Twin core non-linear couplers with gain and loss

Twin core nonlinear couplers that include gain and loss are examined. Of various structures (ranging from couplers composed of two active cores and two lossy cores to those composed of one active or lossy core and one conventional core) considered, the most interesting case is the coupler composed of' one core with a certain amount of gain and the other core with an equal amount of loss where ideal low power switching is possible in a comparatively short coupler. The presence of gain in one core is found to be responsible for reduction in switching power and/or shortening in the device length, while the introduction of the loss in the other core plays a role of idealizing switching. A physical model is also presented to explain the demonstrated merits based on the operation of linear couplers with gain and loss

Surface plasmon resonance under conditions of electromagnetically induced transparency

A scheme for a surface plasmon resonance system under conditions of electromagnetically induced transparency (EIT) is proposed. The system is composed of three layers: a prism, a thin metal film, and a hybrid dielectric consisting of EIT atoms and a background substance. A probe and a coupling laser beam are input. Corresponding analytical formulas are derived for the cases when one or both of the laser beams excite surface plasmon polaritons at the metal/dielectric interface. Under resonance conditions, an extremely sharp dip appears in the reflectivity-frequency spectrum of the probe field, revealing new properties of two-dimensional EIT. The reflectivity is extremely sensitive to shifts in the laser frequencies and atomic levels, and to variations of permittivity of the substrate. This EIT-SPR system may to be used for novel magnetometers and biosensors

Band Gaps for Atoms in Light based Waveguides

The energy spectrum for a system of atoms in a periodic potential can exhibit a gap in the band structure. We describe a system in which a laser is used to produce a mechanical potential for the atoms, and a standing wave light field is used to shift the atomic levels using the Autler-Townes effect, which produces a periodic potential. The band structure for atoms guided by a hollow optical fiber waveguide is calculated in three dimensions with quantised external motion. The size of the band gap is controlled by the light guided by the fiber. This variable band structure may allow the construction of devices which can cool atoms. The major limitation on this device would be the spontaneous emission losses.Comment: 7 pages, four postscript figures, uses revtex.sty, available through http://online.anu.edu.au/Physics/papers/atom.htm

Soliton molecules in trapped vector Nonlinear Schrodinger systems

We study a new class of vector solitons in trapped Nonlinear Schrodinger systems modelling the dynamics of coupled light beams in GRIN Kerr media and atomic mixtures in Bose-Einstein condensates. These solitons exist for different spatial dimensions, their existence is studied by means of a systematic mathematical technique and the analysis is made for inhomogeneous media

Fresnel laws at curved dielectric interfaces of microresonators

We discuss curvature corrections to Fresnel's laws for the reflection and transmission of light at a non-planar refractive-index boundary. The reflection coefficients are obtained from the resonances of a dielectric disk within a sequential-reflection model. The Goos-H\"anchen effect for curved light fronts at a planar interface can be adapted to provide a qualitative and quantitative extension of the ray model which explains the observed deviations from Fresnel's laws.Comment: submitted to Phys. Rev.

Bifurcation and stability for Nonlinear Schroedinger equations with double well potential in the semiclassical limit

We consider the stationary solutions for a class of Schroedinger equations with a symmetric double-well potential and a nonlinear perturbation. Here, in the semiclassical limit we prove that the reduction to a finite-mode approximation give the stationary solutions, up to an exponentially small term, and that symmetry-breaking bifurcation occurs at a given value for the strength of the nonlinear term. The kind of bifurcation picture only depends on the non-linearity power. We then discuss the stability/instability properties of each branch of the stationary solutions. Finally, we consider an explicit one-dimensional toy model where the double well potential is given by means of a couple of attractive Dirac's delta pointwise interactions.Comment: 46 pages, 4 figure

Optical nanofibers and spectroscopy

We review our recent progress in the production and characterization of tapered optical fibers with a sub-wavelength diameter waist. Such fibers exhibit a pronounced evanescent field and are therefore a useful tool for highly sensitive evanescent wave spectroscopy of adsorbates on the fiber waist or of the medium surrounding. We use a carefully designed flame pulling process that allows us to realize preset fiber diameter profiles. In order to determine the waist diameter and to verify the fiber profile, we employ scanning electron microscope measurements and a novel accurate in situ optical method based on harmonic generation. We use our fibers for linear and non-linear absorption and fluorescence spectroscopy of surface-adsorbed organic molecules and investigate their agglomeration dynamics. Furthermore, we apply our spectroscopic method to quantum dots on the surface of the fiber waist and to caesium vapor surrounding the fiber. Finally, towards dispersive measurements, we present our first results on building and testing a single-fiber bi-modal interferometer.Comment: 13 pages, 18 figures. Accepted for publication in Applied Physics B. Changes according to referee suggestions: changed title, clarification of some points in the text, added references, replacement of Figure 13

Spatial Solitons and Anderson Localization

Stochastic (Anderson) localization is the spatial localization of the wave-function of quantum particles in random media. We show, that a corresponding phenomenon can stabilize spatial solitons in optical resonators: spatial solitons in resonators with randomly distorted mirrors are more stable than in perfect mirror resonators. We demonstrate the phenomenon numerically, by investigating solitons in lasers with saturable absorber, and analytically by deriving and analyzing coupled equations of spatially coherent and incoherent field components.Comment: submitted to Phys.Rev.

Listening to the patient voice adds value to cancer clinical trials.

Randomized clinical trials are critical for evaluating the safety and efficacy of interventions in oncology and informing regulatory decisions, practice guidelines, and health policy. Patient-reported outcomes (PROs) are increasingly used in randomized trials to reflect the impact of receiving cancer therapies from the patient perspective and can inform evaluations of interventions by providing evidence that cannot be obtained or deduced from clinicians' reports or from other biomedical measures. This commentary focuses on how PROs add value to clinical trials by representing the patient voice. We employed two previously published descriptive frameworks (addressing how PROs are used in clinical trials and how PROs have an impact, respectively) and selected nine clinical trial publications that illustrate the value of PROs according to the framework categories. These include three trials where PROs were a primary trial endpoint, three trials where PROs as secondary endpoints supported the primary endpoint, and three trials where PROs as secondary endpoints contrast the primary endpoint findings in clinically important ways. The nine examples illustrate that PROs add valuable data to the care and treatment context by informing future patients about how they may feel and function on different treatments and by providing clinicians with evidence to support changes to clinical practice and shared decision-making. Beyond the patient and clinician, PROs can enable administrators to consider the cost-effectiveness of implementing new interventions, and contribute vital information to policy-makers, health technology assessors, and regulators. These examples provide a strong case for the wider implementation of PROs in cancer trials. [Abstract copyright: © The Author(s) (2022). Published by Oxford University Press.