. However, this leads to suboptimal performance, even in the simplest sensor configuration based on the Otto geometry. We present a simplified coupled mode theory approach for evaluating and optimizing the sensing properties of plasmonic waveguide refractive index sensors.

Omnidirectional field enhancements drive giant nonlinearities in epsilon-near-zero waveguides.

Bulk materials with a relative electric permittivity close to zero exhibit giant Kerr nonlinearities. However, harnessing this response in guided-wave geometries is not straightforward, due to the extreme and counterintuitive properties of such epsilon-near-zero materials. Here we investigate, through rigorous calculations of the nonlinear coefficient, how the remarkable nonlinear properties of such materials can be exploited in several structures, including bulk films, plasmonic nanowires, and metal nanoapertures.

Costs and benefits of multifactorial falls prevention in nursing homes in the Netherlands.

Objectives: To investigate whether the implementation of a multifactorial falls intervention in nursing homes is cost-beneficial and alleviates the professional workload.

Design: A comprehensive quantitative model was developed to calculate the impact of investments in multifactorial falls prevention in nursing homes in the Netherlands, comparing the fall incidence using intervention strategies in 1000 nursing home residents with the conditions of usual care over a five-year timeline.

Setting And Participants: We built a model combining several data sources regarding falls and injury prevalence in nursing home residents, health care costs, intervention costs and effectiveness, and demographic statistics.

Self-similar propagation of optical pulses in fibers with positive quartic dispersion.

We study the propagation of ultrashort pulses in optical fiber with gain and positive (or normal) quartic dispersion by self-similarity analysis of the modified nonlinear Schrödinger equation. We find an exact asymptotic solution, corresponding to a triangle-like intensity profile, with a chirp, which is confirmed by numerical simulations. This solution follows different amplitude and width scaling compared to the conventional case with quadratic dispersion.

Modular nonlinear hybrid plasmonic circuit.

Photonic integrated circuits (PICs) are revolutionizing nanotechnology, with far-reaching applications in telecommunications, molecular sensing, and quantum information. PIC designs rely on mature nanofabrication processes and readily available and optimised photonic components (gratings, splitters, couplers). Hybrid plasmonic elements can enhance PIC functionality (e.

Simple model for orthogonal and angled coupling in dielectric-plasmonic waveguides.

We numerically and analytically study orthogonal and angled coupling schemes between a dielectric slab waveguide and a plasmonic slot waveguide for a large range of geometric and material parameters. We obtain high orthogonal coupling transmission efficiencies (up to 78% for 2D calculations, and 54% for 3D calculations) over a wide range of refractive indices, and provide simple analytic arguments that explain the underlying trends. The insights obtained point to angled couplers with even higher coupling efficiencies (up to 86% in 2D, and 61% in 3D).

A theory of waveguide design for plasmonic nanolasers.

We propose a theory for the waveguide design and analysis for plasmonic nanolasers by reformulating the fundamental waveguide requirements. This theory does not rely on further optimizing previously used structures, but examines each possible design without prejudice. Our exploration of one-dimensional (i.

Economic Evaluations of Falls Prevention Programs for Older Adults: A Systematic Review.

Objectives: To provide a comprehensive overview of economic evaluations of falls prevention programs and to evaluate the methodology and quality of these studies.

Design: Systematic review of economic evaluations on falls prevention programs.

Setting: Studies (N=31) of community-dwelling older adults (n=25), of older adults living in residential care facilities (n=3), and of both populations (n=3) published before May 2017.

Increased care demand and medical costs after falls in nursing homes: A Delphi study.

Aims And Objective: To estimate the increased care demand and medical costs caused by falls in nursing homes.

Background: There is compelling evidence that falls in nursing homes are preventable. However, proper implementation of evidence-based guidelines to prevent falls is often hindered by insufficient management support, staff time and funding.

Analysis and design of fibers for pure-quartic solitons.

The recently discovered pure-quartic solitons, arising from the interaction of quartic dispersion and Kerr nonlinearity, open the door to unexplored soliton regimes and ultrafast laser science. Here, we report a general analysis of the dispersion and nonlinear properties necessary to observe pure-quartic solitons in optical platforms. We apply this analysis, in combination with numerical calculations, to the design of pure-quartic soliton supporting microstructured optical fibers.

Stimulated Brillouin scattering enhancement in silicon inverse opal waveguides.

Silicon is an ideal material for on-chip applications, however its poor acoustic properties limit its performance for important optoacoustic applications, particularly for stimulated Brillouin scattering (SBS). We theoretically show that silicon inverse opals exhibit a strongly improved acoustic performance that enhances the bulk SBS gain coefficient by more than two orders of magnitude. We also design a waveguide that incorporates silicon inverse opals and which has SBS gain values that are comparable with chalcogenide glass waveguides.

Metamaterial control of stimulated Brillouin scattering.

Using full opto-acoustic numerical simulations, we demonstrate enhancement and suppression of the SBS gain in a metamaterial comprising a subwavelength cubic array of dielectric spheres suspended in a dielectric background material. We develop a general theoretical framework and present several numerical examples using technologically important materials. For AsS spheres in silicon, we achieve a gain enhancement of more than an order of magnitude compared to pure silicon and for GaAs spheres in silicon, full suppression is obtained.

Pure-quartic solitons.

Temporal optical solitons have been the subject of intense research due to their intriguing physics and applications in ultrafast optics and supercontinuum generation. Conventional bright optical solitons result from the interaction of anomalous group-velocity dispersion and self-phase modulation. Here we experimentally demonstrate a class of bright soliton arising purely from the interaction of negative fourth-order dispersion and self-phase modulation, which can occur even for normal group-velocity dispersion.

Association of Proton Pump Inhibitor Use with Recurrent Falls and Risk of Fractures in Older Women: A Study of Medication Use in Older Fallers.

Objectives: To examine the association between Proton pump inhibitors (PPIs) use and falls and fractures.

Design: A cross-sectional study.

Setting And Participants: 400 female patients aged 70 years or older who were consecutively admitted to the Trauma Center Meidling, Vienna, after a fall and who required hospital admission.

Fano resonances of dielectric gratings: symmetries and broadband filtering.

The guided mode resonances (GMRs) of diffraction gratings surrounded by low index materials can be designed to produce broadband regions of near perfect reflection and near perfect transmission. These have many applications, including in optical isolators, in hybrid lasers cavities and in photovoltaics. The excitation of rapid GMRs occurs in a background of slowly varying Fabry-Perot oscillation, which produces Fano resonances.

New avenues for phase matching in nonlinear hyperbolic metamaterials.

Nonlinear optical processes, which are of paramount importance in science and technology, involve the generation of new frequencies. This requires phase matching to avoid that light generated at different positions interferes destructively. Of the two original approaches to achieve this, one relies on birefringence in optical crystals, and is therefore limited by the dispersion of naturally occurring materials, whereas the other, quasi-phase-matching, requires direct modulation of material properties, which is not universally possible.

Absorption enhancing proximity effects in aperiodic nanowire arrays.

Aperiodic Nanowire (NW) arrays have higher absorption than equivalent periodic arrays, making them of interest for photovoltaic applications. An inevitable property of aperiodic arrays is the clustering of some NWs into closer proximity than in the equivalent periodic array. We focus on the modes of such clusters and show that the reduced symmetry associated with cluster formation allows external coupling into modes which are dark in periodic arrays, thus increasing absorption.

Coherent perfect absorption and reflection in slow-light waveguides.

We identify a family of unusual slow-light modes occurring in lossy multimode grating waveguides, for which either the forward or backward mode components, or both, are degenerate. In the fully degenerate case, the response can be modulated between coherent perfect absorption (zero reflection) and perfect reflection by varying the wave amplitudes in a uniform input waveguide. The perfectly absorbed wave has anomalously short absorption length, scaling as the inverse one-third power of the absorptivity.

Drug cessation in complex older adults: time for action.

Background: general opinion is growing that drug cessation in complex older patients is warranted in certain situations. From a clinical viewpoint, drug cessation seems most warranted in four situations, i.e.

Cavity Optical Pulse Extraction: ultra-short pulse generation as seeded Hawking radiation.

We show that light trapped in an optical cavity can be extracted from that cavity in an ultrashort burst by means of a trigger pulse. We find a simple analytic description of this process and show that while the extracted pulse inherits its pulse length from that of the trigger pulse, its wavelength can be completely different. Cavity Optical Pulse Extraction is thus well suited for the development of ultrashort laser sources in new wavelength ranges.