Photonic molecules with a tunable inter-cavity gap

Optical micro-resonators have broad applications. They are used, for example, to enhance light–matter interactions in optical sensors or as model systems for investigating fundamental physical mechanisms in cavity quantum electrodynamics. Coupling two or more micro-cavities is particularly interesting as it enlarges the design freedom and the field of application. In this context, achieving tunability of the coupling strength and hence the inter-cavity gap is of utmost importance for adjusting the properties of the coupled micro-resonator system. In this paper, we report on a novel coupling approach that allows highly precise tuning of the coupling gap of polymeric micro-resonators that are fabricated side by side on a common substrate. We structure goblet-shaped whispering-gallery-mode resonators on an elastic silicone-based polymer substrate by direct laser writing. The silicone substrate is mechanically stretched in order to exploit the lateral shrinkage to reduce the coupling gap. Incorporating a laser dye into the micro-resonators transforms the cavities into micro-lasers that can be pumped optically. We have investigated the lasing emission by micro-photoluminescence spectroscopy, focusing on the spatial localization of the modes. Our results demonstrate the formation of photonic molecules consisting of two or even three resonators, for which the coupling strengths and hence the lasing performance can be precisely tuned. Flexibility and tunability are key elements in future photonics, making our approach interesting for various photonic applications. For instance, as our coupling approach can also be extended to larger cavity arrays, it might serve as a platform for tunable coupled-resonator optical waveguide devices

Strongly Correlated Quantum Fluids: Ultracold Quantum Gases, Quantum Chromodynamic Plasmas, and Holographic Duality

Strongly correlated quantum fluids are phases of matter that are intrinsically quantum mechanical, and that do not have a simple description in terms of weakly interacting quasi-particles. Two systems that have recently attracted a great deal of interest are the quark-gluon plasma, a plasma of strongly interacting quarks and gluons produced in relativistic heavy ion collisions, and ultracold atomic Fermi gases, very dilute clouds of atomic gases confined in optical or magnetic traps. These systems differ by more than 20 orders of magnitude in temperature, but they were shown to exhibit very similar hydrodynamic flow. In particular, both fluids exhibit a robustly low shear viscosity to entropy density ratio which is characteristic of quantum fluids described by holographic duality, a mapping from strongly correlated quantum field theories to weakly curved higher dimensional classical gravity. This review explores the connection between these fields, and it also serves as an introduction to the Focus Issue of New Journal of Physics on Strongly Correlated Quantum Fluids: from Ultracold Quantum Gases to QCD Plasmas. The presentation is made accessible to the general physics reader and includes discussions of the latest research developments in all three areas.Comment: 138 pages, 25 figures, review associated with New Journal of Physics special issue "Focus on Strongly Correlated Quantum Fluids: from Ultracold Quantum Gases to QCD Plasmas" (http://iopscience.iop.org/1367-2630/focus/Focus%20on%20Strongly%20Correlated%20Quantum%20Fluids%20-%20from%20Ultracold%20Quantum%20Gases%20to%20QCD%20Plasmas

Biosensors for unattended cost-effective and continuous monitoring of environmental pollution: Automated water analyser computer supported system (AWACSS) and river analyser (RIANA)

This work describes our recent progress and achievements in the field of fully automated biosensors (Automated Water Analyser Computer Supported System (AWACSS) and River Analyser (RIANA)) for unattended, cost-effective and continuous monitoring of environmental pollution. We report on ultra-sensitive immunoassays for the hormones progesterone, testosterone and estrone and the pesticides propanil and isoproturon as examples of the outstanding progress made on biosensors in the field of environmental monitoring and water analysis. Most of the bio-active organic pollutants (estrone, progesterone, propanil and isoproturon) were detected at levels as low as 1.0pgm/L or even below. In fact, the reported limits of detection (LOD) were between 0.2 and 6.0pgm/L. For the first time, commercially available derivatives and antibodies were incorporated into immunoassays (progesterone and testosterone) for fully automated biosensors. To verify the assay performance for quantifying testosterone, progesterone, and isoproturon in real-world samples using our immunosensors, we spiked river and drinking water at six different levels from 0.9pgm/L to 90ngm/L. Nearly all recovery rates could be obtained between 70 and 120% as the AOAC International recommends it chiefly for water analysis